PDF(Pubmed)
Abstract：
The adaptive control of walking is often studied on a split-belt treadmill, where people gradually reduce their step length asymmetries (SLAs) by modulating foot placement and timing. Although it is proposed that this adaptation may be driven in part by a desire to reduce instability, it is unknown if changes in asymmetry impact people\'s ability to maintain balance in response to destabilizing perturbations. Here, we used intermittent perturbations to determine if changes in SLA affect reactive balance control as measured by whole-body angular momentum (WBAM) in the sagittal and frontal planes. Sixteen neurotypical older adults (70.0 ± 5.3 years old; 6 males) walked on a treadmill at a 2:1 belt speed ratio with real-time visual feedback of their achieved and target step lengths. We used mixed-effects models to determine if there were associations between SLA or foot placement and WBAM during the applied perturbations. Walking with more positive SLAs was associated with small reductions in forward WBAM (p < 0.001 for fast and slow belts) but increased lateral WBAM (p = 0.045 for fast belt; p = 0.003 for slow belt) during perturbations. When participants walked with more positive SLAs, they shortened their foot placement on the slow belt, and this shortening was associated with moderate reductions in forward WBAM (p < 0.001) and small increases in lateral WBAM (p = 0.008) during slow-belt perturbations. Our findings suggest that spatiotemporal changes that occur during split-belt treadmill walking may improve sagittal-plane stability by reducing people\'s susceptibility to losses of balance, but this may come at the expense of frontal-plane stability.
摘要：
步行的自适应控制通常在分体式跑步机上进行研究，在那里，人们通过调整脚的位置和时间逐渐减少他们的步长不对称（SLA）。尽管有人提出这种适应可能部分地由减少不稳定性的愿望驱动，不对称的变化是否会影响人们在应对不稳定扰动时保持平衡的能力，这是未知的。这里,我们使用间歇性扰动来确定SLA的变化是否会影响通过矢状面和额面中的全身角动量（WBAM）测量的反应平衡控制。16名神经典型的老年人（70.0±5.3岁；6名男性）以2：1的皮带速度比在跑步机上行走，并实时视觉反馈其已达到的步长和目标步长。我们使用混合效应模型来确定在施加扰动期间SLA或足部放置与WBAM之间是否存在关联。在扰动过程中，使用更多积极的SLA行走与前向WBAM的少量减少有关（快带和慢带的p<0.001），但横向WBAM增加（快带的p=0.045；慢带的p=0.003）。当参与者以更积极的SLA行走时，他们缩短了脚在慢腰带上的位置，在慢带扰动期间，这种缩短与正向WBAM的适度减少（p<0.001）和横向WBAM的小幅增加（p=0.008）有关。我们的发现表明，在分裂皮带跑步机行走过程中发生的时空变化可以通过降低人们对失平衡的敏感性来改善矢状面稳定性。但这可能是以牺牲正面稳定为代价的。
