Aging effects on the metabolic and cognitive energy cost of interlimb coordination.

Many everyday motor tasks have high metabolic energy demands, and some require extended practice to learn the required coordination between limbs. Eight older (73.1 +/- 4.4 years) and 8 younger (23.3 +/- 5.9) men practiced a high-energy two-hand coordination task with both 180 degrees and 90 degrees target relative phase. The older group showed greater performance error in both conditions, and performance at 90 degrees was strongly attracted to antiphase coordination (180 degrees). In a retention test one week following the acquisition trials, the older group had learned the 180 degrees condition but did not learn the 90 degrees condition. Metabolic energy cost was not different between groups, but the older men showed higher heart rate and both conditions imposed greater cognitive demands as revealed in auditory probe reaction time. Older adults' motor learning may be inhibited by elevated heart rate at the same oxygen cost, increased cognitive cost, and an attraction toward more established low-energy in-phase or antiphase coordination.