Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada.
Department of Motion and Exercise Science, University of Stuttgart, Germany.
J Biomech. 2019 Mar 27;86:160-166. doi: 10.1016/j.jbiomech.2019.01.054. Epub 2019 Feb 12.
External forces from our environment impose transverse loads on our muscles. Studies in rats have shown that transverse loads result in a decrease in the longitudinal muscle force. Changes in muscle architecture during contraction may contribute to the observed force decrease. The aim of this study was to quantify changes in pennation angle, fascicle dimensions, and muscle thickness during contraction under external transverse load. Electrical stimuli were elicited to evoke maximal force twitches in the right calf muscles of humans. Trials were conducted with transverse loads of 2, 4.5, and 10 kg. An ultrasound probe was placed on the medial gastrocnemius in line with the transverse load to quantify muscle characteristics during muscle twitches. Maximum twitch force decreased with increased transverse muscle loading. The 2, 4.5, and 10 kg of transverse load showed a 9, 13, and 16% decrease in longitudinal force, respectively. Within the field of view of the ultrasound images, and thus directly beneath the external load, loading of the muscle resulted in a decrease in the muscle thickness and pennation angle, with higher loads causing greater decreases. During twitches the muscle transiently increased in thickness and pennation angle, as did fascicle thickness. Higher transverse loads showed a reduced increase in muscle thickness. Smaller increases in pennation angle and fascicle thickness strain also occurred with higher transverse loads. This study shows that increased transverse loading caused a decrease in ankle moment, muscle thickness, and pennation angle, as well as transverse deformation of the fascicles.
环境施加于我们肌肉的外力为横向负荷。在大鼠中的研究表明，横向负荷会导致纵向肌肉力量减小。收缩过程中肌肉结构的变化可能是导致观察到的力减小的原因之一。本研究的目的是定量测量在外部横向负荷下收缩过程中肌斜角、肌束尺寸和肌肉厚度的变化。通过电刺激来诱发人类右小腿肌肉的最大力搐搦。在 2、4.5 和 10kg 的横向负荷下进行试验。将超声探头放置在与横向负荷线一致的内侧腓肠肌上，以在肌肉搐搦期间定量测量肌肉特征。最大搐搦力随横向肌肉负荷的增加而减小。2、4.5 和 10kg 的横向负荷分别导致纵向力降低 9%、13%和 16%。在超声图像的视野内，即在外部负荷的正下方，肌肉的负荷会导致肌肉厚度和肌斜角减小，负荷越高，减小幅度越大。在搐搦过程中，肌肉的厚度和肌斜角会暂时增加，肌束厚度也是如此。较高的横向负荷会导致肌肉厚度的增加减少。较高的横向负荷也会导致肌斜角和肌束厚度应变的增加减少。本研究表明，增加的横向负荷会导致踝关节力矩、肌肉厚度和肌斜角减小，以及肌束的横向变形。
