The Energy Cost of Steady State Physical Activity in Acute Stroke

Abstract

Objective: Cardiorespiratory fitness levels are very low after stroke, indicating that the majority of stroke survivors are unable to independently perform daily activities. Physical fitness training improves exercise capacity poststroke; however, the optimal timing and intensity of training is unclear. Understanding the energy cost of steady-state activity is necessary to guide training prescription early poststroke. We aimed to determine if acute stroke survivors can reach steady state (oxygen-uptake variability ≤2.0 mL O₂/kg/min) during physical activity and if the energy cost of steady state activity differs from healthy controls.

Material and methods: We recruited 23 stroke survivors less than 2 weeks poststroke. Thirteen were able to walk independently and performed a 6-minute walk (median age 78 years, interquartile range [IQR] 70-85), and 7 who were unable to walk independently performed 6 minutes of continuous sit-to-stands (median age 78 years, IQR 74-79) and we recruited 10 healthy controls (median age 73 years, IQR 70-77) who performed both 6 minutes of walking and sit-to-stands. Our primary outcome was energy cost (oxygen-uptake) during steady state activity (i.e., walking and continuous) sit-to-stands, measured by a mobile metabolic cart.

Results: All stroke survivors were able to reach steady state. Energy costs of walking was higher in stroke than in controls (mean difference .10 mL O₂/kg/m, P = .02); the difference in energy costs during sit-to-stands was not significant (mean difference .11 mL O₂/kg/sts, P = .45).

Conclusions: Acute stroke survivors can reach a steady state during activity, indicating they are able to perform cardiorespiratory exercise. Acute stroke survivors require more energy per meter walked than controls.

Keywords: Stroke; acute; energy cost; exercise; indirect calorimetry; oxygen consumption; physical activity.