On the relationship between Muscle Fiber Conduction Velocity and EMG Power Spectrum during Isometric Contraction of Musculus Biceps Brachii

AbstractNeuromuscular assessment of rock climbers has been mainly focused on forearm muscles in the literature. We aimed to extend the body of knowledge investigating on two other upper limb muscles during sport-specific activities in nine male rock climbers. We assessed neuromuscular manifestations of fatigue recording surface electromyographic signals from brachioradialis and teres major muscles, using multi-channel electrode arrays. Participants performed two tasks until volitional exhaustion: a sequence of dynamic pull-ups and an isometric contraction sustaining the body at half-way of a pull-up (with the elbows flexed at 90°). The tasks were performed in randomized order with 10 minutes of rest in between. The normalized rate of change of muscle fiber conduction velocity was calculated as the index of fatigue. The time-to-task failure was significantly shorter in the dynamic (31 ±10 s) than isometric contraction (59 ±19 s). The rate of decrease of muscle fiber conduction velocity was found steeper in the dynamic than isometric task both in brachioradialis (isometric: −0.2 ±0.1%/s; dynamic: −1.2 ±0.6%/s) and teres major muscles (isometric: −0.4±0.3%/s; dynamic: −1.8±0.7%/s). The main finding was that a sequence of dynamic pull-ups lead to higher fatigue than sustaining the body weight in an isometric condition at half-way of a pull-up. Furthermore, we confirmed the possibility to properly record physiological CV estimates from two muscles, which had never been studied before in rock climbing, in highly dynamic contractions.

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Muscle fiber conduction velocity and mean power spectrum frequency in neuromuscular disorders and in fatigue

Muscle & Nerve ◽

10.1002/mus.880150706 ◽

1992 ◽

Vol 15 (7) ◽

pp. 780-787 ◽

Cited By ~ 11

Author(s):

Israel Yaar ◽

Les Niles

Keyword(s):

Power Spectrum ◽

Conduction Velocity ◽

Muscle Fiber ◽

Neuromuscular Disorders ◽

Mean Power ◽

Muscle Fiber Conduction Velocity ◽

Mean Power Spectrum

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Muscle Fiber Conduction Velocity in Right and Left Biceps Brachii for Badminton Players.

The Annals of physiological anthropology ◽

10.2114/ahs1983.12.251 ◽

1993 ◽

Vol 12 (4) ◽

pp. 251-257 ◽

Cited By ~ 6

Author(s):

Satoshi MATSUNAGA ◽

Tsugutake SADOYAMA ◽

Satoru ONOMITU ◽

Tadashi MASUDA ◽

Shigeru KATSUTA

Keyword(s):

Conduction Velocity ◽

Muscle Fiber ◽

Biceps Brachii ◽

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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