Nicol C, Komi P V, Horita T, Kyröläinen H, Takala T E
Department of Biology of Physical Activity, University of Jyväskylä, Finland.
Eur J Appl Physiol Occup Physiol. 1996;72(5-6):401-9. doi: 10.1007/BF00242268.
The stretch-shortening cycle (SSC) is an effective and natural form of muscle function but, when repeated with sufficient intensity or duration, it may lead to muscle damage and functional defects. A reduced tolerance to impact has been reported, which may be partly attributed to a reduced stretch-reflex potentiation. The aim of the present study was to examine the influence of SSC-induced metabolic fatigue and muscle damage on the efficacy of stretch reflexes, as judged by the electromyograph (EMG) response of two shank muscles (lateral gastrocnemius LG, soleus SOL) to controlled ramp stretches. These EMG responses were recorded before and immediately after exhausting SSC-type leg exercise and 2 h, 2 days and 4 days later. Serum concentrations of creatine kinase ([CK]), myoglobin and lactate were measured repetitively along the protocol. Two maximal vertical drop jumps and counter-movement jumps were performed after each reflex test. The exhausting SSC-type exercise induced an immediate reduction (P < 0.05) with a delayed short-term recovery of the LG peak-to-peak reflex amplitude. This was not accompanied by significant changes in the reflex latency. The drop jump performance remained slightly but significantly reduced (P < 0.05) until the 2nd day postexercise. Peak [CK] appeared for all the subjects on the 2nd day, suggesting the presence of muscle damage. The increase in [CK] between the 2nd h and the 2nd day postexercise was found to be negatively related (P < 0.001) to the relative changes in the drop jump height. Furthermore, a significant relationship (P < 0.05) was found between recovery of the stretch reflex in LG and the decrease of [CK] between the 2nd and the 4th day. These findings support the hypothesis of a reduced stretch-reflex sensitivity. While the exact mechanisms of the reflex inhibition remain unclear, it is emphasized that the delayed recovery of the reflex sensitivity could have resulted from the progressive inflammation that develops in cases of muscle damage.
拉长-缩短周期（SSC）是一种有效且自然的肌肉功能形式，但当以足够的强度或持续时间重复进行时，可能会导致肌肉损伤和功能缺陷。据报道，冲击耐受性降低，这可能部分归因于牵张反射增强作用减弱。本研究的目的是通过两块小腿肌肉（外侧腓肠肌LG、比目鱼肌SOL）对受控斜坡拉伸的肌电图（EMG）反应，来检验SSC诱导的代谢性疲劳和肌肉损伤对牵张反射效能的影响。这些EMG反应在进行耗尽性SSC型腿部运动之前、运动结束后即刻以及2小时、2天和4天后进行记录。在整个实验过程中重复测量血清肌酸激酶（[CK]）、肌红蛋白和乳酸的浓度。在每次反射测试后进行两次最大垂直跳和反向移动跳。耗尽性SSC型运动导致LG峰-峰反射幅度立即降低（P<0.05），并伴有短期延迟恢复。这并未伴随着反射潜伏期的显著变化。直到运动后第2天，垂直跳成绩仍略有但显著降低（P<0.05）。所有受试者的[CK]峰值出现在第2天，表明存在肌肉损伤。发现运动后第2小时至第2天[CK]的增加与垂直跳高度的相对变化呈负相关（P<0.001）。此外，发现LG牵张反射的恢复与第2天至第4天[CK]的降低之间存在显著关系（P<0.05）。这些发现支持牵张反射敏感性降低的假说。虽然反射抑制的确切机制尚不清楚，但需要强调的是，反射敏感性的延迟恢复可能是由肌肉损伤情况下发生的进行性炎症导致的。
