Intermittent versus constant aerobic exercise: effects on arterial stiffness.

Aerobic exercises (of sufficient duration and intensity) decreases arterial stiffness. However, the direct relationship between the type of aerobic exercise (i.e. constant versus interval) and the alteration in arterial stiffness has been poorly explored. We evaluated the hemodynamic responses of 11 healthy males (22.5 +/- 0.7 years, height 177.7 +/- 1.1 cm, body mass 70.5 +/- 2.4 kg) following acute constant (CE) and intermittent cycling exercise (IE). Exercise duration and intensity (mean heart rate) were matched during both exercises (142.9 +/- 2.4 bpm for CE and 144.2 +/- 2.4 bpm for IE). Heart rate (HR) and cardiac output (CO) were measured throughout the whole session, while blood pressure and pulse wave velocity (PWV) were measured during pre exercise and 30 min recovery. Arterial stiffness and cardiac autonomic control were assessed through PWV and heart rate variability, respectively. After IE, lower limb arterial stiffness was significantly and steadily decreased compared to pre exercise value (from 8.6 +/- 0.1 to m s(-1) to 7.6 +/- 0.3 to m s(-1) at 30 min) and was lower than after CE (8.2 +/- 0.3 m s(-1) at 30 min, which did not significantly change compared to pre exercise: 8.7 +/- 0.2 m s(-1)). We hypothesized that the higher HR and lower arterial stiffness after IE were likely due to variations in peripheral vascular changes during the exercise which may trigger the release of endothelial or metabolic vasoactive factors. These data appear to show that IE may result in a greater stimulus for vascular adaptations when compared to CE.

Effects of resuming endurance training on arterial stiffness and nitric oxide production during exercise in elite cyclists.

Exercise training improves arterial compliance due to increases in blood flow to skeletal muscle during repeated bouts of daily exercise. The effect of resuming training on arterial stiffness in previously well-trained subjects is poorly documented. Hence, the purpose of this study was to determine the vascular effects induced by return to exercise in highly trained cyclists. Pulse wave velocity (PWV), an index of arterial stiffness, was assessed at rest and during constant moderate-intensity cycle exercises before and after 16 weeks of endurance training. The impact of daily exercise on the concentration of nitric oxide (NO) measured as nitrate in plasma was examined at rest and during maximal exercise before and after the training period. At rest, PWV was significantly lower in the subjects after a training session (6.4 +/- 0.4 vs. 8.1 +/- 0.4 m x s(-1), p < 0.05). During constant exercise, PWV was significantly and positively correlated with increases in blood pressure. The increased PWV induced by exercise was, however, significantly lower after training (9.8 +/- 0.6 vs. 11.4 +/- 0.6 m x s(-1), p < 0.05). After the training program, nitrate plasma levels at rest were higher. During the maximal test, the plasma nitrate concentration was increased in the subjects studied before the training period, but not after. These results show that resumption of chronic endurance training rapidly induces adaptive changes in arterial stiffness and NO release that may contribute to improved physical fitness in athletes.