Purpose: Modulation of vascular function follows an exercise intensity-dependent pattern in young adults. This study aimed to investigate the potential intensity-dependent effects of an acute bout of exercise on conduit and resistance artery function in healthy older adults.
Methods: Eleven healthy older adults (5 males/6 females, 66+/-1 years) completed 30 minutes of recumbent cycling at 50-55% (low-intensity) and 75-80% (high-intensity) of their age-predicted maximal heart rate on two separate study visits. Doppler ultrasound measures of brachial artery flow-mediated dilation (FMD) and reactive hyperemia (RH) were taken at baseline, ten minutes post-exercise, and one hour post-exercise. Additionally, cardiovascular hemodynamics and brachial shear rate were measured every five minutes during exercise.
Results: Brachial artery FMD was enhanced ten minutes after high-intensity (4.8+/-0.2 to 9.1+/-0.3%, P<0.01), but not low-intensity (4.7+/-0.2 to 6.2+/-0.3%, P=0.54) exercise. Peak and total (area under the curve) blood flow during RH (measures of resistance artery function) were enhanced ten minutes post-exercise for both intensities (peak low-intensity 372+/-31 to 444+/-37, peak high-intensity 391+/-30 to 455+/-28 ml/min; total low-intensity 142+/-16 to 205+/-20, total high-intensity 158+/-14 to 240+/-25 ml, main effect of time for both P<0.05). However, the magnitude of change in peak and total blood flow were not different between exercise intensities (interaction effect; P=0.56 and P=0.97, respectively). Independent of exercise intensity, FMD returned to baseline one-hour after exercise (high 5.9+/-0.3; low 5.1+/-0.1%, both P>0.05).
Conclusion: Our data indicate that high-intensity exercise acutely enhances conduit artery function in healthy older adults. Additionally, an acute bout of exercise enhances resistance artery function independent of intensity.
(C) 2017 American College of Sports Medicine