MUSCLE FIBER CONDUCTION VELOCITY IN HUMAN VASTUS LATERALIS DURING ISOMETRIC CONTRACTIONS

Abstract Conduction of electrical signals along the surface of muscle fibers is acknowledged as an essential neuromuscular component which is linked with muscle force production. However, it remains unclear whether muscle fiber conduction velocity (MFCV) is also linked with explosive performance. The aim of the present study was to investigate the relationship between vastus lateralis MFCV and countermovement jumping performance, the rate of force development and maximum isometric force. Fifteen moderately-trained young females performed countermovement jumps as well as an isometric leg press test in order to determine the rate of force development and maximum isometric force. Vastus lateralis MFCV was measured with intramuscular microelectrodes at rest on a different occasion. Maximum MFCV was significantly correlated with maximum isometric force (r = 0.66, p < 0.01), nevertheless even closer with the leg press rate of force development at 100 ms, 150 ms, 200 ms, and 250 ms (r = 0.85, r = 0.89, r = 0.91, r = 0.92, respectively, p < 0.01). Similarly, mean MFCV and type II MFCV were better correlated with the rate of force development than with maximum isometric leg press force. Lower, but significant correlations were found between mean MFCV and countermovement jump power (r = 0.65, p < 0.01). These data suggest that muscle fiber conduction velocity is better linked with the rate of force development than with isometric force, perhaps because conduction velocity is higher in the larger and fastest muscle fibers which are recognized to contribute to explosive actions.

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Test-retest reliability of muscle fiber conduction velocity and fractal dimension of surface EMG during isometric contractions

Physiological Measurement ◽

10.1088/1361-6579/aa614c ◽

2017 ◽

Vol 38 (4) ◽

pp. 616-630 ◽

Cited By ~ 7

Author(s):

Matteo Beretta-Piccoli ◽

Giuseppe D’Antona ◽

Cristian Zampella ◽

Marco Barbero ◽

Ron Clijsen ◽

...

Keyword(s):

Fractal Dimension ◽

Conduction Velocity ◽

Muscle Fiber ◽

Surface Emg ◽

Isometric Contractions ◽

Retest Reliability ◽

Muscle Fiber Conduction Velocity ◽

Test Retest Reliability

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Effect of power, pedal rate, and force on average muscle fiber conduction velocity during cycling

Journal of Applied Physiology ◽

10.1152/japplphysiol.00606.2004 ◽

2004 ◽

Vol 97 (6) ◽

pp. 2035-2041 ◽

Cited By ~ 64

Author(s):

Dario Farina ◽

Andrea Macaluso ◽

Richard A. Ferguson ◽

Giuseppe De Vito

Keyword(s):

Conduction Velocity ◽

Muscle Fiber ◽

External Force ◽

Power Output ◽

Vastus Lateralis ◽

Force Production ◽

Motor Units ◽

Angular Speed ◽

Muscle Fiber Conduction Velocity ◽

Pedal Rate

Muscle fiber conduction velocity (MFCV) provides indications on motor unit recruitment strategies due to the relation between conduction velocity and fiber diameter. The aim of this study was to investigate MFCV of thigh muscles during cycling at varying power outputs, pedal rates, and external forces. Twelve healthy male participants aged between 19 and 30 yr cycled on an electronically braked ergometer at 45, 60, 90, and 120 rpm. For each pedal rate, subjects performed two exercise intensities, one at an external power output corresponding to the previously determined lactate threshold (100% LT) and the other at half of this power output (50% LT). Surface electromyogram signals were detected during cycling from vastus lateralis and medialis muscles with linear adhesive arrays of eight electrodes. In both muscles, MFCV was higher at 100% LT compared with 50% LT for all average pedal rates except 120 rpm (mean ± SE, 4.98 ± 0.19 vs. 4.49 ± 0.18 m/s; P < 0.001). In all conditions, MFVC increased with increasing instantaneous knee angular speed (from 4.14 ± 0.16 to 5.08 ± 0.13 m/s in the range of instantaneous angular speeds investigated; P < 0.001). When MFCV was compared at the same external force production (i.e., 90 rpm/100% LT vs. 45 rpm/50% LT, and 120 rpm/100% LT vs. 60 rpm/50% LT), MFCV was higher at the faster pedal rate (5.02 ± 0.17 vs. 4.64 ± 0.12 m/s, and 4.92 ± 0.19 vs. 4.49 ± 0.11 m/s, respectively; P < 0.05) due to the increase in inertial power required to accelerate the limbs. It was concluded that, during repetitive dynamic movements, MFCV increases with the external force developed, instantaneous knee angular speed, and average pedal rate, indicating progressive recruitment of large, high conduction velocity motor units with increasing muscle force.

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History dependence of human muscle-fiber conduction velocity during voluntary isometric contractions

Journal of Applied Physiology ◽

10.1152/japplphysiol.00208.2011 ◽

2011 ◽

Vol 111 (3) ◽

pp. 630-641 ◽

Cited By ~ 13

Author(s):

Kevin C. McGill ◽

Zoia C. Lateva

Keyword(s):

Firing Rate ◽

Conduction Velocity ◽

Muscle Fiber ◽

Human Muscle ◽

Isometric Contractions ◽

Fiber Membrane ◽

Muscle Fiber Conduction Velocity ◽

Intramuscular Electrodes ◽

Voluntary Contractions ◽

Muscle Fiber Membrane

The conduction velocity (CV) of a muscle fiber is affected by the fiber's discharge history going back ∼1 s. We investigated this dependence by measuring CV fluctuations during voluntary isometric contractions of the human brachioradialis muscle. We recorded electromyogram (EMG) signals simultaneously from multiple intramuscular electrodes, identified potentials belonging to the same motor unit using EMG decomposition, and estimated the CV of each discharge from the interpotential interval. In 12 of 14 subjects, CV increased by ∼10% during the first second after recruitment and then fluctuated by about ±2% in a way that mirrored the fluctuations in the instantaneous firing rate. The CV profile could be precisely described in terms of the discharge history by a simple mathematical model. In the other two subjects, and one subject retested after cooling the arm, the CV fluctuations were inversely correlated with instantaneous firing rate. In all subjects, CV was additionally affected by very short interdischarge intervals (<25 ms): it was increased in doublets at recruitment, but decreased in doublets during continuous firing and after short interdischarge intervals in doubly innervated fibers. CV also exhibited a slow trend of about −0.05%/s that did not depend on the immediate discharge history. We suggest that measurements of CV fluctuations during voluntary contractions, or during stimulation protocols that involve longer and more complex stimulation patterns than are currently being used, may provide a sensitive approach for estimating the dynamic characteristics of ion channels in the human muscle-fiber membrane.

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Muscle fiber conduction velocity in the vastus lateralis and medialis muscles of soccer players after ACL reconstruction

Scandinavian Journal of Medicine and Science in Sports ◽

10.1111/sms.13748 ◽

2020 ◽

Vol 30 (10) ◽

pp. 1976-1984

Author(s):

Stefano Nuccio ◽

Alessandro Del Vecchio ◽

Andrea Casolo ◽

Luciana Labanca ◽

Jacopo Emanuele Rocchi ◽

...

Keyword(s):

Acl Reconstruction ◽

Conduction Velocity ◽

Muscle Fiber ◽

Vastus Lateralis ◽

Soccer Players ◽

Muscle Fiber Conduction Velocity

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Changes in muscle fiber conduction velocity indicate recruitment of distinct motor unit populations

Journal of Applied Physiology ◽

10.1152/japplphysiol.00665.2002 ◽

2003 ◽

Vol 95 (3) ◽

pp. 1045-1054 ◽

Cited By ~ 81

Author(s):

C. J. Houtman ◽

D. F. Stegeman ◽

J. P. Van Dijk ◽

M. J. Zwarts

Keyword(s):

Conduction Velocity ◽

Muscle Fiber ◽

Tibialis Anterior Muscle ◽

Maximum Voluntary Contraction ◽

Isometric Exercise ◽

Motor Units ◽

Voluntary Contraction ◽

Type I ◽

Muscle Fiber Conduction Velocity ◽

Depth Study

To obtain more insight into the changes in mean muscle fiber conduction velocity (MFCV) during sustained isometric exercise at relatively low contraction levels, we performed an in-depth study of the human tibialis anterior muscle by using multichannel surface electromyogram. The results show an increase in MFCV after an initial decrease of MFCV at 30 or 40% maximum voluntary contraction in all of the five subjects studied. With a peak velocity analysis, we calculated the distribution of conduction velocities of action potentials in the bipolar electromyogram signal. It shows two populations of peak velocities occurring simultaneously halfway through the exercise. The MFCV pattern implies the recruitment of two different populations of motor units. Because of the lowering of MFCV of the first activated population of motor units, the newly recruited second population of motor units becomes visible. It is most likely that the MFCV pattern can be ascribed to the fatiguing of already recruited predominantly type I motor units, followed by the recruitment of fresh, predominantly type II, motor units.

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