CUTANEOMUSCULAR REFLEXES RECORDED FROM THE LOWER-LIMB IN MAN DURING DIFFERENT TASKS

1. Cutaneomuscular reflexes have been recorded in ten adult subjects f rom extensor digitorum brevis (EDB), tibialis anterior (TA), soleus (S ol), quadriceps femoris (Quad) and erector spinae (ES) following elect rical stimulation of the digital nerves of the second toe. 2. Recordin gs were made while subjects were instructed to activate voluntarily th e relevant muscles and also when these muscles were active posturally. 3. Reflex responses could comprise three components: an initial incre ase in EMG (E1), followed by a decrease (I1), followed by a second inc rease (E2). E1 and I1. were confined to muscles acting at the ankle an d in the foot. E2 was most pronounced in EDB but also found in TA, Sol , Quad (1 subject) and ES. No responses were recorded contralateral to the stimulus. 4. E2 was significantly larger when the reflex was reco rded during voluntary contraction of the muscle, rather than when the muscle was active posturally. 5. E1 and I1 components are mediated via spinal pathways. E2 requires the integrity of the dorsal columns, sen sorimotor cortex and corticospinal tract (Jenner and Stephens, 1982; R owlandson and Stephens, 1985b). The present study suggests that one or more of these supraspinal pathways is more active during voluntary co ntraction of lower limb muscles than when these muscles are active pos turally.