Microvascular Reperfusion is Enhanced Following Submaximal but Not Maximal Cycling

Muscle blood flow increases during exercise in proportion to the intensity. However, sympathetic activity in the acute timeframe following maximal intensity exercise may impair skeletal muscle microvascular reperfusion. PURPOSE: Determine the effect of maximal vs. submaximal cycling on post-exercise skeletal muscle microvascular reperfusion. METHODS: N =18 (N = 14 male; 22 ± 4 years) visited the lab on two occasions. A NIRS device was placed on the belly of the VL muscle of the subject’s right leg. A pneumatic cuff capable of rapid inflation was placed on the same leg proximal to the tibiofemoral joint. Laying supine, a vascular occlusion test (VOT) was performed consisting of 2 min baseline, 5 min of arterial occlusion at a pressure of 300 mmHg, and 3 min of recovery. Participants then performed a progressive maximal exercise test on a cycle ergometer to exhaustion (MAX), and a VOT was assessed again 15 min after exercise. One week later, the protocol was repeated before and after a submaximal test at 60% VO 2 peak for the time to match the caloric expenditure of the maximal exercise test (SUBMAX). Analyses of NIRS data were performed using the halftime to peak reperfusion of the tissue oxygen saturation (%StO 2 ) signal (reported in seconds) and the 10-second recovery slope of the StO 2 signal immediately following cuff release (Slope 2, reported as % s -1 ). A repeated measures ANOVA (time * trial) was performed with statistical significance accepted at P £ 0.05. RESULTS: There was a significant trial*time interaction for StO 2 halftime (P = 0.006) and Slope 2 (P < 0.001). There were no significant differences in StO 2 halftime following the MAX (10.2 ± 1.9 vs. 10.3 ± 2.3 seconds pre- and post-exercise, respectively; P = 0.857). However, there was a significantly faster StO 2 halftime post-exercise after SUBMAX (10.4 ± 1.2 vs. 8.7 ± 1.6 seconds pre- and post-exercise, respectively; P <0.001). Similarly, there were no significant differences in Slope 2 following MAX (1.918 ± 0.611 vs. 1.714 ± 0.609 % s -1 pre- vs. post-exercise, respectively P = 0.079). Following the SUBMAX, Slope 2 was significantly higher (1.983 ± 0.586 % s -1 ) compared with pre-exercise values (1.725 ± 0.439 %/s; P = 0.007). There were no differences between trials at baseline in either StO 2 halftime (P = 0.686) or Slope 2 (P = 0.072). CONCLUSIONS: These findings indicate greater microvascular reperfusion in the acute recovery period following submaximal but not maximal exercise. These findings support a lower exercise intensity to enhance post-exercise skeletal muscle microvascular blood flow, which has implications for both clinical and athletic populations. Supported by Towson University (TU) School of Emerging Technology, TU College of Health Professions, and the Summer Undergraduate Research Institute. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.