University of Paris Est Creteil, BIOTN, Creteil, France; EMEIS Group, Clinique du Parc de Belleville, Paris, France.
University of Paris Est Creteil, BIOTN, Creteil, France.
Ultrasound Med Biol. 2024 Dec;50(12):1987-1994. doi: 10.1016/j.ultrasmedbio.2024.09.004. Epub 2024 Sep 28.
This study aimed: (i) to investigate the impact of fatigue, triggered by maximal isometric contraction exercises, on the active and passive stiffness of plantar flexors (PF), and (ii) to examine the relationship between changes in mechanical parameters and neuromuscular alterations after fatigue.
A healthy cohort (n = 12; age = 27.3 ± 5.5 y; BMI = 24.4 ± 2.35 kg/m²) was instructed to perform 60 isometric contractions, each lasting 4 s with a 1-s rest interval, using an ergometer. Several measures were taken before and after the fatigue protocol. First, the stiffness of the PF-tendon complex (PFC) was quantified during passive ankle mobilization both during and after the fatigue protocol using the ergometer. Additionally, from shear wave elastography, the active and passive stiffness of the gastrocnemius medialis (GM) were measured during passive ankle mobilization and isometric maximal voluntary contraction (MVC), respectively. Finally, the peak torque and the rate of torque development (RFD) of PF were assessed during the MVC using the ergometer. Ankle muscle activities (surface electromyograph [SEMG]) were recorded during all evaluations using electromyography.
After the fatigue protocol, the results revealed a decline in active stiffness, peak torque of PF, RFD and SEMG activity of the GM (p < 0.001). Furthermore, significant correlation was identified between the decrease of the peak torque of PF and the active stiffness of the GM (r = 0.6; p < 0.05). A decrease in the PFC stiffness (p < 0.001) and a decrease in the shear modulus of the GM at 20° (p < 0.001) were also observed.
Isometric fatiguing exercises modify the mechanical properties of both the contractile and elastic components. Notably, decreases in both passive and active stiffness may be critical for athletes, as these changes could potentially increase the risk of injury.
本研究旨在：（i）探讨最大等长收缩运动引起的疲劳对跖屈肌（PF）主动和被动刚度的影响；（ii）研究疲劳后机械参数变化与神经肌肉改变之间的关系。
一个健康的队列（n = 12；年龄 = 27.3 ± 5.5 岁；BMI = 24.4 ± 2.35 kg/m²）被指示使用测力计进行 60 次持续 4 秒的等长收缩，每次收缩之间休息 1 秒。在疲劳方案前后进行了几项测量。首先，在疲劳方案期间和之后，使用测力计在被动踝关节活动期间量化 PF 肌腱复合体（PFC）的刚度。此外，从剪切波弹性成像中，在被动踝关节活动和等长最大自主收缩（MVC）期间分别测量内侧腓肠肌（GM）的主动和被动刚度。最后，使用测力计在 MVC 期间评估 PF 的峰值扭矩和扭矩发展速率（RFD）。在所有评估过程中，使用肌电图记录踝关节肌肉活动（表面肌电图 [SEMG]）。
疲劳方案后，结果显示主动刚度、PF 的峰值扭矩、RFD 和 GM 的 SEMG 活动均下降（p < 0.001）。此外，还发现 PF 的峰值扭矩下降与 GM 的主动刚度之间存在显著相关性（r = 0.6；p < 0.05）。还观察到 PFC 刚度降低（p < 0.001）和 GM 在 20°时的剪切模量降低（p < 0.001）。
等长疲劳运动改变了收缩和弹性成分的机械性能。值得注意的是，被动和主动刚度的降低可能对运动员至关重要，因为这些变化可能会增加受伤的风险。
