Jakobi J M, Cafarelli E
Faculty of Pure and Applied Science, York University, Toronto, Ontario, Canada.
J Appl Physiol (1985). 1998 Jan;84(1):200-6. doi: 10.1152/jappl.1998.84.1.200.
Several investigators have studied the deficit in maximal voluntary force that is said to occur when bilateral muscle groups contract simultaneously. A true bilateral deficit (BLD) would suggest a significant limitation of neuromuscular control; however, some of the data from studies in the literature are equivocal. Our purpose was to determine whether there is a BLD in the knee extensors of untrained young male subjects during isometric contractions and whether this deficit is associated with a decreased activation of the quadriceps, increased activation of the antagonist muscle, or an alteration in motor unit firing rates. Twenty subjects performed unilateral (UL) and bilateral (BL) isometric knee extensions at 25, 50, 75, and 100% maximal voluntary contraction. Total UL and BL force (delta 3%) and maximal rate of force generation (delta 2.5%) were not significantly different. Total UL and BL maximal vastus lateralis electromyographic activity (EMG; 2.7 +/- 0.28 vs. 2.6 +/- 0.24 mV) and coactivation (0.17 +/- 0.02 vs. 0.20 +/- 0.02 mV) were also not different. Similarly, the ratio of force to EMG during submaximal UL and BL contractions was not different. Analysis of force production by each leg in UL and BL conditions showed no differences in force, rate of force generation, EMG, motor unit firing rates, and coactivation. Finally, assessment of quadriceps activity with the twitch interpolation technique indicated no differences in the degree of voluntary muscle activation (UL: 93.6 +/- 2.51 Hz, BL: 90.1 +/- 2.43 Hz). These results provide no evidence of a significant limitation in neuromuscular control between BL and UL isometric contractions of the knee extensor muscles in young male subjects.
几位研究者研究了据说在双侧肌肉群同时收缩时出现的最大随意力缺陷。真正的双侧缺陷（BLD）将表明神经肌肉控制存在显著限制；然而，文献中的一些研究数据并不明确。我们的目的是确定未经训练的年轻男性受试者在等长收缩期间，其膝伸肌是否存在BLD，以及这种缺陷是否与股四头肌激活减少、拮抗肌激活增加或运动单位放电频率改变有关。20名受试者在最大随意收缩的25%、50%、75%和100%时进行单侧（UL）和双侧（BL）等长膝伸展。总的UL和BL力量（差值3%）以及最大力量产生速率（差值2.5%）没有显著差异。总的UL和BL股外侧肌最大肌电图活动（EMG；2.7±0.28对2.6±0.24 mV）和共同激活（0.17±0.02对0.20±0.02 mV）也没有差异。同样，次最大UL和BL收缩期间力量与EMG的比值也没有差异。对UL和BL条件下每条腿的力量产生分析表明，在力量、力量产生速率、EMG、运动单位放电频率和共同激活方面没有差异。最后，用抽搐插值技术评估股四头肌活动表明，自愿肌肉激活程度没有差异（UL：93.6±2.51 Hz，BL：90.1±2.43 Hz）。这些结果没有提供证据表明年轻男性受试者膝伸肌的BL和UL等长收缩之间神经肌肉控制存在显著限制。
