De Monte Gianpiero, Arampatzis Adamantios
Institute of Biomechanics and Orthopaedics, German Sport University Cologne, Carl-Diem-Weg 6, 50933 Cologne, Germany.
J Biomech. 2008 Jul 19;41(10):2272-8. doi: 10.1016/j.jbiomech.2008.04.008. Epub 2008 May 22.
The purpose of this study was to examine the influence of different shortening velocities preceding the stretch on moment generation of the triceps surae muscles and architecture of the m. gastrocnemius medialis after shortening-stretch cycles of equal magnitude in vivo. Eleven male subjects (31.6+/-5.8 years, 178.4+/-7.3cm, 80.6+/-9.6kg) performed a series of electro-stimulated (85Hz) shortening-stretch plantar flexion contractions. The shortening-stretch cycles were performed at three constant angular velocities (25, 50, 100 degrees /s) in the plantar flexion direction (shortening) and at 50 degrees /s in the dorsiflexion direction (stretching). The resultant ankle joint moments were calculated through inverse dynamics. Pennation angle and fascicle length of the m. gastrocnemius medialis at rest and during contractions were measured using ultrasonography. The corresponding ankle moments, kinematics and changes in muscle architecture were analysed at seven time intervals. An analysis of variance for repeated measurements and post hoc test with Bonferroni correction was used to check the velocity-related effects on moment enhancement (alpha=0.05). The results show an increase in pennation angles and a decrease in fascicle lengths after the shortening-stretch cycle. The ankle joint moment ratio (post to pre) was higher (p<0.01) than 1.0 indicating a moment enhancement after the shortening-stretch cycle. The found ankle joint moment enhancement was 2-5% after the shortening-stretch cycle and was independed of the shortening velocity. Furthermore, the decrease in fascicle length after the shortening-stretch cycle indicates that the moment enhancement found in the present study is underestimated at least by 1-3%. Considering that the experiments have been done at the ascending limb of the force-length curve and that force enhancement is higher at the descending and the plateau region of the force-length curve, we conclude that the moment enhancement after shortening-stretch cycle can have important physiological affects while locomotion.
本研究的目的是在体内同等幅度的缩短-拉伸循环后，考察拉伸前不同缩短速度对小腿三头肌力矩产生以及腓肠肌内侧头肌纤维结构的影响。11名男性受试者（年龄31.6±5.8岁，身高178.4±7.3厘米，体重80.6±9.6千克）进行了一系列电刺激（85赫兹）的缩短-拉伸跖屈收缩。缩短-拉伸循环在三个恒定角速度（25、50、100度/秒）下在跖屈方向（缩短）进行，在背屈方向（拉伸）以50度/秒进行。通过逆动力学计算得到踝关节力矩。使用超声测量腓肠肌内侧头肌纤维静止和收缩时的羽状角和肌束长度。在七个时间间隔分析相应的踝关节力矩、运动学和肌肉结构变化。采用重复测量方差分析和经Bonferroni校正的事后检验来检查速度对力矩增强的影响（α=0.05）。结果显示，缩短-拉伸循环后羽状角增加，肌束长度减小。踝关节力矩比（收缩后与收缩前）高于1.0（p<0.01），表明缩短-拉伸循环后力矩增强。缩短-拉伸循环后发现的踝关节力矩增强为2%-5%，且与缩短速度无关。此外，缩短-拉伸循环后肌束长度的减小表明，本研究中发现的力矩增强至少被低估了1%-3%。考虑到实验是在力-长度曲线的上升支进行的，且在力-长度曲线的下降支和平原区域力的增强更高，我们得出结论，缩短-拉伸循环后的力矩增强在运动时可能具有重要的生理影响。
