张力亢进(Hypertonia、压力过高、肌<肉>张力亢进、肌<肉>强直)，在文献中、有时等同于反射亢进(Spasticity/hyperreflexia)，指的是中枢神经系统周围损伤所引起的亢进、亦即"上运动脑部病变"。 病症为受损运动神经元(Motor neuron)调节能力下降且产生脊髓反射失调、肌梭(Muscle spindle)兴奋性增高，及减少突触抑制。 这些结果导致"对症肌肉"(symptomatic muscles)肌张力(Muscle tone)增高之病症。 一些学者建议，对于目前"反射亢进"的定义，即"牵张反射(stretch reflex/myotatic reflex)速度相关的<过度活动(over-activity)>"，在于它没有充分考虑到患者显示出在没有"牵张反射"(stretch reflex)<过度活动>时、"肌张力"增高之情况。他们反而认为，"可逆亢进"(reversible hypertonia)是比较合适的定义，也显示出可治疗的条件，即是反应出各种治疗方式像是药物"和/或"物理的治疗。

Hypertonia is a term sometimes used synonymously with spasticity in the literature surrounding damage to the central nervous system, namely upper motor neuron lesions. Impaired ability of damaged motor neurons to regulate descending pathways gives rise to disordered spinal reflexes, increased excitability of muscle spindles, and decreased synaptic inhibition. These consequences result in abnormally increased muscle tone of symptomatic muscles. Some authors suggest that the current definition for spasticity, the velocity-dependent over-activity of the stretch reflex, is not sufficient as it fails to take into account patients exhibiting increased muscle tone in the absence of stretch reflex over-activity. They instead suggest that “reversible hypertonia” is more appropriate and represents a treatable condition that is responsive to various therapy modalities like drug and/or physical therapy.