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Soleus H-Reflex Gain in Healthy Elderly and Young Adults When Lying, Standing, and Balancing

^a Department of Physical Education, Health and Recreation, Western Washington University, Bellingham

Gordon R. Chalmers, Department of Physical Education, Health and Recreation, MS-9067, Western Washington University, 516 High Street, Bellingham, WA 98225-9067 E-mail: chalmers{at}cc.wwu.edu.

Decision Editor: John A. Faulkner, PhD

Soleus Hoffman-reflex (H-reflex) gain was compared at the same background level of electromyographic 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 decrease 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.