Abstract
AIM: 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. METHODS: 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% VO(2) peak). NIRS was used to assess total hemoglobin (tHb) (i.e., blood volume) before, during, and after exercise, as well as muscle oxygen consumption (mVO(2)) and microvascular reactivity (StO(2)% s(-1)) pre- and post-exercise. RESULTS: 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.). mVO(2) 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). CONCLUSION: 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.