FATIGUE EFFECTS ON MUSCLE EXCITABILITY

Citation
T. Hortobagyi et al., FATIGUE EFFECTS ON MUSCLE EXCITABILITY, International journal of sports medicine, 17(6), 1996, pp. 409-414
Citations number
25
Categorie Soggetti
Sport Sciences
ISSN journal
01724622
Volume
17
Issue
6
Year of publication
1996
Pages
409 - 414
Database
ISI
SICI code
0172-4622(1996)17:6<409:FEOME>2.0.ZU;2-L
Abstract
Repeated isometric or shortening contractions of skeletal muscle cause muscle fatigue but several prior studies have reported an apparent ab sence of muscle fatigue when humans performed up to 70 lengthening con tractions. We pursued the hypothesis that perhaps muscle excitability is a factor that aids force preservation with repeated eccentric actio ns, Soleus compound muscle action potential (M-wave) latency, peak-to- peak amplitude (PPA), duration, and area under the curve were examined in 12 subjects (mean age 24.3 y) over 4 testing days that included: n o exercise, isometric exercise (neutral ankle angle), isokinetic (0.5 rad . s(-1)) concentric and eccentric exercise of the plantar flexors in the seated position on a Biodex dynamometer. Supramaximal shocks we re delivered to the tibial nerve in the popliteal fossa at baseline (3 shocks, 1 min apart), during exercise(1 shock-after each of 5 bouts/1 0 contractions), and during 10-min recovery. From initial to final con tractions, concentric, isometric, and eccentric fatigue was -32, -41 a nd +2% (Condition by Trial interaction, F-2,F-22 = 25.1, p = 0.000). N o changes occurred in latency or duration (p > 0.05), but PPA (Conditi on by Time interaction, F-51,F-561 = 3.7, p = 0.000) increased during isometric and eccentric exercise and remained elevated during recovery . Area increased (F-51,F-561 = 3.1, p = 0.000) significantly during al l three exercise conditions and approximated baseline by minute 8 of r ecovery, It was concluded that although the potentiation of the action potential of individual muscle fibers seems to be the common mechanis m underlying the increase in muscle excitability during plantar flexio n exercise, it is possible that different factors could cause such a n on-specific response.