Gollhofer A, Komi P V, Fujitsuka N, Miyashita M
Int J Sports Med. 1987 Mar;8 Suppl 1:38-47.
Detailed electromyographic (EMG) analysis of primarily triceps brachii muscle was carried out on subjects who performed 100 repeated and exhaustive stretch-shortening cycle (SSC) exercises on a special sledge apparatus incorporating a force plate. The fatigue contractions were performed on submaximal levels but the before-after comparison included also maximal "drop jumps" on the sledge as well as falls on to the floor. SSC contractions caused clear reduction in the mechanical performance capacity of the muscles. EMG analysis revealed that integrated EMG (IEMG) increased during the course of fatigue both during eccentric and concentric phases of the cycle. However, when IEMG was time-normalized, the changes were nonsignificant. The IEMG/force ratio increased especially during the eccentric phase both in submaximal and maximal drops. In maximal drops, there was also a great reduction in concentric IEMG. Rectified EMG curves were also averaged in blocks of ten successive fatigue contractions. This analysis revealed clear appearance of short (SLC), medium (MLC), and long (LLC) latency reflex components in most of the subjects during the early contact on the platform. The fatigue effects on these components were individual and also condition dependent so that in maximal drops there was a trend for reflex potentiation. In maximal drops on to the floor, which represented the highest stretch loads on the muscles, there was a tendency for reduction of amplitudes of the reflex components. The results suggest that in exhaustive SSC exercise muscular activation processes are reduced and primarily in the eccentric phase. Muscle spindles are suggested to become differentially affected by fatigue substances depending on the load intensity during eccentric contraction.
对在配备测力板的特殊雪橇装置上进行100次重复且彻底的拉长-缩短循环（SSC）练习的受试者，主要针对肱三头肌进行了详细的肌电图（EMG）分析。疲劳收缩在次最大水平进行，但前后比较还包括在雪橇上的最大“下落跳”以及跳到地面上。SSC收缩导致肌肉机械性能能力明显下降。EMG分析显示，在循环的离心和向心阶段，积分肌电图（IEMG）在疲劳过程中均增加。然而，当IEMG进行时间标准化时，变化不显著。IEMG/力比值尤其在次最大和最大下落的离心阶段增加。在最大下落时，向心IEMG也有很大降低。整流后的EMG曲线也在连续十次疲劳收缩的组中进行平均。该分析显示，在大多数受试者中，在接触平台的早期，明显出现了短潜伏期成分（SLC）、中潜伏期成分（MLC）和长潜伏期成分（LLC）。疲劳对这些成分的影响因人而异，也取决于具体情况，因此在最大下落时存在反射增强的趋势。在跳到地面的最大下落中，这代表了对肌肉的最高拉伸负荷，反射成分的幅度有降低的趋势。结果表明，在彻底的SSC运动中，肌肉激活过程减少，主要发生在离心阶段。肌肉纺锤体被认为会根据离心收缩期间的负荷强度受到疲劳物质的不同影响。
