Institute of Population Health, University of Liverpool, Liverpool L69 7ZA, UK; Institute of Life Course & Medical Sciences, University of Liverpool, Liverpool L7 8TX, UK.
Institute of Life Course & Medical Sciences, University of Liverpool, Liverpool L7 8TX, UK.
Hum Mov Sci. 2020 Oct;73:102676. doi: 10.1016/j.humov.2020.102676. Epub 2020 Sep 18.
Peripheral vision often deteriorates with age, disrupting our ability to maintain normal locomotion. Laboratory based studies have shown that lower visual field loss, in particular, is associated with changes in gaze and gait behaviour whilst walking and this, in turn, increases the risk of falling in the elderly. Separately, gaze and gait behaviours change and fall risk increases when walking over complex surfaces. It seems probable, but has not yet been established, that these challenges to stability interact.
How does loss of the lower visual field affect gaze and gait behaviour whilst walking on a variety of complex surfaces outside of the laboratory? Specifically, is there a synergistic interaction between the effects on behaviour of blocking the lower visual field and increased surface complexity?
We compared how full vision versus simulated lower visual field loss affected a diverse range of behavioural measures (head pitch angle, eye angle, muscle coactivation, gait speed and walking smoothness as measured by harmonic ratios) in young participants. Participants walked over a range of surfaces of different complexity, including pavements, grass, steps and pebbles.
In both full vision and blocked lower visual field conditions, surface complexity influenced gaze and gait behaviour. For example, more complex surfaces were shown to be associated with lowered head pitch angles, increased leg muscle coactivation, reduced gait speed and decreased walking smoothness. Relative to full vision, blocking the lower visual field caused a lowering of head pitch, especially for more complex surfaces. However, crucially, muscle coactivation, gait speed and walking smoothness did not show a significant change between full vision and blocked lower visual field conditions. Finally, head pitch angle, muscle coactivation, gait speed and walking smoothness were all correlated highly with each other.
Our study showed that blocking the lower visual field did not significantly change muscle coactivation, gait speed or walking smoothness. This suggests that young people cope well when walking with a blocked lower visual field, making minimal behavioural changes. Surface complexity had a greater effect on gaze and gait behaviour than blocking the lower visual field. Finally, head pitch angle was the only measure that showed a significant synergistic interaction between surface complexity and blocking the lower visual field. Together our results indicate that, first, a range of changes occur across the body when people walk over more complex surfaces and, second, that a relatively simple behavioural change (to gaze) suffices to maintain normal gait when the lower visual field is blocked, even in more challenging environments. Future research should assess whether young people cope as effectively when several impairments are simulated, representative of the comorbidities found with age.
周边视觉通常会随着年龄的增长而恶化，从而扰乱我们维持正常运动的能力。基于实验室的研究表明，特定情况下，视野下部的损失与行走时注视和步态行为的变化有关，而这反过来又增加了老年人跌倒的风险。另外，在行走于复杂表面时，注视和步态行为会发生变化，跌倒的风险也会增加。虽然还没有得到证实，但很有可能这些稳定性挑战是相互作用的。
在实验室以外的各种复杂表面上行走时，视野下部的损失如何影响注视和步态行为？具体来说，下部视野受阻和表面复杂性增加对行为的影响是否存在协同作用？
我们比较了在年轻人参与者中，全视野和模拟下部视野损失对多种行为测量指标（头部俯仰角、眼睛角度、肌肉协同激活、步速和行走平稳度，以谐波比衡量）的影响。参与者在不同复杂程度的一系列表面上行走，包括人行道、草地、台阶和鹅卵石。
在全视野和下部视野受阻的情况下，表面复杂性都影响了注视和步态行为。例如，更复杂的表面与较低的头部俯仰角、增加的腿部肌肉协同激活、降低的步速和降低的行走平稳度有关。与全视野相比，下部视野受阻会导致头部俯仰角降低，特别是在更复杂的表面上。然而，至关重要的是，肌肉协同激活、步速和行走平稳度在全视野和下部视野受阻的情况下并没有明显变化。最后，头部俯仰角、肌肉协同激活、步速和行走平稳度彼此之间高度相关。
我们的研究表明，下部视野受阻不会显著改变肌肉协同激活、步速或行走平稳度。这表明，当年轻人在下部视野受阻的情况下行走时，他们能够很好地应对，只做出最小的行为改变。表面复杂性对注视和步态行为的影响大于下部视野受阻。最后，头部俯仰角是唯一一项在表面复杂性和下部视野受阻之间表现出显著协同作用的测量指标。总的来说，我们的研究结果表明，首先，当人们在更复杂的表面上行走时，身体会发生一系列变化；其次，即使在更具挑战性的环境中，当下部视野受阻时，相对简单的行为改变（注视）足以维持正常的步态。未来的研究应该评估当模拟多种与年龄相关的共病时，年轻人是否能同样有效地应对。
