Fitts R H, Holloszy J O
J Appl Physiol Respir Environ Exerc Physiol. 1978 Dec;45(6):899-902. doi: 10.1152/jappl.1978.45.6.899.
The contractile properties of frog sartorius muscles were evaluated during development of fatigue and recovery. Muscles were stimulated under anaerobic conditions at a rate of 30 stimuli/min. Twitch tension (Pt) decreased 59% and tetanic tension (Po) decreased 52% during 15 min of stimulation. Contraction time and one-half relaxation time increased markedly during the first 6 min and then leveld off. The peak rate of twitch tension development (dP/dt) progressively declined to 33% of its initial value. Maximum shortening velocity did not change significantly. Large increases in Pt and twitch dP/dt occurred during the first 15 s of recovery while Po did not increase significantly in this time. Thereafter, Pt, Po, and, dP/dt all progressively returned towards normal over 30 min. These results show that the initial rapid recovery in Pt is not due to an increase in the capacity to generate force. Po is a better indicator of the force-generating capacity of a muscle because, unlike Pt, it is not affected by changes in the rate of tension development.
在疲劳发展和恢复过程中评估了青蛙缝匠肌的收缩特性。在无氧条件下以30次刺激/分钟的频率刺激肌肉。在刺激15分钟期间，单收缩张力（Pt）下降了59%，强直张力（Po）下降了52%。收缩时间和半松弛时间在前6分钟显著增加，然后趋于平稳。单收缩张力发展的峰值速率（dP/dt）逐渐下降至其初始值的33%。最大缩短速度没有显著变化。在恢复的前15秒内，Pt和单收缩dP/dt大幅增加，而在此期间Po没有显著增加。此后，Pt、Po和dP/dt在30分钟内都逐渐恢复到正常水平。这些结果表明，Pt最初的快速恢复不是由于产生力的能力增加。Po是肌肉产生力能力的更好指标，因为与Pt不同，它不受张力发展速率变化的影响。
