Background

Individuals post-stroke walk slower than their able-bodied peers, which limits participation. This might be attributed to neurological impairments, but could also be caused by a mismatch between aerobic capacity and aerobic load of walking leading to an unsustainable relative aerobic load at most economic speed and preference for a lower walking speed.

Research question

What is the impact of aerobic capacity and aerobic load of walking on walking ability post-stroke?

Methods

Forty individuals post-stroke (more impaired N = 21; preferred walking speed (PWS)<0.8 m/s, less impaired N = 19), and 15 able-bodied individuals performed five, 5-minute treadmill walking trials at 70 %, 85 %, 100 %, 115 % and 130 % PWS. Energy expenditure (mlO₂/kg/min) and energy cost (mlO₂/kg/m) were derived from oxygen uptake (${\dot{\text{V}}\text{O}}_2$). Relative load was defined as energy expenditure divided by peak aerobic capacity (%${\dot{\text{V}}\text{O}}_2$peak) and by ${\dot{\text{V}}\text{O}}_2$ at ventilatory threshold (%${\dot{\text{V}}\text{O}}_2$-VT). Relative load and energy cost at PWS were compared with one-way ANOVA’s. The effect of speed on these parameters was modeled with Generalized Estimating Equations.

Results

Both more and less impaired individuals post-stroke showed lower PWS than able-bodied controls (0.44 [0.19−0.76] and 1.04 [0.81−1.43] vs 1.36 [0.89−1.53] m/s) and higher relative load at PWS (50.2 ± 14.4 and 51.7 ± 16.8 vs 36.2 ± 7.6 %${\dot{\text{V}}\text{O}}_2$peak and 101.9 ± 20.5 and 97.0 ± 27.3 vs 64.9 ± 13.8 %${\dot{\text{V}}\text{O}}_2$-VT). Energy cost at PWS of more impaired (0.30 [.19–1.03] mlO₂/kg/m) was higher than less-impaired (0.19[0.10−0.24] mlO₂/kg/m) and able-bodied (0.15 [0.13−0.18] mlO₂/kg/m). For post-stroke individuals, increasing walking speed above PWS decreased energy cost, but resulted in a relative load above endurance threshold.

Significance

Individuals post-stroke seem to reduce walking speed to prevent unsustainably high relative aerobic loads at the expense of reduced economy. When aiming to improve walking ability post-stroke, it is important to consider training aerobic capacity.

中文翻译：

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卒中后个体相对有氧负荷、能量消耗和步行速度之间的关系

背景

中风后的个体比健全的同龄人走得慢，这限制了参与。这可能归因于神经系统损伤，但也可能是由于步行的有氧能力和有氧负荷之间的不匹配导致在大多数经济速度下的相对有氧负荷不可持续，并且偏爱较低的步行速度。

研究问题

步行的有氧能力和有氧负荷对卒中后步行能力的影响是什么？

方法

中风后 40 人（受损较多的 N = 21；首选步行速度 (PWS) <0.8 m/s，受损较少的 N = 19），15 名身体健全的人以 70% 的速度进行了五次 5 分钟的跑步机步行试验， 85%、100%、115% 和 130% PWS。能量消耗 (mlO ₂ /kg/min) 和能量消耗 (mlO ₂ /kg/m) 来自摄氧量 (${\dot{\text{伏}}\text{哦}}_2$）。相对负荷定义为能量消耗除以峰值有氧能力（%${\dot{\text{伏}}\text{哦}}_2$峰值）和 ${\dot{\text{伏}}\text{哦}}_2$ 在通气阈值 (%${\dot{\text{伏}}\text{哦}}_2$-VT)。PWS 的相对负载和能源成本与单向方差分析进行了比较。速度对这些参数的影响用广义估计方程建模。

结果

中风后受损程度较高和较轻的个体均表现出比身体健全的对照组更低的 PWS（0.44 [0.19-0.76] 和 1.04 [0.81-1.43] vs 1.36 [0.89-1.53​​] m/s），并且 PWS 的相对负荷更高 (50.2 ± 14.4 和 51.7 ± 16.8 与 36.2 ± 7.6 %${\dot{\text{伏}}\text{哦}}_2$峰值和 101.9 ± 20.5 和 97.0 ± 27.3 与 64.9 ± 13.8 %${\dot{\text{伏}}\text{哦}}_2$-VT)。在 PWS 中，更多受损 (0.30 [.19–1.03] mlO ₂ /kg/m) 的能源成本高于受损较轻 (0.19[0.10-0.24] mlO ₂ /kg/m) 和健全 (0.15 [0.13 ] mlO ₂ /kg/m) -0.18]mlO ₂ /kg/m)。对于中风后的个体，将步行速度提高到 PWS 以上会降低能量成本，但会导致相对负荷高于耐力阈值。

意义

中风后的个体似乎以降低经济性为代价降低步行速度以防止不可持续的高相对有氧负荷。当旨在提高中风后步行能力时，重要的是要考虑训练有氧能力。