The Energy Cost of Steady State Physical Activity in Acute Stroke

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.

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.

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).

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.