Stable and Unstable Load Carriage Effects on the Postural Control of Older Adults

摘要

The aim of this study was to investigate the effects of backpack load carriage on quiet standing postural control and limits of stability (LOS) of older adults. Fourteen older adults (65 [6] y) performed quiet standing and a forward, right, and left LOS test in 3 conditions, unloaded, stable, and unstable backpack loads while activity of 4 leg muscles was recorded. Stable and unstable loads decreased postural sway (main effect eta(2)(p) = .84, stable P .001, unstable P .001), mediolateral (main effect eta(2)(p) = .49, stable P = .002, unstable P = .018) and anterior-posterior (main effect eta(2)(p) = .64, stable P .001, unstable P = .001) fractal dimension, and LOS distance (main effect eta(2)(p) = .18, stable P = .011, unstable P = .046) compared with unloaded. Rectus femoris (main effect eta(2)(p) = .39, stable P = .001, unstable P = .010) and gastrocnemius (main effect eta(2)(p) = .30, unstable P = .027) activity increased in loaded conditions during LOS and quiet standing. Gastrocnemius-tibialis anterior coactivation was greater in unstable load than stable loaded quiet standing (main effect eta(2)(p) = .24, P = .040). These findings suggest older adults adopt conservative postural control strategies minimizing the need for postural corrections in loaded conditions. Reduced LOS may also increase fall risk when carrying a load. However, there was no difference between unstable and stable loads for postural control variables.