Wang Zheng, Hoffman Ernest M, Litchy William J, Shin Alexander Y, Rhee Peter C, Kaufman Kenton R, Lieber Richard L
Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota, United States.
Department of Neurology, Mayo Clinic, Rochester, Minnesota, United States.
J Neurophysiol. 2025 Oct 1;134(4):1069-1074. doi: 10.1152/jn.00274.2025. Epub 2025 Sep 5.
Spasticity results from upper motor neuron lesions and can create a deforming force and pain, and is often accompanied by contracture. Although the origin of spasticity is neural, there is ample evidence of secondary muscle changes. Here, we use direct measurement of the force-frequency relationship (FFR) to characterize human muscle's physiological properties. This study directly quantified the FFR of both healthy and spastic human skeletal muscles. Muscle force was measured intraoperatively in healthy gracilis ( = 13; aged 39.4 ± 10.6 yr; surgery due to brachial plexus injury) and spastic biceps brachii muscle ( = 8; aged 53.3 ± 10.3 yr; surgery due to stroke or traumatic brain injury). Nerve stimulation was applied at frequencies ranging from 1 to 70 Hz. Twitch contraction parameters, including time to peak tension (TPT) and half-relaxation time (HRT), were also compared. The FFR of the two muscles was modeled with sigmoid functions, and differences between muscles were assessed with an extra sum-of-squares test. TPT did not significantly differ between groups ( = 0.12), whereas HRT was prolonged in the spastic biceps ( < 0.05). Despite small differences in twitch kinetics, both muscles exhibited nearly identical FFR profiles. This study represents the first direct in vivo report of spastic human muscle kinetic properties and shows that these contractile kinetics are similar in healthy and spastic muscles. This may suggest that there are no dramatic calcium handling or myosin heavy chain changes in the biceps muscle secondary to spasticity. This study presents the first in vivo intraoperative measurement of the kinetic properties of spastic human muscle. Despite slower relaxation in spastic biceps, the force-frequency relationship was similar to that of the healthy gracilis muscle. This suggests that spasticity does not substantially alter frequency-dependent force summation, possibly due to similar fiber-type compositions and limited changes in calcium handling or myosin isoforms in human spastic muscle.
痉挛源于上运动神经元损伤，可产生变形力和疼痛，且常伴有挛缩。尽管痉挛的起因是神经方面的，但有充分证据表明会继发肌肉变化。在此，我们通过直接测量力-频率关系（FFR）来描述人类肌肉的生理特性。本研究直接对健康和痉挛的人体骨骼肌的FFR进行了量化。在健康的股薄肌（n = 13；年龄39.4±10.6岁；因臂丛神经损伤接受手术）和痉挛的肱二头肌（n = 8；年龄53.3±10.3岁；因中风或创伤性脑损伤接受手术）术中测量肌肉力量。以1至70赫兹的频率施加神经刺激。还比较了抽搐收缩参数，包括达到峰值张力的时间（TPT）和半松弛时间（HRT）。用S形函数对两块肌肉的FFR进行建模，并用额外平方和检验评估肌肉之间的差异。两组之间的TPT无显著差异（P = 0.12），而痉挛肱二头肌的HRT延长（P < 0.05）。尽管抽搐动力学存在细微差异，但两块肌肉的FFR曲线几乎相同。本研究是关于痉挛人体肌肉动力学特性的首个直接体内报告，表明这些收缩动力学在健康和痉挛肌肉中相似。这可能表明，继发于痉挛的肱二头肌在钙处理或肌球蛋白重链方面没有显著变化。本研究首次在体内术中测量了痉挛人体肌肉的动力学特性。尽管痉挛肱二头肌的松弛较慢，但其力-频率关系与健康股薄肌相似。这表明痉挛不会显著改变频率依赖性力的总和，可能是由于人类痉挛肌肉中纤维类型组成相似以及钙处理或肌球蛋白同工型变化有限。
