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Cabral HV, Inglis JG, Cudicio A, Cogliati M, Orizio C, Yavuz US, Negro F. Muscle contractile properties directly influence shared synaptic inputs to spinal motor neurons. J Physiol 2024; 602:2855-2872. [PMID: 38709959 DOI: 10.1113/jp286078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Accepted: 04/18/2024] [Indexed: 05/08/2024] Open
Abstract
Alpha band oscillations in shared synaptic inputs to the alpha motor neuron pool can be considered an involuntary source of noise that hinders precise voluntary force production. This study investigated the impact of changing muscle length on the shared synaptic oscillations to spinal motor neurons, particularly in the physiological tremor band. Fourteen healthy individuals performed low-level dorsiflexion contractions at ankle joint angles of 90° and 130°, while high-density surface electromyography (HDsEMG) was recorded from the tibialis anterior (TA). We decomposed the HDsEMG into motor units spike trains and calculated the motor units' coherence within the delta (1-5 Hz), alpha (5-15 Hz), and beta (15-35 Hz) bands. Additionally, force steadiness and force spectral power within the tremor band were quantified. Results showed no significant differences in force steadiness between 90° and 130°. In contrast, alpha band oscillations in both synaptic inputs and force output decreased as the length of the TA was moved from shorter (90°) to longer (130°), with no changes in delta and beta bands. In a second set of experiments (10 participants), evoked twitches were recorded with the ankle joint at 90° and 130°, revealing longer twitch durations in the longer TA muscle length condition compared to the shorter. These experimental results, supported by a simple computational simulation, suggest that increasing muscle length enhances the muscle's low-pass filtering properties, influencing the oscillations generated by the Ia afferent feedback loop. Therefore, this study provides valuable insights into the interplay between muscle biomechanics and neural oscillations. KEY POINTS: We investigated whether changes in muscle length, achieved by changing joint position, could influence common synaptic oscillations to spinal motor neurons, particularly in the tremor band (5-15 Hz). Our results demonstrate that changing muscle length from shorter to longer induces reductions in the magnitude of alpha band oscillations in common synaptic inputs. Importantly, these reductions were reflected in the oscillations of muscle force output within the alpha band. Longer twitch durations were observed in the longer muscle length condition compared to the shorter, suggesting that increasing muscle length enhances the muscle's low-pass filtering properties. Changes in the peripheral contractile properties of motor units due to changes in muscle length significantly influence the transmission of shared synaptic inputs into muscle force output. These findings prove the interplay between muscle mechanics and neural adaptations.
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Affiliation(s)
- Hélio V Cabral
- Department of Clinical and Experimental Sciences, Università degli Studi di Brescia, Brescia, Italy
| | - J Greig Inglis
- Department of Clinical and Experimental Sciences, Università degli Studi di Brescia, Brescia, Italy
| | - Alessandro Cudicio
- Department of Clinical and Experimental Sciences, Università degli Studi di Brescia, Brescia, Italy
| | - Marta Cogliati
- Department of Clinical and Experimental Sciences, Università degli Studi di Brescia, Brescia, Italy
| | - Claudio Orizio
- Department of Clinical and Experimental Sciences, Università degli Studi di Brescia, Brescia, Italy
| | - Utku S Yavuz
- Biomedical Signals and Systems, University of Twente, Enschede, Netherlands
| | - Francesco Negro
- Department of Clinical and Experimental Sciences, Università degli Studi di Brescia, Brescia, Italy
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Kunugi S, Holobar A, Nakagoshi A, Kawabe K, Watanabe K. Effects of repetition of a car-driving pedal maneuver and neural output in older adults. J Electromyogr Kinesiol 2024; 76:102883. [PMID: 38569438 DOI: 10.1016/j.jelekin.2024.102883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 03/11/2024] [Accepted: 03/30/2024] [Indexed: 04/05/2024] Open
Abstract
Understanding the ability of older adults to control pedal position angle and investigating whether this ability can be enhanced through practice may contribute to the prevention of traffic accidents. This study aimed to investigate repetitive effects on variability of the pedal position and neural drive during car-pedal operation in older adults. Thirteen older and 11 young adults performed 105 (21 sets × 5 repetitions) pedal angle control tasks with plantar flexor contraction. High-density surface electromyograms were recorded of triceps surae muscles. A cumulative spike train as a neural drive was calculated using continuously active motor unit activities. The coefficient of variation of the angle was higher in older (1.47 ± 1.06 %) than young (0.41 ± 0.21 %) adults in the first sets, and improved to 0.67 ± 0.51 % in the final sets in older adults only. There was no significant difference in neural drive variability between older and young adults. Our results suggest that repetition improves angular steadiness in older adults. However, this effect could not be explained by neural output which is estimated from lower threshold motor units that are continuously active.
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Affiliation(s)
- Shun Kunugi
- Center for General Education, Aichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota-shi, Aichi 470-0392, Japan; Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University 101 Tokodachi, Kaizu-cho, Toyota-shi, Aichi 470-0393, Japan.
| | - Aleš Holobar
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Koroška cesta 46, 2000 Maribor, Slovenia
| | - Akira Nakagoshi
- Advanced Mobility System Development, Toyota Motor Corporation, 1 Toyota-cho, Toyota-shi, Aichi 471-8571, Japan
| | - Kyosuke Kawabe
- Advanced Mobility System Development, Toyota Motor Corporation, 1 Toyota-cho, Toyota-shi, Aichi 471-8571, Japan
| | - Kohei Watanabe
- Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University 101 Tokodachi, Kaizu-cho, Toyota-shi, Aichi 470-0393, Japan
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Amiridis IG, Kannas T, Sahinis C, Negro F, Trypidakis G, Kellis E, Enoka RM. More Variability in Tibialis Anterior Function during the Adduction of the Foot than Dorsiflexion of the Ankle. Med Sci Sports Exerc 2024; 56:851-859. [PMID: 38190382 DOI: 10.1249/mss.0000000000003377] [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: 01/10/2024]
Abstract
INTRODUCTION The aim of the study was to compare maximal force, force steadiness, and the discharge characteristics of motor units in the tibialis anterior (TA) muscle during submaximal isometric contractions for ankle dorsiflexion and adduction of the foot. METHODS Nineteen active young adults performed maximal and submaximal isometric dorsiflexion and adduction contractions at five target forces (5%, 10%, 20%, 40%, and 60% maximal voluntary contraction [MVC]). The activity of motor units in TA was recorded by high-density EMG. RESULTS The maximal force was similar between dorsiflexion and adduction, despite EMG amplitude for TA being greater ( P < 0.05) during dorsiflexion than adduction. Τhe coefficient of variation (CV) for force (force steadiness) during dorsiflexion was always less ( P < 0.05) than during adduction, except of 5% MVC force. No differences were observed for mean discharge rate; however, the regression between the changes in discharge rate relative to the change of force was significant for dorsiflexion ( R2 = 0.25, P < 0.05) but not for adduction. Discharge variability, however, was usually less during dorsiflexion. The CV for interspike interval was less ( P < 0.05) at 10%, 20%, and 40% MVC but greater at 60% MVC during dorsiflexion than adduction. Similarly, the SD values of the filtered cumulative spike train of the motor units in TA were less ( P < 0.05) at 5%, 10%, 20%, and 40% MVC during dorsiflexion than adduction. CONCLUSIONS Although the mean discharge rate of motor units in TA was similar during foot adduction and ankle dorsiflexion, discharge variability was less during dorsiflexion resulting in less accurate performance of the steady adduction contractions. The neural drive to bifunctional muscles differs during their accessory function, which must be considered for training and rehabilitation interventions.
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Affiliation(s)
- Ioannis G Amiridis
- Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Serres, GREECE
| | - Theodoros Kannas
- Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Serres, GREECE
| | - Chrysostomos Sahinis
- Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Serres, GREECE
| | - Francesco Negro
- Department of Clinical and Experimental Sciences, University of Brescia, Brescia, ITALY
| | - Georgios Trypidakis
- Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Serres, GREECE
| | - Eleftherios Kellis
- Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Serres, GREECE
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, CO
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Darendeli A, Enoka RM. Control of motor output during steady submaximal contractions is modulated by contraction history. Exp Brain Res 2024; 242:675-683. [PMID: 38260992 PMCID: PMC10894765 DOI: 10.1007/s00221-023-06774-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Accepted: 12/22/2023] [Indexed: 01/24/2024]
Abstract
The purpose of the study was to investigate the influence of contraction history on force steadiness and the associated EMG activity during submaximal isometric contractions performed with the dorsiflexor muscles. The key feature of the protocol was a triangular ramp contraction performed in the middle of a steady contraction at a lower target force. The target force during the ramp contraction was 20% MVC greater than that during the steady contraction. Thirty-seven healthy individuals (21 men and 16 women) performed the submaximal tasks with the ankle dorsiflexors. Electromyography (EMG) signals were recorded from tibialis anterior with a pair of surface electrodes. The coefficient of variation for force was significantly greater during the second steady contraction compared with the first one at each of the seven target forces (p < 0.015; d = 0.38-0.92). Although the average applied force during the steady contractions before and after the triangular contraction was the same (p = 0.563), the mean EMG amplitude for the steady contractions performed after the triangular contraction was significantly greater at each of the seven target forces (p < 0.0001; d = 0.44-0.68). Also, there were significant differences in mean EMG frequency between the steady contractions performed before and after the triangular contraction (p < 0.01; d = 0.13-0.82), except at 10 and 20% MVC force. The greater force fluctuations during a steady submaximal contraction after an intervening triangular contraction indicate a change in the discharge characteristics of the involved motor units.
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Affiliation(s)
- Abdulkerim Darendeli
- Movement Neuroscience Laboratory, Department of Physical Therapy, Movement, and Rehabilitation Sciences, Northeastern University, Boston, MA, 02115, USA.
- Faculty of Sport Sciences, Sivas Cumhuriyet University, Sivas, Turkey.
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO, USA.
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO, USA
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Petrovic I, Amiridis IG, Kannas T, Tsampalaki Z, Holobar A, Sahinis C, Kellis E, Stankovic D, Enoka RM. Footedness but not dominance influences force steadiness during isometric dorsiflexion in young men. J Electromyogr Kinesiol 2023; 73:102828. [PMID: 37782992 DOI: 10.1016/j.jelekin.2023.102828] [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: 06/14/2023] [Revised: 09/18/2023] [Accepted: 09/28/2023] [Indexed: 10/04/2023] Open
Abstract
The aim of the study was to assess the potential influence of footedness and dominance on maximal force, force fluctuations and neural drive during dorsiflexion. Fifteen left-footed (LF) and fifteen right-footed (RF) young adults performed 2 maximal voluntary contractions (MVC) and 3 steady submaximal isometric contractions at five target forces (5, 10, 20, 40 and 60% MVC) with the dorsiflexors of both legs. High-density electromyography (EMG) was used to record the discharge characteristics of motor units (MUs) of Tibialis Anterior. MVC force and EMG amplitude (root mean square) were similar between the two legs and groups (p > 0.05). Force fluctuations (Coefficient of Variation, CoV for force), mean discharge rate of MUs, discharge variability (CoV of interspike interval), and variability in neural drive (standard deviation of filtered cumulative spike train) were greater (p < 0.05) and the input-output gain of the MUs (ΔDR/ΔF) was lower (p < 0.05) for the LF relative to the RF group. The differences in force fluctuations during steady contractions with the dorsiflexors were associated with footedness but not with dominance. They reflect greater variability in motor neuron output, as suggested by coefficient of variation for interspike interval (independent input) and the standard deviation of the smoothed discharge times (common input).
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Affiliation(s)
- Ivana Petrovic
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Greece; Faculty of Sport and Physical Education, University of Niš, Serbia
| | - Ioannis G Amiridis
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Greece.
| | - Theodoros Kannas
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Greece
| | - Zoi Tsampalaki
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Greece
| | - Ales Holobar
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Slovenia
| | - Chrysostomos Sahinis
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Greece
| | - Eleftherios Kellis
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Greece
| | - Daniel Stankovic
- Faculty of Sport and Physical Education, University of Niš, Serbia
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, CO, USA
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Petrović I, Amiridis IG, Holobar A, Trypidakis G, Sahinis C, Kannas T, Kellis E, Enoka RM. Alternating or Bilateral Exercise Training does not Influence Force Control during Single-Leg Submaximal Contractions with the Dorsiflexors. J Sports Sci Med 2023; 22:245-253. [PMID: 37293414 PMCID: PMC10244987 DOI: 10.52082/jssm.2023.245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 04/26/2023] [Indexed: 06/10/2023]
Abstract
The aim of the study was to assess the influence of habitual training history on force steadiness and the discharge characteristics of motor units in tibialis anterior during submaximal isometric contractions. Fifteen athletes whose training emphasized alternating actions (11 runners and 4 cyclists) and fifteen athletes who relied on bilateral actions with leg muscles (7 volleyball players, 8 weight-lifters) performed 2 maximal voluntary contractions (MVC) with the dorsiflexors, and 3 steady contractions at 8 target forces (2.5%, 5%, 10%, 20%, 30%, 40%, 50% and 60% MVC). The discharge characteristics of motor units in tibialis anterior were recorded using high-density electromyography grids. The MVC force and the absolute (standard deviation) and normalized (coefficient of variation) amplitudes of the force fluctuations at all target forces were similar between groups. The coefficient of variation for force decreased progressively from 2.5% to 20% MVC force, then it plateaued until 60% MVC force. Mean discharge rate of the motor units in tibialis anterior was similar at all target forces between groups. The variability in discharge times (coefficient of variation for interspike interval) and the variability in neural drive (coefficient of variation of filtered cumulative spike train) was also similar for the two groups. These results indicate that athletes who have trained with either alternating or bilateral actions with leg muscles has similar effects on maximal force, force control, and variability in the independent and common synaptic input during a single-limb isometric task with the dorsiflexors.
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Affiliation(s)
- Ivana Petrović
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Greece
- Faculty of Sport and Physical Education, University of Niš, Serbia
| | - Ioannis G Amiridis
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Greece
| | - Ales Holobar
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Slovenia
| | - Georgios Trypidakis
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Greece
| | - Chrysostomos Sahinis
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Greece
| | - Theodoros Kannas
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Greece
| | - Eleftherios Kellis
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Greece
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, CO, USA
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Choi YJ, Chalatzoglidis G, Trapezanidou M, Delmas S, Savva E, Yacoubi B, Arabatzi F, Christou EA. Adolescent boys who participate in sports exhibit similar ramp torque control with young men despite differences in strength and tendon characteristics. Eur J Appl Physiol 2023; 123:965-974. [PMID: 36607415 PMCID: PMC10718087 DOI: 10.1007/s00421-022-05130-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 12/26/2022] [Indexed: 01/07/2023]
Abstract
PURPOSE The goal of this paper was to determine if sports participation influences torque control differently for adolescent boys and young men during a slow ramp task. METHODS Twenty-one adolescent boys (11 athletes) and 31 young men (16 athletes) performed a slow ramp increase in plantar flexion torque from 0 to maximum. We quantified torque control as the coefficient of variation (CV) of torque during the ramp and quantified the Achilles tendon mechanical properties using ultrasonography. RESULTS Relative to adolescent boys, young men were taller, heavier, stronger, and had a longer and stiffer Achilles tendon. However, these characteristics were not different between athletes and non-athletes in adolescent boys. For the CV of torque, there was a significant interaction with sports participation, indicating that only adolescent boys who were non-athletes had greater variability than young men. The CV of torque of all participants was predicted from the maximum torque and torque oscillations from 1 to 2 Hz, whereas the CV of torque for adolescent boys was predicted only from torque oscillations from 1 to 2 Hz. CONCLUSION These findings suggested that adolescent boys who participate in sports exhibited lower torque variability during a slow ramp task, which was not explained by differences in Achilles tendon properties or strength.
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Affiliation(s)
- Yoon Jin Choi
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, 32611-8205, USA
| | - George Chalatzoglidis
- Laboratory of Neuromechanics, Department of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, Serres, Greece
| | - Martha Trapezanidou
- Laboratory of Neuromechanics, Department of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, Serres, Greece
| | - Stefan Delmas
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, 32611-8205, USA
| | - Evangelia Savva
- Laboratory of Neuromechanics, Department of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, Serres, Greece
| | - Basma Yacoubi
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, 32611-8205, USA
| | - Fotini Arabatzi
- Laboratory of Neuromechanics, Department of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, Serres, Greece
| | - Evangelos A Christou
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, 32611-8205, USA.
- Department of Neurology, Fixel Institute for Neurological Diseases, University of Florida, Gainesville, FL, USA.
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Kunugi S, Hirono T, Yoshimura A, Holobar A, Watanabe K. Association between force fluctuation during isometric ankle abduction and variability of neural drive in peroneus muscles. J Electromyogr Kinesiol 2023; 70:102780. [PMID: 37126978 DOI: 10.1016/j.jelekin.2023.102780] [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: 01/22/2023] [Revised: 04/21/2023] [Accepted: 04/22/2023] [Indexed: 05/03/2023] Open
Abstract
Analyzing motor unit (MU) activities of peroneus muscles may reveal the causes of force control deficits of ankle eversion. This study aimed to examine peroneus muscles' MU discharge characteristics and associations between force fluctuation and variability of the neural drive in healthy participants. Thirty-one healthy males participated in this study. MU activities were identified from high-density surface electromyography of peroneus muscles during ankle eversion at 15 and 30% of maximal voluntary contraction (MVC). Participants increased the contraction level until reaching the target and held it for 15 s. The central 10 s of the hold phase were used for analysis. A cumulative spike train (CST) was calculated using MU firings. Variabilities of the force and CST are represented by the coefficient of variation (CoV). Spearman's rank correlation coefficient was used to assess the association between CoV of force and CoV of CST. For 15 and 30 % MVC trials, CoV of force was 1.86 ± 1.59 and 1.57 ± 1.26%, and CoV of CST was 5.01 ± 3.24 and 4.51 ± 2.78%, respectively. The correlation was significant at 15% (rho = 0.27, p < 0.001) and 30% (rho = 0.32, p < 0.001) MVC. Our findings suggest that in peroneus muscles, force fluctuation weakly to moderately correlates with neural drive variability.
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Affiliation(s)
- Shun Kunugi
- Center for General Education, Aichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota-shi, Aichi 470-0392, Japan; Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University 101 Tokodachi, Kaizu-cho, Toyota-shi, Aichi 470-0393, Japan.
| | - Tetsuya Hirono
- Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University 101 Tokodachi, Kaizu-cho, Toyota-shi, Aichi 470-0393, Japan
| | - Akane Yoshimura
- Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University 101 Tokodachi, Kaizu-cho, Toyota-shi, Aichi 470-0393, Japan
| | - Aleš Holobar
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Koroška cesta 46, 2000 Maribor, Slovenia
| | - Kohei Watanabe
- Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University 101 Tokodachi, Kaizu-cho, Toyota-shi, Aichi 470-0393, Japan
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Petrovic I, Amiridis IG, Holobar A, Trypidakis G, Kellis E, Enoka RM. Leg Dominance Does Not Influence Maximal Force, Force Steadiness, or Motor Unit Discharge Characteristics. Med Sci Sports Exerc 2022; 54:1278-1287. [PMID: 35324535 DOI: 10.1249/mss.0000000000002921] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE The aim of our study was to compare maximal force, force steadiness, and discharge characteristics of motor units in tibialis anterior during contractions with the dorsiflexors of the dominant and nondominant legs at low-to-moderate target forces and three ankle angles. METHODS Twenty young adults performed maximal and submaximal isometric contractions (5%, 10%, 20%, 40%, and 60% of maximal voluntary contraction (MVC)) with the dorsiflexors of the dominant and nondominant legs at three ankle angles (75°, short length; 90°, intermediate length; 105°, long length). High-density EMG signals from the tibialis anterior muscle of each leg were recorded. RESULTS Maximal force (average dominant, 182.9 ± 64.5 N; nondominant, 179.0 ± 58.8 N) and the fluctuations in force, quantified as absolute (SD) and normalized amplitudes (coefficient of variation (CoV)), were similar between the two legs across the three ankle angles (average CoV for dominant, 1.5% ± 1.0%; nondominant, 1.7% ± 1.3%). The CoV for force for both legs decreased from 5% to 20% MVC force, and then it plateaued at 40% and 60% MVC force. EMG amplitude, mean discharge rate of motor units, discharge variability (interspike interval), and the variability in neural drive (filtered cumulative spike train) were similar between the two legs across the submaximal contractions. CONCLUSIONS MVC force and force steadiness were similar across ankle angles and target forces between the dominant and nondominant legs. The attributes that underlie the self-reported identification of a dominant leg were not associated with the force capacity or the control of force for the dorsiflexor muscles, at least during isometric contractions.
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Affiliation(s)
| | - Ioannis G Amiridis
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Thessaloniki, GREECE
| | - Ales Holobar
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, SLOVENIA
| | - Georgios Trypidakis
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Thessaloniki, GREECE
| | - Eleftherios Kellis
- Laboratory of Neuromechanics, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Thessaloniki, GREECE
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, CO
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Mazzo MR, Holobar A, Enoka RM. Association between effective neural drive to the triceps surae and fluctuations in plantar-flexion torque during submaximal isometric contractions. Exp Physiol 2022; 107:489-507. [PMID: 35218261 DOI: 10.1113/ep090228] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 02/11/2022] [Indexed: 11/08/2022]
Abstract
What is the central question of this study? What is the association between the fluctuations in various estimates of effective neural drive to the triceps surae muscles and fluctuations in net plantar-flexion torque during steady submaximal contractions? What is the main finding and its importance? The fluctuations in estimates of effective neural drive to the triceps surae were moderately correlated with fluctuations in net torque at light and moderate plantar-flexion torques. Significant variability was observed in the association between neural drive and torque across participants, trials, short epochs of individual contractions, and varying motor unit number. ABSTRACT: The influence of effective neural drive on low-frequency fluctuations in torque during steady contractions can be estimated from the cumulative spike train (CST) or first principal component (FPC) of smoothed motor unit discharge rates obtained with high-density electromyography. However, the association between these estimates of total neural drive to synergist muscles and the fluctuations in net torque has not been investigated. We exposed the variability and compared the correlations between estimates of effective neural drive to the triceps surae muscles and fluctuations in plantar-flexion torque during steady contractions at 10% and 35% of maximal voluntary contraction (MVC) torque. Both neural drive estimates were moderately correlated with torque (CST, 0.55 ± 0.14, FPC, 0.58 ± 0.16) and highly correlated with one another (0.81 ± 0.1) during the 30-s steady contractions. There was substantial variability in cross-correlation values across participants, trials, and the 1-s and 5-s epochs of single contractions. Moreover, epoch duration significantly influenced cross-correlation values. Motor unit number was weakly associated with cross-correlation strength at 35% MVC (marginal R2 0.09 - 0.11; all p < 2.2×10-5 ), but not at 10% MVC (all p > 0.37). Approximately one fifth of the variance in the coefficient of variation (CV) for torque was explained by CV for the CST estimate of neural drive (p = 6.6×10-13 , R2 = 0.21). Estimates of total neural drive to the synergistic triceps surae muscles obtained by pooling motor unit discharge times were moderately correlated with fluctuations in net plantar-flexion torque. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Melissa R Mazzo
- Department of Integrative Physiology, University of Colorado, Boulder, CO
| | - Aleš Holobar
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, Slovenia
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, CO
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Hanson MR, Swanson CW, Whittier TT, Fling BW. Inhibitory signaling as a predictor of leg force control in young and older adults. Exp Brain Res 2022; 240:1005-1016. [PMID: 35171308 DOI: 10.1007/s00221-022-06321-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: 11/08/2021] [Accepted: 01/29/2022] [Indexed: 11/04/2022]
Abstract
As the populations of the United States and developed nations age, motor control performance is adversely impacted, resulting in functional impairments that can diminish quality of life. Generally, force control in the lower limb worsens with age, with older adults (OA) displaying more variable and less accurate submaximal forces. Corticospinal inhibitory signaling may influence force control, with those OA who maintain corticospinal inhibitory signaling capacity achieving steadier forces. This study aimed to assess the relationships between lower limb force control and transcranial magnetic stimulation (TMS) measures of corticospinal inhibition (i.e., cortical silent period (cSP) duration and depth). 15 OA and 14 young adults (YA) were recruited for this study. All subjects underwent a TMS protocol to elicit the cSP while maintaining 15% of their maximal force in their knee extensor muscles. OA and YA did not display differences in force control metrics or corticospinal inhibitory measures. However, in OA, maximal cSP depth (%dSP max) was associated with lower force variability. No other significant relationships existed in the YA or OA groups. Future studies will benefit from evaluating a range of target forces and target muscles to assess potential relationships between sensorimotor inhibitory capacity and control of muscle force output.
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Affiliation(s)
- Moriah R Hanson
- Department of Occupational Therapy, Colorado State University, Fort Collins, CO, USA
| | - Clayton W Swanson
- Department of Health & Exercise Science, Colorado State University, 1582 Campus Delivery, Moby B-201A, Fort Collins, CO, 80523, USA
| | - Tyler T Whittier
- Department of Health & Exercise Science, Colorado State University, 1582 Campus Delivery, Moby B-201A, Fort Collins, CO, 80523, USA
| | - Brett W Fling
- Department of Health & Exercise Science, Colorado State University, 1582 Campus Delivery, Moby B-201A, Fort Collins, CO, 80523, USA. .,Molecular, Cellular, and Integrative Neuroscience Program, Colorado State University, Fort Collins, CO, USA.
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Bersotti FM, Mochizuki L, Brech GC, Soares ALDS, Soares-Junior JM, Baracat EC, Greve JMD, Alonso AC. The variability of isokinetic ankle strength is different in healthy older men and women. Clinics (Sao Paulo) 2022; 77:100125. [PMID: 36327639 PMCID: PMC9636544 DOI: 10.1016/j.clinsp.2022.100125] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 08/19/2022] [Accepted: 09/29/2022] [Indexed: 11/20/2022] Open
Abstract
CONTEXT In the elderly, weak lower limb muscles impair functional tasks' performance. OBJECTIVE To evaluate the healthy elderly's ankle dorsiflexion and plantarflexion maximum torque and its variability in two sets of 5 RM isokinetics evaluation. METHOD 50 women (68.0 ± 4.6 years old) and 50 men (72.7 ± 8.5 years old) did two sets of ankle plantar flexor and dorsiflexor isokinetic tests at 30°/s. Peak torque, total work, and coefficient of variation were analyzed. RESULTS Men did the strongest plantarflexion torque (p < 0.05) and dorsiflexion torque (p < 0.05); their highest peak torque occurred at set 2 (p < 0.05), while the largest plantarflexion torque variability (p < 0.05), dorsiflexion torque variability (p < 0.05), and the largest plantarflexion torque variability occurred at set 1 (p < 0.05). Men did the highest plantarflexion and dorsiflexion total work (p < 0.05) at set 2 (p < 0.05). CONCLUSION Older men are stronger than older women. The torque variability, in men, was higher during the first set, suggesting an adaptation to the isokinetics evaluation. Clinicians and researchers should consider that different muscles might need different numbers of sets and trials to measure their maximal muscle strength.
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Affiliation(s)
| | - Luis Mochizuki
- School of Arts Sciences and Humanities, Universidade de São Paulo, São Paulo, SP, Brazil; Department of Orthopedics and Traumatology, Faculdade de Medicina da Universidade de São Paulo, São Paulo, SP, Brazil
| | - Guilherme Carlos Brech
- Graduate Program in Aging Sciences, Universidade São Judas Tadeu, São Paulo, SP, Brazil; Department of Orthopedics and Traumatology, Faculdade de Medicina da Universidade de São Paulo, São Paulo, SP, Brazil.
| | | | - Jose Maria Soares-Junior
- Discipline of Gynecology, Department of Obstetrics and Gynecology, Hospital das Clínicas da Faculdade de Medicina da USP (FMUSP), São Paulo, SP, Brazil
| | - Edmund Chada Baracat
- Discipline of Gynecology, Department of Obstetrics and Gynecology, Hospital das Clínicas da Faculdade de Medicina da USP (FMUSP), São Paulo, SP, Brazil
| | - Julia Maria D'Andrea Greve
- Department of Orthopedics and Traumatology, Faculdade de Medicina da Universidade de São Paulo, São Paulo, SP, Brazil
| | - Angelica Castilho Alonso
- Graduate Program in Aging Sciences, Universidade São Judas Tadeu, São Paulo, SP, Brazil; Department of Orthopedics and Traumatology, Faculdade de Medicina da Universidade de São Paulo, São Paulo, SP, Brazil
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