Wohlfart B, Grimm A F, Edman K A
Acta Physiol Scand. 1977 Oct;101(2):155-64. doi: 10.1111/j.1748-1716.1977.tb05994.x.
Isometric peak twitch force (stimulation frequency 0.5/s; 29.5-30.5 degrees C) was correlated with sarcomere length in isolated papillary muscles of the rabbit. Sarcomere length was measured from photographic recordings (1.5 ms exposure time) performed at rest between contractions and at the time of isometric peak twitch force. The sarcomere length at rest was found to be relatively uniform throughout the preparation and to be linearly related to the overall muscle length within the range Lmax-0.85Lmax. The distribution of sarcomere lengths increased considerably as the muscle went from rest to activity. Studies of surface markers showed different degrees of shortening (or elongation) of individual segments along the length of the preparation. The mean resting sarcomere length at Lmax (the optimum muscle length for force production) was 2.44 +/- 0.01 micron (grand mean +/- S.E., 7 muscles). The means active sarcomere length at Lmax was 2.29 +/- 0.04 micron. Active force declined steeply as the muscle length was reduced below Lmax. At a resting sarcomere length of 2.0 micron, active force was approximately 1/3 of the maximum. The observed differences between the length-tension relat-onships in myocardium (twitch responses) and skeletal muscle (tetanic contractions) are discussed on the basis of a length dependency of the activation process in cardiac muscle.
等长收缩峰值抽搐力（刺激频率0.5/s；29.5 - 30.5摄氏度）与兔离体乳头肌中的肌节长度相关。肌节长度通过在收缩间期静止时以及等长收缩峰值抽搐力时进行的摄影记录（曝光时间1.5毫秒）来测量。发现在整个标本中静止时的肌节长度相对均匀，并且在Lmax - 0.85Lmax范围内与整体肌肉长度呈线性相关。随着肌肉从静止状态转变为活动状态，肌节长度的分布显著增加。表面标记物的研究表明，沿着标本长度的各个节段有不同程度的缩短（或伸长）。在Lmax（产生力量的最佳肌肉长度）时的平均静止肌节长度为2.44 +/- 0.01微米（总体平均值 +/- 标准误，7块肌肉）。在Lmax时的平均活动肌节长度为2.29 +/- 0.04微米。当肌肉长度缩短至低于Lmax时，主动力急剧下降。在静止肌节长度为2.0微米时，主动力约为最大值的1/3。基于心肌激活过程的长度依赖性，讨论了心肌（抽搐反应）和骨骼肌（强直收缩）长度 - 张力关系之间观察到的差异。
