van den Tillaar Roland, Larsen Stian
Department of Sports Sciences and Physcial Education, Nord University, Levanger, Norway.
Sports Med Int Open. 2020 Jul 16;4(2):E59-E66. doi: 10.1055/a-1195-1039. eCollection 2020 Aug.
The purpose of the study was to compare kinematics and muscle activity between two variations of unilateral squats under different stability conditions. Twelve male volunteers (age: 23±5 years, mass: 80±17 kg, height: 1.81±0.11 m, strength-training experience: 4.3±1.9 years) performed four repetitions with the same external load (≈4RM). Two variations (with the non-stance leg forwards vs. backwards) were performed in a Smith-machine and free-weight condition. The variables were barbell velocity, lifting time and surface electromyography activity of the lower extremity and trunk muscles during the descending and ascending phase. The main findings were 1) peak force was higher when performing the unilateral squats in the Smith machine; 2) peak ascending barbell velocity increased from repetition 3-4 with free weight; and 3) muscle activity from the rectus femoris, vastus lateral, biceps femoris, gluteus medius, and erector spinae increased with repetitions, whereas gluteus, and medial vastus and shank muscles were affected by the conditions. It was concluded that more peak force could be produced because of increased stability. However, peak barbell velocity increased from repetition to repetition in free-weight unilateral squats, which was probably because the participants grew more comfortable. Furthermore, increased instability causes more gluteus and vastus medial activation and foot variations mainly affected the calf muscles.
本研究的目的是比较在不同稳定性条件下单侧深蹲的两种变式之间的运动学和肌肉活动情况。12名男性志愿者（年龄：23±5岁，体重：80±17千克，身高：1.81±0.11米，力量训练经验：4.3±1.9年）以相同的外部负荷（约4RM）进行了4次重复动作。在史密斯机和自由重量条件下进行了两种变式（非支撑腿向前与向后）。变量包括杠铃速度、举起时间以及下肢和躯干肌肉在下降和上升阶段的表面肌电图活动。主要研究结果为：1）在史密斯机上进行单侧深蹲时峰值力更高；2）自由重量条件下，从第3次到第4次重复，杠铃上升峰值速度增加；3）股直肌、股外侧肌、股二头肌、臀中肌和竖脊肌的肌肉活动随重复次数增加，而臀肌、股内侧肌和小腿肌肉受条件影响。研究得出结论，由于稳定性增加，可产生更大的峰值力。然而，自由重量单侧深蹲中杠铃峰值速度逐次增加，这可能是因为参与者越来越适应。此外，不稳定性增加会导致更多臀肌和股内侧肌激活，足部变化主要影响小腿肌肉。
