Soleus H-reflex gain in healthy elderly and young adults when lying, standing, and balancing

Soleus Hoffman-reflex (H-reflex) gain was compared at the same background level of elec-tromyographic activity across lying, natural standing, and tandem stance postures, in 12 young and 16 elderly adults. When compared to a lying posture, young adults significantly depressed soleus H-reflex gain when in a natural standing (19 % decrease) and a tandem stance position (30 % decrease; p.0125 for both positions). For elderly adults, there was no significant de-crease in H-reflex gain while standing naturally, but there was a significant 28 % decrease when performing tandem stance ( p.0125). The data indicate that, although the mild motor control challenge of natural standing does not induce a decrease in soleus H-reflex gain in the elderly adults, as it does in young adults, in the more difficult task of tandem stance, soleus H-reflex gain is significantly decreased in both young and elderly adults. UMEROUS studies have demonstrated in young adults that the size of the soleus Hoffmann reflex (H reflex) is modulated across different motor tasks. For example, th