Muscle activities used by young and old adults when stepping to regain balance during a forward fall

The current study was undertaken to determine if age-related differences in muscle activities might relate to older adults being significantly less ab le than young adults to recover balance during a forward fall. Fourteen you ng and twelve older healthy males were released from forward leans of vario us magnitudes and asked to regain standing balance by taking a single forwa rd step. Myoelectric signals were recorded from 12 lower extremity muscles and processed to compare the muscle activation patterns of young and older adults. Young adults successfully recovered from significantly larger leans than older adults using a single step (32.2 degrees vs. 23.5 degrees). Mus cular latency times, the time between release and activity onset, ranged fr om 73 to 114 ms with no significant age-related differences in the shortest muscular latency times. The overall response muscular activation patterns were similar for young and older adults. However older adults were slower t o deactivate three stance leg muscles and also demonstrated delays in activ ating the step leg hip flexors and knee extensors prior to and during the s wing phase. In the forward fall paradigm studied, age-differences in balanc e recovery performance do not seem due to slowness in response onset but ma y relate to differences in muscle activation timing during the stepping mov ement. (C) 2000 Elsevier Science Ltd. All rights reserved.