Cunnane Brandon, Sinha Usha, Malis Vadim, Hernandez Ryan, Smitaman Edward, Sinha Shantanu
San Diego State University.
University of California, San Diego.
Res Sq. 2023 Feb 9:rs.3.rs-2548171. doi: 10.21203/rs.3.rs-2548171/v1.
Muscle force production is influenced by muscle fiber and aponeurosis architecture. This prospective cohort study utilizes special MR imaging sequences to examine the structure-function in the Medial Gastrocnemius (MG) at three-ankle angles (dorsiflexion, neutral, and plantar flexion) and two sub-maximal levels of maximum voluntary contraction (25% and 50% MVC). The study was performed on 6 young male subjects. Muscle fiber and aponeurosis strain, fiber strain normalized to force, fiber length and pennation angle (at rest and peak contraction) were analyzed for statistical differences between ankle positions and %MVC. A two-way repeated measures ANOVA and post hoc Bonferroni-adjusted tests were conducted for normal data. A related samples test with Friedman's 2-way ANOVA by ranks with corrections for multiple comparisons was conducted for non-normal data. The dorsiflexed ankle position generated significantly higher force with lower fiber strain than neutral and plantarflexed positions. Sarcomere length extracted from muscle fiber length at each ankle angle was used to track the location on the Force-Length curve and showed the MG operates on the curve's ascending limb. Muscle force changes predicted from the F-L curve going from dorsi- to plantarflexion was less than that experimentally observed suggesting other determinants of force changes with ankle position.
肌肉力量的产生受肌纤维和腱膜结构的影响。这项前瞻性队列研究利用特殊的磁共振成像序列，在三个踝关节角度（背屈、中立位和跖屈）以及两个次最大自主收缩水平（25%和50%最大自主收缩）下，检查内侧腓肠肌（MG）的结构-功能。该研究对6名年轻男性受试者进行。分析了肌纤维和腱膜应变、归一化至力的纤维应变、纤维长度和羽状角（静息时和收缩峰值时）在踝关节位置和最大自主收缩百分比之间的统计学差异。对正态数据进行双向重复测量方差分析和事后Bonferroni校正检验。对非正态数据进行相关样本检验，采用Friedman双向秩和方差分析并进行多重比较校正。背屈的踝关节位置比中立位和跖屈位置产生显著更高的力，且纤维应变更低。从每个踝关节角度的肌纤维长度提取的肌节长度用于追踪力-长度曲线上的位置，结果显示内侧腓肠肌在该曲线的上升支上运作。从背屈到跖屈，根据力-长度曲线预测的肌肉力量变化小于实验观察到的变化，这表明还有其他因素决定了随着踝关节位置变化的力量变化。
