Knee and ankle range of motion during stepping down in elderly compared to young men.

A major factor limiting mobility in elderly subjects is their difficulty with descending steps but the physiological and biomechanical basis of this problem is not well understood. To address this question we have compared the kinematics of stepping down in six elderly male subjects and six weight- and height-matched younger subjects. Five reflective markers were positioned on the lower limbs and subjects were filmed stepping down from four heights (200, 250, 300, and 335 mm). Maximum angular displacements for the knee and ankle of the supporting limb were expressed as a percentage of each subject's passive range of motion (ROM). Time spent in 'foot flat' during single support was also compared. The results show the elderly subjects sustained dorsiflexion and a 'foot flat' position of the support limb for a significantly ( P<0.05) longer period than the young (approximately 20%). Consequently, elderly subjects utilised a greater percentage of their passive ankle ROM compared to the young (elderly approximately 200%; young approximately 125%). We conclude that the elderly maintained a 'foot flat' position for a longer period possibly to increase the time spent on a larger base of support. These results suggest that exercise prescription in the elderly should include stretching in order to increase the ROM at the ankle joint.