Purpose: Aerobic training (AT) and high-intensity intermittent training (HIIT) reduce arterial stiffness, whereas resistance training (RT) induces deterioration of or no change in arterial stiffness. However, the molecular mechanism of these effects of different exercise modes remains unclear. This study aimed to clarify the difference of different exercise effects on endothelial nitric oxide synthase (eNOS) signaling pathway and arterial stiffness in rats and humans.
Methods: In the animal study, forty 10-wk-old male Sprague-Dawley rats were randomly divided into four groups: sedentary control (CON), AT (treadmill running, 60 min at 30 m·min, 5 d·wk for 8 wk), RT (ladder climbing, 8-10 sets per day, 3 d·wk for 8 wk), and HIIT (14 repeats of 20-s swimming session with 10-s pause between sessions, 4 d·wk for 6 wk from 12-wk-old) groups (n = 10 in each group). In the human study, we confirmed the effects of 6-wk HIIT and 8-wk AT interventions on central arterial stiffness and plasma nitrite/nitrate level in untrained healthy young men in randomized controlled trial (HIIT, AT, and CON; n = 7 in each group).
Results: In the animal study, the effect on aortic pulse wave velocity (PWV), as an index of central arterial stiffness, after HIIT was the same as the decrease in aortic PWV and increase in arterial eNOS/Akt phosphorylation after AT, which was not changed by RT. A negative correlation between aortic PWV and eNOS phosphorylation was observed (r = -0.38, P < 0.05). In the human study, HIIT- and AT-induced changes in carotid-femoral PWV (HIIT -115.3 ± 63.4 and AT -157.7 ± 45.7 vs CON 71.3 ± 61.1 m·s, each P < 0.05) decreased, and plasma nitrite/nitrate level increased compared with those in CON.
Conclusions: HIIT may reduce central arterial stiffness via the increase in aortic nitric oxide bioavailability despite it being done in a short time and short term and has the same effects as AT.