Gregory J E, Morgan D L, Allen T J, Proske U
Department of Physiology, Monash University, Clayton, VIC, Australia.
Eur J Appl Physiol. 2007 Mar;99(4):431-41. doi: 10.1007/s00421-006-0363-x. Epub 2006 Dec 22.
Eccentric exercise can produce damage to muscle fibres. Here damage indicators are measured in the medial gastrocnemius muscle of the anaesthetised cat after eccentric contractions on the descending limb of the muscle's length-tension relation, compared with eccentric contractions on the ascending limb and concentric contractions on the descending limb. One damage indicator is a shift of the optimum length for peak active tension, in the direction of longer muscle lengths. The shift has been attributed to an increase in muscle compliance. It is a corollary of a current theory for the mechanism of the damage. With the intention of seeking further support for the theory, in these experiments we test the idea that other damage indicators, specifically the fall in twitch:tetanus ratio and in muscle force are due, in part, to such an increase in compliance. This was tested in an undamaged muscle by insertion of a compliant spring (0.19 mm N(-1)) in series with the muscle. This led to a fall in tetanic tension by 17%, a shift in optimum length of 1.7 mm in the direction of longer muscle lengths and a fall in twitch tetanus ratio by 15%. The fall in tension is postulated to be due to development of non-uniform sarcomere lengths within muscle fibres. It is concluded that after a series of eccentric contractions of a muscle, the fall in force is the result of a number of interdependent factors, not all of which are a direct consequence of the damage process.
离心运动可导致肌肉纤维损伤。在此，我们对麻醉猫的腓肠肌内侧进行了研究，在肌肉长度 - 张力关系的下降支进行离心收缩后，测量损伤指标，并与在上升支进行的离心收缩以及在下降支进行的向心收缩进行比较。一个损伤指标是产生最大主动张力的最佳长度向更长肌肉长度方向的偏移。这种偏移被认为是由于肌肉顺应性增加所致。这是当前损伤机制理论的一个必然结果。为了寻求对该理论的进一步支持，在这些实验中，我们测试了这样一种观点，即其他损伤指标，特别是单收缩与强直收缩比值的下降以及肌肉力量的下降，部分是由于顺应性的这种增加。我们通过在肌肉串联插入一个顺应性弹簧（0.19 mm N⁻¹），在未受损肌肉中对此进行了测试。这导致强直张力下降了17%，最佳长度向更长肌肉长度方向偏移了1.7 mm，单收缩与强直收缩比值下降了15%。张力下降被推测是由于肌肉纤维内肌节长度不均匀发展所致。得出的结论是，肌肉经过一系列离心收缩后，力量下降是多种相互依存因素的结果，并非所有因素都是损伤过程的直接后果。
