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 ${\eta }_{\mathrm{p}}^2=.84$, stable P < .001, unstable P < .001), mediolateral (main effect ${\eta }_{\mathrm{p}}^2=.49$, stable P = .002, unstable P = .018) and anterior–posterior (main effect ${\eta }_{\mathrm{p}}^2=.64$, stable P < .001, unstable P = .001) fractal dimension, and LOS distance (main effect ${\eta }_{\mathrm{p}}^2=.18$, stable P = .011, unstable P = .046) compared with unloaded. Rectus femoris (main effect ${\eta }_{\mathrm{p}}^2=.39$, stable P = .001, unstable P = .010) and gastrocnemius (main effect ${\eta }_{\mathrm{p}}^2=.30$, 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 ${\eta }_{\mathrm{p}}^2=.24$, 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.

本研究的目的是调查背包负重运输对老年人安静站立姿势控制和稳定性极限 (LOS) 的影响。14 名老年人 (65 [6] 岁) 在 3 种情况下进行安静站立和前向、右向和左向 LOS 测试，即卸载、稳定和不稳定的背包负载，同时记录 4 条腿部肌肉的活动。稳定和不稳定的负载减少姿势摇摆（主要效果${\eta }_{\mathrm{p}}^2=.84$，稳定P  < .001，不稳定P  < .001)，内侧（主效应${\eta }_{\mathrm{p}}^2=.49$，稳定P  = .002，不稳定P  = .018）和前后（主效应${\eta }_{\mathrm{p}}^2=.64$，稳定P  < .001，不稳定P  = .001) 分形维数和 LOS 距离（主效应${\eta }_{\mathrm{p}}^2=.18$，稳定P  = .011，不稳定P  = .046) 与空载相比。股直肌（主要作用${\eta }_{\mathrm{p}}^2=.39$，稳定P  = .001，不稳定P  = .010）和腓肠肌（主效应${\eta }_{\mathrm{p}}^2=.30$，不稳定P  = .027) 在 LOS 和安静站立期间的负载条件下活动增加。腓肠肌-胫骨前肌的协同激活在不稳定负荷下比稳定负荷安静站立时更大（主效应${\eta }_{\mathrm{p}}^2=.24$，P  = .040)。这些发现表明，老年人采取保守的姿势控制策略，最大限度地减少在负荷条件下进行姿势矫正的需要。视线降低也可能会增加负重时跌倒的风险。然而，姿势控制变量的不稳定负载和稳定负载之间没有差异。