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Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Plantar flexion fatigue and muscle fiber type in power and endurance athletes. Med. Sci. Sports Exercise, Vol. 12, No. 4, pp. 262-267, 1980. The relationship between isometric plantar flexion strength fatigue patterns and muscle fiber type composition of the gastrocnemius was assessed in endurance (N = 8) and power (N = 8) trained males. Following baseline strength assessment, subjects were administered two different 25 trial isometric exercise regimens: on one exercise day each 10-sec fatigue trial was separated by a five-sec intertrial rest period, while on the second exercise day the 10-sec fatigue trials was separated by a 20-sec intertrial rest periods. Muscle biopsies were secured from the right medial gastrocnemius. Significantly different fatigue patterns resulted between power and endurance groups, with the power group fatiguing five times faster than the endurance group in the 10.5 condition and demonstrating more complex fatigue curves in both exercise conditions. Slow twitch fiber percent number correlated with rate of fatigability as measured by linear trend coefficients in power (r = .84) and endurance groups (r = .26). Rate of fatigability correlated with maximum isometric strength in both power (r = -.66) and endurance (r = .86) groups. Thus, maximum isometric strength was a better predictor of rate of fatigability than muscle fiber type composition.
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PMID:Plantar flexion fatigue and muscle fiber type in power and endurance athletes. 742 76

Nine healthy men (22-45 yr) completed 100 repetitive maximal isometric contractions of the ankle plantar flexor muscles in two knee positions of full extension (K0) and flexion at 90 degrees (K90), positions that varied the contribution of the gastrocnemii. Electromyographic activity was recorded from the medial and lateral gastrocnemii and soleus muscles by using surface electrodes. Plantar flexion torque in K0 was greater and decreased more rapidly than in K90. The electromyographic amplitude decreased over time, and there were no significant differences between muscles and knee joint positions. The level of voluntary effort, assessed by a supramaximal electrical stimulation during every 10th contraction, decreased from 96 to 70% (P < 0.05) with no difference between K0 and K90. It was suggested that a decrease in plantar flexion torque was attributable to both central and peripheral fatigue and that greater fatigability in K0 than in K90 would result from a greater contribution and hence more pronounced fatigue of the gastrocnemius muscle. Further support for this possibility was provided from changes in twitch torque.
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PMID:Fatigue responses of human triceps surae muscles during repetitive maximal isometric contractions. 1084 7