Affiliation:
1. Department of Public Health, Aarhus University, DK-8000 Aarhus C, Denmark
2. Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark
Abstract
In skeletal muscles the ability to generate power is reduced during fatigue. Maximal power can in isolated muscles be calculated from the force-velocity relationship. This relationship is well described by the Hill equation, which contains three parameters: 1) Maximal isometric force, 2) maximum contraction velocity, and 3) curvature. Here, we investigated the hypothesis that a fatigue-induced loss of power will be associated with changes in curvature of the force-velocity curve in slow-twitch muscles but not in fast-twitch muscles during the development of fatigue. Isolated rat soleus (slow-twitch) and EDL (fast-twitch) muscles were incubated in Krebs-Ringer solution at 30°C and stimulated electrically at 60 Hz (soleus) and 150 Hz (EDL) to perform a series of concentric contractions to fatigue. Force-velocity data were fitted to the Hill equation, and curvature was determined as the ratio of the curve parameters a/F0 (inversely related to curvature). At the end of the fatiguing protocol, maximal power decreased by 58±5% (soleus) and 69±4% (EDL) compared to initial values in non-fatigued muscles. At the end of the fatiguing sequence, curvature increased as judged from the decrease in a/F0 by 81±20% in soleus and by 31±12% in EDL. However, during the initial phases of fatiguing stimulation we observed a small decrease in curvature in EDL muscles, but not soleus, which may be a result of post-activation potentiation. In conclusion, fatigue-induced loss of power is strongly associated with an increased curvature of the force-velocity relationship, particularly in slow-twitch muscles.
Funder
Danish Council for Independent Research
Helga and Peter Kvornings foundation
Publisher
The Company of Biologists
Subject
Insect Science,Molecular Biology,Animal Science and Zoology,Aquatic Science,Physiology,Ecology, Evolution, Behavior and Systematics
Cited by
8 articles.
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