Age causes a redistribution of joint torques and powers during gait

At self-selected walking speeds, elderly compared with young adults generat e decreased joint torques and powers in the lower extremity. These differen ces may be actual gait-limiting factors and neuromuscular adaptations with age or simply a consciously selected motor pattern to produce a slower gait . The purpose of the study was to compare joint torques and powers of young and elderly adults walking at the same speed. Twelve elderly and fourteen young adults (ages 69 and 21 yr) walked at 1.48 mis over a force platform w hile being videotaped. Hip, knee, and ankle torques and powers were calcula ted from the reaction force and kinematic data. A support torque was calcul ated as the sum of the three joint torques. Extensor angular impulse during stance and positive work at each joint were derived from the torques and p owers. Step length was 4% shorter and cadence was 4% higher in elderly adul ts (both P < 0.05) compared with young adults. Support angular impulse was nearly identical between groups, but elderly adults had 58% greater angular impulse and 279% more work at the hip, 50% less angular impulse and 39% le ss work at the knee, and 23% less angular impulse and 29% less work at the ankle compared with young adults (t-test, all P < 0.05). Age caused a redis tribution of joint torques and powers, with the elderly using their hip ext ensors more and their knee extensors and ankle plantar flexors less than yo ung adults when walking at the same speed. Along with a reduction in motor and sensory functions, the natural history of aging causes a shift in the l ocus of function in motor performance.