Contractile properties and susceptibility to exercise-induced damage of normal and mdx mouse tibialis anterior muscle.

摘要: 1. The functional properties of tibialis anterior muscles normal adult (C57BL/10) and age-matched dystrophin-deficient (C57BL/10 mdx) mice have been investigated in situ. Comparisons were made between muscle strength, rates force development relaxation, force-frequency responses fatiguability. Subjecting mdx C57 to a regimen eccentric exercise allowed the hypothesis be tested that are more susceptible exercise-induced damage. 2. were, on average, 30% stronger than almost 80% heavier, but both had similar lengths. Thus, although absolute terms, their estimated per unit cross-sectional area was significantly less muscles. 3. relationships differed whilst, at 40 Hz, former developed 70% 100 latter only 55% maximal force. Twitch muscles, contraction time shortened, consequent reduction fusion frequency probably explains differences observed two groups. 4. fatiguable when stimulated repeatedly Hz. It is possible lower relative Hz entailed energy demand thus slower rate fatigue seen 5. Eccentrically exercised showed large loss for up 12 days after exercise. Maximal occurred 3 (55% non-exercised muscle), which also corresponded with period greatest fibre necrosis. reduced Hz/100 ratio 1 This primarily due twitch amplitude rather change course twitch. unlikely, therefore, altered contractile characteristics result presence damaged otherwise fibres. 6. displayed degrees Furthermore, recovery nadir very By exercise, recovered 76% control respectively. Our findings do not support