Prior exercise enhances skeletal muscle microvascular blood flow and mitigates microvascular flow impairments induced by a high-glucose mixed meal in healthy young men

Key points

• Exercise, insulin-infusion and low-glucose mixed-nutrient meal ingestion increases muscle microvascular blood flow which in part facilitates glucose delivery and disposal. In contrast, high-glucose ingestion impairs muscle microvascular blood flow which may contribute to impaired postprandial metabolism.
• We investigated the effects of prior cycling exercise on postprandial muscle microvascular blood flow responses to a high-glucose mixed-nutrient meal ingested 3 and 24 h post-exercise.
• Prior exercise enhanced muscle microvascular blood flow and mitigated microvascular impairments induced by a high-glucose mixed meal ingested 3 h post-exercise, and to a lesser extent 24 h post-exercise.
• High-glucose ingestion 3 h post-exercise leads to greater postprandial blood glucose, non-esterified fatty acids, and fat oxidation, and a delay in the insulin response to the meal compared to control.
• Effects of acute exercise on muscle microvascular blood flow persist well after the cessation of exercise which may be beneficial for conditions characterized by microvascular and glycaemic dysfunction.

Exercise, insulin-infusion and low-glucose mixed-nutrient meal ingestion lead to increased muscle microvascular blood flow (MBF), whereas high-glucose ingestion impairs MBF. We investigated whether prior cycling exercise could enhance postprandial muscle MBF and prevent MBF impairments induced by high-glucose mixed-nutrient meal ingestion. In a randomized cross-over design, eight healthy young men ingested a high-glucose mixed-nutrient meal (1.1 g glucose/kg body weight; 45% carbohydrate, 20% protein and 35% fat) after an overnight fast (no-exercise control) and 3 h and 24 h after moderate-intensity cycling exercise (1 h at 70–75% urn:x-wiley:00223751:media:tjp14439:tjp14439-math-0001). Skeletal muscle MBF, measured directly by contrast-enhanced ultrasound, was lower at 60 min and 120 min postprandially compared to baseline in all conditions (P < 0.05), with a greater decrease occurring from 60 min to 120 min in the control (no-exercise) condition only (P < 0.001). Despite this meal-induced decrease, MBF was still markedly higher compared to control in the 3 h post-exercise condition at 0 min (pre-meal; 74%, P = 0.004), 60 min (112%, P = 0.002) and 120 min (223%, P < 0.001), and in the 24 h post-exercise condition at 120 min postprandially (132%, P < 0.001). We also report that in the 3 h post-exercise condition postprandial blood glucose, non-esterified fatty acids (NEFAs), and fat oxidation were substantially elevated, and the insulin response to the meal delayed compared to control. This probably reflects a combination of increased post-exercise exogenous glucose appearance, substrate competition, and NEFA-induced insulin resistance. We conclude that prior cycling exercise elicits long-lasting effects on muscle MBF and partially mitigates MBF impairments induced by high-glucose mixed-nutrient meal ingestion.