(ă-kil′ēz)

[Achilles, hero of the Iliad, whose vulnerable spot was his heel]
Plantar flexion resulting from contraction of the calf muscles after a sharp blow to the Achilles tendon, activating the S1 spinal reflex. The variations and their significance correspond closely to those of the knee jerk. It is exaggerated in upper motor neuron disease and diminished or absent in lower motor neuron disease.
SYN: SEE: Achilles jerk; SEE: ankle reflex; SEE: triceps surae jerk; SEE: triceps surae reflex