Department of Physical Education and Sport Science, Democritus University of Thrace, Komotini, Greece.
J Strength Cond Res. 2010 Aug;24(8):2122-31. doi: 10.1519/JSC.0b013e3181a5bc44.
The purpose of this study was to examine (a) the mechanical power and the electromyographic (EMG) activity during a moderate load muscular endurance session and (b) the maximal mechanical power output and EMG activity using a light load and a heavy load afterward. Sixteen men (age: 20.7 +/- 1.1 years) performed 4 sets of 20 repetitions with an initial load of 50% of 1 repetition maximum (1RM), and 2 minutes of rest, in the squat exercise. Furthermore, the subjects performed 4 repetitions with loads of 40 and 80% of 1RM before, immediately after, and 30 minutes after the end of the session. Average power and EMG activity from vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) were recorded during the concentric phase of the lift. Average power did not change during the first 2 sets, while it decreased (p < 0.05) during the third and the fourth set. Average quadriceps (AQ), VM, VL, and RF activity increased (p < 0.05) until the 11th repetition, approximately, during each set while it increased gradually from set to set. Maximal power and AQ, VM, and VL activity with the loads of 40 and 80% of 1RM were decreased (p < 0.05) after the session. Blood lactate reached 10.2 +/- 2.5 and 13.1 +/- 4.1 mmolxL after the second and the fourth set, respectively. It appears that during a muscular endurance session with submaximal power output, mechanical performance may gradually decrease, probably due to metabolic fatigue, while muscle electrical activity may increase. Following this type of a session, maximal power output and muscle activation with a light and especially with a heavy load are reduced.
(a) 在中等负荷肌肉耐力训练期间的机械功率和肌电图（EMG）活动；(b) 随后使用轻负荷和重负荷的最大机械功率输出和 EMG 活动。16 名男性（年龄：20.7±1.1 岁）进行了 4 组 20 次重复的深蹲运动，起始负荷为 1 次最大重复次数（1RM）的 50%，每组之间休息 2 分钟。此外，受试者在训练结束前、结束后即刻和结束后 30 分钟分别进行了 4 次 40%和 80%1RM 的重复运动。在提升的向心阶段，记录了股直肌（VM）、股外侧肌（VL）和股四头肌（RF）的平均功率和 EMG 活动。在前 2 组中，平均功率没有变化，而在第 3 组和第 4 组中，平均功率下降（p<0.05）。在每组中，AQ、VM、VL 和 RF 的平均活动在大约第 11 次重复时增加（p<0.05），并且随着组与组之间的增加而逐渐增加。在训练结束后，40%和 80%1RM 负荷的最大功率和 AQ、VM 和 VL 活动均下降（p<0.05）。血乳酸在第二组和第四组后分别达到 10.2±2.5 和 13.1±4.1mmolxL。在以次最大功率输出进行肌肉耐力训练期间，机械性能可能会逐渐下降，这可能是由于代谢疲劳，而肌肉电活动可能会增加。在这种类型的训练后，轻负荷和尤其是重负荷的最大功率输出和肌肉激活都会减少。
