stylistic:tone
Diagnosis

Spasticity is assessed by feeling the resistance of the muscle to passive lengthening in its most relaxed state. A spastic muscle will have immediately noticeable, often quite forceful, increased resistance to passive stretch when moved with speed and/or while attempting to be stretched out, as compared to the non-spastic muscles in the same person's body (if any exist). Spasticity can be differentiated from rigidity with the help of simple clinical examination, as rigidity is a uniform increase in the tone of agonist and antagonist muscles which is not related to the velocity at which the movement is performed passively and remains the same throughout the range of movement while spasticity is a velocity-dependent increase in tone resulting from the hyperexcitability of stretch reflexes. It primarily involves the antigravity muscles – flexors of the upper limb and extensors of the lower limb. During the passive stretch, a brief "free interval" is appreciated in spasticity but not in rigidity because the resting muscle is electromyographically silent in spasticity. In contrast, in rigidity, the resting muscle shows firing.