Long-term passive leg stretch improves systemic vascular responsiveness as much as single-leg exercise training

Purpose: The current study compared the local and systemic vascular responsiveness after small muscle mass endurance training or passive stretching training (PST). Methods: Thirty-six sex-matched healthy participants underwent 8-week single-leg knee extension (SLKE) (N = 12) training or PST (N = 12), or no intervention (control, N = 12). Before and after the intervention, local and systemic vascular responsiveness was assessed by Doppler ultrasound at the femoral (local effect) and brachial artery (systemic effect) during single passive leg movement (sPLM) and brachial flow-mediated dilation (FMD) test, respectively. Results: After training, delta femoral blood flow (representing the local vascular responsiveness) increased after SLKE and PST by +54(7)% (effect size: 2.72, P < 0.001) and + 20(2)%, (effect size: 2.43, P < 0.001), respectively, albeit with a greater extent in SLKE [post-SLKE vs. post-PST: +56(8)%, (effect size: 2.92, P < 0.001)]. Interestingly, the %FMD (standing for the systemic effect) increased after SLKE and PST by +12(2)% (effect size: 0.68, P < 0.001) and + 11(1)% (effect size: 0.83, P < 0.001), respectively, without any between-groups difference (P > 0.05). No changes occurred in control. Conclusion: The present findings revealed that both active and passive training modalities induced similar improvements in the brachial artery dilatation capacity, while the former was more effective in improving femoral artery blood flow. Passive stretching could be used in people with limited mobility to improve vascular responsiveness both at the local and systemic level, and in this latter case has similar effects as small muscle mass endurance training.