In this study, we described a sequence of changes of the electromyogra
phic (EMG) and depression of the soleus (Sol) H-reflex that precede an
d follow the onset of ballistic head rotation in freely standing human
subjects. During head rotation, a sequence of EMG changes occurred si
multaneously in Sol and in biceps femoris muscle (BF). Specifically, c
hanges to Sol EMG included deactivations (EMG silent period) and H-ref
lex depression coincident with BF excitation. Thus, in the case of bal
listic head movement, control commands for anticipatory postural adjus
tment appear to excite BF and inhibit Sol in a similar way to that pre
viously described for the onset of arm movement.