Department of Nutrition and Integrative Physiology, University of Utah, 250 S. 1850 E. Room 214, Salt Lake City, UT 84112-0920, USA
J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, 1275 Center Drive, Gainesville, FL 32611, USA.
J Exp Biol. 2018 Jul 10;221(Pt 13):jeb180109. doi: 10.1242/jeb.180109.
Fish, birds and lizards sometimes perform locomotor activities with maximized muscle power. Whether humans maximize muscle power is unknown because current experimental techniques cannot be applied non-invasively. This study leveraged simulated muscle work loops to examine whether voluntary maximal cycling is characterized by maximized muscle power. The simulated work loops used experimentally measured joint angles, anatomically realistic muscle parameters (muscle-tendon lengths, velocities and moment arms) and a published muscle model to calculate power and force for 38 muscles. For each muscle, stimulation onset and offset were optimized to maximize muscle work and power for the complete shortening/lengthening cycle. Simulated joint power and total leg power (i.e. summed muscle power) were compared with previously reported experimental joint and leg power. Experimental power values were closely approximated by simulated maximal power for the leg [intraclass correlation coefficient (ICC)=0.91], the hip (ICC=0.92) and the knee (ICC=0.95), but less closely for the ankle (ICC=0.74). Thus, during maximal cycling, humans maximize muscle power at the hip and knee, but the ankle acts to transfer (instead of maximize) power. Given that only the timing of muscle stimulation onset and offset were altered, these results suggest that human motor control strategies may optimize muscle activation to maximize power. The simulations also provide insight into biarticular muscle function by demonstrating that the power values at each joint spanned by a biarticular muscle can be substantially greater than the net power produced by the muscle. Our work-loop simulation technique may be useful for examining clinical deficits in muscle power production.
鱼类、鸟类和蜥蜴有时会进行最大限度地发挥肌肉力量的运动活动。人类是否最大限度地发挥肌肉力量尚不清楚，因为目前的实验技术无法进行非侵入性应用。本研究利用模拟肌肉工作循环来检验自愿性最大骑行是否以最大限度地发挥肌肉力量为特征。模拟工作循环使用实验测量的关节角度、解剖学上逼真的肌肉参数（肌肉-肌腱长度、速度和力臂）和已发表的肌肉模型来计算 38 块肌肉的功率和力。对于每块肌肉，刺激的起始和结束时间都经过优化，以最大限度地提高整个缩短/延长周期的肌肉做功和功率。模拟关节功率和总腿部功率（即肌肉功率总和）与之前报道的实验关节和腿部功率进行了比较。实验功率值与模拟最大功率非常接近，包括腿部[组内相关系数（ICC）=0.91]、臀部（ICC=0.92）和膝盖（ICC=0.95），但脚踝（ICC=0.74）则不太接近。因此，在最大骑行时，人类在髋关节和膝关节处最大限度地发挥肌肉力量，但踝关节的作用是传递（而不是最大限度地发挥）力量。鉴于只有肌肉刺激起始和结束时间发生了变化，这些结果表明，人类运动控制策略可能会优化肌肉激活以最大限度地发挥力量。模拟还通过证明跨越双关节肌肉的每个关节的功率值可以大大超过肌肉产生的净功率，为双关节肌肉的功能提供了深入的了解。我们的工作循环模拟技术可能有助于检查肌肉力量产生的临床缺陷。
