Age-associated adaptations in lower limb motor patterns during walking and cycling

Muscular strength and power generating ability decline with advancing age. Older adults adapt their lower limb motor patterns to cope with these declines in muscle function. When mechanical demands approach limits of lower limb muscular capacity, motor patterns must be adapted to produce a desired movement. The term “motor pattern” is used to broadly represent the kinematic and kinetic profile of a person accomplishing a given task. Generally, these adaptations involve higher reliance on stronger proximal muscles to compensate for limitations or weakness of distal muscles. Three studies were conducted to examine factors affecting differences between older and young adults in lower extremity mechanics for walking and cycling. In the first two studies, the effects of physical activity status, walking speed, and step length on lower extremity motor patterns of older and young adults were examined. As walking speed and step length increased, lower extremity muscular effort, as reflected by joint moments and power, increased. Differences in motor patterns between older and young participants, were preserved for multiple speed and step length conditions. In general, older adults showed higher reliance on hip musculature to compensate for lower muscle strength of plantarflexors. Moreover, sedentary and older groups, who had lower leg strength, exhibited similar lower limb motor patterns during walking. Likewise, physically active and young participants, who had higher lower extremity strength, displayed similar lower limb motor patterns. Consistent with the 2008 Physical Activity Guidelines for Americans, these results suggest that adopting and maintaining a physically active life-style can