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Cuadra C, Wolf SL, Lyle MA. Heteronymous feedback from quadriceps onto soleus in stroke survivors. RESEARCH SQUARE 2024:rs.3.rs-4540327. [PMID: 38978589 PMCID: PMC11230478 DOI: 10.21203/rs.3.rs-4540327/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/10/2024]
Abstract
Background Recent findings suggest increased excitatory heteronymous feedback from quadriceps onto soleus may contribute to abnormal coactivation of knee and ankle extensors after stroke. However, there is lack of consensus on whether persons post-stroke exhibit altered heteronymous reflexes and, when present, the origin of increased excitation (i.e. increased excitation alone and/or decreased inhibition). This study examined heteronymous excitation and inhibition from quadriceps onto soleus in paretic, nonparetic, and age-matched control limbs to determine whether increased excitation was due to excitatory and/or reduced inhibitory reflex circuits. A secondary purpose was to examine whether heteronymous reflex magnitudes were related to clinical measures of lower limb recovery, walking-speed, and dynamic balance. Methods Heteronymous excitation and inhibition from quadriceps onto soleus were examined in fourteen persons post-stroke and fourteen age-matched unimpaired participants. Heteronymous feedback was elicited by femoral nerve and quadriceps muscle stimulation in separate trials while participants tonically activated soleus at 20% max. Fugl-Myer assessment of lower extremity, 10-meter walk test, and Mini-BESTest were assessed in stroke survivors. Results Heteronymous excitation and inhibition onsets, durations, and magnitudes were not different between paretic, nonparetic or age-matched unimpaired limbs. Quadriceps stimulation elicited excitation that was half the magnitude of femoral nerve stimulation. Femoral nerve elicited paretic limb heteronymous excitation was positively correlated with walking speed but did not reach significance because only a subset of paretic limbs exhibited excitation (n = 8, Spearman r = 0.69, P = 0.058). Conclusions Heteronymous feedback from quadriceps onto soleus assessed in a seated posture was not impaired in persons post-stroke. Despite being unable to identify whether reduced inhibition contributes to abnormal excitation reported in prior studies, our results indicate quadriceps stimulation may allow a better estimate of heteronymous inhibition in those that exhibit exaggerated excitation. Heteronymous excitation magnitude in the paretic limb was positively correlated with self-selected walking speed suggesting paretic limb excitation at the higher end of a normal range may facilitate walking ability after stroke. Future studies are needed to identify whether heteronymous feedback from Q onto SOL is altered after stroke in upright postures and during motor tasks as a necessary next step to identify mechanisms underlying motor impairment.
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Marina M, Torrado P, Duchateau J, Baudry S. Neural Adjustments during Repeated Braking and Throttle Actions on a Motorcycle Setup. Int J Sports Med 2024; 45:125-133. [PMID: 38096909 DOI: 10.1055/a-2197-0967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2024]
Abstract
The aim of the study was to assess neuromuscular changes during an intermittent fatiguing task designed to replicate fundamental actions and ergonomics of road race motorcycling. Twenty-eight participants repeated a sequence of submaximal brake-pulling and gas throttle actions, interspaced by one maximal brake-pulling, until failure. During the submaximal brake-pulling actions performed at 30% MVC, force fluctuations, surface EMG, maximal M-wave (Mmax) and H-reflex were measured in the flexor digitorum superficialis. At the end of the task, the MVC force and associated EMG activity decreased (P<0.001) by 46% and 26%, respectively. During the task, force fluctuation and EMG activity increased gradually (106% and 61%, respectively) with respect to the pre-fatigue state (P≤0.029). The Mmax first phase did not change (P≥0.524), whereas the H-reflex amplitude, normalized to Mmax, increased (149%; P≤0.039). Noteworthy, the relative increase in H-reflex amplitude was correlated with the increase in EMG activity during the task (r=0.63; P<0.001). During the 10-min recovery, MVC force and EMG activity remained depressed (P≤0.05) whereas H-reflex amplitude and force fluctuation returned to pre-fatigue values. In conclusion, contrarily to other studies, our results bring forward that when mimicking motorcycling brake-pulling and gas throttle actions, supraspinal neural mechanisms primarily limit the duration of the performance.
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Affiliation(s)
- Michel Marina
- Research Group in Physical Activity and Health (GRAFAiS), Institut Nacional d'Educació Física de Catalunya (INEFC) - Universitat de Barcelona (UB), Barcelona, Spain
| | - Priscila Torrado
- Research Group in Physical Activity and Health (GRAFAiS), Institut Nacional d'Educació Física de Catalunya (INEFC) - Universitat de Barcelona (UB), Barcelona, Spain
| | - Jacques Duchateau
- Laboratory of Applied Biology, Research Unit in Applied Neurophysiology (LABNeuro), ULB Université Libre de Bruxelles, Bruxelles, Belgium
| | - Stephane Baudry
- Laboratory of Applied Biology, Research Unit in Applied Neurophysiology (LABNeuro), ULB Université Libre de Bruxelles, Bruxelles, Belgium
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Theodosiadou A, Henry M, Duchateau J, Baudry S. Revisiting the use of Hoffmann reflex in motor control research on humans. Eur J Appl Physiol 2023; 123:695-710. [PMID: 36571622 DOI: 10.1007/s00421-022-05119-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 12/17/2022] [Indexed: 12/27/2022]
Abstract
Research in movement science aims at unravelling mechanisms and designing methods for restoring and maximizing human functional capacity, and many techniques provide access to neural adjustments (acute changes) or long-term adaptations (chronic changes) underlying changes in movement capabilities. First described by Paul Hoffmann over a century ago, when an electrical stimulus is applied to a peripheral nerve, this causes action potentials in afferent axons, primarily the Ia afferents of the muscle spindles, which recruit homonymous motor neurons, thereby causing an electromyographic response known as the Hoffmann (H) reflex. This technique is a valuable tool in the study of the neuromuscular function in humans and has provided relevant information in the neural control of movement. The large use of the H reflex in motor control research on humans relies in part to its relative simplicity. However, such simplicity masks subtleties that require rigorous experimental protocols and careful data interpretation. After highlighting basic properties and methodological aspects that should be considered for the correct use of the H-reflex technique, this brief narrative review discusses the purpose of the H reflex and emphasizes its use as a tool to assess the effectiveness of Ia afferents in discharging motor neurones. The review also aims to reconsider the link between H-reflex modulation and Ia presynaptic inhibition, the use of the H-reflex technique in motor control studies, and the effects of ageing. These aspects are summarized as recommendations for the use of the H reflex in motor control research on humans.
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Affiliation(s)
- Anastasia Theodosiadou
- Laboratory of Applied Biology, Research Unit in Applied Neurophysiology (LABNeuro), Faculty of Motor Sciences, ULB-Neurosciences Institute (UNI), Université Libre de Bruxelles (ULB), 808 Route de Lennik, CP 640, 1070, Brussels, Belgium
| | - Mélanie Henry
- Laboratory of Applied Biology, Research Unit in Applied Neurophysiology (LABNeuro), Faculty of Motor Sciences, ULB-Neurosciences Institute (UNI), Université Libre de Bruxelles (ULB), 808 Route de Lennik, CP 640, 1070, Brussels, Belgium
| | - Jacques Duchateau
- Laboratory of Applied Biology, Research Unit in Applied Neurophysiology (LABNeuro), Faculty of Motor Sciences, ULB-Neurosciences Institute (UNI), Université Libre de Bruxelles (ULB), 808 Route de Lennik, CP 640, 1070, Brussels, Belgium
| | - Stéphane Baudry
- Laboratory of Applied Biology, Research Unit in Applied Neurophysiology (LABNeuro), Faculty of Motor Sciences, ULB-Neurosciences Institute (UNI), Université Libre de Bruxelles (ULB), 808 Route de Lennik, CP 640, 1070, Brussels, Belgium.
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Colard J, Jubeau M, Duclay J, Cattagni T. Regulation of primary afferent depolarization and homosynaptic post-activation depression during passive and active lengthening, shortening and isometric conditions. Eur J Appl Physiol 2023; 123:1257-1269. [PMID: 36781424 DOI: 10.1007/s00421-023-05147-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Accepted: 01/26/2023] [Indexed: 02/15/2023]
Abstract
PURPOSE This study aimed to determine whether the modulation of primary afferent depolarization (PAD) and homosynaptic post-activation depression (HPAD) are involved in the lower efficacy of Ia-afferent-α-motoneuron transmission commonly observed during lengthening compared to isometric and shortening conditions. METHODS 15 healthy young individuals participated in two experimental sessions dedicated to measurement in passive and active muscle states, respectively. In each session, PAD, HPAD and the efficacy of Ia-afferent-α-motoneuron transmission were evaluated during lengthening, shortening and isometric conditions. PAD was evaluated with D1 inhibition technique. Posterior tibial nerve stimulation was used to study HPAD and the efficacy of the Ia-afferent-α-motoneuron transmission through the recording of the soleus Hoffmann reflex (H reflex). RESULTS PAD was increased in lengthening than shortening (11.2%) and isometric (12.3%) conditions regardless of muscle state (P < 0.001). HPAD was increased in lengthening than shortening (5.1%) and isometric (4.2%) conditions in the passive muscle state (P < 0.05), while no difference was observed in the active muscle state. H reflex was lower in lengthening than shortening (- 13.2%) and isometric (- 9.4%) conditions in both muscle states (P < 0.001). CONCLUSION These results highlight the specific regulation of PAD and HPAD during lengthening conditions. However, the differences observed during passive lengthening compared to shortening and isometric conditions seem to result from an increase in Ia-afferent discharge, while the variations highlighted during active lengthening might come from polysynaptic descending pathways involving supraspinal centres that could regulate PAD mechanism.
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Affiliation(s)
- Julian Colard
- Nantes University, Movement-Interactions-Performance, MIP, 25 Bis Boulevard Guy Mollet-BP 72206, UR 4334, 44322, Nantes, France
| | - Marc Jubeau
- Nantes University, Movement-Interactions-Performance, MIP, 25 Bis Boulevard Guy Mollet-BP 72206, UR 4334, 44322, Nantes, France.
| | - Julien Duclay
- Toulouse NeuroImaging Center, Université de Toulouse, Inserm, UPS, Toulouse, France
| | - Thomas Cattagni
- Nantes University, Movement-Interactions-Performance, MIP, 25 Bis Boulevard Guy Mollet-BP 72206, UR 4334, 44322, Nantes, France
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Lebesque L, Scaglioni G, Martin A. The impact of submaximal fatiguing exercises on the ability to generate and sustain the maximal voluntary contraction. Front Physiol 2022; 13:970917. [DOI: 10.3389/fphys.2022.970917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Accepted: 08/04/2022] [Indexed: 11/13/2022] Open
Abstract
Neuromuscular fatigability is a failure to produce or maintain a required torque, and commonly quantified with the decrease of maximal torque production during a few seconds-long maximal voluntary contraction (MVC). The literature shows that the MVC reduction after exercises with different torque-time integral (TTI), is often similar. However, it was shown that after a fatiguing exercise, the decline in the capacity to sustain the maximal voluntary contraction for 1 min (MVC1-MIN) differs from the decrease in the capacity to perform a brief-MVC, suggesting that this latter can only partially assess neuromuscular fatigability. This study aims to highlight the relevance of using a sustained MVC to further explore the neuromuscular alterations induced by fatiguing exercises with different TTI. We used two contraction intensities (i.e., 20% and 40% MVC) to modulate the TTI, and two exercise modalities [i.e., voluntary (VOL) and electrical induced (NMES)], since the letter are known to be more fatiguing for a given TTI. Thirteen subjects performed a plantar-flexors MVC1-MIN before and after the fatiguing exercises. A similar MVC loss was obtained for the two exercise intensities despite a greater TTI at 40% MVC, regardless of the contraction modality. On the other hand, the torque loss during MVC1-MIN was significantly greater after the 40% compared to 20% MVC exercise. These findings are crucial because they demonstrate that maximal torque production and sustainability are two complementary features of neuromuscular fatigability. Hence, MVC1-MIN assessing simultaneously both capacities is essential to provide a more detailed description of neuromuscular fatigability.
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Sensory enhancement of warm-up amplifies subsequent grip strength and cycling performance. Eur J Appl Physiol 2022; 122:1695-1707. [PMID: 35471257 DOI: 10.1007/s00421-022-04952-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Accepted: 04/08/2022] [Indexed: 11/03/2022]
Abstract
PURPOSE In sport and exercise, warm-ups induce various physiological changes that facilitate subsequent performance. We have shown that delivering patterned stimulation to cutaneous afferents during sprint cycling mitigates fatigue-related decrements in performance, and that repeated sensory stimulation amplifies spinal reflex excitability. Therefore, the purpose of this study was to assess whether sensory enhancement of warm-up would affect subsequent high-intensity arm cycling performance. METHODS Participants completed three experimental sessions, in which they randomly performed either a control, stim, or sleeve warm-up condition prior to maximal duration arm cycling. During the control condition, warmup consisted of low-intensity arm cycling for 15 min. The stim condition was the same, except they received alternating pulses (400 ms, 50 Hz) of stimulation just above their perceptual threshold to the wrists during warm-up. The third condition required participants to wear custom fabricated compression sleeves around the elbow during warm-up. Grip strength and spinal reflex excitability were measured before and after each warm-up and fatigue protocol, which required participants to arm cycle at 85% of peak power output until they reached volitional fatigue. Peak power output was determined during an incremental test at minimum 72 h prior to the first session. RESULTS Both sensory enhanced warm-up conditions amplified subsequent high-intensity arm cycling performance by ~ 30%. Additionally, the stim and sleeve warm-up conditions yielded improvements in grip strength (increased by ~ 5%) immediately after the sensory enhanced warm-ups. Ergogenic benefits from the sensory enhanced warm-up conditions did not differ between one another. CONCLUSION These findings demonstrate that enhanced sensory input during warm-up can elicit improvements in both maximal and submaximal performance measures.
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Marshall PW, Finn HT, Enoka RM. Declines in muscle contractility and activation during isometric contractions of the knee extensors vary with contraction intensity and exercise volume. Exp Physiol 2021; 106:2096-2106. [PMID: 34411379 DOI: 10.1113/ep089788] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 08/16/2021] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Is there a critical threshold beyond which the loss of muscle contractility is regulated by the level of muscle activation during single-limb exercise of differing intensities and volumes? What is the main finding and its importance? Plateaus in the decline in muscle contractility during single-limb knee extension depended on both exercise volume and contraction intensity. A plateau was only evident with an increase in exercise volume. Muscle activation increased and did not decline despite substantial reductions in contractility. The findings indicate that the decrease in muscle contractility exhibited by resistance-trained men during the performance of submaximal isometric contractions with the knee extensors was not regulated by the level of muscle activation. ABSTRACT Our study examined the influence of contraction intensity and exercise volume on changes in muscle contractility and activation of the knee extensor muscles. Maximal voluntary torque (MVT) and rate of change in torque, surface electromyograms, voluntary activation, V-waves and quadriceps resting twitch measures were assessed in 10 resistance-trained men during two experimental sessions. Each session began with an initial baseline series of contractions at a fixed intensity of 40% or 80% MVT. The 40%-only session continued with five contractions to task failure at 40% MVT. The 80% session continued with five contractions to failure each at 80%, 60% and 40% MVT. Greater reductions in MVT were observed during the baseline contractions of the 40%-only session compared with the 80% session at each matched-volume time point (P < 0.05), with similar changes in twitch values (P < 0.001). MVT and twitch values plateaued at each intensity during the 80% session and were significantly different across intensities: 80% > 60% > 40% (P < 0.001). There were no differences for measures during the five contractions at 40% MVT performed on the different days, despite a greater volume of exercise performed prior to the 40% MVT during the 80% session. At each contraction intensity, a plateau in contractility loss was observed as more contractions were performed. We found that initial increases in muscle activation were maintained in the presence of increases in exercise volume and, in contrast to the critical-threshold hypothesis, did not decline in parallel with reductions in muscle contractility.
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Affiliation(s)
- Paul W Marshall
- Department of Exercise Sciences, University of Auckland, Auckland, New Zealand.,Human Performance Laboratory, School of Health Sciences, Western Sydney University, Sydney, Australia
| | - Harrison T Finn
- Neuroscience Research Australia (NeuRA), Sydney, Australia.,University of New South Wales, Sydney, Australia
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, CO, USA
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Marshall PW, Melville GW, Cross R, Marquez J, Harrison I, Enoka RM. Fatigue, pain, and the recovery of neuromuscular function after consecutive days of full-body resistance exercise in trained men. Eur J Appl Physiol 2021; 121:3103-3116. [PMID: 34350481 DOI: 10.1007/s00421-021-04777-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 07/25/2021] [Indexed: 11/28/2022]
Abstract
PURPOSE This study measured the self-reported level of fatigue, pain, and neuromuscular function of the knee extensor muscles over a three-day period that included two consecutive days of full-body resistance exercises. METHODS 10 resistance-trained men performed two consecutive days of full-body resistance exercise. Muscle activation (electromyography and voluntary activation), contractility, and presynaptic inhibition of Ia afferents (homosynaptic and GABA mediated presynaptic inhibition) for the quadriceps were examined from femoral and posterior tibial nerve stimulation. RESULTS Fatigue and pain were elevated after Day 1, and were not reduced to pre-exercise levels at the start of Day 2 (p < 0.05). Maximal voluntary torque (- 51.4 Nm, 95% CI = 12.4-90.4 Nm, p = 0.005) and rate of torque development (- 469 Nm.s-1, 95% CI = 109-829 Nm.s-1, p = 0.006) were reduced after Day 1, had recovered by Day 2, and did not change after the second training session. The maximal amplitude and rate of rise for the quadriceps twitch were reduced after both training sessions (p < 0.01), with recovery 24 h each session. The maximal amplitude and rate of early muscle activation were reduced after Day 1 (p < 0.01), but no changes were observed for voluntary activation, H-reflex size and shape, or measures of Ia presynaptic inhibition. CONCLUSION Resistance exercise in the presence of elevated fatigue and pain from a previous training session does not worsen recovery, or lead to significant alterations in quadriceps neuromuscular function. Reduction in muscle contractility, in the absence of declines in muscle activation, does not lead to decreased voluntary torque.
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Affiliation(s)
- Paul W Marshall
- Human Performance Laboratory, School of Health Science, Western Sydney University, Penrith, Australia. .,Department of Exercise Science, University of Auckland, Building 907, Newmarket, Auckland, 1023, New Zealand.
| | - Geoffrey W Melville
- Faculty of Science, Medicine, and Health, University of Wollongong, Wollongong, Australia
| | - Rebecca Cross
- Human Performance Laboratory, School of Health Science, Western Sydney University, Penrith, Australia
| | - John Marquez
- Human Performance Laboratory, School of Health Science, Western Sydney University, Penrith, Australia
| | - Isaac Harrison
- Human Performance Laboratory, School of Health Science, Western Sydney University, Penrith, Australia
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, CO, USA
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Lee H, Son SJ, Kim H, Han S, Seeley M, Hopkins JT. Submaximal Force Steadiness and Accuracy in Patients With Chronic Ankle Instability. J Athl Train 2021; 56:454-460. [PMID: 33150436 DOI: 10.4085/15-20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
CONTEXT Patients with chronic ankle instability (CAI) have demonstrated sensorimotor impairments. Submaximal force steadiness and accuracy measure sensory, motor, and visual function via a feedback mechanism, which helps researchers and clinicians comprehend the sensorimotor deficits associated with CAI. OBJECTIVE To determine if participants with CAI experienced deficits in hip and ankle submaximal force steadiness and accuracy compared with healthy control participants. DESIGN Case-control study. SETTING Research laboratory. PATIENTS OR OTHER PARTICIPANTS Twenty-one patients with CAI and 21 uninjured individuals. MAIN OUTCOME MEASURE(S) Maximal voluntary isometric contraction (MVIC) and force steadiness and accuracy (10% and 30% of MVIC) of the ankle evertors and invertors and hip abductors were assessed using the central 10 seconds (20%-87% of the total time) of the 3 trials. RESULTS Relative to the control group, the CAI group demonstrated less accuracy of the invertors (P < .001). Across all motions, the CAI group showed less steadiness (P < .001) and less accuracy (P < .01) than the control group at 10% of MVIC. For MVIC, the CAI group displayed less force output in hip abduction than the uninjured group (P < .0001). CONCLUSIONS Patients with CAI were unable to control ongoing fine force (10% and 30% of MVIC) through a feedback mechanism during an active test. These findings suggested that deficits in sensorimotor control predisposed patients with CAI to injury positions because they had difficulty integrating the peripheral information and correcting their movements in relation to visual information.
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Affiliation(s)
- Hyunwook Lee
- Department of Exercise Sciences, Brigham Young University, Provo, UT
| | - S Jun Son
- Graduate School of Sports Medicine, CHA University, Seongnam-si, Korea
| | - Hyunsoo Kim
- Department of Kinesiology, West Chester University, PA
| | - Seunguk Han
- Department of Exercise Sciences, Brigham Young University, Provo, UT
| | - Matthew Seeley
- Department of Exercise Sciences, Brigham Young University, Provo, UT
| | - J Ty Hopkins
- Department of Exercise Sciences, Brigham Young University, Provo, UT
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Cè E, Coratella G, Doria C, Rampichini S, Borrelli M, Longo S, Esposito F. No effect of passive stretching on neuromuscular function and maximum force-generating capacity in the antagonist muscle. Eur J Appl Physiol 2021; 121:1955-1965. [PMID: 33770238 PMCID: PMC8192325 DOI: 10.1007/s00421-021-04646-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 02/14/2021] [Indexed: 11/25/2022]
Abstract
Purpose The present study investigated whether or not passive stretching increases the force-generating capacity of the antagonist muscle, and the possible neuromuscular mechanisms behind. Methods To this purpose, the neuromuscular function accompanying the force-generating capacity was assessed in 26 healthy male volunteers after passive stretching and in a control session. Before and after passive intermittent static stretching of the plantar flexors consisting of five sets × 45 s + 15 s-rest, maximum voluntary isometric contraction (MVC) and surface electromyographic root mean square (sEMG RMS) were measured in the tibialis anterior (the antagonist muscle). Additionally, evoked V wave, H-reflex, and M wave were elicited by nerve stimulation at rest and during MVC. Ankle range of motion (ROM) and plantar flexors MVC and EMG RMS were measured to check for the effectiveness of the stretching manoeuvre. Results No change in MVC [p = 0.670; effect size (ES) − 0.03] and sEMG RMS/M wave during MVC (p = 0.231; ES − 0.09) was observed in the antagonist muscle after passive stretching. Similarly, no change in V wave (p = 0.531; ES 0.16), H-reflex at rest and during MVC (p = 0.656 and 0.597; ES 0.11 and 0.23, respectively) and M wave at rest and during MVC (p = 0.355 and 0.554; ES 0.04 and 0.01, respectively) was observed. An increase in ankle ROM (p < 0.001; ES 0.55) and a decrease in plantar flexors MVC (p < 0.001; ES − 1.05) and EMG RMS (p < 0.05; ES − 1.72 to − 0.13 in all muscles) indicated the effectiveness of stretching protocol. Conclusion No change in the force-generating capacity and neuromuscular function of the antagonist muscle after passive stretching was observed.
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Affiliation(s)
- Emiliano Cè
- Department of Biomedical Sciences for Health, Università degli Studi di Milano, Via Giuseppe Colombo 71, 20133, Milano, Italy
- IRCSS Galeazzi Orthopaedic Institute, Milano, Italy
| | - Giuseppe Coratella
- Department of Biomedical Sciences for Health, Università degli Studi di Milano, Via Giuseppe Colombo 71, 20133, Milano, Italy.
| | - Christian Doria
- Department of Biomedical Sciences for Health, Università degli Studi di Milano, Via Giuseppe Colombo 71, 20133, Milano, Italy
| | - Susanna Rampichini
- Department of Biomedical Sciences for Health, Università degli Studi di Milano, Via Giuseppe Colombo 71, 20133, Milano, Italy
| | - Marta Borrelli
- Department of Biomedical Sciences for Health, Università degli Studi di Milano, Via Giuseppe Colombo 71, 20133, Milano, Italy
| | - Stefano Longo
- Department of Biomedical Sciences for Health, Università degli Studi di Milano, Via Giuseppe Colombo 71, 20133, Milano, Italy
| | - Fabio Esposito
- Department of Biomedical Sciences for Health, Università degli Studi di Milano, Via Giuseppe Colombo 71, 20133, Milano, Italy
- IRCSS Galeazzi Orthopaedic Institute, Milano, Italy
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11
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Magalhães IEJ, Burgo VC, Neto RB, Mezzarane RA. Changes in the input-output relation of the Hoffmann reflex recruitment curve after submaximal fatiguing contraction of the antagonist muscles. Somatosens Mot Res 2020; 38:54-59. [PMID: 33169647 DOI: 10.1080/08990220.2020.1845135] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
PURPOSE The central nervous system adapts strategies to compensate the decreased motor capacities of a fatigued muscle. However, data on neurophysiological adaptations of muscles other than those under fatigue are scarce. The present study was designed to evaluate the effects of submaximal fatiguing contraction (leading to a task failure) induced in ankle dorsiflexors muscles on the excitability of the Hoffmann reflex (H-reflex) of an ankle plantarflexor (soleus muscle). MATERIALS AND METHODS Twenty-three physically active males (75.5 ± 8.3 kg; 1.77 ± 0.08 m; 27.0 ± 8.0 years) were asked to maintain the contraction level of the right ankle dorsiflexors at 60% of the maximal isometric voluntary contraction (MIVC). Task failure was defined when the force level dropped below 40% MIVC for 5 consecutive seconds. The input-output relation of the ascending limb of the recruitment curve of the soleus H-reflex was examined at 0 min, 5 min, 10 min, 15 min and 20 min after the task failure. RESULTS The amplitude parameter representing the first recruited motoneurons (threshold H-reflex - H@th) was significantly higher at 5 min, 10 min, 15 min and 20 min after task failure as compared to control (Hth) (p < 0.05). On the other hand, the parameter that represents the activation of the relatively higher threshold motoneurons (H@100) was reduced (as compared to control - H100), but only at 20 min after the task failure (p < 0.05). CONCLUSIONS These results suggest differential reflex modulation of the soleus H-reflex after fatigue of the ankle dorsiflexors, that probably reflects neuronal adaptations underlying motor control around the ankle joint.
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Affiliation(s)
- Igor E J Magalhães
- Laboratory of Signal Processing and Motor Control, Universidade de Brasília-UnB, Brasília, Brazil
| | - Vinícius C Burgo
- Laboratory of Signal Processing and Motor Control, Universidade de Brasília-UnB, Brasília, Brazil
| | - Roque B Neto
- Laboratory of Signal Processing and Motor Control, Universidade de Brasília-UnB, Brasília, Brazil
| | - Rinaldo A Mezzarane
- Laboratory of Signal Processing and Motor Control, Universidade de Brasília-UnB, Brasília, Brazil
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12
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Pereira HM, de Lima FF, Silva BM, Kohn AF. Sex differences in fatigability after ischemic preconditioning of non-exercising limbs. Biol Sex Differ 2020; 11:59. [PMID: 33109241 PMCID: PMC7590792 DOI: 10.1186/s13293-020-00338-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 10/18/2020] [Indexed: 12/11/2022] Open
Abstract
Background Ischemic preconditioning (IPC) is suggested to decrease fatigability in some individuals but not others. Sex differences in response to IPC may account for this variability and few studies systematically investigated the effects of IPC in men and women. The goal of this study was to determine if time to task failure, perception of pain, and neuromuscular mechanisms of fatigability were altered by IPC in men and women. Methods Ten women (29 ± 5 years old) and 10 men (28 ± 6 years old) performed isometric contractions with the plantar flexor muscles of the dominant leg at 20% of maximal voluntary contraction until task failure. We used a repeated measures design where each individual performed 3 randomized and counterbalanced test sessions: (A) IPC session, cuff inflation and deflation (5 min each repeated 3 times) performed before the exercise by inflating cuffs to the non-dominant leg and arm; (B) sham session, cuffs were inflated for a short period (1 min); and (C) control session, no cuffs were involved. Results Compared with control, IPC increased time to task failure in men (mean difference, 5 min; confidence interval (CI) of mean difference, 2.2; 7.8 min; P = 0.01) but not women (mean difference, − 0.6 min; CI of mean difference, − 3.5; 2.4 min; P = 0.51). In men, but not women, the IPC-induced increase in time to task failure was associated with lower response to pressure pain (r = − 0.79). IPC further exposed sex differences in arterial pressure during fatiguing contractions (session × sex: P < 0.05). Voluntary activation, estimated with the twitch interpolation technique, and presynaptic inhibition of leg Ia afferents were not altered after IPC for men and women. The tested variables were not altered with sham. Conclusions The ergogenic effect of IPC on time to task failure was observed only in men and it was associated with reductions in the perception of pain. This pilot data suggest the previously reported inter-individual variability in exercise-induced fatigability after IPC could be a consequence of the sex and individual response to pain.
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Affiliation(s)
- Hugo M Pereira
- Department of Health and Exercise Science, University of Oklahoma, 1401 Asp Ave, Norman, OK, 73019, USA.
| | - Felipe F de Lima
- Biomedical Engineering Laboratory/EPUSP, University of São Paulo, São Paulo, SP, Brazil
| | - Bruno M Silva
- Department of Physiology, Federal University of São Paulo, São Paulo, SP, Brazil
| | - André F Kohn
- Biomedical Engineering Laboratory/EPUSP, University of São Paulo, São Paulo, SP, Brazil
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13
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Jeon S, Miller WM, Ye X. A Comparison of Motor Unit Control Strategies between Two Different Isometric Tasks. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2020; 17:ijerph17082799. [PMID: 32325707 PMCID: PMC7215511 DOI: 10.3390/ijerph17082799] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 04/12/2020] [Accepted: 04/15/2020] [Indexed: 11/17/2022]
Abstract
Background: This study examined the motor unit (MU) control strategies for non-fatiguing isometric elbow flexion tasks at 40% and 70% maximal voluntary isometric contraction. Methods: Nineteen healthy individuals performed two submaximal tasks with similar torque levels: contracting against an immovable object (force task), and maintaining the elbow joint angle against an external load (position task). Surface electromyographic (EMG) signals were collected from the agonist and antagonist muscles. The signals from the agonist were decomposed into individual action potential trains. The linear regression analysis was used to examine the MU recruitment threshold (RT) versus mean firing rates (MFR), and RT versus derecruitment threshold (DT) relationships. Results: Both agonist and antagonist muscles’ EMG amplitudes did not differ between two tasks. The linear slopes of the MU RT versus MFR and RT versus DT relationships during the position task were more negative (p = 0.010) and more positive (p = 0.023), respectively, when compared to the force task. Conclusions: To produce a similar force output, the position task may rely less on the recruitment of relatively high-threshold MUs. Additionally, as the force output decreases, MUs tend to derecruit at a higher force level during the position task.
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Affiliation(s)
| | | | - Xin Ye
- Correspondence: ; Tel.: +1-662-915-1630
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14
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Changes in the quadriceps spinal reflex pathway after repeated sprint cycling are not influenced by ischemic preconditioning. Eur J Appl Physiol 2020; 120:1189-1202. [PMID: 32239310 DOI: 10.1007/s00421-020-04359-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Accepted: 03/24/2020] [Indexed: 12/11/2022]
Abstract
PURPOSE We examined the effect of ischemic preconditioning (IPC) on changes in muscle force, activation, and the spinal reflex pathway during and after repeated sprint cycling. METHODS Eight recreationally active men (high-intensity cardiorespiratory training > 3 times per week, > 6 months) completed two exercise sessions (5 sets of 5 cycling sprints, 150% max W), preceded by either IPC (3 × 5 min leg occlusions at 220 mmHg) or SHAM (3 × 5 min at 20 mmHg). Knee extensor maximal force and rate of force were measured before (PRE), immediately post (POST), 1H, and 24H after cycling. Twitch interpolation and resting potentiated twitches were applied to estimate voluntary activation and muscle contractility, respectively. Quadriceps H-reflex recruitment curves were collected at all time-points using 10 Hz doublet stimulation to allow estimation of H-reflex post-activation depression. Surface electromyograms and tissue oxygenation (via near-infrared spectroscopy) were continuously recorded during cycling. RESULTS IPC did not affect any measure of neuromuscular function or performance during cycling. Maximal force and muscle contractility were significantly lower at POST and 1H compared to PRE and 24H by up to 50% (p < 0.01). Maximal force was lower than PRE at 24H by 8.7% (p = 0.028). Voluntary activation and rate of force were unchanged. A rightwards shift was observed for the H-reflex recruitment curve POST, and post-activation depression was higher than all other time-points at 24H (p < 0.05). Muscle activation and oxygenation decreased during cycling. CONCLUSIONS IPC has a nominal effect on mechanisms associated with neuromuscular function during and after exercise in healthy populations.
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15
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Pearcey GEP, Sun Y, Zehr EP. Plantarflexion force is amplified with sensory stimulation during ramping submaximal isometric contractions. J Neurophysiol 2020; 123:1427-1438. [PMID: 32159422 DOI: 10.1152/jn.00650.2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Stimulating cutaneous nerves, causing tactile sensations, reduces the perceived heaviness of an object, suggesting that either descending commands are facilitated or the perception of effort is reduced when tactile sensation is enhanced. Sensory stimulation can also mitigate decrements in motor output and spinal cord excitability that occur with fatigue. The effects of sensory stimulation applied with coincident timing of voluntary force output, however, are yet to be examined. Therefore, the purpose of this study was to examine effects of sensory enhancement to nerves innervating opposed skin areas of the foot (top or bottom) on force production during voluntary plantarflexion or dorsiflexion contractions. Stimulation trains were applied for 2 s at either a uniform 150 Hz or a modulated frequency that increased linearly from 50 to 150 Hz and were delivered at the initiation of the contraction. Participants were instructed to perform a ramp contraction [~10% maximal voluntary contraction (MVC)/s] to ~20% MVC and then to hold ~20% MVC for 2 s while receiving real-time visual feedback. Cutaneous reflexes were evoked 75 ms after initiating the hold (75 ms after sensory enhancement ended). Force output was greater for all sensory-enhanced conditions compared with control during plantarflexion; however, force output was not amplified during dorsiflexion. Cutaneous reflexes evoked after sensory enhancement were unaltered. These results indicate that sensory enhancement can amplify plantarflexion but not dorsiflexion, likely as a result of differences in neuroanatomical projections to the flexor and extensor motor pools. Further work is required to elucidate the mechanisms of enhanced force during cutaneous stimulation.NEW & NOTEWORTHY The efficacy of behaviorally timed sensory stimulation to enhance sensations and amplify force output has not been examined. Here we show cutaneous nerve sensory stimulation can amplify plantarflexion force output. This amplification in force occurs irrespective of whether the cutaneous field that is stimulated resides on the surface that is producing the force or the opposing surface. This information may provide insights for the development of technologies to improve performance and/or rehabilitation training.
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Affiliation(s)
- Gregory E P Pearcey
- Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, British Columbia, Canada.,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, British Columbia, Canada.,Centre for Biomedical Research, University of Victoria, Victoria, British Columbia, Canada
| | - Yao Sun
- Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, British Columbia, Canada.,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, British Columbia, Canada.,Centre for Biomedical Research, University of Victoria, Victoria, British Columbia, Canada
| | - E Paul Zehr
- Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, British Columbia, Canada.,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, British Columbia, Canada.,Centre for Biomedical Research, University of Victoria, Victoria, British Columbia, Canada.,Division of Medical Sciences, University of Victoria, Victoria, British Columbia, Canada.,Zanshin Consulting, Inc., Victoria, British Columbia, Canada
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16
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Oza PD, Dudley-Javoroski S, Shields RK. Sustained submaximal contraction yields biphasic modulation of soleus Post-activation depression in healthy humans. Scand J Med Sci Sports 2019; 29:944-951. [PMID: 30892718 DOI: 10.1111/sms.13421] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 02/01/2019] [Accepted: 03/14/2019] [Indexed: 12/23/2022]
Abstract
The amplitude of the H-reflex during the development and progression of fatigue reflects a complex interplay between central and peripheral factors. The purpose of this study is to characterize H-reflex homosynaptic post-activation depression (PAD) in an online fashion during a sustained submaximal fatigue task. The task required a high motor output in order to increase the likelihood of creating partial muscle ischemia with accumulation of fatigue metabolites, an important potential inhibitory influence upon the H-reflex during the progression of fatigue. Eleven subjects without neurologic impairment maintained volitional, isometric plantar flexion at 60% of maximal voluntary contraction until exhaustion. A paired-pulse stimulus (2 Hz) was delivered to the tibial nerve to elicit paired H-reflexes before, during, and after the fatigue protocol. The normalized amplitude of the second H-reflex (depression ratio) served as an estimate of PAD. Depression ratio increased during the first half of the fatigue protocol (P < 0.001), indicating a diminution of PAD, and then returned as exhaustion approached. The biphasic behavior of homosynaptic H-reflex depression during fatigue to exhaustion suggests a role for metabolic mediators of post-activation depression during fatigue.
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Affiliation(s)
- Preeti D Oza
- Department of Physical Therapy, University of the Pacific, Stockton, California
| | - Shauna Dudley-Javoroski
- Department of Physical Therapy Rehabilitation Science, Roy J. and Lucille A. Carver College of Medicine, The University of Iowa, Iowa City, Iowa
| | - Richard K Shields
- Department of Physical Therapy Rehabilitation Science, Roy J. and Lucille A. Carver College of Medicine, The University of Iowa, Iowa City, Iowa
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17
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Jeon S, Ye X, Miller WM. Sex comparisons of agonist and antagonist muscle electromyographic parameters during two different submaximal isometric fatiguing tasks. Physiol Rep 2019; 7:e14022. [PMID: 30839175 PMCID: PMC6401663 DOI: 10.14814/phy2.14022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 02/03/2019] [Accepted: 02/11/2019] [Indexed: 02/03/2023] Open
Abstract
To examine the task failure time of the force- and position-based submaximal elbow flexion fatiguing tasks for both sexes, twelve men and eight women visited the laboratory for two separate experimental occasions. During the experiment, they pulled against a rigid restraint for the force task and maintained a constant elbow joint angle to support an equivalent inertial load for the position task. For both fatiguing tasks (50% of the isometric strength at the elbow joint angle of 135 degree), the task failure time, along with the surface electromyographic (EMG) amplitude and mean frequency (MNF) were measured. The average failure time was longer for the force task than that for the position task (sexes combined: 39.6 ± 16.6 sec vs. 33.9 ± 14.9 sec, P = 0.033). In addition, men were overall less fatigable than women (tasks combined: 42.0 ± 14.7 sec vs. 28.7 ± 10.3 sec, P = 0.020). The multiple regression analyses showed that the task failure time in women was solely predicted by the rate of change of the triceps EMG MNF. Thus, more fatigability of women in this study was likely due to the quicker fatiguing rate of the antagonist triceps brachii muscle. Different from most previous studies that have used 90-degree elbow joint angle, the current 135-degree joint angle setup might have created a situation where greater muscle activity from the related muscles (e.g., the antagonist) were required for women than for men to stabilize the joint, thereby resulting in a shorter task failure time.
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Affiliation(s)
- Sunggun Jeon
- Department of Health, Exercise Science, and Recreation ManagementThe University of MississippiUniversityMississippi
| | - Xin Ye
- Department of Health, Exercise Science, and Recreation ManagementThe University of MississippiUniversityMississippi
| | - William M. Miller
- Department of Health, Exercise Science, and Recreation ManagementThe University of MississippiUniversityMississippi
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18
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Collins BW, Pearcey GE, Buckle NC, Power KE, Button DC. Neuromuscular fatigue during repeated sprint exercise: underlying physiology and methodological considerations. Appl Physiol Nutr Metab 2018; 43:1166-1175. [DOI: 10.1139/apnm-2018-0080] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Neuromuscular fatigue occurs when an individual’s capacity to produce force or power is impaired. Repeated sprint exercise requires an individual to physically exert themselves at near-maximal to maximal capacity for multiple short-duration bouts, is extremely taxing on the neuromuscular system, and consequently leads to the rapid development of neuromuscular fatigue. During repeated sprint exercise the development of neuromuscular fatigue is underlined by a combination of central and peripheral fatigue. However, there are a number of methodological considerations that complicate the quantification of the development of neuromuscular fatigue. The main goal of this review is to synthesize the results from recent investigations on the development of neuromuscular fatigue during repeated sprint exercise. Hence, we summarize the overall development of neuromuscular fatigue, explain how recovery time may alter the development of neuromuscular fatigue, outline the contributions of peripheral and central fatigue to neuromuscular fatigue, and provide some methodological considerations for quantifying neuromuscular fatigue during repeated sprint exercise.
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Affiliation(s)
- Brandon W. Collins
- BioMedical Sciences, Faculty of Medicine, Memorial University, St. John’s, NL A1C 5S7, Canada
| | - Gregory E.P. Pearcey
- Rehabilitation Neuroscience Laboratory and Centre for Biomedical Research, University of Victoria, Victoria, BC V8W 2Y2, Canada
- Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC V5Z 1M9, Canada
| | - Natasha C.M. Buckle
- School of Human Kinetics and Recreation and BioMedical Sciences, Faculty of Medicine, Memorial University, St. John’s, NL A1C 5S7, Canada
| | - Kevin E. Power
- School of Human Kinetics and Recreation and BioMedical Sciences, Faculty of Medicine, Memorial University, St. John’s, NL A1C 5S7, Canada
| | - Duane C. Button
- School of Human Kinetics and Recreation and BioMedical Sciences, Faculty of Medicine, Memorial University, St. John’s, NL A1C 5S7, Canada
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19
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Pearcey GEP, Noble SA, Munro B, Zehr EP. Spinal Cord Excitability and Sprint Performance Are Enhanced by Sensory Stimulation During Cycling. Front Hum Neurosci 2017; 11:612. [PMID: 29326570 PMCID: PMC5741677 DOI: 10.3389/fnhum.2017.00612] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Accepted: 12/04/2017] [Indexed: 12/18/2022] Open
Abstract
Spinal cord excitability, as assessed by modulation of Hoffmann (H-) reflexes, is reduced with fatiguing isometric contractions. Furthermore, spinal cord excitability is reduced during non-fatiguing arm and leg cycling. Presynaptic inhibition of Ia terminals is believed to contribute to this suppression of spinal cord excitability. Electrical stimulation to cutaneous nerves reduces Ia presynaptic inhibition, which facilitates spinal cord excitability, and this facilitation is present during arm cycling. Although it has been suggested that reducing presynaptic inhibition may prolong fatiguing contractions, it is unknown whether sensory stimulation can alter the effects of fatiguing exercise on performance or spinal cord excitability. Thus, the aim of this experiment was to determine if sensory stimulation can interfere with fatigue-related suppression of spinal cord excitability, and alter fatigue rates during cycling sprints. Thirteen participants randomly performed three experimental sessions that included: unloaded cycling with sensory stimulation (CONTROL + STIM), sprints with sensory stimulation (SPRINT + STIM) and sprints without stimulation (SPRINT). Seven participants also performed a fourth session (CONTROL), which consisted of unloaded cycling. During SPRINT and SPRINT + STIM, participants performed seven, 10 s cycling sprints interleaved with 3 min rest. For CONTROL and CONTROL + STIM, participants performed unloaded cycling for ~30 min. During SPRINT + STIM and CONTROL + STIM, participants received patterned sensory stimulation to nerves of the right foot. H-reflexes and M-waves of the right soleus were evoked by stimulation of the tibial nerve at multiple time points throughout exercise. Sensory stimulation facilitated soleus H-reflexes during unloaded cycling, whereas sprints suppressed soleus H-reflexes. While receiving sensory stimulation, there was less suppression of soleus H-reflexes and slowed reduction in average power output, compared to sprints without stimulation. These results demonstrate that sensory stimulation can substantially mitigate the fatiguing effects of sprints.
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Affiliation(s)
- Gregory E P Pearcey
- Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, BC, Canada.,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada.,Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada
| | - Steven A Noble
- Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, BC, Canada.,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada.,Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada
| | - Bridget Munro
- Nike Exploration Team Sport Research Laboratory, Nike Inc., Beaverton, OR, United States
| | - E Paul Zehr
- Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, BC, Canada.,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada.,Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada.,Division of Medical Sciences, University of Victoria, Victoria, BC, Canada
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20
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Marshall PWM, Cross R, Haynes M. The fatigue of a full body resistance exercise session in trained men. J Sci Med Sport 2017; 21:422-426. [PMID: 28716692 DOI: 10.1016/j.jsams.2017.06.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Revised: 04/04/2017] [Accepted: 06/27/2017] [Indexed: 12/23/2022]
Abstract
OBJECTIVES We examined the fatigue and recovery for 48h following a full-body resistance exercise session in trained men. DESIGN Experimental cross-sectional study. METHODS Eight resistance trained men volunteered to participate (mean±SD; age 27.0±6.0 years, height 1.79±0.05m, weight 81.8±6.8kg, training experience 7.8±5.0 years). Fatigue and pain was measured before, after, 1h post, 24h and 48h post the full-body resistance exercise session, which was based on in-season models used in contact team sports (e.g. AFL, NRL). Other measures included maximal torque and rate of torque development, central motor output (quadriceps muscle activation, voluntary activation, H-reflexes), and muscle contractility (evoked twitch responses). Linear mixed-model ANOVA procedures were used for data analysis. RESULTS Fatigue, soreness, and muscle pain did not return to pre-exercise levels until after 48h rest. Quadriceps maximal torque and muscle contractility were reduced from pre-exercise (p<0.01), and did not return to pre-exercise levels until 24h. Early rates of torque development and muscle activation were unchanged. The amplitude and slope of the normalized quadriceps H-reflex was higher immediately after exercise (p<0.05). CONCLUSIONS Full-body resistance exercise including multiple lower limb movements immediately reduced maximal torque, muscle contractility, and increased pain. While recovery of voluntary and evoked torque was complete within a day, 48h rest was required for fatigue and pain to return to baseline. Maximal voluntary effort may be compromised for lower-limb training (i.e. sprinting, jumping) prescribed in the 48h after the session.
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Affiliation(s)
- Paul W M Marshall
- Human Performance Laboratory, School of Science and Health, Western Sydney University, Australia.
| | - Rebecca Cross
- Human Performance Laboratory, School of Science and Health, Western Sydney University, Australia
| | - Michael Haynes
- Human Performance Laboratory, School of Science and Health, Western Sydney University, Australia
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21
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Russ DW, Ross AJ, Clark BC, Thomas JS. The Effects of Task Type on Time to Task Failure During Fatigue: A Modified Sørensen Test. J Mot Behav 2017; 50:96-103. [DOI: 10.1080/00222895.2017.1286628] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- David W. Russ
- School of Rehabilitation and Communication Sciences, Division of Physical Therapy, Ohio University, Athens
- Ohio Musculoskeletal & Neurological Institute, Ohio University, Athens
| | - Andrew J. Ross
- School of Rehabilitation and Communication Sciences, Division of Physical Therapy, Ohio University, Athens
| | - Brian C. Clark
- Ohio Musculoskeletal & Neurological Institute, Ohio University, Athens
- Department of Biomedical Sciences, Ohio University Heritage College of Osteopathic Medicine, Athens
| | - James S. Thomas
- School of Rehabilitation and Communication Sciences, Division of Physical Therapy, Ohio University, Athens
- Ohio Musculoskeletal & Neurological Institute, Ohio University, Athens
- Department of Biomedical Sciences, Ohio University Heritage College of Osteopathic Medicine, Athens
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22
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Dynamic Fatigue Does Not Alter Soleus H-Reflexes Conditioned by Homonymous or Heteronymous Pathways. Motor Control 2016; 21:345-358. [PMID: 27736308 DOI: 10.1123/mc.2016-0030] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
H-reflex depression (diminution of amplitude after a conditioning stimulus) is mediated presynaptically and therefore can help distinguish central versus peripheral mechanisms of fatigue. We examined the effects of a dynamic exercise protocol on H-reflex depression using two conditioning methods: homonymous conditioning (paired-pulse tibial nerve stimulation); and heteronymous conditioning (common peroneal nerve stimulation). Ten subjects performed dynamic contractions of the soleus muscle through 30° ankle range of motion. The concentric phase required a target force of 10% of maximum voluntary isometric contraction (MVIC) and the eccentric phase force target was 80% MVIC. Fatigue persisted for >20 min after cessation of the exercise. Compared with prefatigue values, the dynamic fatigue protocol did not increase presynaptic inhibition after either homonymous or heteronymous conditioning. Peak to peak amplitude of unconditioned H-reflexes was likewise unchanged despite a long term depression of muscle force (long duration fatigue). These results suggest that persistent fatigue after dynamic exercise is attributed to muscle changes and not altered spinal mechanisms.
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23
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Gould JR, Cleland BT, Mani D, Amiridis IG, Enoka RM. Motor unit activity in biceps brachii of left-handed humans during sustained contractions with two load types. J Neurophysiol 2016; 116:1358-65. [PMID: 27334949 DOI: 10.1152/jn.00147.2016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 06/18/2016] [Indexed: 11/22/2022] Open
Abstract
The purpose of the study was to compare the discharge characteristics of single motor units during sustained isometric contractions that required either force or position control in left-handed individuals. The target force for the two sustained contractions (24.9 ± 10.5% maximal force) was identical for each biceps brachii motor unit (n = 32) and set at 4.7 ± 2.0% of maximal voluntary contraction (MVC) force above its recruitment threshold (range: 0.5-41.2% MVC force). The contractions were not sustained to task failure, but the duration (range: 60-330 s) was identical for each motor unit and the decline in MVC force immediately after the sustained contractions was similar for the two tasks (force: 11.1% ± 13.7%; position: 11.6% ± 9.9%). Despite a greater increase in the rating of perceived exertion during the position task (task × time interaction, P < 0.006), the amplitude of the surface-recorded electromyogram for the agonist and antagonist muscles increased similarly during the two tasks. Nonetheless, mean discharge rate of the biceps brachii motor units declined more during the position task (task × time interaction, P < 0.01) and the variability in discharge times (coefficient of variation for interspike interval) increased only during the position task (task × time interaction, P < 0.008). When combined with the results of an identical study on right-handers (Mottram CJ, Jakobi JM, Semmler JG, Enoka RM. J Neurophysiol 93: 1381-1392, 2005), the findings indicate that handedness does not influence the adjustments in biceps brachii motor unit activity during sustained submaximal contractions requiring either force or position control.
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Affiliation(s)
- Jeffrey R Gould
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado; and
| | - Brice T Cleland
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado; and
| | - Diba Mani
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado; and
| | - Ioannis G Amiridis
- Department of Physical Education and Sport Sciences, Aristotle University of Thessaloniki, Serres, Greece
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado; and
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24
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Chung-Hoon K, Tracy BL, Dibble LE, Marcus RL, Burgess P, LaStayo PC. The Association Between Knee Extensor Force Steadiness, Force Accuracy, and Mobility in Older Adults Who Have Fallen. J Geriatr Phys Ther 2016; 39:1-7. [PMID: 25695470 PMCID: PMC4540703 DOI: 10.1519/jpt.0000000000000044] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
BACKGROUND Older adults often experience limited mobility, lower extremity muscle weakness, and increased fall risk. Furthermore, when older adults perform tasks that require control of submaximal force, impairments in their ability to maintain steady and accurate force output have been reported. Such problems may be related to deteriorating levels of mobility, particularly in older adults who have fallen. PURPOSE The purpose of this study was to determine whether an association exists between muscle force steadiness (MFS) or muscle force accuracy (MFA) of the knee extensors and mobility in older adults who have fallen. METHODS Twenty older adults ((Equation is included in full-text article.)= 77.5 ± 7 years, 5 males and 15 females) with 2 or more comorbid conditions and who experienced a fall in the past year underwent assessment of maximal voluntary isometric contraction of the knee extensors. A submaximal target force of 50% of their maximal voluntary isometric contraction was used to determine concentric and eccentric (ECC) steadiness (the fluctuations in force production) and accuracy (the average distance of the mean force from the target force) measures. Mobility was indicated by the 6-minute walk test, the Timed Up and Go, stair ascent, and stair descent tests. Correlation analysis was used to assess the relationship between measures of muscle force control and mobility. RESULTS The correlations between muscle force steadiness and mobility were not significant (P > .05) for either contraction type. However, MFA during ECC contractions only was correlated significantly with all measures of mobility-6 minute walk test (r = -0.48; P = .03), Timed Up and Go (r = 0.68; P = .01), stair ascent (r = 0.60; P = .01), and stair descent (r = 0.75; P < .01). CONCLUSION The identification of the relationship between ECC MFA and mobility in older adults who have fallen is novel. Although the correlations are not causal, these relationships suggest that inaccurate force output during ECC contractions of the knee extensors is linked to impaired mobility.
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Affiliation(s)
- Kaiwi Chung-Hoon
- University of Utah, Department of Physical Therapy, 520 Wakara Way, SLC, UT 84108
| | - Brian L. Tracy
- Colorado State University, Department of Health and Exercise Science, 220 Moby-B Complex, Fort Collins, CO 80523
| | - Leland E. Dibble
- University of Utah, Department of Physical Therapy, 520 Wakara Way, SLC, UT 84108
| | - Robin L. Marcus
- University of Utah, Department of Physical Therapy, 520 Wakara Way, SLC, UT 84108
| | - Paul Burgess
- University of Utah, Department of Physical Therapy, 520 Wakara Way, SLC, UT 84108
| | - Paul C. LaStayo
- University of Utah, Department of Physical Therapy, 520 Wakara Way, SLC, UT 84108
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Magalhães FH, Elias LA, da Silva CR, de Lima FF, de Toledo DR, Kohn AF. D1 and D2 Inhibitions of the Soleus H-Reflex Are Differentially Modulated during Plantarflexion Force and Position Tasks. PLoS One 2015; 10:e0143862. [PMID: 26599909 PMCID: PMC4658029 DOI: 10.1371/journal.pone.0143862] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 11/10/2015] [Indexed: 01/05/2023] Open
Abstract
Presynaptic inhibition (PSI) has been shown to modulate several neuronal pathways of functional relevance by selectively gating the connections between sensory inputs and spinal motoneurons, thereby regulating the contribution of the stretch reflex circuitry to the ongoing motor activity. In this study, we investigated whether a differential regulation of Ia afferent inflow by PSI may be associated with the performance of two types of plantarflexion sensoriomotor tasks. The subjects (in a seated position) controlled either: 1) the force level exerted by the foot against a rigid restraint (force task, FT); or 2) the angular position of the ankle when sustaining inertial loads (position task, PT) that required the same level of muscle activation observed in FT. Subjects were instructed to maintain their force/position at target levels set at ~10% of maximum isometric voluntary contraction for FT and 90° for PT, while visual feedback of the corresponding force/position signals were provided. Unconditioned H-reflexes (i.e. control reflexes) and H-reflexes conditioned by electrical pulses applied to the common peroneal nerve with conditioning-to-test intervals of 21 ms and 100 ms (corresponding to D1 and D2 inhibitions, respectively) were evoked in a random fashion. A significant main effect for the type of the motor task (FT vs PT) (p = 0.005, η2p = 0.603) indicated that PTs were undertaken with lower levels of Ia PSI converging onto the soleus motoneuron pool. Additionally, a significant interaction between the type of inhibition (D1 vs D2) and the type of motor task (FT vs PT) (p = 0.038, η2p = 0.395) indicated that D1 inhibition was associated with a significant reduction in PSI levels from TF to TP (p = 0.001, η2p = 0.731), whereas no significant difference between the tasks was observed for D2 inhibition (p = 0.078, η2p = 0.305). These results suggest that D1 and D2 inhibitions of the soleus H-reflex are differentially modulated during the performance of plantarflexion FT and PT. The reduced level of ongoing PSI during PT suggests that, in comparison to FT, there is a larger reliance on inputs from muscle spindles primary afferents when the neuromuscular system is required to maintain position-controlled plantarflexion contractions.
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Affiliation(s)
- Fernando Henrique Magalhães
- School of Arts, Sciences and Humanities, Universidade de São Paulo, EACH-USP, São Paulo, SP, Brazil.,Biomedical Engineering Laboratory, Universidade de São Paulo, EPUSP, Avenida Professor Luciano Gualberto, Travessa 3, n.158, São Paulo, SP, Brazil.,Neuroscience Program, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Leonardo Abdala Elias
- Biomedical Engineering Laboratory, Universidade de São Paulo, EPUSP, Avenida Professor Luciano Gualberto, Travessa 3, n.158, São Paulo, SP, Brazil.,Department of Biomedical Engineering, School of Electrical and Computer Engineering, University of Campinas, Campinas, SP, Brazil
| | - Cristiano Rocha da Silva
- Biomedical Engineering Laboratory, Universidade de São Paulo, EPUSP, Avenida Professor Luciano Gualberto, Travessa 3, n.158, São Paulo, SP, Brazil.,Neuroscience Program, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Felipe Fava de Lima
- Biomedical Engineering Laboratory, Universidade de São Paulo, EPUSP, Avenida Professor Luciano Gualberto, Travessa 3, n.158, São Paulo, SP, Brazil
| | - Diana Rezende de Toledo
- Biomedical Engineering Laboratory, Universidade de São Paulo, EPUSP, Avenida Professor Luciano Gualberto, Travessa 3, n.158, São Paulo, SP, Brazil
| | - André Fabio Kohn
- Biomedical Engineering Laboratory, Universidade de São Paulo, EPUSP, Avenida Professor Luciano Gualberto, Travessa 3, n.158, São Paulo, SP, Brazil.,Neuroscience Program, Universidade de São Paulo, São Paulo, SP, Brazil
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Marshall PWM, Finn HT, Siegler JC. The Magnitude of Peripheral Muscle Fatigue Induced by High and Low Intensity Single-Joint Exercise Does Not Lead to Central Motor Output Reductions in Resistance Trained Men. PLoS One 2015; 10:e0140108. [PMID: 26439261 PMCID: PMC4595208 DOI: 10.1371/journal.pone.0140108] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2015] [Accepted: 08/25/2015] [Indexed: 11/18/2022] Open
Abstract
Purpose To examine quadriceps muscle fatigue and central motor output during fatiguing single joint exercise at 40% and 80% maximal torque output in resistance trained men. Method Ten resistance trained men performed fatiguing isometric knee extensor exercise at 40% and 80% of maximal torque output. Maximal torque, rate of torque development, and measures of central motor output and peripheral muscle fatigue were recorded at two matched volumes of exercise, and after a final contraction performed to exhaustion. Central motor output was quantified from changes in voluntary activation, normalized surface electromyograms (EMG), and V-waves. Quadriceps muscle fatigue was assessed from changes in the size and shape of the resting potentiated twitch (Q.pot.tw). Central motor output during the exercise protocols was estimated from EMG and interpolated twitches applied during the task (VAsub). Results Greater reductions in maximal torque and rate of torque development were observed during the 40% protocol (p<0.05). Maximal central motor output did not change for either protocol. For the 40% protocol reductions from pre-exercise in rate and amplitude variables calculated from the Q.pot.tw between 66.2 to 70.8% (p<0.001) exceeded those observed during the 80% protocol (p<0.01). V-waves only declined during the 80% protocol between 56.8 ± 35.8% to 53.6 ± 37.4% (p<0.05). At the end of the final 80% contraction VAsub had increased from 91.2 ± 6.2% to 94.9 ± 4.7% (p = 0.005), but a greater increase was observed during the 40% contraction where VAsub had increased from 67.1 ± 6.1% to 88.9 ± 9.6% (p<0.001). Conclusion Maximal central motor output in resistance trained men is well preserved despite varying levels of peripheral muscle fatigue. Upregulated central motor output during the 40% contraction protocol appeared to elicit greater peripheral fatigue. V-waves declines during the 80% protocol suggest intensity dependent modulation of the Ia afferent pathway.
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Affiliation(s)
- Paul W. M. Marshall
- Human Performance Laboratory, School of Science and Health, University of Western Sydney, Sydney, Australia
- * E-mail:
| | - Harrison T. Finn
- Human Performance Laboratory, School of Science and Health, University of Western Sydney, Sydney, Australia
- Neuroscience Research Australia (NeuRA), Sydney, Australia
| | - Jason C. Siegler
- Human Performance Laboratory, School of Science and Health, University of Western Sydney, Sydney, Australia
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Stutzig N, Siebert T. Influence of joint position on synergistic muscle activity after fatigue of a single muscle head. Muscle Nerve 2015; 51:259-67. [PMID: 24890377 DOI: 10.1002/mus.24305] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 05/21/2014] [Accepted: 05/29/2014] [Indexed: 11/11/2022]
Abstract
INTRODUCTION We investigated synergistic muscle activity after fatigue of a single muscle in different joint positions. METHODS Two experimental groups (n = 12 each) performed maximal voluntary contractions (MVCs) before and after fatiguing the gastrocnemius lateralis (GL), using neuromuscular electrical stimulation (NMES). Neuromuscular tests, including muscle activity during MVC, H-reflex, and twitch interpolation, were performed. One group completed the experiment in a knee-extended position with the second group in a knee-flexed position. RESULTS In the knee-flexed position, the muscle activity increased in non-stimulated synergistic muscles. In contrast, in the knee-extended position, muscle activity of the synergistic muscles remained unaltered. The MVC force remained unaltered in the flexed position and decreased in the extended position. CONCLUSIONS Synergistic muscles compensate for the fatigued muscle in the flexed position but not in the extended position. Compensation mechanisms seem to depend on joint position.
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Affiliation(s)
- Norman Stutzig
- Exercise Science, Institute of Sport and Movement Science, University of Stuttgart, Allmandring 28, 70569, Stuttgart, Germany; Exercise Science, Institute of Sport Science, Friedrich Schiller University Jena, Seidelstraße 20, 07749 Jena, Germany
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Kirimoto H, Tamaki H, Suzuki M, Matsumoto T, Sugawara K, Kojima S, Onishi H. Sensorimotor modulation differs with load type during constant finger force or position. PLoS One 2014; 9:e108058. [PMID: 25233353 PMCID: PMC4169486 DOI: 10.1371/journal.pone.0108058] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 08/23/2014] [Indexed: 11/19/2022] Open
Abstract
During submaximal isometric contraction, there are two different load types: production of a constant force against a rigid restraint (force task), and maintenance of position against a constant load (position task). Previous studies reported that the time to task failure during a fatigue task was twice as long in the force task compared with the position task. Sensory feedback processing may contribute to these differences. The purpose of the current study was to determine the influence of load types during static muscle contraction tasks on the gating effect, i.e., attenuation of somatosensory-evoked potentials (SEPs) and the cortical silent period (cSP). Ten healthy subjects contracted their right first dorsal interosseus muscle by abducting their index finger for 90 s, to produce a constant force against a rigid restraint that was 20% of the maximum voluntary contraction (force task), or to maintain a constant position with 10° abduction of the metacarpophalangeal joint against the same load (position task). Somatosensory evoked potentials (SEPs) were recorded from C3' by stimulating either the right ulnar or median nerve at the wrist while maintaining contraction. The cortical silent period (cSP) was also elicited by transcranial magnetic stimulation. Reduction of the amplitude of the P45 component of SEPs was significantly larger during the position task than during the force task and under control rest conditions when the ulnar nerve, but not the median nerve, was stimulated. The position task had a significantly shorter cSP duration than the force task. These results suggest the need for more proprioceptive information during the position task than the force task. The shorter duration of the cSP during the position task may be attributable to larger amplitude of heteronymous short latency reflexes. Sensorimotor modulations may differ with load type during constant finger force or position tasks.
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Affiliation(s)
- Hikari Kirimoto
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan
| | - Hiroyuki Tamaki
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan
| | - Makoto Suzuki
- School of Allied Health Sciences, Kitasato University, Kanagawa, Japan
| | - Takuya Matsumoto
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan
- Graduate School of Health and Welfare, Niigata University of Health and Welfare, Niigata, Japan
| | - Kazuhiro Sugawara
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan
| | - Syo Kojima
- Graduate School of Health and Welfare, Niigata University of Health and Welfare, Niigata, Japan
- Tokyo Bay Rehabilitation Hospital, Chiba, Japan
| | - Hideaki Onishi
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan
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Williams PS, Hoffman RL, Clark BC. Cortical and spinal mechanisms of task failure of sustained submaximal fatiguing contractions. PLoS One 2014; 9:e93284. [PMID: 24667484 PMCID: PMC3965562 DOI: 10.1371/journal.pone.0093284] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 03/04/2014] [Indexed: 01/19/2023] Open
Abstract
In this and the subsequent companion paper, results are presented that collectively seek to delineate the contribution that supraspinal circuits have in determining the time to task failure (TTF) of sustained submaximal contractions. The purpose of this study was to compare adjustments in supraspinal and spinal excitability taken concurrently throughout the performance of two different fatigue tasks with identical mechanical demands but different TTF (i.e., force-matching and position-matching tasks). On separate visits, ten healthy volunteers performed the force-matching or position-matching task at 15% of maximum strength with the elbow flexors to task failure. Single-pulse transcranial magnetic stimulation (TMS), paired-pulse TMS, paired cortico-cervicomedullary stimulation, and brachial plexus electrical stimulation were delivered in a 6-stimuli sequence at baseline and every 2-3 minutes throughout fatigue-task performance. Contrary to expectations, the force-matching task TTF was 42% shorter (17.5 ± 7.9 min) than the position-matching task (26.9 ± 15.11 min; p<0.01); however, both tasks caused the same amount of muscle fatigue (p = 0.59). There were no task-specific differences for the total amount or rate of change in the neurophysiologic outcome variables over time (p>0.05). Therefore, failure occurred after a similar mean decline in motorneuron excitability developed (p<0.02, ES = 0.35-0.52) coupled with a similar mean increase in measures of corticospinal excitability (p<0.03, ES = 0.30-0.41). Additionally, the amount of intracortical inhibition decreased (p<0.03, ES = 0.32) and the amount of intracortical facilitation (p>0.10) and an index of upstream excitation of the motor cortex remained constant (p>0.40). Together, these results suggest that as fatigue develops prior to task failure, the increase in corticospinal excitability observed in relationship to the decrease in spinal excitability results from a combination of decreasing intracortical inhibition with constant levels of intracortical facilitation and upstream excitability that together eventually fail to provide the input to the motor cortex necessary for descending drive to overcome the spinal cord resistance, thereby contributing to task failure.
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Affiliation(s)
- Petra S. Williams
- Ohio Musculoskeletal & Neurological Institute (OMNI), Ohio University, Athens, Ohio, United States of America
- Department of Physical Therapy and Athletic Training, Northern Arizona University, Flagstaff, Arizona, United States of America
| | - Richard L. Hoffman
- Ohio Musculoskeletal & Neurological Institute (OMNI), Ohio University, Athens, Ohio, United States of America
| | - Brian C. Clark
- Ohio Musculoskeletal & Neurological Institute (OMNI), Ohio University, Athens, Ohio, United States of America
- Department of Biomedical Sciences, Ohio University, Athens, Ohio, United States of America
- Department of Geriatric Medicine and Gerontology, Ohio University, Athens, Ohio, United States of America
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Independent control of presynaptic inhibition by reticulospinal and sensory inputs at rest and during rhythmic activities in the cat. J Neurosci 2013; 33:8055-67. [PMID: 23637195 DOI: 10.1523/jneurosci.2911-12.2013] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
To be functionally relevant during movement, the transmission from primary afferents must be efficiently controlled by presynaptic inhibition. Sensory feedback, central pattern generators, and supraspinal structures can all evoke presynaptic inhibition, but we do not understand how these inputs interact during movement. Here, we investigated the convergence of inputs from the reticular formation and sensory afferents on presynaptic inhibitory pathways and their modulation at rest and during two fictive motor tasks (locomotion and scratch) in decerebrate cats. The amplitude of primary afferent depolarization (PAD), an estimate of presynaptic inhibition, was recorded in individual afferents with intra-axonal recordings and in a mix of afferents in lumbar dorsal rootlets (dorsal root potential [DRP]) with bipolar electrodes. There was no spatial facilitation between inputs from reticulospinal and sensory afferents with DRPs or PADs, indicating an absence of convergence. However, spatial facilitation could be observed by combining two sensory inputs, indicating that convergence was possible. Task-dependent changes in the amplitude of responses were similar for reticulospinal and sensory inputs, increasing during fictive locomotion and decreasing during fictive scratch. During fictive locomotion, DRP and PAD amplitudes evoked by reticulospinal inputs were increased during the flexion phase, whereas sensory-evoked DRPs and PADs showed maximal amplitude in either flexion or extension phases. During fictive scratch, the amplitudes of DRPs and PADs evoked by both sources were maximal in flexion. The absence of spatial facilitation and different phase-dependent modulation patterns during fictive locomotion are consistent with independent presynaptic inhibitory pathways for reticulospinal and sensory inputs.
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Rudroff T, Kalliokoski KK, Block DE, Gould JR, Klingensmith WC, Enoka RM. PET/CT imaging of age- and task-associated differences in muscle activity during fatiguing contractions. J Appl Physiol (1985) 2013; 114:1211-9. [PMID: 23412899 DOI: 10.1152/japplphysiol.01439.2012] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The study compared positron emission tomography/computed tomography (PET/CT) of [(18)F]-2-fluoro-2-deoxy-D-glucose ([(18)F]-FDG) uptake by skeletal muscles and the amount of muscle activity as indicated by surface electromyographic (EMG) recordings when young and old men performed fatiguing isometric contractions that required either force or position control. EMG signals were recorded from thigh muscles of six young men (26 ± 6 yr) and six old men (77 ± 6 yr) during fatiguing contractions with the knee extensors. PET/CT scans were performed immediately after task failure. Glucose uptake in 24 leg muscles, quantified as standardized uptake values, was greater for the old men after the force task and differed across tasks for the young men (force, 0.64 ± 0.3 g/ml; position, 0.73 ± 0.3 g/ml), but not the old men (force, 0.84 ± 0.3 g/ml; position, 0.79 ± 0.26 g/ml) (age × task interaction; P < 0.001). In contrast, the rate of increase in EMG amplitude for the agonist muscles was greater for the young men during the two contractions and there was no difference for either group of subjects in the rate of increase in EMG amplitude across the two tasks. The imaging estimates of glucose uptake indicated age- and task-dependent differences in the spatial distribution of [(18)F]-FDG uptake by skeletal muscles during fatiguing contractions. The findings demonstrate that PET/CT imaging of [(18)F]-FDG uptake, but not surface EMG recordings, detected the modulation of muscle activity across the fatiguing tasks by the young men but not the old men.
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Affiliation(s)
- Thorsten Rudroff
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado 80523-1582, USA.
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Gordon NM, Rudroff T, Enoka JA, Enoka RM. Handedness but not dominance influences variability in endurance time for sustained, submaximal contractions. J Neurophysiol 2012; 108:1501-10. [DOI: 10.1152/jn.01144.2011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of this study was to compare endurance time and accompanying neuromuscular adjustments when left- and right-handed subjects used the dominant and nondominant arms to sustain submaximal contractions that required either force or position control. Ten left-handed and 10 right-handed healthy adults (21 ± 5 yr) participated in the study. Each subject exerted a similar net torque about the elbow joint during the force and position tasks to achieve a target force of 20% maximal voluntary contraction (MVC) force (56 ± 18 N). MVC force declined to a similar level immediately after task failure for left- and right-handed subjects (27 ± 13 vs. 25 ± 15%, P = 0.9). Endurance time for the position task was similar for the dominant and nondominant arms (task × dominance interaction, P = 0.17). Although the difference in endurance time between the two tasks was similar for left-handed (136 ± 165 s) and right-handed individuals (92 ± 73 s, task × handedness interaction, P = 0.38), there was greater variance in the ratio of the endurance times for the force and position tasks for left-handed (0.77) than right-handed subjects (0.13, P < 0.001; see Fig. 2 ). Furthermore, endurance time for the force and position tasks was significantly correlated for right-handed subjects ( r2 = 0.62, P < 0.001), but not for left-handed subjects ( r2 = 0.004, P = 0.79). Multiple regression analyses identified sets of predictor variables for each endurance time, and these differed with handedness and task. Hand dominance, however, did not influence endurance time for either group of subjects. These findings indicate that endurance times for the elbow flexors when performing submaximal isometric contractions that required either force or position control were not influenced by hand dominance but did depend on handedness.
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Affiliation(s)
- Nicole M. Gordon
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado
| | - Thorsten Rudroff
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado
| | - Joel A. Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado
| | - Roger M. Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado
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Booghs C, Baudry S, Enoka R, Duchateau J. Influence of neural adjustments and muscle oxygenation on task failure during sustained isometric contractions with elbow flexor muscles. Exp Physiol 2012; 97:918-29. [DOI: 10.1113/expphysiol.2011.064303] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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