Age effects on the inter-joint coordination during obstacle-crossing.

Seventeen healthy elderly and 17 young adults walked and crossed obstacles of different heights, while sagittal angles (x) and angular velocities (x') of each joint were measured and their phase angles (phi) calculated as tan(-1)(x'/x). Relative phase angles (RPA) were also obtained, i.e., phi(hip-knee) and phi(knee-ankle). The standard deviations of the RPA curve points were averaged to obtain deviation phase (DP) values for the stance and swing phase for each obstacle height. Both groups had similar RPA patterns, for both the leading and the trailing limb. The elderly were found to cross obstacles with increased leading toe-clearance, but unaltered inter-joint coordination patterns. During the leading limb crossing, greater variability of the inter-joint coordination, correlated to the increased toe-clearance, indicates that aging increases the variability of the way the lower limb joints are controlled during obstacle-crossing. The elderly did not change the pattern and variability of the inter-joint coordination during the trailing limb crossing, possibly because it is relatively easy for the elderly to meet the mechanical demands despite increased age-related organismic constraints. The normal baseline inter-joint coordination data in the healthy aging population will be useful for future identification of coordination impairments and evaluation of subsequent treatment in those patients with diseases who may have an increased risk of falling.