Disagreement exists regarding the effects of muscle length on fatigue. One concern with the previous reports from human muscle is that force levels at each muscle length were not adequately controlled. This study examined the effects of muscle length on the fatigue of human quadriceps femoris muscle when identical initial force levels were used. Twelve healthy subjects participated. Each subject was tested at near optimal and short muscle lengths (90° and 15° of knee flexion, respectively). Fatigue was produced by repetitive activation of the muscle (180 contractions) with 14-pulse, 40 pps trains delivered 1/s using an intensity that initially produced 20% of the subject's maximum voluntary contraction at the short length. The muscle was tested with 14.3, 40 and 60 pps trains to determine the amount of fatigue. The percentage decline (fatigue) in Force-Time Integral and peak force was: 14.3 pps 40 pps 60 pps FTI Peak FTI Peak FTI Peak 15 Deg 59% 59% 37% 42% 38% 49% 90 Deg 76% 78% 51% 52% 38% 56% The results show that less fatigue was produced at the shorter muscle length and that the difference was greatest at the lowest frequency. These results suggest that there is greater impairment of excitation contraction coupling at the optimal muscle length than at the shorter length.
|Original language||English (US)|
|State||Published - 1997|
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Biochemistry, Genetics and Molecular Biology(all)
- Cell Biology