School of Human Movement and Nutrition Sciences, The University of Queensland, Blair Drive 26B, St Lucia, Brisbane, 4067, Australia.
School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane, Australia.
Eur J Appl Physiol. 2023 Aug;123(8):1801-1808. doi: 10.1007/s00421-023-05188-2. Epub 2023 Apr 13.
To investigate the effect of muscle force during active stretch on quantitative and qualitative indicators of exercise-induced muscle damage (EIMD) in the medial gastrocnemius (MG) muscle.
Twelve recreationally active volunteers performed two trials of an eccentric heel drop exercise. Participants performed a single bout of low-load (body weight) and high-load (body weight + 30% body weight) exercises on separate legs. The total mechanical work output for each condition was matched between legs. Before, two hours and 48 h after each bout of eccentric exercise, electrically stimulated triceps surae twitch torque, muscle soreness, MG active fascicle length at maximum twitch torque and muscle passive stiffness were collected. Triceps surae electromyographic (EMG) activity, MG fascicle stretch and MG muscle-tendon unit (MTU) length were measured during the eccentric tasks.
The high-load condition increased triceps surae muscle activity by 6-9%, but reduced MG fascicle stretch (p < 0.001). MTU stretch was similar between conditions. The greater muscle force during stretch did not give rise to additional torque loss (5 vs 6%) or intensify muscle soreness.
Adding 30% body weight during eccentric contractions has a modest impact on exercise-induced muscle damage in the medial gastrocnemius muscle. These results suggest that muscle load may not be an important determinant of stretch-induced muscle damage in the human MG muscle. The muscle investigated does exhibit large pennation angles and high series elastic compliance; architectural features that likely buffer muscle fibres against stretch and damage.
研究主动拉伸过程中肌肉力量对内侧腓肠肌（MG）运动诱导性肌肉损伤（EIMD）的定量和定性指标的影响。
12 名有规律运动的志愿者进行了两次跟腱离心伸展运动。参与者在两条腿上分别进行低负荷（体重）和高负荷（体重+30%体重）的离心运动。两条腿的每个条件的总机械功输出相匹配。在每次离心运动前后两小时和 48 小时，采集电刺激比目鱼肌单次收缩扭矩、肌肉酸痛、最大收缩扭矩时的 MG 主动肌纤维长度和肌肉被动僵硬度。在离心任务期间测量比目鱼肌肌电图（EMG）活动、MG 肌纤维拉伸和 MG 肌肉肌腱单元（MTU）长度。
高负荷条件增加了 6-9%的比目鱼肌肌肉活动，但减少了 MG 肌纤维拉伸（p<0.001）。MTU 拉伸在两种情况下相似。在拉伸过程中增加肌肉力量并没有导致额外的扭矩损失（5%对 6%）或加剧肌肉酸痛。
在离心收缩中增加 30%的体重对内侧腓肠肌的运动诱导性肌肉损伤只有适度的影响。这些结果表明，肌肉负荷可能不是人类 MG 肌肉中拉伸诱导性肌肉损伤的重要决定因素。所研究的肌肉具有较大的羽状角和较高的串联弹性顺应性；这些结构特征可能缓冲肌肉纤维免受拉伸和损伤。
