Cognitive tasks alter inter-joint coordination in older women during stair descent

This study evaluated the impact of cognitive task interference on the interaction and and coordination of lower limb joints in older women during stair descent. Kinematic data of the hip, knee, and ankle joints were collected using a Vicon infrared motion capture system during stair descent, both with and without cognitive task interference in twenty young and twenty older women. The continuous relative phase angles of the dominant hip-knee and knee-ankle joints were calculated for the support and swing phases. The older group exhibited significantly larger mean absolute relative phase (MARP) and deviation phase (DP) for the hip-knee joint, and DP for the knee-ankle joint during the support phase compared with the young group. Conversely, the older group showed significantly smaller MARP and DP for the hip-knee joint, the minimum value of the knee-ankle joint continuous relative phase (CRP), and MARP value during the swing phase. During cognitive tasks, the hip-knee joint MARP and DP during the support phase were significantly larger, while the minimum value of the knee-ankle joint CRP during the swing phase was significantly smaller. The study concluded that cognitive task interference diminishes inter-joint coordinated control during stair descent. The hip-knee joint's coupling and coordinated control were particularly affected in older women, both during the support and swing phases. It is recommended that older women enhance the inter-joint coupling and coordination of their lower limb joints by exercising to reduce the risk of falls during stair descent, particularly when cognitively distracted.