Sports and Movement Science Centre, Lithuanian Academy of Physical Education, Kaunas, Lithuania.
Appl Physiol Nutr Metab. 2011 Jun;36(3):353-60. doi: 10.1139/h11-023. Epub 2011 May 16.
The aim of the present study was to compare the time-course of indirect symptoms of exercise-induced muscle damage after 50 and 100 drop jumps. A high-force, low intensity exercise protocol was used to avoid discrepancies regarding metabolic fatigue immediately after exercise. Healthy untrained men performed 50 ("50 group", n = 13) or 100 ("100 group", n = 13) intermittent (30-s interval between each jump) drop jumps, respectively, from the height of 0.5 m with a counter-movement to a 90° knee flexion angle and immediate maximal rebound. Voluntary and electrically evoked knee extensor strength was assessed using an isokinetic dynamometer immediately before and at 2 min after exercise, as well as 3, 7, and 14 days after exercise. Creatine kinase (CK) activity and muscle soreness within 7 days after exercise were also determined. The results showed that the decrease in voluntary isometric and isokinetic torque as well as 100 Hz stimulation torque at the end of the 50 and 100 drop jumps was very similar, while substantial differences were found in low-frequency fatigue, shift in optimal knee joint angle, muscle soreness, and CK activity. In addition, there was slower muscle strength recovery after the 100 drop jumps. It is concluded that the predictive value of strength loss immediately after exercise as an indicator of muscle damage decreases as the jump number increases. Still, stimuli must be large enough for muscle torque to reach the reduction plateau. Therefore, magnitude of exercise becomes a major factor in accuracy of muscle damage predictions.
本研究旨在比较 50 次和 100 次落差跳后间接性运动引起的肌肉损伤症状的时程变化。采用高强度、低强度的运动方案，以避免运动后即刻代谢疲劳造成的差异。健康未训练的男性分别进行 50 次（“50 组”，n = 13）或 100 次（“100 组”，n = 13）间歇性落差跳（每次跳跃之间间隔 30 秒），从 0.5 米的高度进行反跳，屈膝至 90°，并立即进行最大反弹。使用等速测力计在运动前即刻和运动后 2 分钟以及运动后 3、7 和 14 天评估膝关节伸肌的自愿和电诱发力量。还在运动后 7 天内测定肌酸激酶（CK）活性和肌肉酸痛。结果表明，50 次和 100 次落差跳结束时，自愿等长和等速扭矩以及 100Hz 刺激扭矩的下降非常相似，而低频疲劳、最佳膝关节角度移位、肌肉酸痛和 CK 活性存在显著差异。此外，100 次落差跳后肌肉力量恢复较慢。结论是，作为肌肉损伤指标的运动后即刻力量下降的预测价值随着跳跃次数的增加而降低。然而，刺激必须足够大，以使肌肉扭矩达到下降平台。因此，运动的幅度成为肌肉损伤预测准确性的主要因素。
