Kay Anthony D, Blazevich Anthony J
Sport, Exercise and Life Sciences, The Univ. of Northampton, Park Campus, Boughton Green Rd., Northampton NN2 7AL, UK.
J Appl Physiol (1985). 2009 Oct;107(4):1181-9. doi: 10.1152/japplphysiol.00281.2009. Epub 2009 Jul 30.
The effects of isometric contractions and passive stretching on muscle-tendon mechanics and muscle activity were studied in 16 healthy human volunteers. First, peak concentric and passive ankle joint moment data were recorded on an isokinetic dynamometer with electromyographic monitoring of the triceps surae; real-time motion analysis of the lower leg and ultrasound imaging of the Achilles-medial gastrocnemius muscle-tendon junction were simultaneously conducted. Second, the subjects performed six 8-s maximal voluntary isometric contractions (MVICs) before repeating the passive and active trials. Although there was no decrease in isometric joint moment after MVICs, peak concentric moment was significantly reduced (11.5%, P < 0.01). This was accompanied by, and correlated with (r = 0.90, P < 0.01), significant reductions in peak triceps surae electromyographic amplitude (21.0%, P < 0.01). Achilles tendon stiffness (10.9%, P < 0.01) and passive joint moment (4.9%, P < 0.01) were also significantly reduced. Third, the subjects performed three 60-s static plantar flexor stretches before being retested 2 and 30 min after stretch. The stretch protocol caused no significant change in any measure. At 30 min after stretching, significant recovery in concentric moment and muscle activity was detected at dorsiflexed joint angles, while Achilles tendon stiffness and passive joint moment remained significantly reduced. These data show that the performance of MVICs interrupts the normal stretch-induced losses in active and passive plantar flexor joint moment and neuromuscular activity, largely because concentric strength and tendon properties were already affected. Importantly, the decrease in Achilles tendon stiffness remained 30 min later, which may be an important etiological factor for muscle-tendon strain injury risk.
在16名健康人类志愿者中研究了等长收缩和被动拉伸对肌腱力学和肌肉活动的影响。首先，在等速测力计上记录了峰值向心和被动踝关节力矩数据，并对小腿三头肌进行肌电图监测；同时对小腿进行实时运动分析以及对跟腱-腓肠肌内侧肌腱连接处进行超声成像。其次，受试者在重复被动和主动试验前进行了6次8秒的最大自主等长收缩（MVIC）。虽然MVIC后等长关节力矩没有下降，但峰值向心力矩显著降低（11.5%，P<0.01）。这伴随着小腿三头肌峰值肌电图振幅的显著降低（21.0%，P<0.01），且二者相关（r = 0.90，P<0.01）。跟腱刚度（10.9%，P<0.01）和被动关节力矩（4.9%，P<0.01）也显著降低。第三，受试者在拉伸后2分钟和30分钟重新测试前进行了3次60秒的静态跖屈肌拉伸。该拉伸方案在任何测量指标上均未引起显著变化。在拉伸后30分钟，在背屈关节角度检测到向心力矩和肌肉活动有显著恢复，而跟腱刚度和被动关节力矩仍显著降低。这些数据表明，MVIC的执行中断了主动和被动跖屈关节力矩及神经肌肉活动中正常的拉伸诱导损失，很大程度上是因为向心力量和肌腱特性已经受到影响。重要的是，30分钟后跟腱刚度仍降低，这可能是肌腱拉伤风险的一个重要病因因素。
