Abstract
Background: An acute bout of exercise can improve endothelial function and insulin sensitivity when measured on the day following exercise. Our aim was to compare acute high-intensity continuous exercise (HICE) to high-intensity interval exercise (HIIE) on circulating endothelial microparticles (EMPs) and insulin sensitivity in overweight/obese men and women. Methods: Inactive males (BMI = 30 ± 3, 25 ± 6 yr, n = 6) and females (BMI = 28 ± 2, 21 ± 3 yr, n = 7) participated in three experimental trials in a randomized counterbalanced crossover design: 1) No exercise control (Control); 2) HICE (20 min cycling @ just above ventilatory threshold); 3) HIIE (10 X 1-min @ ∼ 90% peak aerobic power). Exercise conditions were matched for external work and diet was controlled post-exercise. Fasting blood samples were obtained ∼ 18 hr after each condition. CD62E(+) and CD31(+)/CD42b- EMPs were assessed by flow cytometry and insulin resistance (IR) was estimated by homeostasis model assessment (HOMA-IR). Results: There was a significant sex X exercise interaction for CD62E(+) EMPs, CD31(+)/CD42b- EMPs, and HOMA-IR (all P < 0.05). In males, both HICE and HIIE reduced EMPs compared to Control (P ≤ 0.05). In females, HICE increased CD62E(+) EMPs (P < 0.05 vs. Control) whereas CD31(+)/CD42b- EMPs were unaltered by either exercise type. There was a significant increase in HOMA-IR in males but a decrease in females following HIIE compared to Control (P<0.05). Conclusions: Overweight/obese males and females appear to respond differently to acute bouts of high-intensity exercise. A single session of HICE and HIIE reduced circulating EMPs measured on the morning following exercise in males but in females CD62E(+) EMPs were increased following HICE. Next day HOMA-IR paradoxically increased in males but was reduced in females following HIIE. Future research is needed to investigate mechanisms responsible for potential differential responses between males and females.