Involvement of membrane excitation failure in fatigue induced by intermittent submaximal voluntary contraction of the first dorsal interosseous muscle.
Factors involving muscle fatigue were studied at intermittent isometric contraction of the first dorsal interosseous muscle (FDI). Subjects made repeated contraction of 6 s, 40% of maximal voluntary contraction (40% MVC) (= target force) followed by 4 s rest until the target force could no longer be maintained. Measurement of MVC, recording of M wave evoked from the relaxed muscle, force measurement during tetanic electrical stimulation and measurement of serum K+ concentration were performed every 2 min during the fatiguing exercise and after 10 min of recovery. The declining rate of MVC force was always smaller than that of the force generated by 50 Hz stimulation, suggesting that no central nervous system (CNS) failure was involved. The amplitude and the area of the M wave declined while the duration of the wave increased, accompanied by the rise in serum K+ concentration. After 10 min of recovery, all parameters except the MVC force were restored. Thus we concluded that the failure in muscle membrane excitation, as well as the failure in excitation/contraction coupling, is involved in the deteriorating force generating capacity of FDI during intermittent isometric contraction.
Fujimoto
T
T
Department of Physiology and Biomechanics, National Institute of Fitness and Sports, Kagoshima, Japan.
Nishizono
H
H
D000328:Adult; D004558:Electric Stimulation; D004576:Electromyography; D005221:Fatigue / Q000097:blood / Q000503:physiopathology*; D005385:Fingers; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D007773:Lactates / Q000097:blood; D008297:Male; D008564:Membrane Potentials / Q000502:physiology*; D009132:Muscles / Q000294:innervation / Q000378:metabolism / Q000503:physiopathology*; D009210:Myofibrils / Q000378:metabolism / Q000502:physiology; D005082:Physical Exertion / Q000502:physiology; D011188:Potassium / Q000097:blood; D014459:Ulnar Nerve / Q000502:physiology
D007773:Lactates; D011188:Potassium