Examination of post-exercise microvascular reactivity in healthy adults

Skeletal muscle blood volume responds to the metabolic demands of exercise and augmented microvasculature reactivity. We sought to explore the effects of exercise intensity (maximal vs. submaximal) on near-infrared spectroscopy (NIRS)-derived blood volume and microvascular reactivity in the acute post-exercise timeframe.

Healthy individuals (N = 18) between 18 and 35 years completed a vascular occlusion test (VOT) followed by a maximal cycling test. A second VOT was performed 15-min post-exercise. One week later, the protocol was repeated before and after a submaximal bout of cycling (60% VO₂ peak). NIRS was used to assess total hemoglobin (tHb) (i.e., blood volume) before, during, and after exercise, as well as muscle oxygen consumption (mVO₂) and microvascular reactivity (StO₂% s^-1) pre- and post-exercise.

Compared with pre-exercise, tHb was elevated at the end of exercise (p < 0.001) and remained elevated 15-min post-exercise (p < 0.001) regardless of trial (combined means pre: 5.39 ± 0.82, during: 14.01 ± 1.73, and post-exercise: 10.89 ± 1.24 O.D.). mVO₂ was greater post-exercise in the max vs. submax trial (- 0.36 ± 0.12 vs. - 0.22 ± 0.11% s^-1; p < 0.001). Compared with pre-exercise, microvascular reactivity was unchanged following the max trial (1.91 ± 0.61 vs. 1.71 ± 0.61% s^-1; p = 0.079) but was greater following the submax trial (1.72 ± 0.43 vs. 1.98 ± 0.59; p = 0.007).

Cycling at a submaximal, but not maximal, intensity results in augmented post-exercise microvascular reactivity, while post-exercise increases in skeletal muscle blood volume were found regardless of exercise intensity.