Department of Kinesiology and Physical Education, Pine Avenue West 475, Montreal (QC), Canada.
J Biomech. 2009 Dec 11;42(16):2808-12. doi: 10.1016/j.jbiomech.2009.08.011. Epub 2009 Sep 17.
The main goal of this study was to evaluate the dynamics of sarcomeres during isometric activation of skeletal muscle myofibrils. Rabbit psoas myofibrils (n=14) were attached between a pair of cantilevers for force measurements at one side and a rigid glass needle at the other side, and their images were used for measurements of individual sarcomere lengths (SL) during contractions. Myofibrils were set at average SL between 2.13 and 3.06 microm, and were activated and held isometric for 20-35s during which SL and force were continuously measured. SL dispersion increased from the rest state to activation, but it remained mostly constant during the activation period. Even with the length non-uniformity developed during myofibril activation, most sarcomeres stabilized their length changes during the isometric contraction. As a result, sarcomeres contracted at different degrees of filament overlap while producing similar forces. When the myofibrils were separated in two groups that produced force at averaged short (< or =2.5 microm) or long (> or =2.5 microm) SL, the initial non-uniformity was greater in long lengths, but changes observed in sarcomeres during the activation period were similar, suggesting that sarcomere stability is not length-dependent.
本研究的主要目的是评估在骨骼肌肌原纤维等长激活过程中肌节的动力学。将兔腰大肌肌原纤维（n=14）附着在一对悬梁之间，一侧用于力测量，另一侧用刚性玻璃针，在收缩过程中用于测量各个肌节长度（SL）。肌原纤维设定在平均 SL 为 2.13 到 3.06 微米之间，并在激活时保持等长 20-35 秒，在此期间连续测量 SL 和力。SL 分散度从静息状态增加到激活状态，但在激活期间基本保持不变。即使在肌原纤维激活过程中出现长度不均匀性，大多数肌节在等长收缩期间稳定其长度变化。结果，肌节在产生相似力的情况下以不同程度的纤维重叠收缩。当将肌原纤维分为两组，分别在平均短（<或=2.5 微米）或长（>或=2.5 微米）SL 下产生力时，在长 SL 下初始不均匀性更大，但在激活期间观察到的肌节变化相似，表明肌节稳定性不依赖于长度。
