Changes In The Reactive Hyperemia Index After Continuous And Interval Exercise

High intensity interval exercise (HIIE) is more effective than moderate intensity interval exercise (MICE) for improving macrovascular function (e.g. flow-mediated dilation) but less is known regarding the effect of HIIE on microvascular function (e.g. peripheral arterial tonometry). PURPOSE: To examine the effects of HIIE and MICE on microvascular function. METHODS: Ten healthy adults (26 ± 5 y, 170 ± 10 cm, 75.6 ± 15 kg) completed the MICE protocol (20 min of cycling at 60% of maximum power output) and the HIIE protocol (12 min warm up of cycling at 50% of subjects’ maximum power output immediately followed by an 8-min Tabata cycling protocol of alternating efforts of 20 s of maximum effort cycling and 10 s of rest) on separate days. Reactive hyperemia index (RHI) was measured before, immediately after, and 1 h after exercise and compared by two-way repeated measures ANOVA. RESULTS: There was a main effect of time (p = 0.009) such that, compared to baseline, RHI increased 1 h after exercise in the MICE condition only (p = 0.02) There was a time by condition effect (p < 0.001) such that HR was higher during MICE at minutes 5 and 10 (p = 0.02) and higher during HIIE at minute 20 (p = 0.001)(Figure 1). Similarly, RPE demonstrated a time by condition effect (p < 0.001) such that RPE was higher during MICE (5 ± 1) compared to HIIE (3 ± 1) at minute 10 (p = 0.02) and higher during HIIE at minutes 15 (6 ± 1) and 20 (8 ± 1) compared to MICE (Min 15; 5 ± 1, Min 20; 5 ± 2, p = 0.05). CONCLUSION: Within a sample of healthy adults, microvascular function assessed using the RHI was improved 1 h after a single session of MICE but not HIIE in contrast to previous studies comparing MICE and HIIE effects on macrovascular function. Future research is needed to determine if this difference is due to measurement technique or study population.