Alpha- and beta-band coherence between leg muscles during upright standing on rigid and foam surfaces in young and older adults.

PURPOSE: The purpose of our study was to compare the influence of standing on a rigid surface or a foam pad on lower-leg intermuscular coherence in young and older adults. METHODS: Bipolar surface electromyography from the soleus, gastrocnemius medialis, and tibialis anterior was recorded in 18 young adults [mean ± standard deviation, 26 ± 4 yrs] and 18 older adults [71 ± 5 yrs] while they stood on a rigid surface or on a foam mat. Intermuscular coherence was calculated as the mean coherence between pairs of agonist (soleus, gastrocnemius medialis) and antagonist (soleus, tibialis anterior) muscles in the alpha (8-13 Hz) and beta (13-35 Hz) bands. RESULTS: Mean CoP velocity was greater when standing on foam than on a rigid surface in both groups (p < 0.001). When standing on foam compared with the rigid surface, mean alpha-band coherence increased in young (p < 0.001) but decreased in older adults (p = 0.036), regardless of the muscle pair. Agonist and antagonist beta-band coherence was greater when standing on foam compared with the rigid surface in both groups (p < 0.001). SIGNIFICANCE: Our findings provide novel evidence that support-surface compliance modulates intermuscular coherence between lower-leg muscle pairs during quiet standing. The difference in alpha-band coherence between young and older adults suggests an age-related reorganization of shared neural drive to postural muscles.