Slow-Speed Low-Intensity but Not Normal-Speed High-Intensity Resistance Exercise Maintains Endothelial Function

Purpose: High-intensity resistance exercise two or three times a week has been considered optimal for muscle hypertrophy, although it can remarkably elevate blood pressure (BP). In contrast, slow-speed resistance exercise with low intensity and tonic force generation (slow-low) can induce muscle hypertrophy without elevating BP. However, it is unclear how endothelial function changes after slow-low. Therefore, this study examined whether slow-low would maintain brachial artery endothelial function in comparison with normal-speed with high intensity resistance exercise (normal-high) and normal-speed with low-intensity resistance exercise (normal-low). Methods: Eleven healthy young men performed leg-extensions with slow-low (3 sets of 8 repetitions at 50% of 1RM), normal-high (3 sets of 8 repetitions at 80% of 1RM), and normal-low (3 sets of 8 repetitions at 50% of 1RM). Flow-mediated dilation (FMD) in the brachial artery was evaluated at pre-exercise and at 10, 30, and 60 min after exercise. Result: The results showed that normal-high caused significant impairment of FMD at 30 (3.7 ± 2.7%) and 60 (3.7 ± 2.8%) min after exercise (P < .05). In contrast, slow-low and normal-low showed no significant difference from baseline. FMD was significantly lower in normal-high compared with slow-low and normal-low at 30 and 60 min after exercise (P < .05). Additionally, systolic BP was significantly higher during normal-high compared with slow-low and normal-low (P < .05). Conclusion: We concluded that slow-low did not impair brachial artery FMD concomitant with lower systolic BP, and may therefore be a useful mode of exercise training to improve muscle hypertrophy without provoking transient endothelial dysfunction.