Movement-Interactions-Performance, MIP, UR 4334, Nantes Université, Nantes, France.
CIAMS, Université d'Orléans, Orléans, France.
Scand J Med Sci Sports. 2022 Sep;32(9):1335-1345. doi: 10.1111/sms.14191. Epub 2022 Jun 6.
Large inter-individual variability of activation strategies is observed during hamstring strengthening exercises but their consequences remain unexplored. The objective of this study was to determine whether individual activation strategies are related to the distribution of damage across the hamstring muscle heads semimembranosus (SM), semitendinosus (ST), and biceps femoris (BF) after eccentric contractions. 24 participants performed 5 sets of 15 maximal eccentric contractions of knee flexors on a dynamometer, while activation of each muscle head was assessed using surface electromyography. Knee flexion maximal isometric strength was assessed before exercise and 48 h afterward. Shear modulus was measured using shear wave elastography before exercise and 30 min afterward to quantify the distribution of damage across the hamstring muscle heads. At 48 h, maximal knee flexion torque had decreased by 15.9% ± 16.9% (p < 0.001). Although no differences between activation ratios of each muscle were found during the eccentric exercise (all p > 0.364), we reported a heterogeneous distribution of damage, with a larger change in shear modulus of ST/Hams than SM/Hams (+70.8%, p < 0.001) or BF/Hams (+50.3%, p < 0.001). A large correlation was found between the distribution of activation and the distribution of damage for ST/Hams (r = 0.69; p < 001). This study provides evidence that the distribution of activation during maximal eccentric contractions has mechanical consequences for synergist muscles. Further studies are needed to understand whether individual activation strategies influence the distribution of structural adaptations after a training program.
在进行腘绳肌强化训练时，观察到个体之间激活策略的变异性很大，但它们的后果仍不清楚。本研究的目的是确定个体激活策略是否与离心收缩后腘绳肌头部半膜肌（SM）、半腱肌（ST）和股二头肌（BF）的损伤分布有关。24 名参与者在测力计上进行了 5 组 15 次最大的膝关节屈肌离心收缩，同时使用表面肌电图评估每个肌肉头部的激活情况。在运动前和 48 小时后评估膝关节最大等长强度。在运动前和 30 分钟后使用剪切波弹性成像测量剪切模量，以量化腘绳肌头部的损伤分布。在 48 小时时，最大膝关节屈曲扭矩下降了 15.9%±16.9%（p<0.001）。尽管在离心运动期间未发现每个肌肉的激活比率之间存在差异（所有 p>0.364），但我们报告了损伤分布不均匀，ST/Hams 的剪切模量变化大于 SM/Hams（+70.8%，p<0.001）或 BF/Hams（+50.3%，p<0.001）。激活分布与 ST/Hams 的损伤分布之间存在很大的相关性（r=0.69；p<0.001）。这项研究提供了证据表明，最大离心收缩期间的激活分布对协同肌肉有机械后果。需要进一步的研究来了解个体激活策略是否会影响训练计划后的结构适应分布。
