Effect of Protein Supplementation on Cardiorespiratory Fitness with Aerobic Training in Chronic Stroke: a Multicenter Randomized Controlled Trial.

Background: Decreased cardiorespiratory fitness (CRF) is prevalent in stroke patients, and aerobic training can improve CRF in this population. Protein supplementation has been proposed as a strategy to enhance exercise adaptations by promoting muscle protein synthesis, reducing muscle loss, and improving physical function. However, the potential of protein supplementation to further improve CRF during aerobic training among stroke patients remains unclear. This study aims to evaluate the effect of protein supplementation on CRF and physical performance in patients with chronic stroke undergoing aerobic training. Methods: This multicenter, participant- and assessor-blinded, randomized clinical trial enrolled 114 ambulatory adults with chronic stroke at four teaching hospitals. Participants were randomized to receive protein supplementation (n = 58) or an isocaloric carbohydrate placebo (n = 56) during 30 supervised aerobic training sessions over 10 weeks. The primary outcome was the change in peak oxygen consumption (V̇O₂peak, mL/kg/min) at 11 weeks. Secondary outcomes included CRF-related measures, body composition (total lean and fat mass), and physical performance (Short Physical Performance Battery [SPPB], Physical Performance Test, Berg Balance Scale, and Timed Up and Go test). Results: Participants had a mean age of 57.2 years, 30% were women, and 87% completed the primary outcome assessment. At the 11-week follow-up, V̇O₂peak increased by 1.7 mL/kg/min (95% CI, 1.0–2.4) in the protein group and 1.6 mL/kg/min (95% CI, 0.9–2.3) in the placebo group, with no between-group difference (mean difference, 0.1 mL/kg/min; 95% CI, −0.8 to 1.1; P = 0.43). Both groups showed improvements in most CRF-related and physical performance measures. At 20 weeks, the protein group demonstrated greater SPPB improvement (mean difference, 0.7 points; 95% CI, 0.1–1.3; P = 0.03) and lower fat mass at 11 weeks (mean difference, −0.6 kg; 95% CI, −1.2 to −0.06; P = 0.04). Conclusions: Protein supplementation during aerobic training did not significantly enhance CRF compared with an isocaloric placebo. These findings warrant further investigation in populations with a broader range of baseline protein intake.