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Dong S, Liu Y, Liu Z, Shen P, Sun H, Zhang P, Fong DTP, Song Q. Can Arthrogenic Muscle Inhibition Exist in Peroneal Muscles Among People with Chronic Ankle Instability? A Cross-sectional Study. SPORTS MEDICINE - OPEN 2024; 10:35. [PMID: 38598018 PMCID: PMC11006644 DOI: 10.1186/s40798-024-00710-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Accepted: 03/27/2024] [Indexed: 04/11/2024]
Abstract
BACKGROUND Ankle sprains lead to an unexplained reduction of ankle eversion strength, and arthrogenic muscle inhibition (AMI) in peroneal muscles is considered one of the underlying causes. This study aimed to observe the presence of AMI in peroneal muscles among people with chronic ankle instability (CAI). METHODS Sixty-three people with CAI and another sixty-three without CAI conducted maximal voluntary isometric contraction (MVIC) and superimposed burst (SIB) tests during ankle eversion, then fifteen people with CAI and fifteen without CAI were randomly invited to repeat the same tests to calculate the test-retest reliability. Electrical stimulation was applied to the peroneal muscles while the participants were performing MVIC, and the central activation ratio (CAR) was obtained by dividing MVIC torque by the sum of MVIC and SIB torques, representing the degree of AMI. RESULTS The intra-class correlation coefficients were 0.77 (0.45-0.92) and 0.92 (0.79-0.97) for the affected and unaffected limbs among people with CAI, and 0.97 (0.91-0.99) and 0.93 (0.82-0.97) for the controlled affected and unaffected limbs among people without CAI; Significant group × limb interaction was detected in the peroneal CAR (p = 0.008). The CARs were lower among people with CAI in the affected and unaffected limbs, compared with those without CAI (affected limb = 82.54 ± 9.46%, controlled affected limb = 94.64 ± 6.37%, p < 0.001; unaffected limb = 89.21 ± 8.04%, controlled unaffected limb = 94.93 ± 6.01%, p = 0.016). The CARs in the affected limbs were lower than those in the unaffected limbs among people with CAI (p = 0.023). No differences between limbs were found for CAR in the people without CAI (p = 0.10). CONCLUSIONS Bilateral AMI of peroneal muscles is observed among people with CAI. Their affected limbs have higher levels of AMI than the unaffected limbs.
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Affiliation(s)
- Shiyu Dong
- College of Sports and Health, Shandong Sport University, Jinan, 250102, Shandong, China
| | - Yanhao Liu
- College of Sports and Health, Shandong Sport University, Jinan, 250102, Shandong, China
| | - Ziyin Liu
- College of Sports and Health, Shandong Sport University, Jinan, 250102, Shandong, China
| | - Peixin Shen
- College of Sports and Health, Shandong Sport University, Jinan, 250102, Shandong, China
| | - Hao Sun
- National Centre for Sport and Exercise Medicine, Loughborough University, Loughborough, UK
| | - Ping Zhang
- National Centre for Sport and Exercise Medicine, Loughborough University, Loughborough, UK
| | - Daniel T P Fong
- National Centre for Sport and Exercise Medicine, Loughborough University, Loughborough, UK
| | - Qipeng Song
- College of Sports and Health, Shandong Sport University, Jinan, 250102, Shandong, China.
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Prevc P, Misotic N, Stirn I, Tomazin K. Perceived Discomfort and Voluntary Activation of Quadriceps Muscle Assessed with Interpolated Paired or Triple Electrical Stimuli. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2023; 20:4799. [PMID: 36981708 PMCID: PMC10049235 DOI: 10.3390/ijerph20064799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 03/07/2023] [Accepted: 03/07/2023] [Indexed: 06/18/2023]
Abstract
Voluntary drive of the exercising muscle is usually assessed with the interpolated twitch technique (ITT), using paired supramaximal electrical stimuli. The aim of this study was to directly compare voluntary activation (VA) of the quadriceps muscle (QM) measured with the ITT, using paired and triple electrical stimuli during maximal voluntary isometric contraction (MVIC). In addition, perceived discomfort was compared with the use of paired and triple electrical stimuli during ITT. Ten healthy participants (23.6 ± 1.6 years) were included. They performed four MVIC, with paired or triple stimuli, in random order. MVIC torque, superimposed evoked torque, evoked torque at rest, VA, and visual analogue scale for pain (VAS-pain), were analysed. The amplitude of the triplet-evoked torque was higher than doublet-evoked torque, i.e., the signal-to-noise ratio increased. However, the differences between the estimation of VA with paired and triple stimuli were not significant (p = 0.136). Triple stimuli yielded higher VAS-pain scores than paired stimuli (p = 0.016). The limits of agreement for the VA using the Bland-Altman method were 7.66/0.629. It seems that the use of additional electrical stimuli is not a recommended solution for the evaluation of VA, because the advantages (i.e., better signal-to-noise ratio) do not outweigh the disadvantages (i.e., an increase in pain).
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Panda AK, Sitaramgupta VSN, Pandya HJ, Basu B. Electrical waveform dependent osteogenesis on PVDF/BaTiO 3 composite using a customized and programmable cell stimulator. Biotechnol Bioeng 2022; 119:1578-1597. [PMID: 35244212 DOI: 10.1002/bit.28076] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 02/22/2022] [Accepted: 02/23/2022] [Indexed: 11/07/2022]
Abstract
Directing cellular functionalities using biomaterial-based bioelectronic stimulation remains a significant constraint in translating research outcomes to address specific clinical challenges. Electrical stimulation is now being clinically used as a therapeutic treatment option to promote bone tissue regeneration and to improve neuromuscular functionalities. However, the nature of the electrical waveforms during the stimulation and underlying biophysical rationale are still not scientifically well explored. Furthermore, bone-mimicking implant-based bioelectrical regulation of osteoinductivity has not been translated to clinics. The present study demonstrates the role of the waveform in electrical signal to direct differentiation of stem cells on an electroactive polymeric substrate, using monophasic DC, square wave, and biphasic wave. In this regard, an in-house electrical stimulation device has been fabricated for the uninterrupted delivery of programmed electrical signals to stem cells in culture. To provide a functional platform for stem cells to differentiate, barium titanate (BaTiO3 , BT) reinforced PVDF has been developed with mechanical properties similar to bone. The electrical stimulation of human mesenchymal stem cells (hMSCs) on PVDF/BT composite inhibited proliferation rate at day 7, indicating early commitment for differentiation. The phenotypical characteristics of DC stimulated hMSCs provided signatures of differentiation towards osteogenic lineage, which was subsequently confirmed using ALP assay, collagen deposition, matrix mineralization, and genetic expression. Our findings suggest that DC stimulation induced early osteogenesis in hMSCs with a higher level of intracellular reactive oxygen species (ROS), whereas the stimulation with square wave directed late osteogenesis with a lower ROS regeneration. In summary, the present study critically analyzes the role of electrical stimulation and its waveforms in regulating osteogenesis, without external biochemical differentiation inducers, on a bone-mimicking functional substrate. Such a strategy can potentially be adopted to develop orthopedic implant-based bioelectronic medicine for bone regeneration. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Asish Kumar Panda
- Laboratory for Biomaterials, Materials Research Centre, Indian Institute of Science, Bangalore, India
| | - V S N Sitaramgupta
- Department of Electronic Systems Engineering, Indian Institute of Science, Bangalore, India
| | - Hardik J Pandya
- Department of Electronic Systems Engineering, Indian Institute of Science, Bangalore, India
- Centre for Product Design and Manufacturing, Indian Institute of Science, Bangalore, India
| | - Bikramjit Basu
- Laboratory for Biomaterials, Materials Research Centre, Indian Institute of Science, Bangalore, India
- Centre for Biosystems Science and Engineering, Indian Institute of Science, Bangalore, India
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Orssatto LBR, Wiest MJ, Moura BM, Collins DF, Diefenthaeler F. Neuromuscular determinants of explosive torque: Differences among strength-trained and untrained young and older men. Scand J Med Sci Sports 2020; 30:2092-2100. [PMID: 32749004 DOI: 10.1111/sms.13788] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 07/22/2020] [Accepted: 07/27/2020] [Indexed: 02/03/2023]
Abstract
This study compared the differences in neural and muscular mechanisms related to explosive torque in chronically strength-trained young and older men (>5 years). Fifty-four participants were allocated into four groups according to age and strength training level: older untrained (n = 14; 65.6 ± 2.9 years), older trained (n = 12; 63.6 ± 3.8 years), young untrained (n = 14; 26.2 ± 3.7 years), and young trained (n = 14; 26.7 ± 3.4 years). Knee extension isometric voluntary explosive torque (absolute and normalized as a percentage of maximal voluntary torque) was assessed at the beginning of the contraction (ie, 50, 100, and 150 ms-T50, T100, and T150, respectively), and surface electromyogram (sEMG) amplitude (normalized as a percentage of sEMG recorded during maximal voluntary isometric contraction) at 0-50, 50-100, and 100-150 time windows. Supramaximal electrically evoked T50 was assessed with octet trains delivered to the femoral nerve (8 pulses at 300 Hz). Voluntary T50, T100, and T150 were higher for trained than untrained in absolute (P < 0.001) and normalized (P < 0.030) terms, accompanied by higher sEMG at 0-50, 50-100, and 100-150 ms (P < 0.001), and voluntary T50/octet T50 ratio for trained. Greater octet T50 was observed for the young trained (P < 0.001) but not for the older trained (P = 0.273) compared to their untrained counterparts. Age effect was observed for voluntary T50, T100, and T150 (P < 0.050), but normalization removed these differences (P > 0.417). Chronically strength-trained young and older men presented a greater explosive torque than their untrained pairs. In young trained, the greater explosive performance was attributed to enhanced muscular and neural mechanisms, while in older trained to neural mechanisms only.
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Affiliation(s)
- Lucas B R Orssatto
- School of Exercise and Nutrition Sciences, Faculty of Health, Queensland University of Technology, Brisbane, QLD, Australia.,Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, QLD, Australia
| | - Matheus J Wiest
- Neural Engineering & Therapeutic Team, KITE, Toronto Rehab, University Health Network, Toronto, ON, Canada
| | - Bruno M Moura
- Biomechanics Laboratory, Federal University of Santa Catarina, Florianópolis, Brazil
| | - David F Collins
- Human Neurophysiology Laboratory, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, AB, Canada
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Abstract
Determining volitional activation (VA) can provide insights on the cause of muscle weakness in orthopedic and neurological populations. Two electrical stimulation techniques are traditionally used to quantify VA: interpolation (IT) and superimposition (CAR). IT allows for a more accurate VA estimation, however it requires individuals to be stimulated twice, compared to once for CAR, and thus increases stimulation associated discomfort. To date, there is no agreement on what is the best practical technique for calculating quadriceps VA. This paper aims to address this problem by determining what reference force (i.e., using either peak force or force at the time of stimulation) and type of stimulation (train of pulses (burst), doublet, and twitch) is the best technique to use. Our findings showed that the IT with the force at the time of stimulation as a reference should be used to determine VA and that when a burst was used, the VA ratio computations were more accurate. Additionally, using a twitch with a 2ms pulse duration produced reliable VA calculations and may be an acceptable alternative for pain-sensitive subjects. Accurate assessment of VA deficits can help clinicians design rehabilitation programs that are based on subject-specific strength impairments and are more effective.
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Doguet V, Rivière V, Guével A, Guilhem G, Chauvet L, Jubeau M. Specific joint angle dependency of voluntary activation during eccentric knee extensions. Muscle Nerve 2016; 56:750-758. [PMID: 27997698 DOI: 10.1002/mus.25515] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 12/06/2016] [Accepted: 12/09/2016] [Indexed: 01/04/2023]
Abstract
INTRODUCTION This study compared voluntary activation during isometric, concentric, and eccentric maximal knee extensions at different joint angles. METHODS Fifteen participants performed isometric, concentric, and eccentric protocols (9 contractions each). For each protocol, the central activation ratio (CAR) was randomly measured at 50°, 75°, or 100° of knee joint angle (0° = full knee extension) using superimposed supramaximal paired nerve stimulations during contractions. RESULTS CAR increased between 50° and 100° during isometric (93.6 ± 3.1 vs. 98.5 ± 1.4%), concentric (92.4 ± 5.4 vs. 99.2 ± 1.2%), and eccentric (93.0 ± 3.5 vs. 96.6 ± 3.8%) contractions. CAR was lower during eccentric than both isometric and concentric contractions at 75° and 100°, but similar between contraction types at 50°. CONCLUSIONS The ability to activate muscle maximally is impaired during eccentric contractions compared with other contraction types at 75° and 100°, but not at 50°. Muscle Nerve 56: 750-758, 2017.
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Affiliation(s)
- Valentin Doguet
- Laboratory "Movement, Interactions, Performance" (EA 4334), 25 bis Boulevard Guy Mollet, Faculty of Sport Sciences, University of Nantes, 44322, Nantes, France
| | - Valentin Rivière
- Laboratory "Movement, Interactions, Performance" (EA 4334), 25 bis Boulevard Guy Mollet, Faculty of Sport Sciences, University of Nantes, 44322, Nantes, France
| | - Arnaud Guével
- Laboratory "Movement, Interactions, Performance" (EA 4334), 25 bis Boulevard Guy Mollet, Faculty of Sport Sciences, University of Nantes, 44322, Nantes, France
| | - Gaël Guilhem
- French National Institute of Sport (INSEP), Research Department, Laboratory Sport, Expertise and Performance (EA 7370), Paris, France
| | - Lucile Chauvet
- Laboratory "Movement, Interactions, Performance" (EA 4334), 25 bis Boulevard Guy Mollet, Faculty of Sport Sciences, University of Nantes, 44322, Nantes, France
| | - Marc Jubeau
- Laboratory "Movement, Interactions, Performance" (EA 4334), 25 bis Boulevard Guy Mollet, Faculty of Sport Sciences, University of Nantes, 44322, Nantes, France
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Unhjem R, Nygård M, van den Hoven LT, Sidhu SK, Hoff J, Wang E. Lifelong strength training mitigates the age-related decline in efferent drive. J Appl Physiol (1985) 2016; 121:415-23. [DOI: 10.1152/japplphysiol.00117.2016] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 06/17/2016] [Indexed: 12/31/2022] Open
Abstract
Recently, we documented age-related attenuation of efferent drive to contracting skeletal muscle. It remains elusive if this indication of reduced muscle strength is present with lifelong strength training. For this purpose, we examined evoked potentials in the calf muscles of 11 [71 ± 4 (SD) yr] strength-trained master athletes (MA) contrasted with 10 (71 ± 4 yr) sedentary (SO) and 11 (73 ± 6 yr) recreationally active (AO) old subjects, as well as 9 (22 ± 2 yr) young controls. As expected, MA had higher leg press maximal strength (MA, 185 ± 32 kg; AO, 128 ± 15 kg; SO, 106 ± 11 kg; young, 147 ± 22 kg, P < 0.01) and rate of force development (MA, 5,588 ± 2,488 N/s; AO, 2,156 ± 1,100 N/s; SO, 2,011 ± 825 N/s; young, 3,663 ± 1,140 N/s, P < 0.05) than the other groups. MA also exhibited higher musculus soleus normalized V waves during maximal voluntary contractions (MVC) [maximal V wave amplitude/maximal M wave during MVC (Vsup/Msup); 0.28 ± 0.15] than AO (0.13 ± 0.06, P < 0.01) and SO (0.11 ± 0.05, P < 0.01), yet lower than young (0.45 ± 0.12, P < 0.01). No differences were apparent between the old groups in H reflex recorded at rest or during MVC [maximal H reflex amplitude/maximal M wave during rest (Hmax/Mmax); maximal H reflex amplitude during MVC/maximal M wave during MVC (Hsup/Msup)], and all were lower ( P < 0.01) than young. MA (34.4 ± 2.1 ms) had shorter ( P < 0.05) H reflex latency compared with AO (36.4 ± 3.7 ms) and SO (37.3 ± 3.2 ms), but longer ( P < 0.01) than young (30.7 ± 2.0 ms). Using interpolated twitch analysis, MA (89 ± 7%) had plantar flexion voluntary activation similar to young (90 ± 6%), and this was higher ( P < 0.05), or tended to be higher ( P = 0.06–0.09), than SO (83 ± 10%) and AO (84 ± 5%). These observations suggest that lifelong strength training has a protective effect against age-related attenuation of efferent drive. In contrast, no beneficial effect seems to derive from habitual recreational activity, indicating that strength training may be particularly beneficial for counteracting age-related loss of neuromuscular function.
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Affiliation(s)
- Runar Unhjem
- Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
| | - Mona Nygård
- Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
| | - Lene T. van den Hoven
- Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
| | - Simranjit K. Sidhu
- Discipline of Physiology, School of Medicine, The University of Adelaide, Adelaide, Australia
| | - Jan Hoff
- Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
- Department of Physical Medicine and Rehabilitation, St. Olav's University Hospital, Trondheim, Norway
| | - Eivind Wang
- Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
- Department of Research and Development, St. Olav's University Hospital, Trondheim, Norway; and
- Department of Medicine, University of Utah, Salt Lake City, Utah
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Pereira JS, Lemos FDA, Di Naso FC, Krüger R, de Oliveira A, Knorst MM, Dias AS. Effect of 6-minute walk test on neuromuscular properties of patients with chronic obstructive pulmonary disease. CLINICAL RESPIRATORY JOURNAL 2015; 11:812-819. [PMID: 26620735 DOI: 10.1111/crj.12420] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 10/22/2015] [Accepted: 11/29/2015] [Indexed: 11/28/2022]
Abstract
OBJECTIVE The objective of this study was to evaluate the neuromechanical properties of the knee extensor muscles before and after the 6-minute walk test (6MWT) in chronic obstructive pulmonary disease (COPD) patients and control subjects. MATERIALS AND METHODS COPD patients from the Department of Pulmonology of the Hospital de Clinicas de Porto Alegre and age- and sex-matched control volunteers without COPD were included in this study. Body composition and lower limb strength assessed by maximal voluntary isometric contraction (MVIC) of the knee extensors) were assessed before and after the 6MWT. The total reaction time (TRT), premotor time (PMT) and motor time (MT) were assessed using surface electromyography of the rectus femoris and vastus lateralis knee extensor muscles. RESULTS Eighteen patients COPD patients (10 men, FEV1 36 ± 12% of predicted) and 8 control subjects (5 men, FEV1 82 ± 7% of predicted) were included. COPD patients had lower muscle strength before (21.77 ± 7.86 kg) and after the 6MWT (11.16 ± 4.70 kg) compared with control subjects (33.50 ± 14.01 kg before; 29.25 ± 16.66 kg after). After the 6MWT, COPD patients showed a significant reduction in the MVIC and a significant increase in the TRT and PMT, which did not occur in control subjects. The reaction time parameters were higher in COPD patients after the 6MWT compared with control subjects. The TRT (r = -0.535, P < 0.005) and PMT (r = -0.549, P < 0.005) were inversely correlated with the MVIC after the 6MWT. CONCLUSIONS Neuromuscular changes associated with upper motor neuron activation contribute to MVIC impairment in COPD patients after performing a functional test.
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Affiliation(s)
| | - Fernando de Aguiar Lemos
- Program of Human Movement Sciences, Faculty of Physical Education and Physiotherapy, Federal University of Rio Grande do Sul
| | | | - Renata Krüger
- Program of Human Movement Sciences, Faculty of Physical Education and Physiotherapy, Federal University of Rio Grande do Sul
| | - Alice de Oliveira
- Faculty of Physical Education and Physiotherapy, Federal University of Rio Grande do Sul
| | - Marli Maria Knorst
- Service of Pneumology, Hospital de Clinicas de Porto Alegre, Postgraduate Pulmonology Program, UFRGS
| | - Alexandre Simões Dias
- Postgraduate Program in Respiratory Sciences and Human Movement Sciences, UFRGS.,Physiotherapy Service of Hospital de Clinicas de Porto Alegre
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Rozand V, Grosprêtre S, Stapley PJ, Lepers R. Assessment of Neuromuscular Function Using Percutaneous Electrical Nerve Stimulation. J Vis Exp 2015. [PMID: 26436986 DOI: 10.3791/52974] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Percutaneous electrical nerve stimulation is a non-invasive method commonly used to evaluate neuromuscular function from brain to muscle (supra-spinal, spinal and peripheral levels). The present protocol describes how this method can be used to stimulate the posterior tibial nerve that activates plantar flexor muscles. Percutaneous electrical nerve stimulation consists of inducing an electrical stimulus to a motor nerve to evoke a muscular response. Direct (M-wave) and/or indirect (H-reflex) electrophysiological responses can be recorded at rest using surface electromyography. Mechanical (twitch torque) responses can be quantified with a force/torque ergometer. M-wave and twitch torque reflect neuromuscular transmission and excitation-contraction coupling, whereas H-reflex provides an index of spinal excitability. EMG activity and mechanical (superimposed twitch) responses can also be recorded during maximal voluntary contractions to evaluate voluntary activation level. Percutaneous nerve stimulation provides an assessment of neuromuscular function in humans, and is highly beneficial especially for studies evaluating neuromuscular plasticity following acute (fatigue) or chronic (training/detraining) exercise.
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Affiliation(s)
- Vianney Rozand
- INSERM U1093, Faculty of Sport Sciences, Univ. Bourgogne Franche-Comté;
| | - Sidney Grosprêtre
- INSERM U1093, Faculty of Sport Sciences, Univ. Bourgogne Franche-Comté
| | - Paul J Stapley
- Neural Control of Movement Laboratory, School of Medicine, Faculty of Science, Medicine and Health, University of Wollongong
| | - Romuald Lepers
- INSERM U1093, Faculty of Sport Sciences, Univ. Bourgogne Franche-Comté
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Kim HE, Corcos DM, Hornby TG. Increased spinal reflex excitability is associated with enhanced central activation during voluntary lengthening contractions in human spinal cord injury. J Neurophysiol 2015; 114:427-39. [PMID: 25972590 DOI: 10.1152/jn.01074.2014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Accepted: 05/10/2015] [Indexed: 11/22/2022] Open
Abstract
This study of chronic incomplete spinal cord injury (SCI) subjects investigated patterns of central motor drive (i.e., central activation) of the plantar flexors using interpolated twitches, and modulation of soleus H-reflexes during lengthening, isometric, and shortening muscle actions. In a recent study of the knee extensors, SCI subjects demonstrated greater central activation ratio (CAR) values during lengthening (i.e., eccentric) maximal voluntary contractions (MVCs), compared with during isometric or shortening (i.e., concentric) MVCs. In contrast, healthy controls demonstrated lower lengthening CAR values compared with their isometric and shortening CARs. For the present investigation, we hypothesized SCI subjects would again produce their highest CAR values during lengthening MVCs, and that these increases in central activation were partially attributable to greater efficacy of Ia-α motoneuron transmission during muscle lengthening following SCI. Results show SCI subjects produced higher CAR values during lengthening vs. isometric or shortening MVCs (all P < 0.001). H-reflex testing revealed normalized H-reflexes (maximal SOL H-reflex-to-maximal M-wave ratios) were greater for SCI than controls during passive (P = 0.023) and active (i.e., 75% MVC; P = 0.017) lengthening, suggesting facilitation of Ia transmission post-SCI. Additionally, measures of spinal reflex excitability (passive lengthening maximal SOL H-reflex-to-maximal M-wave ratio) in SCI were positively correlated with soleus electromyographic activity and CAR values during lengthening MVCs (both P < 0.05). The present study presents evidence that patterns of dynamic muscle activation are altered following SCI, and that greater central activation during lengthening contractions is partly due to enhanced efficacy of Ia-α motoneuron transmission.
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Affiliation(s)
- Hyosub E Kim
- Graduate Program in Neuroscience, University of Illinois at Chicago, Chicago, Illinois; Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, Illinois
| | - Daniel M Corcos
- Department of Physical Therapy & Human Movement Sciences, Northwestern University, Chicago, Illinois; and
| | - T George Hornby
- Graduate Program in Neuroscience, University of Illinois at Chicago, Chicago, Illinois; Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, Illinois; Department of Physical Therapy, University of Illinois at Chicago, Chicago, Illinois
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Clarke N, Farthing JP, Lanovaz JL, Krentz JR. Direct and indirect measurement of neuromuscular fatigue in Canadian football players. Appl Physiol Nutr Metab 2015; 40:464-73. [PMID: 25894521 DOI: 10.1139/apnm-2014-0465] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study assessed the effects of a fatiguing game simulation (G-Sim) on the balance of collegiate Canadian football players. The purpose of the study was to evaluate postural control as a potential tool for monitoring neuromuscular fatigue (NMF) in collision-based team sports. Fifteen male Canadian football players were recruited (mean ± SD: age 21.8 ± 1.6 years, weight 97.6 ± 14.7 kg). Indirect NMF measures (postural sway and countermovement jump (CMJ)) were performed 24 h before (TBase), immediately before (TPre) and after (TPost), and 24 h (T24) and 48 h after (T48) a Canadian football G-Sim. Peak isometric knee extensor torque of a maximal voluntary contraction (MVC) and electrically evoked tetani at 20 Hz (P20) and 80 Hz (P80) were also recorded as direct NMF measures at TBase, TPre, TPost, and T48. At TPost, we observed significant declines in MVC, P20, and the MVC/P80 ratio (–15.3%, –15.7%, and –12.1%, respectively; n = 12) along with reductions in CMJ takeoff velocity and peak power (–6.9% and –6.5%, respectively; n = 12) and larger area of the center of pressure trajectory (95.2%; n = 10) during a 60-s postural sway task. All variables were no longer different than baseline by T48. Acute neuromuscular impairment in this cohort is likely attributable to alterations in excitation–contraction coupling due to structural damage and central activation failure. Congruency between the direct and indirect measures of NMF suggests monitoring postural sway has the potential to identify both neuromuscular and somatosensory alterations induced by acute game-induced fatigue in collision-based team sports players.
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Affiliation(s)
- Nick Clarke
- College of Kinesiology, University of Saskatchewan, Saskatoon, SK S7N 5B2, Canada
- Canadian Sport Institute Pacific, Victoria, BC V9E 2C5, Canada
| | - Jonathan P. Farthing
- College of Kinesiology, University of Saskatchewan, Saskatoon, SK S7N 5B2, Canada
| | - Joel L. Lanovaz
- College of Kinesiology, University of Saskatchewan, Saskatoon, SK S7N 5B2, Canada
| | - Joel R. Krentz
- College of Kinesiology, University of Saskatchewan, Saskatoon, SK S7N 5B2, Canada
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12
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Morel B, Rouffet DM, Saboul D, Rota S, Clémençon M, Hautier CA. Peak torque and rate of torque development influence on repeated maximal exercise performance: contractile and neural contributions. PLoS One 2015; 10:e0119719. [PMID: 25901576 PMCID: PMC4406491 DOI: 10.1371/journal.pone.0119719] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2014] [Accepted: 01/16/2015] [Indexed: 11/28/2022] Open
Abstract
Rapid force production is critical to improve performance and prevent injuries. However, changes in rate of force/torque development caused by the repetition of maximal contractions have received little attention. The aim of this study was to determine the relative influence of rate of torque development (RTD) and peak torque (Tpeak) on the overall performance (i.e. mean torque, Tmean) decrease during repeated maximal contractions and to investigate the contribution of contractile and neural mechanisms to the alteration of the various mechanical variables. Eleven well-trained men performed 20 sets of 6-s isokinetic maximal knee extensions at 240°·s-1, beginning every 30 seconds. RTD, Tpeak and Tmean as well as the Rate of EMG Rise (RER), peak EMG (EMGpeak) and mean EMG (EMGmean) of the vastus lateralis were monitored for each contraction. A wavelet transform was also performed on raw EMG signal for instant mean frequency (ifmean) calculation. A neuromuscular testing procedure was carried out before and immediately after the fatiguing protocol including evoked RTD (eRTD) and maximal evoked torque (eTpeak) induced by high frequency doublet (100 Hz). Tmean decrease was correlated to RTD and Tpeak decrease (R²=0.62; p<0.001; respectively β=0.62 and β=0.19). RER, eRTD and initial ifmean (0-225 ms) decreased after 20 sets (respectively -21.1±14.1, -25±13%, and ~20%). RTD decrease was correlated to RER decrease (R²=0.36; p<0.05). The eTpeak decreased significantly after 20 sets (24±5%; p<0.05) contrary to EMGpeak (-3.2±19.5 %; p=0.71). Our results show that reductions of RTD explained part of the alterations of the overall performance during repeated moderate velocity maximal exercise. The reductions of RTD were associated to an impairment of the ability of the central nervous system to maximally activate the muscle in the first milliseconds of the contraction.
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Affiliation(s)
- Baptiste Morel
- Center of Research and Innovation on Sport, University of Lyon 1, Villeurbanne, France
- * E-mail:
| | - David M. Rouffet
- Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Australia
| | - Damien Saboul
- Center of Research and Innovation on Sport, University of Lyon 1, Villeurbanne, France
- Almerys, Clermont-Ferrand, France
| | - Samuel Rota
- Center of Research and Innovation on Sport, University of Lyon 1, Villeurbanne, France
| | - Michel Clémençon
- Center of Research and Innovation on Sport, University of Lyon 1, Villeurbanne, France
| | - Christophe A. Hautier
- Center of Research and Innovation on Sport, University of Lyon 1, Villeurbanne, France
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Kim HE, Thompson CK, Hornby TG. Muscle activation varies with contraction mode in human spinal cord injury. Muscle Nerve 2014; 51:235-45. [PMID: 24825184 DOI: 10.1002/mus.24285] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/09/2014] [Indexed: 11/06/2022]
Abstract
INTRODUCTION To better understand volitional force generation after chronic incomplete spinal cord injury (SCI), we examined muscle activation during single and repeated isometric, concentric, and eccentric knee extensor (KE) maximal voluntary contractions (MVCs). METHODS Torque and electromyographic (EMG) activity were recorded during single and repeated isometric and dynamic KE MVCs in 11 SCI subjects. Central activation ratios (CARs) were calculated for all contraction modes in SCI subjects and 11 healthy controls. RESULTS SCI subjects generated greater torque, KE EMG, and CARs during single eccentric vs. isometric and concentric MVCs (all P < 0.05). Torque and EMG remained similar during repeated eccentric MVCs; however, both increased during repeated isometric (>25%) and concentric (>30%) MVCs. CONCLUSIONS SCI subjects demonstrated greater muscle activation during eccentric MVCs vs. isometric and concentric MVCs. This pattern of activation contrasts with the decreased eccentric activation demonstrated by healthy controls. Such information may aid development of novel rehabilitation interventions.
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Affiliation(s)
- Hyosub E Kim
- Graduate Program in Neuroscience, University of Illinois at Chicago, 1919 West Taylor Street, M/C 898, Chicago, Illinois, 60612, USA
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14
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Christian RJ, Bishop DJ, Billaut F, Girard O. Peripheral fatigue is not critically regulated during maximal, intermittent, dynamic leg extensions. J Appl Physiol (1985) 2014; 117:1063-73. [PMID: 25213635 DOI: 10.1152/japplphysiol.00988.2013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Central motor drive to active muscles is believed to be reduced during numerous exercise tasks to prevent excessive peripheral fatigue development. The purpose of the present study was to use hypoxia to exacerbate physiological perturbations during a novel, intermittent exercise task and to explore the time-course and interplay between central and peripheral neuromuscular adjustments. On separate days, 14 healthy men performed four sets of 6 × 5 maximal-intensity, isokinetic leg extensions (1 repetition lasting ∼7 s) at 300°/s (15 and 100 s of passive rest between repetitions and sets, respectively) under normoxia (NM, fraction of inspired O2 0.21), moderate (MH, 0.14), and severe normobaric hypoxia (SH, 0.10). Neuromuscular assessments of the knee extensors were conducted before and immediately after each set. There was an interaction between time and condition on the mean peak torque produced during each set (P < 0.05). RMS/M-wave activity of the rectus femoris decreased across the four sets of exercise, but there was no difference between conditions (8.3 ± 5.1% all conditions compounded, P > 0.05). Potentiated twitch torque decreased post set 1 in all conditions (all P < 0.05) with greater reductions following each set in SH compared with NM but not MH (end-exercise reductions 41.3 ± 3.0% vs. 28.0 ± 3.2%, P < 0.05 and 32.1 ± 3.3%, P > 0.05). In conclusion, severe hypoxia exacerbates both peripheral fatigue development and performance decrements during maximal, intermittent, dynamic leg extensions. In contrast to observations with other exercise modes, during exercise involving a single muscle group the attenuation of central motor drive does not appear to independently regulate the development of peripheral muscle fatigue.
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Affiliation(s)
- Ryan J Christian
- College of Sport and Exercise Science, Victoria University, Melbourne, Australia; Aspetar - Qatar Orthopaedic and Sports Medicine Hospital, Doha, Qatar;
| | - David J Bishop
- Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Australia
| | - François Billaut
- Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Australia; Université Laval, Département de Kinésiologie, Québec, Québec, Canada; and
| | - Olivier Girard
- Aspetar - Qatar Orthopaedic and Sports Medicine Hospital, Doha, Qatar; Faculty of Biology and Medicine, Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland
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15
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Shanb ASA, Youssef EF. EFFECTS OF ADDING BIOFEEDBACK TRAINING TO ACTIVE EXERCISES AFTER TOTAL KNEE ARTHROPLASTY. ACTA ACUST UNITED AC 2014. [DOI: 10.1142/s0218957714500018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The purpose of this study was to evaluate the effects of adding biofeedback training to active exercise training on quadriceps torque, voluntary activation and functional activity after total knee arthroplasty (TKA). A total of 45 patients with unilateral TKA participated in this study; their ages ranged from 58 to 67 years. They were assigned randomly to two groups. Group I comprised 21 patients who practiced an active exercise training program for 30 to 45 min/session, two sessions/week, for 4 months. Group II contained 24 patients who practiced biofeedback training in addition to the active exercise training program for 30 to 45 min/session, two sessions/week, for 4 months. Isometric peak torque of the quadriceps, voluntary activation and knee functional activity were measured. The results revealed significant improvements in quadriceps torque, voluntary activation and knee functional activity for both groups, with more improvement in knee functional activities in group II. There were nonsignificant differences between the two groups in both quadriceps peak torque and voluntary activation after training (p > 0.05). Conclusion: An active exercise program can enhance quadriceps peak torque, voluntary activation and knee functional activity after unilateral TKA. The addition of biofeedback training increases the benefits for the knee functional activity of a patient.
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Affiliation(s)
- Al-Sayed A. Shanb
- Physical Therapy Department, College of Applied Medical Sciences, University of Dammam, Kingdom of Saudi Arabia
| | - Enas F. Youssef
- Physical Therapy Department, College of Applied Medical Sciences, University of Dammam, Kingdom of Saudi Arabia
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16
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Burdon CA, Easthope CS, Johnson NA, Chapman PG, O'Connor H. The influence of ice slushy on voluntary contraction force following exercise-induced hyperthermia. Appl Physiol Nutr Metab 2014; 39:781-6. [PMID: 24971678 DOI: 10.1139/apnm-2013-0394] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study aimed to investigate the effect of exercise-induced hyperthermia on central fatigue and force decline in exercised and nonexercised muscles and whether ingestion of ice slushy (ICE) ameliorates fatigue. Eight participants (5 males, 3 females) completed 45 s maximal voluntary isometric contractions (MVIC) with elbow flexors and knee extensors at baseline and following an exercise-induced rectal temperature (Trec) of 39.3 ± 0.2 °C. Percutaneous electrical muscle stimulation was superimposed at 15, 30 and 44 s during MVICs to assess muscle activation. To increase Trec to 39.3 °C, participants cycled at 60% maximum power output for 42 ± 11 min in 40 °C and 50% relative humidity. Immediately prior to each MVIC, participants consumed 50 g of ICE (-1 °C) or thermoneutral drink (38 °C, CON) made from 7.4% carbohydrate beverage. Participants consumed water (19 °C) during exercise to prevent hypohydration. Voluntary muscle force production and activation in both muscle groups were unchanged at Trec 39.3 °C with ICE (knee extensors: 209 ± 152 N) versus CON (knee extensors: 255 ± 157 N, p = 0.19). At Trec 39.3 °C, quadriceps mean force (232 ± 151 N) decreased versus baseline (302 ± 180 N, p < 0.001) and mean voluntary activation was also decreased (by 15% ± 11%, p < 0.001). Elbow flexor mean force decreased from 179 ± 67 N to 148 ± 65 N when Trec was increased to 39.3 °C (p < 0.001) but mean voluntary activation was not reduced at 39.3 °C (5% ± 25%, p = 0.79). After exercise-induced hyperthermia, ICE had no effect on voluntary activation or force production; however, both were reduced from baseline in the exercised muscle group. Peripheral fatigue was greater than the central component and limited the ability of an intervention designed to alter central fatigue.
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Affiliation(s)
- Catriona A Burdon
- a Exercise and Sport Science, University of Sydney, 75 East St., Lidcombe 2141, NSW, Australia
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17
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Grindstaff TL, Threlkeld AJ. Optimal Stimulation Parameters to Detect Deficits in Quadriceps Voluntary Activation. J Strength Cond Res 2014; 28:381-9. [DOI: 10.1519/jsc.0b013e3182986d5f] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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18
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Mau-Moeller A, Behrens M, Lindner T, Bader R, Bruhn S. Age-related changes in neuromuscular function of the quadriceps muscle in physically active adults. J Electromyogr Kinesiol 2013; 23:640-8. [PMID: 23453325 DOI: 10.1016/j.jelekin.2013.01.009] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Revised: 12/10/2012] [Accepted: 01/10/2013] [Indexed: 12/13/2022] Open
Abstract
Substantial evidence exists for the age-related decline in maximal strength and strength development. Despite the importance of knee extensor strength for physical function and mobility in the elderly, studies focusing on the underlying neuromuscular mechanisms of the quadriceps muscle weakness are limited. The aim of this study was to investigate the contributions of age-related neural and muscular changes in the quadriceps muscle to decreases in isometric maximal voluntary torque (iMVT) and explosive voluntary strength. The interpolated twitch technique and normalized surface electromyography (EMG) signal during iMVT were analyzed to assess changes in neural drive to the muscles of 15 young and 15 elderly volunteers. The maximal rate of torque development as well as rate of torque development, impulse and neuromuscular activation in the early phase of contraction were determined. Spinal excitability was estimated using the H reflex technique. Changes at the muscle level were evaluated by analyzing the contractile properties and lean mass. The age-related decrease in iMVT was accompanied by a decline in voluntary activation and normalized surface EMG amplitude. Mechanical parameters of explosive voluntary strength were reduced while the corresponding muscle activation remained primarily unchanged. The spinal excitability of the vastus medialis was not different while M wave latency was longer. Contractile properties and lean mass were reduced. In conclusion, the age-related decline in iMVT of the quadriceps muscle might be due to a reduced neural drive and changes in skeletal muscle properties. The decrease in explosive voluntary strength seemed to be more affected by muscular than by neural changes.
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Affiliation(s)
- Anett Mau-Moeller
- Department of Exercise Science, University of Rostock, Ulmenstrasse 69, 18057 Rostock, Germany.
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19
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Elboim-Gabyzon M, Rozen N, Laufer Y. Does neuromuscular electrical stimulation enhance the effectiveness of an exercise programme in subjects with knee osteoarthritis? A randomized controlled trial. Clin Rehabil 2012; 27:246-57. [DOI: 10.1177/0269215512456388] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Objective: To determine whether neuromuscular electrical stimulation applied to the quadriceps femoris muscle will enhance the effectiveness of an exercise programme in patients with knee osteoarthritis. Design: A randomized trial with parallel intervention treatment groups. Setting: Outpatient physical therapy clinic. Subjects: Fifty participants (mean age (SD) 68.9 (7.7) years) with symptomatic idiopathic knee osteoarthritis and radiographic evidence (grade ≥II Kelgren’s classification). Interventions: Participants were randomized into one of two groups receiving 12 biweekly treatments: An exercise-only group or an exercise combined with neuromuscular electrical stimulation group (biphasic pulses, at 75 Hz and 250 µs phase duration). Main measures: Knee pain intensity; maximal voluntary isometric contraction and voluntary activation of the quadriceps femoris muscle; measures of functional performance. Results: A significant interaction effect ( P = 0.01) indicated greater improvement in pain for the electrical stimulation group. The mean (SD) change in pain intensity was from 7.5 ± 2 to 5 ± 2.2 and from 7.4 ± 1.9 to 3.3 ± 2.4 in the exercise and electrical stimulation groups, respectively. A significant treatment effect was also noted for the voluntary activation of the quadriceps femoris, which increased by 22.2% in the electrical stimulation group and by 9.6% in the exercise group ( P = 0.045). Significant improvements were observed in both groups in all remaining measures, with no differences between groups. Conclusions: Electrical stimulation treatment to the quadriceps femoris enhanced the effectiveness of an exercise programme in alleviating pain and improving voluntary activation in patients with knee osteoarthritis, but did not enhance its effect on muscle strength or functional performance.
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Affiliation(s)
- M Elboim-Gabyzon
- Physical Therapy Department, Faculty of Social Welfare and Health Sciences, University of Haifa, Israel
| | - N Rozen
- Emek Medical Center, Afulla, Israel
| | - Y Laufer
- Physical Therapy Department, Faculty of Social Welfare and Health Sciences, University of Haifa, Israel
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20
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Thompson CK, Lewek MD, Jayaraman A, Hornby TG. Central excitability contributes to supramaximal volitional contractions in human incomplete spinal cord injury. J Physiol 2011; 589:3739-52. [PMID: 21610138 DOI: 10.1113/jphysiol.2011.212233] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Despite greater muscle fatigue in individuals with spinal cord injury (SCI) when compared to neurologically intact subjects using neuromuscular electrical stimulation (NMES)protocols, few studies have investigated the extent of volitional fatigue in motor incomplete SCI. Using an established protocol of 20 repeated, intermittent, maximal volitional effort (MVE) contractions, we previously demonstrated that subjects with incomplete SCI unexpectedly demonstrated a 15% increase in peak knee extensor torques within the first five MVEs with minimal evidence of fatigue after 20 contraction. In the present study, we investigated potential segmental mechanisms underlying this supramaximal torque generation. Changes in twitch properties and maximum compound muscle action potentials (M-waves) were assessed prior to and following one, three and five MVEs, revealing a significant 17% increase only in maximum twitch torques after a single MVE. Despite this post-activation potentiation of the muscle, use of conventional NMES protocols to elicit repeated muscular contractions resulted in a significant decrease in evoked torque generation, suggesting limited the muscular contributions to the observed phenomenon. To evaluate potential central mechanisms underlying the augmented torques, non-linear responses to wide-pulse width (1 ms), low-intensity, variable-frequency (25–100 Hz) NMES were also tested prior to and following repeated MVEs.When variable-frequency NMES was applied following the repeated MVEs, augmented and prolonged torques were observed and accompanied by sustained quadriceps electromyographic activity often lasting > 2s after stimulus termination. Such data suggest a potential contribution of elevated spinal excitability to the reserve in volitional force generation in incomplete SCI.
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Affiliation(s)
- Christopher K Thompson
- Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, IL 60612, USA
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21
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Park J, Ty Hopkins J. Quadriceps activation normative values and the affect of subcutaneous tissue thickness. J Electromyogr Kinesiol 2011; 21:136-40. [DOI: 10.1016/j.jelekin.2010.09.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2010] [Revised: 09/22/2010] [Accepted: 09/22/2010] [Indexed: 10/19/2022] Open
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22
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Neuromuscular function following prolonged intense self-paced exercise in hot climatic conditions. Eur J Appl Physiol 2010; 111:1561-9. [DOI: 10.1007/s00421-010-1781-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/08/2010] [Indexed: 11/25/2022]
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Johnson AW, Myrer JW, Hunter I, Feland JB, Hopkins JT, Draper DO, Eggett D. Whole-body vibration strengthening compared to traditional strengthening during physical therapy in individuals with total knee arthroplasty. Physiother Theory Pract 2010; 26:215-25. [PMID: 20397856 DOI: 10.3109/09593980902967196] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
This study investigated the use of whole-body vibration (WBV) as an alternative strengthening regimen in the rehabilitation of individuals with total knee arthroplasty (TKA) compared with traditional progressive resistance exercise (TPRE). Individuals post TKA (WBV n = 8; TPRE n = 8) received physical therapy with WBV or with TPRE for 4 weeks. Primary dependent variables were knee extensor strength, quadriceps muscle activation, mobility, pain, and range of motion (ROM). There was a significant increase in knee extensor strength and improvements in mobility, as measured by maximal volitional isometric contraction and the Timed Up and Go Test (TUG), respectively, for both groups (p < 0.01). The WBV knee extensor strength improved 84.3% while TPRE increased 77.3%. TUG scores improved 31% in the WBV group and 32% for the TPRE group. There were no significant differences between groups for strength or muscle activation (Hotelling's T(2) = 0.42, p = 0.80) or for mobility (F = 0.54; p = 0.66). No adverse side effects were reported in either group. In individuals with TKA, both WBV and TPRE showed improved strength and function. Influence of WBV on muscle activation remains unclear, as muscle activation levels were near normal for both groups.
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Affiliation(s)
- A Wayne Johnson
- Department of Exercise Sciences, Brigham Young University, Provo, Utah 84602, USA.
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Hornby TG, Lewek MD, Thompson CK, Heitz R. Repeated maximal volitional effort contractions in human spinal cord injury: initial torque increases and reduced fatigue. Neurorehabil Neural Repair 2009; 23:928-38. [PMID: 19478056 PMCID: PMC5603074 DOI: 10.1177/1545968309336147] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Substantial data indicate greater muscle fatigue in individuals with spinal cord injury (SCI) compared with healthy control subjects when tested by using electrical stimulation protocols. Few studies have investigated the extent of volitional fatigue in motor incomplete SCI. METHODS Repeated, maximal volitional effort (MVE) isometric contractions of the knee extensors (KE) were performed in 14 subjects with a motor incomplete SCI and in 10 intact subjects. Subjects performed 20 repeated, intermittent MVEs (5 seconds contraction/5 seconds rest) with KE torques and thigh electromyographic (EMG) activity recorded. RESULTS Peak KE torques declined to 64% of baseline MVEs with repeated efforts in control subjects. Conversely, subjects with SCI increased peak torques during the first 5 contractions by 15%, with little evidence of fatigue after 20 repeated efforts. Increases in peak KE torques and the rate of torque increase during the first 5 contractions were attributed primarily to increases in quadriceps EMG activity, but not to decreased knee flexor co-activation. The observed initial increases in peak torque were dependent on the subject's volitional activation and were consistent on the same or different days, indicating little contribution of learning or accommodation to the testing conditions. Sustained MVEs did not elicit substantial increases in peak KE torques as compared to repeated intermittent efforts. CONCLUSIONS These data revealed a marked divergence from expected results of increased fatigability in subjects with SCI, and may be a result of complex interactions between mechanisms underlying spastic motor activity and changes in intrinsic motoneuron properties.
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Affiliation(s)
- T George Hornby
- Department of Physical Medicine and Rehabilitation, Northwestern University Medical School, Chicago, Illinois 60612, USA.
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25
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Scopaz KA, Piva SR, Gil AB, Woollard JD, Oddis CV, Fitzgerald GK. Effect of baseline quadriceps activation on changes in quadriceps strength after exercise therapy in subjects with knee osteoarthritis. ACTA ACUST UNITED AC 2009; 61:951-7. [PMID: 19565548 DOI: 10.1002/art.24650] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
OBJECTIVE To examine whether pretreatment magnitude of quadriceps activation (QA) helps predict changes in quadriceps strength after exercise therapy in subjects with knee osteoarthritis (OA). We hypothesized that subjects with lower magnitudes of QA (greater failure of muscle activation) would have smaller gains in strength compared with those with higher magnitudes of QA following exercise therapy. METHODS One hundred eleven subjects with knee OA (70 women) participated. Baseline measures included demographic information, quadriceps muscle strength, and QA using a burst-superimposition isometric torque test. Following baseline testing, subjects underwent a 6-week supervised exercise program designed to improve strength, range of motion, balance and agility, and physical function. On completion of the program, quadriceps strength and QA were reassessed. Multiple regression analysis was used to determine whether baseline QA predicted quadriceps strength scores at the 2-month followup. RESULTS Bivariate correlations demonstrated that baseline QA was significantly associated with quadriceps strength at baseline (rho = 0.30, P < 0.01) and 2-month followup (rho = 0.23, P = 0.01). Greater magnitude of baseline QA correlated with higher strength. While controlling for baseline quadriceps strength and type of exercise therapy, the level of QA did not predict quadriceps strength at the 2-month followup (beta = -0.04, P = 0.18). CONCLUSION Baseline QA did not predict changes in quadriceps strength following exercise therapy. Measurement of QA using the central activation ratio method does not appear to be helpful in identifying subjects with knee OA who will have difficulty improving quadriceps strength with exercise therapy.
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Herzog W. Twitch interpolation represents muscle activation in a qualitative manner only. J Appl Physiol (1985) 2009; 107:365-6; discussion 367-8. [PMID: 19670471 DOI: 10.1152/japplphysiol.00362.2009] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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de Haan A, Gerrits KHL, de Ruiter CJ. Counterpoint: the interpolated twitch does not provide a valid measure of the voluntary activation of muscle. J Appl Physiol (1985) 2009; 107:355-7; discussion 357-8. [PMID: 19567806 DOI: 10.1152/japplphysiol.91220.2008a] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- A de Haan
- Research Institute MOVE, Faculty of Human Movement Sciences, VU University Amsterdam, The Netherlands
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KREMENIC IANJ, GLACE BETHW, BEN-AVI SSIMON, NICHOLAS STEPHENJ, McHUGH MALACHYP. Central Fatigue after Cycling Evaluated Using Peripheral Magnetic Stimulation. Med Sci Sports Exerc 2009; 41:1461-6. [DOI: 10.1249/mss.0b013e318199eb75] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Scaglioni G, Martin A. Assessment of plantar flexors activation capacity: nerve versus muscle stimulation by single versus double pulse. Eur J Appl Physiol 2009; 106:563-72. [PMID: 19350263 DOI: 10.1007/s00421-009-1049-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/20/2009] [Indexed: 10/20/2022]
Abstract
This study was designed to investigate if the relationship between the interpolated twitch-torque (IT) and voluntary torque (VT) is affected by the number of electrical stimuli (single vs. double) and the stimulation site (nerve trunk vs. muscle). The results showed that the IT-VT relationship of the plantar flexors is appropriately described by a composite (linear + curvilinear) model. Indeed, whatever the stimulation method, the IT-VT relationship was linear between approximately 25 and 75% of the maximal voluntary torque (MVT) and curvilinear for higher contraction intensities. The four stimulation conditions are equivalent in assessing the maximal voluntary activation (VA% range 96.2 +/- 5.0 to 98.5 +/- 3.1%) as well as in determining the true maximal torque expected for total twitch occlusion (MT(exp) range 171.4 +/- 21.2 to 179.0 +/- 26.8 Nm). The gap between the MVT and MT(exp) should be viewed as an index of muscle inactivation. This gap was comparable for the four stimulation methods (2-6%) and close to the deficit in VA% (2-4%). No pulse-number effect was found on the IT-VT relationship when the nerve was stimulated but an effect on the concavity of the composite relationship was observed when the stimulation was applied over the muscle. Even though the four stimulation techniques are equivalent in assessing the maximal activation capacity our results demonstrate that the neural stimulation method is the most consistent as it guarantees the same motor pool recruitment independently from the number of pulses.
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Affiliation(s)
- Gil Scaglioni
- Faculté des Sciences du Sport, Equipe INSERM/U887 Motricité-Plasticité, Université de Bourgogne, BP 27877, 21078 Dijon Cedex, France.
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Theurel J, Lepers R. Neuromuscular fatigue is greater following highly variable versus constant intensity endurance cycling. Eur J Appl Physiol 2008; 103:461-8. [PMID: 18415118 DOI: 10.1007/s00421-008-0738-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/25/2008] [Indexed: 11/26/2022]
Abstract
The present study compared neuromuscular fatigue of the knee extensor muscles following highly variable versus constant power output cycling. Ten subjects performed two 33-min cycling trials of the same average power output, in a random order. Cycling exercise was performed either at constant (CST) power output, corresponding to 70% of the maximal aerobic power (MAP), or at variable (VAR) power output with alternating high (200, 150 and 100% of MAP during 10, 15 and 20 s, respectively) and moderate (50% of MAP) power output periods. Neuromuscular tests were performed before and immediately after the two trials. Heart rate (HR) was measured during exercise and blood lactate concentration ([La]) at the end of both trials. Reductions in maximal voluntary contraction torque, voluntary activation level and peak doublet were significantly greater after VAR than after CST. HR and [La] were significantly higher during VAR than during CST. Cycling at a varying power output in comparison to constant power resulted in additional muscular fatigue that may be explained by greater anaerobic contribution and muscle solicitation during the highly variable power output protocol.
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Affiliation(s)
- Jean Theurel
- INSERM U887, Faculté des Sciences du Sport, Université de Bourgogne, BP 27877, 21078 Dijon Cedex, France.
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The role of pulse duration and stimulation duration in maximizing the normalized torque during neuromuscular electrical stimulation. J Orthop Sports Phys Ther 2008; 38:508-16. [PMID: 18678958 PMCID: PMC2554670 DOI: 10.2519/jospt.2008.2734] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
STUDY DESIGN Controlled laboratory study OBJECTIVES To determine the effects of pulse duration and stimulation duration on the evoked torque after controlling for the activated area by using magnetic resonance imaging (MRI). BACKGROUND Neuromuscular electrical stimulation (NMES) is commonly used in the clinic without considering the physiological implications of its parameters. METHODS AND MEASURES Seven able-bodied, college students (mean +/- SD age, 28 +/- 4 years) participated in this study. Two NMES protocols were applied to the knee extensor muscle group in a random order. Protocol A applied 100-Hz, 450-microsecond pulses for 5 minutes in a 3-seconds-on 3-seconds-off duty cycle. Protocol B applied 60-Hz, 250-microsecond pulses for 5 minutes in a 10-seconds-on 20-seconds-off duty cycle. The amplitude of the current was similar in both protocols. Torque, torque time integral, and normalized torque for the knee extensors were measured for both protocols. MRI scans were taken prior to, and immediately after, each protocol to measure the cross-sectional area of the stimulated muscle. RESULTS The skeletal muscle cross-sectional areas activated after both protocols were similar. The longer pulse duration in protocol A elicited 22% greater torque output than that of protocol B (P<.05). After considering the activated area in both protocols, the normalized torque with protocol A was 38% greater than that with protocol B (P<.05). Torque time integral was 21% greater with protocol A (P = .029). Protocol B failed to maintain torque at the start and the end of the 10-second activation. CONCLUSIONS Longer pulse duration, but not stimulation duration, resulted in a greater evoked and normalized torque compared to the shorter pulse duration, even after controlling for the activated muscular cross-sectional areas with both protocols. LEVEL OF EVIDENCE Therapy, level 5.
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Pietrosimone BG, Hammill RR, Saliba EN, Hertel J, Ingersoll CD. Joint angle and contraction mode influence quadriceps motor neuron pool excitability. Am J Phys Med Rehabil 2008; 87:100-8. [PMID: 17912136 DOI: 10.1097/phm.0b013e31815882e0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE The purpose of the study was to compare the central activation ratio (CAR) of eccentric contractions to isometric contractions at 30 and 70 degrees of knee flexion. DESIGN A repeated-measures design was used. CARs were measured at 30 and 70 degrees of knee flexion in 16 healthy subjects during both eccentric and isometric modes of contraction. CARs were measured using the superimposed burst technique. RESULTS Isometric CARs at 30 degrees (0.88+/-0.069) of knee flexion were significantly higher (P<0.001) than at 70 degrees (0.77+/-0.116). Eccentric CARs were significantly higher (P=0.013) at 70 degrees (0.87+/-0.085) of knee flexion compared with 30 degrees (0.8+/-0.09). At 30 degrees of knee flexion, isometric CARs were significantly higher (P=0.003) than eccentric CARs. At 70 degrees, eccentric CARs were higher (P<0.001) when compared with isometric CARs. CONCLUSIONS Our results provide evidence that isometric measures at a single joint angle are not sufficient in generalizing activation of an entire muscle group for dynamic movements. CARs are significantly affected by joint angle and mode of contraction.
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Affiliation(s)
- Brian G Pietrosimone
- Exercise & Sport Injury Laboratory, University of Virginia, Charlottesville, Virginia, USA
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Eichelberger TD, Bilodeau M. Central fatigue of the first dorsal interosseous muscle during low-force and high-force sustained submaximal contractions. Clin Physiol Funct Imaging 2007; 27:298-304. [PMID: 17697026 DOI: 10.1111/j.1475-097x.2007.00751.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The aim of this study was to compare the extent of central fatigue in the first dorsal interosseous (FDI) muscle of healthy adults in low, moderate and high-force submaximal contractions. Nine healthy adults completed four experimental sessions where index finger abduction force was recorded during voluntary contractions and in response to brief trains (five pulses at 100 Hz) of electrical stimulation. The ability to maximally activate FDI under volition, or voluntary activation, and its change with sustained activity (central fatigue) was assessed using the twitch interpolation technique. The fatigue tasks consisted of continuous isometric index finger abduction contractions held until exhaustion at four target force levels: 30%, 45%, 60% and 75% of the maximal voluntary contraction. The main finding was the presence of central fatigue for the 30% task, but not for the three other fatigue tasks. The extent of central fatigue was also associated with changes in a measure reflecting the status of peripheral structures/mechanisms. It appears that central fatigue contributed to task failure for the lowest force fatigue task (30%), but not for the other (higher) contraction intensities.
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Affiliation(s)
- Tamara D Eichelberger
- Graduate Program in Physical Therapy and Rehabilitation Science, Carver College of Medicine, University of Iowa, IA, USA.
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Girard O, Lattier G, Maffiuletti NA, Micallef JP, Millet GP. Neuromuscular fatigue during a prolonged intermittent exercise: Application to tennis. J Electromyogr Kinesiol 2007; 18:1038-46. [PMID: 17611122 DOI: 10.1016/j.jelekin.2007.05.005] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2007] [Revised: 04/24/2007] [Accepted: 05/11/2007] [Indexed: 10/23/2022] Open
Abstract
The time course of alteration in neuromuscular function of the knee extensor muscles was characterized during a prolonged intermittent exercise. Maximal voluntary contraction (MVC) and surface EMG activity of both vastii were measured during brief interruptions before (T(0)), during (30, 60, 90, 120, 150 and 180min: T(30), T(60), T(90), T(120), T(150), T(180)) and 30min after (T(+30)) a 3h tennis match in 12 trained players. M-wave and twitch contractile properties were analyzed following single stimuli. Short tetani at 20Hz and 80Hz were also applied to six subjects at T(0) and T(180). Significant reductions in MVC (P<0.05; -9%) and electromyographic activity normalized to the M wave for both vastii (P<0.01) occurred with fatigue at T(180). No significant changes in M-wave duration and amplitude nor in twitch contractile properties were observed. The ratio between the torques evoked by 20Hz and 80Hz stimulation declined significantly (P<0.001; -12%) after exercise. Central activation failure and alterations in excitation-contraction coupling are probable mechanisms contributing to the moderate impairment of the neuromuscular function during prolonged tennis playing.
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Affiliation(s)
- Olivier Girard
- UPRES - EA 2991, Faculty of Sport Sciences, Montpellier, France.
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35
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Folland JP, Williams AG. Methodological issues with the interpolated twitch technique. J Electromyogr Kinesiol 2007; 17:317-27. [PMID: 16798011 DOI: 10.1016/j.jelekin.2006.04.008] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2005] [Revised: 03/31/2006] [Accepted: 04/25/2006] [Indexed: 10/24/2022] Open
Abstract
A number of methodological issues in the use of the interpolated twitch technique were investigated for their effect on true maximum force (TMF) and activation (ACT): timing of control (pre- vs post-contraction) and superimposed twitches (first vs second); type of twitch stimulus (primarily magnitude); and the type of extrapolation utilised. On three occasions subjects performed a series of maximal and sub-maximal contractions of the knee extensors, with electrically evoked twitches delivered before, during and after each contraction. The twitch-voluntary force relationship was concave for all types of twitch stimuli, and extrapolation using this relationship typically calculated TMF 39N (7%) higher, and ACT 7% lower than linear extrapolation. The timing of the control (2-4%) and superimposed twitches (approximately 4%) both influenced TMF and ACT. Despite the different twitch stimuli being a range of magnitudes (13-32% maximum voluntary force) they did not affect TMF and ACT. A novel finding was that prior potentiation changed the shape of the twitch-voluntary force relationship. For precise measurement of TMF and ACT it is recommended that: extrapolation is based on the twitch-voluntary force relationship of the experimental model; and post-contraction potentiated twitches be used, as the superimposed twitch on a high level contraction appears to be potentiated.
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Affiliation(s)
- Jonathan P Folland
- School of Sport and Exercise Sciences, Loughborough University, Loughborough, Leicestershire, UK.
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36
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Dousset E, Avela J, Ishikawa M, Kallio J, Kuitunen S, Kyröláinen H, Linnamo V, Komi PV. Bimodal Recovery Pattern in Human Skeletal Muscle Induced by Exhaustive Stretch-Shortening Cycle Exercise. Med Sci Sports Exerc 2007; 39:453-60. [PMID: 17473771 DOI: 10.1249/mss.0b013e31802dd74e] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
INTRODUCTION/PURPOSE Recovery of force and stretch reflex from exhaustive stretch-shortening cycle (SSC) exercise is usually bimodal, characterized as immediate exercise-induced performance reduction, with its quick recovery followed by a longer-lasting reduction in performance. A clear parallel exists between the respective changes in performance, neural activation, and metabolic or structural exercise-induced changes. This implies the existence of potential coupling between muscle failure and the induced neural adjustments that take place along its recovery. The present study was designed to explore the evidence of this coupling more thoroughly. METHODS H- and stretch reflexes were measured before and periodically after exhaustive SSC exercise in human subjects. Several markers of muscle damage and inflammation were also measured during the 8-d postexercise follow-up period. RESULTS The results indicate that acute changes of H- and stretch reflex patterns and maximal isometric force are associated with significant increases in lactate, interleukin 6, and prostaglandin E2 concentrations. The delayed changes in reflexes and isometric force occurred concomitantly with increases in muscle thickness, C reactive protein, and substance P concentrations and also in serum creatine kinase activity. CONCLUSION The immediate postexercise decreases in H- and stretch reflexes are probably partially caused by activation of group III and IV afferent fibers by high lactate concentration in combination with possible increases in potassium outflow. Both of these parameters recovered quickly (i.e., 2 h after exercise). The events after the 2-h postexercise point are very likely to be related to muscle damage and associated inflammation. Group III and IV afferent fibers are probably reactivated during this period by mechanical factors.
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Affiliation(s)
- Erick Dousset
- Neuromuscular Research Centre, Department of Biology of Physical Activity, University of Jyväskylä, Finland.
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Trowbridge ER, Wei JT, Fenner DE, Ashton-Miller JA, Delancey JOL. Effects of Aging on Lower Urinary Tract and Pelvic Floor Function in Nulliparous Women. Obstet Gynecol 2007; 109:715-20. [PMID: 17329525 DOI: 10.1097/01.aog.0000257074.98122.69] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE To evaluate the effects of aging, independent of parity, on pelvic organ and urethral support, urethral function, and levator function in a sample of nulliparous women. METHODS A cohort of 82 nulliparous women, aged 21-70 years, were recruited from the community through advertisements. Subjects underwent pelvic examination using pelvic organ prolapse quantification, urethral angles by cotton-tipped swab, and multichannel urodynamics and uroflow. Vaginal closure force was quantified using an instrumented vaginal speculum. Subjects were grouped into five age categories and analyses performed using t tests, Fisher exact tests, Kruskal-Wallace, and Pearson correlation coefficients. Multiple linear regression modeling was performed to adjust for factors that might confound the results of our primary outcomes. RESULTS Increasing age was associated with decreasing maximal urethral closure pressure (r=-0.758, P<.001) with a 15-cm-H(2)O decrease in pressure per decade. Pelvic organ support as measured by pelvic organ prolapse quantification did not differ by age group. Levator function as measured by resting vaginal closure force and augmentation of vaginal closure force also did not change with increasing age. CONCLUSION In a sample of nulliparous women between 21 and 70 years of age maximal urethral closure pressure in the senescent urethra was 40% of that in the young urethra; increasing age did not affect clinical measures of pelvic organ support, urethral support, and levator function. LEVEL OF EVIDENCE III.
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Affiliation(s)
- Elisa Rodriguez Trowbridge
- Division of Gynecology, Department of Obstetrics and Gynecology, University of Michigan Medical Center, University of Michigan, Ann Arbor, Michigan 48109, USA.
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Racinais S, Bishop D, Denis R, Lattier G, Mendez-Villaneuva A, Perrey S. Muscle Deoxygenation and Neural Drive to the Muscle during Repeated Sprint Cycling. Med Sci Sports Exerc 2007; 39:268-74. [PMID: 17277590 DOI: 10.1249/01.mss.0000251775.46460.cb] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE To investigate muscle deoxygenation and neural drive-related changes during repeated cycling sprints in a fatiguing context. METHODS Nine healthy male subjects performed a repeated-sprint test (consisting of 10 x 6-s maximal sprints interspaced by 30 s of recovery). Oxygen uptake was measured breath-by-breath; muscle deoxygenation of the vastus lateralis was assessed continuously using the near-infrared spectroscopy technique. Surface electromyograms (RMS) of both vastus lateralis and biceps femoris were also recorded. Furthermore, before and after the repeated-sprint test, the percentage of muscle activation by voluntary drive (twitch-interpolated method) was measured during a maximal voluntary contraction. RESULTS AND DISCUSSION Consistent with previous research, our data showed a significant power decrement during repeated-sprint exercise. There was also a progressive muscle deoxygenation, but our data showed that the ability of the subjects to use available O2 throughout the entire repeated-sprint test was well preserved. Our data displayed a significant decrement in the RMS activity during the acceleration phase of each sprint across the repeated-sprint exercise. Moreover, decrement in motor drive was confirmed after exercise by a significant decrease in both percentage of voluntary activation and RMS/M-wave ratio during a maximal voluntary contraction. CONCLUSION In this experimental design, our findings suggest that the ability to repeat short-duration (6 s) sprints was associated with the occurrence of both peripheral and central fatigue.
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Miller M, Flansbjer UB, Downham D, Lexell J. Superimposed electrical stimulation: assessment of voluntary activation and perceived discomfort in healthy, moderately active older and younger women and men. Am J Phys Med Rehabil 2006; 85:945-50. [PMID: 17116999 DOI: 10.1097/01.phm.0000247648.62957.19] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
OBJECTIVE An inability of the nervous system to fully activate the muscle is one factor that can contribute to age-related muscle weakness. Superimposed electrical stimulation can be used to determine voluntary muscle activation (VA). The aim of this study was to assess VA of the quadriceps muscle in healthy older and younger subjects. DESIGN Electrical stimulation causes moderate discomfort in younger subjects, but no study has assessed discomfort in older subjects. The quadriceps muscle in 20 moderately active older subjects (mean age, 75 yrs) and 12 younger subjects (mean age, 25 yrs) was stimulated during two maximal voluntary contractions using a 100-Hz pulse train. A visual analog scale for pain (VAS-pain) was used to evaluate discomfort. RESULTS Ability to activate the quadriceps muscle was generally very high, and there was no significant difference between the older (mean, 0.96) and younger (mean, 0.98) subjects. Discomfort did not differ between the older (mean VAS-pain score, 41 mm) and younger (mean VAS-pain score, 37 mm) subjects. CONCLUSIONS Our results indicate that healthy, moderately active older subjects have the ability to almost complete VA of the quadriceps muscle and that discomfort during electrical stimulation is generally moderate.
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Affiliation(s)
- Michael Miller
- Department of Health Sciences, Lund University, Lund, Sweden
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Miller M, Holmbäck AM, Downham D, Lexell J. Voluntary activation and central activation failure in the knee extensors in young women and men. Scand J Med Sci Sports 2006; 16:274-81. [PMID: 16895533 DOI: 10.1111/j.1600-0838.2005.00479.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Quadriceps muscle weakness is common after knee injuries. This weakness is caused, in part, by reduced voluntary activation (VA) because of central activation failure (CAF). Superimposed electrical stimulation techniques are used to assess VA and to detect CAF. The aim of this study was to assess VA during knee extension in young healthy women and men, and to evaluate subjective discomfort from the electrical stimulation. The quadriceps muscle in six young healthy women (mean age 22 years) and six young healthy men (mean age 29 years) was stimulated during maximal voluntary contractions using a 100 Hz pulse train. Data were collected from two test sessions separated by 6-8 days and each session comprised of two trials. A visual analog scale for pain (VAS-pain) was used to evaluate subjective discomfort. Overall, young healthy, moderately active men and women did have the ability to fully activate their knee extensors isometrically, but they did not achieve full activation on every trial. In those trials where a CAF was detected, the degree was small (mean less than 2%), and did not vary between the two test sessions. Subjective discomfort was generally moderate and tolerable (mean VAS-pain score 35 mm). These results will assist the clinical assessment of muscle weakness following a knee injury and facilitate the design and evaluation of appropriate rehabilitation interventions.
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Affiliation(s)
- M Miller
- Department of Health Sciences, Lund University, Lund, Sweden.
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41
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Klass M, Baudry S, Duchateau J. Voluntary activation during maximal contraction with advancing age: a brief review. Eur J Appl Physiol 2006; 100:543-51. [PMID: 16763836 DOI: 10.1007/s00421-006-0205-x] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2006] [Accepted: 04/20/2006] [Indexed: 10/24/2022]
Abstract
It is well established that the loss of muscle mass (i.e. sarcopenia) is the primary factor contributing to the reduction in muscle force with ageing. Based on the observation that force declines at a faster rate than muscle mass, neural alterations are also thought to contribute to muscle weakness by reducing central drive to the agonist muscles and by increasing coactivation of the antagonist muscles. Researchers have attempted to quantify the contribution of impaired voluntary drive to the decline in muscle force using superimposed electrical stimulation during maximal voluntary contractions (MVCs) and by recording surface electromyographic (EMG) activity. Although reduced voluntary activation of agonist muscles and increased coactivation of antagonist muscles during a MVC have been reported with advancing age, such changes are not supported by all studies. These discrepancies may be explained by differences in sensitivity between the methods used to assess voluntary activation, as well as differences between the characteristics of the study population, the muscle group that is tested, and the type of contraction that is performed. The objective of this review is to summarize current knowledge regarding the activation of agonist and antagonist muscles during MVC in elderly and to try to clarify the disparities in literature concerning the influence of a possible deficit in voluntary activation on the maximal force capacity of muscles in elderly adults.
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Affiliation(s)
- Malgorzata Klass
- Laboratory of Applied Biology, Université Libre de Bruxelles, 28 avenue P. Héger, CP 168, 1000 Brussels, Belgium
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Bampouras TM, Reeves ND, Baltzopoulos V, Maganaris CN. Muscle activation assessment: Effects of method, stimulus number, and joint angle. Muscle Nerve 2006; 34:740-6. [PMID: 17013889 DOI: 10.1002/mus.20610] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Activation capacity has traditionally been assessed using the interpolated twitch technique (ITT) and central activation ratio (CAR). However, the quantitative agreement of the two methods and the physiological mechanisms underpinning any possible differences have not been fully elucidated. The aim of this study was to compare and assess the sensitivity of the ITT and CAR to potential errors introduced by (1) evoking inadequate force, by manipulating the number of stimuli, and (2) neglecting differences in series elasticity between conditions, by manipulating joint angle. Ten subjects performed knee extension contractions at 30 degrees and 90 degrees knee-joint angles during which the ITT and CAR methods were applied using 1, 2, 4, and 8 electrical stimuli. Joint angle influenced the ITT outcome with higher values taken at 90 degrees (P < 0.05), while the number of stimuli influenced the CAR outcome with a higher number of stimuli yielding lower values (P < 0.05). For any given joint angle and stimulus number, the CAR method produced higher activation values than the ITT method by 8%-16%. Therefore, in the quantification of voluntary drive with the ITT and CAR methods consideration should be given not only to the number of stimuli applied but also to the effect of series elasticity due to joint-angle differences, since these factors may differently affect the outcome of the calculation, depending on the approach followed.
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Affiliation(s)
- Theodoros M Bampouras
- Institute for Biophysical and Clinical Research into Human Movement, Manchester Metropolitan University, Alsager, United Kingdom.
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Presland JD, Dowson MN, Cairns SP. Changes of motor drive, cortical arousal and perceived exertion following prolonged cycling to exhaustion. Eur J Appl Physiol 2005; 95:42-51. [PMID: 15976997 DOI: 10.1007/s00421-005-1395-3] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/10/2005] [Indexed: 12/20/2022]
Abstract
The aims of this study were to (1) quantify any central fatigue that occurs following prolonged dynamic exercise, i.e. reduced muscle force caused by impaired motor drive from the central nervous system and (2) determine whether decreased cortical arousal, assessed using critical flicker fusion threshold (CFF), occurs and is related to impaired exercise performance. Fifteen healthy men cycled at 70% VO2peak until exhaustion. The peak force of maximum voluntary isometric contractions (MVC) of the quadriceps muscle group was reduced by 30% at exhaustion. The voluntary activation ratio determined using superimposed tetanic stimulation fell from 0.99 to 0.86 at exhaustion. The central fatigue (%) at exhaustion was 33+/-12% (+/- SD) (assessed via the tetanus interpolation technique) and 54+/-32% (assessed via the relative decline of MVC and peak tetanic force) of the total fatigue. The MVC only partially recovered and central fatigue persisted at 30 min post-exercise. CFF increased from 39.2+/-2.3 to 41.8+/-3.5 Hz at exhaustion, but did not correlate with central fatigue. Every subject reached the highest rating of perceived exertion (RPE) at exhaustion of 20 on the Borg scale. The time to exhaustion was related to how quickly the RPE increased and to the ability to sustain exercise at very high RPE. These data suggest that with prolonged cycling: (1) there is considerable and a persistent form of central fatigue, (2) there is an increased level of cortical arousal, and (3) exhaustion is linked to very high subjective RPE.
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Affiliation(s)
- Jarrod D Presland
- Division of Sport and Recreation, Faculty of Health and Environmental Sciences, Auckland University of Technology, Auckland, 1020, New Zealand
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44
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Paillard T, Noé F, Passelergue P, Dupui P. Electrical Stimulation Superimposed onto Voluntary Muscular Contraction. Sports Med 2005; 35:951-66. [PMID: 16271009 DOI: 10.2165/00007256-200535110-00003] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Electrical stimulation (ES) reverses the order of recruitment of motor units (MU) observed with voluntary muscular contraction (VOL) since under ES, large MU are recruited before small MU. The superimposition of ES onto VOL (superimposed technique: application of an electrical stimulus during a voluntary muscle action) can theoretically activate more motor units than VOL performed alone, which can engender an increase of the contraction force. Two superimposed techniques can be used: (i) the twitch interpolation technique (ITT), which consists of interjecting an electrical stimulus onto the muscle nerve; and (ii) the percutaneous superimposed electrical stimulation technique (PST), where the stimulation is applied to the muscle belly. These two superimposed techniques can be used to evaluate the ability to fully activate a muscle. They can thus be employed to distinguish the central or peripheral nature of fatigue after exhausting exercise. In general, whatever the technique employed, the superimposition of ES onto volitional exercise does not recruit more MU than VOL, except with eccentric actions. Nevertheless, the neuromuscular response associated with the use of the superimposed technique (ITT and PST) depends on the parameter of the superimposed current. The sex and the training level of the subjects can also modify the physiological impact of the superimposed technique. Although the motor control differs drastically between training with ES and VOL, the integration of the superimposed technique in training programmes with healthy subjects does not reveal significant benefits compared with programmes performed only with voluntary exercises. Nevertheless, in a therapeutic context, training programmes using ES superimposition compensate volume and muscle strength deficit with more efficiency than programmes using VOL or ES separately.
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Affiliation(s)
- Thierry Paillard
- Sports Performance Analysis Laboratory, Department of Sports Sciences, University of Pau, Tarbes, France
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45
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Lewek MD, Rudolph KS, Snyder-Mackler L. Quadriceps femoris muscle weakness and activation failure in patients with symptomatic knee osteoarthritis. J Orthop Res 2004; 22:110-5. [PMID: 14656668 PMCID: PMC3073134 DOI: 10.1016/s0736-0266(03)00154-2] [Citation(s) in RCA: 222] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
PURPOSE Quadriceps weakness is common in patients with knee osteoarthritis (OA), and has been attributed to failure of voluntary activation. Methodological differences may have contributed to previous reports of extensive failure of voluntary activation in patients with osteoarthritis. The purpose of this study was to determine the extent of quadriceps muscle weakness and activation failure in middle aged patients with symptomatic medial knee osteoarthritis using maximum voluntary isometric contractions (MVIC) and a burst superimposition technique. METHODS Measurements of quadriceps MVIC and extent of voluntary activation were made in 12 subjects with knee OA and 12 similarly aged uninjured subjects. Voluntary activation was tested by superimposing a train of electrical stimulation on a maximal effort volitional contraction of the quadriceps muscle. RESULTS The group of subjects with knee OA had significantly less quadriceps strength relative to body mass index (BMI) than the group of control subjects (p=0.010). No difference in voluntary activation was observed (p=0.233), however, 50% of the OA group, and only 25% of the control group failed to fully activate the quadriceps. DISCUSSION The finding of quadriceps weakness is consistent with past literature. Providing adequate instruction, feedback, and several attempts to maximally contract the muscle likely yielded greater volitional activation (thus less activation failure) than had been reported previously. This finding has implications for the rehabilitation of weakened quadriceps in patients with knee osteoarthritis.
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Affiliation(s)
- Michael D Lewek
- Department of Physical Therapy and Biomechanics and Movement Science Program, 301 McKinly Laboratory, University of Delaware, Newark, DE 19716, USA
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Stevens JE, Mizner RL, Snyder-Mackler L. Neuromuscular electrical stimulation for quadriceps muscle strengthening after bilateral total knee arthroplasty: a case series. J Orthop Sports Phys Ther 2004; 34:21-9. [PMID: 14964588 DOI: 10.2519/jospt.2004.34.1.21] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
STUDY DESIGN A case series. OBJECTIVES The purpose of this case series was to assess the effect of high-intensity neuromuscular electrical stimulation (NMES) on quadriceps strength and voluntary activation following total knee arthroplasty (TKA). BACKGROUND Following TKA, patients exhibit long-term weakness of the quadriceps and diminished functional capacity compared to age-matched healthy controls. The pain and swelling that results from surgery may contribute to quadriceps weakness. The use of high-intensity NMES has previously been shown to be effective in quickly restoring quadriceps strength in patients with weakness after surgery. METHODS AND MEASURES All patients were treated for 6 weeks, 2 to 3 visits per week, in outpatient rehabilitation. Five patients (NMES group) participated in a voluntary exercise program for both knees and NMES for the weaker knee. Three patients (exercise group) participated in a voluntary exercise program for both knees without NMES. For each treatment session, 10 isometric electrically elicited muscle contractions were administered at maximally tolerated doses to the initially weaker leg of the NMES group. Quadriceps strength and muscle activation were repeatedly assessed up to 6 months after surgery using burst superimposition techniques. RESULTS At 6 months, the weak NMES-treated legs of 4 of 5 patients in the NMES group had surpassed the strength of the contralateral leg. In contrast, none of the weak legs in the exercise group were stronger than the contralateral leg at 6 months. Changes in quadriceps muscle activation mirrored the changes exhibited in strength. CONCLUSION When NMES was added to a voluntary exercise program, deficits in quadriceps muscle strength and activation resolved quickly after TKA.
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Affiliation(s)
- Jennifer E Stevens
- Department of Physical Therapy, University of Florida, Gainesville, FL, USA
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Millet GY, Lepers R. Alterations of Neuromuscular Function After Prolonged Running, Cycling and Skiing Exercises. Sports Med 2004; 34:105-16. [PMID: 14965189 DOI: 10.2165/00007256-200434020-00004] [Citation(s) in RCA: 232] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
It is well known that impairment of performance resulting from muscle fatigue differs according to the types of contraction involved, the muscular groups tested and the exercise duration/intensity. Depending on these variables, strength loss with fatigue can originate from several sites from the motor cortex through to contractile elements. This has been termed 'task dependency of muscle fatigue'. Only recently have studies focused on the origin of muscle fatigue after prolonged exercise lasting 30 minutes to several hours. Central fatigue has been shown to contribute to muscle fatigue during long-distance running by using different methods such as the twitch interpolation technique, the ratio of the electromyogram (EMG) signal during maximal voluntary contraction normalised to the M-wave amplitude or the comparison of the forces achieved with voluntary- and electrically-evoked contractions. Some central activation deficit has also been observed for knee extensor muscles in cycling but central fatigue after activities inducing low muscular damage was attenuated compared with running. While supraspinal fatigue cannot be ruled out, it can be suggested that spinal adaptation, such as inhibition from type III and IV group afferents or disfacilitation from muscle spindles, contributes to the reduced neural drive after prolonged exercise. It has been shown that after a 30 km run, individuals with the greatest knee extensor muscle strength loss experienced a significant activation deficit. However, central fatigue alone cannot explain the entire strength loss after prolonged exercise. Alterations of neuromuscular propagation, excitation-contraction coupling failure and modifications of the intrinsic capability of force production may also be involved. Electrically-evoked contractions and associated EMG can help to characterise peripheral fatigue. The purpose of this review is to further examine the central and peripheral mechanisms contributing to strength loss after prolonged running, cycling and skiing exercises.
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Affiliation(s)
- Guillaume Y Millet
- Research Group Physiology and Physiopathology of Exercise and Handicap, University of Saint-Etienne, Saint-Etienne, France.
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Abstract
The twitch interpolation technique is commonly employed to assess the completeness of skeletal muscle activation during voluntary contractions. Early applications of twitch interpolation suggested that healthy human subjects could fully activate most of the skeletal muscles to which the technique had been applied. More recently, however, highly sensitive twitch interpolation has revealed that even healthy adults routinely fail to fully activate a number of skeletal muscles despite apparently maximal effort. Unfortunately, some disagreement exists as to how the results of twitch interpolation should be employed to quantify voluntary activation. The negative linear relationship between evoked twitch force and voluntary force that has been observed by some researchers implies that voluntary activation can be quantified by scaling a single interpolated twitch to a control twitch evoked in relaxed muscle. Observations of non-linear evoked-voluntary force relationships have lead to the suggestion that the single interpolated twitch ratio can not accurately estimate voluntary activation. Instead, it has been proposed that muscle activation is better determined by extrapolating the relationship between evoked and voluntary force to provide an estimate of true maximum force. However, criticism of the single interpolated twitch ratio typically fails to take into account the reasons for the non-linearity of the evoked-voluntary force relationship. When these reasons are examined, it appears that most are even more challenging to the validity of extrapolation than they are to the linear equation. Furthermore, several factors that contribute to the observed non-linearity can be minimised or even eliminated with appropriate experimental technique. The detection of small activation deficits requires high resolution measurement of force and careful consideration of numerous experimental details such as the site of stimulation, stimulation intensity and the number of interpolated stimuli. Sensitive twitch interpolation techniques have revealed small to moderate deficits in voluntary activation during brief maximal efforts and progressively increasing activation deficits (central fatigue) during exhausting exercise. A small number of recent studies suggest that resistance training may result in improved voluntary activation of the quadriceps femoris and ankle plantarflexor muscles but not the biceps brachii. A significantly larger body of evidence indicates that voluntary activation declines as a consequence of bed-rest, joint injury and joint degeneration. Twitch interpolation has also been employed to study the mechanisms by which caffeine and pseudoephedrine enhance exercise performance.
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Affiliation(s)
- Anthony Shield
- School of Exercise Science and Sport Management, Southern Cross University, Lismore, New South Wales, Australia.
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Oskouei MAE, Van Mazijk BCF, Schuiling MHC, Herzog W. Variability in the interpolated twitch torque for maximal and submaximal voluntary contractions. J Appl Physiol (1985) 2003; 95:1648-55. [PMID: 12777410 DOI: 10.1152/japplphysiol.01189.2002] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The superimposed twitch technique is frequently used to study the degree of motor unit activation during voluntary effort. This technique is one of the preferred methods to determine the activation deficit (AD) in normal, athletic, and patient populations. One of the limitations of the superimposed twitch technique is its variability under given contractile conditions. The objective of this research was to determine the source(s) of variability in the superimposed twitch force (STF) for repeat measurements. We hypothesized that the variability in the AD measurements may be caused by the timing of the twitch force relative to the onset of muscle activation, by force transients during the twitch application, by small variations in the actual force from the nominal target force, and by variations in the resting twitch force. Twenty-eight healthy subjects participated in this study. Sixteen of these subjects participated in a protocol involving contractions at 50% of their maximal voluntary contraction (MVC) effort, whereas the remaining 12 participated in a protocol involving contractions at 100% of their MVC. Doublet-twitch stimuli were superimposed onto the 50 and 100% effort knee extensor muscle contractions, and the resting twitch forces, voluntary knee extensor forces, and STFs were then measured. The mean resting twitch forces obtained before and after 8 s of 50% of MVC were the same. Similarly, the mean STFs determined at 1, 3, 5, and 7 s into the 50% MVC were the same. The variations in twitch force were significantly smaller after accounting for the actual force at twitch application than those calculated from the prescribed forces during the 50% MVC protocol (P < 0.05). Furthermore, the AD and the actual force showed statistically significant negative correlations for the 50% MVC tests. The interpolated twitch torque determined for the maximal effort contractions ranged from 1 to 70%. In contrast to the protocol at 50% of MVC, negative correlations were only observed in 5 of the 12 subjects during the 100% effort contractions. These results suggest that small variations in the actual force from the target force can account for the majority of the variations in the STFs for submaximal but not maximal effort contractions. For the maximal effort contractions, large variations in the STF exist due to undetermined causes.
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Millet GY, Martin V, Maffiuletti NA, Martin A. Neuromuscular fatigue after a ski skating marathon. CANADIAN JOURNAL OF APPLIED PHYSIOLOGY = REVUE CANADIENNE DE PHYSIOLOGIE APPLIQUEE 2003; 28:434-45. [PMID: 12955870 DOI: 10.1139/h03-032] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of this study was to characterize neuromuscular fatigue in knee extensor muscles after a marathon skiing race (mean +/- SD duration = 159.7 +/- 17.9 min). During the 2 days preceding the event and immediately after, maximal percutaneous electrical stimulations (single twitch, 0.5-s tetanus at 20 and 80 Hz) were applied to the femoral nerve of 11 trained skiers. Superimposed twitches were also delivered during maximal voluntary contraction (MVC) to determine maximal voluntary activation (% VA). EMG was recorded from the vastus lateralis muscle. MVC decreased with fatigue from 171.7 +/- 33.7 to 157.3 +/- 35.2 Nm (-8.4%; p < 0.005) while % VA did not change significantly. The RMS measured during MVC and peak-to-peak amplitude of the compound muscle action potential (PPA) from the vastus lateralis decreased with fatigue by about 30% (p < 0.01), but RMS.PPA-1 was similar before and after the ski marathon. Peak tetanus tension at 20 Hz and 80 Hz (P(0)20 and P(0)80, respectively) did not change significantly, but P(0)20.P(0)80-1 increased (p < 0.05) after the ski marathon. Data from electrically evoked single twitches showed greater peak mechanical response, faster rate of force development, and shorter contraction time in the fatigued state. From these results it can be concluded that a ski skating marathon (a) alters slightly but significantly maximal voluntary strength of the knee extensors without affecting central activation, and (b) induces both potentiation and fatigue.
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Affiliation(s)
- Guillaume Y Millet
- INSERM/ERIT-M 0207 Motricité-Plasticité, Faculté des Sciences du Sport, Université de Bourgogne, BP 27 877-21078 Dijon, France
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