Vision and Eye Research Institute, School of Medicine, Faculty of Health, Education, Medicine, and Social Care, Anglia Ruskin University, Cambridge, Cambridgeshire, United Kingdom.
Cambridge Centre for Sport and Exercise Science, Anglia Ruskin University, Cambridge, Cambridgeshire, United Kingdom.
PeerJ. 2023 Feb 20;11:e14743. doi: 10.7717/peerj.14743. eCollection 2023.
To investigate the effects of age and central field loss on the landing mechanics and balance control when stepping up to a new level under time-pressure.
Eight older individuals with age-related macular degeneration (AMD), eight visually normal older and eight visually normal younger individuals negotiated a floor-based obstacle followed by a 'step-up to a new level' task. The task was performed under (1) no-pressure; (2) time-pressure: an intermittent tone was played that increased in frequency and participants had to complete the task before the tone ceased. Landing mechanics and balance control for the step-up task was assessed with a floor-mounted force plate on the step.
Increased ground reaction forces and loading rates were observed under time-pressure for young and older visual normals but not for AMD participants. Across conditions, loading rates and ground reaction forces were higher in young normals compared to older normals and AMD participants. Young visual normals also demonstrated 35-39% shorter double support times prior to and during the step-up compared to older normals and AMD participants. All groups shortened their double support times (31-40%) and single support times (7-9%) in the time-pressure compared to no-pressure condition. Regarding balance control, the centre-of-pressure displacement and velocity in the anterior-poster direction were increased under time-pressure for young and older visual normals but not for AMD participants. The centre-of-pressure displacement and velocity in the medial-lateral direction were decreased for the AMD participants under time-pressure but not for young and older visual normals.
Despite walking faster, AMD participants did not adapt their landing mechanics under time-pressure (., they remained more cautious), whilst older and young adults with normal vision demonstrated more forceful landing mechanics with the young being most forceful. A more controlled landing might be a safety strategy to maintain balance control during the step-up, especially in time-pressure conditions when balance control in the anterior-posterior direction is more challenged.
探讨年龄和中央视野损失对时间压力下上台阶时的着地势力学和平衡控制的影响。
8 名年龄相关性黄斑变性（AMD）老年患者、8 名视力正常的老年患者和 8 名视力正常的年轻患者在完成基于地面的障碍物后，进行了“上台阶到新高度”任务。任务在以下两种情况下进行：（1）无压力；（2）时间压力：播放间歇频率增加的音调，参与者必须在音调停止前完成任务。使用安装在台阶上的地面安装力板评估上台阶任务的着地势力学和平衡控制。
在时间压力下，年轻和老年视力正常者的地面反作用力和加载率增加，但 AMD 参与者没有。在所有条件下，年轻视力正常者的加载率和地面反作用力均高于老年视力正常者和 AMD 参与者。年轻视力正常者在上台阶前和上台阶期间的双支撑时间也比老年视力正常者和 AMD 参与者短 35-39%。与无压力条件相比，所有组在时间压力下都缩短了双支撑时间（31-40%）和单支撑时间（7-9%）。关于平衡控制，在时间压力下，年轻和老年视力正常者的前-后向中心压力位移和速度增加，但 AMD 参与者没有。在时间压力下，AMD 参与者的中-侧向中心压力位移和速度减小，但年轻和老年视力正常者没有。
尽管 AMD 参与者行走速度更快，但他们在时间压力下并未调整其着地势力学（即他们仍然更加谨慎），而视力正常的老年和年轻成年人则表现出更有力的着地力学，其中年轻人最为有力。更受控的着陆可能是在时间压力下维持平衡控制的安全策略，特别是在中-后向平衡控制更具挑战性的情况下。
