Reduced glucose tolerance and insulin sensitivity after prolonged exercise in endurance athletes

Abstract

Aim The purpose of this study was to 1. investigate if glucose tolerance is affected after one acute bout of different types of exercise; 2. assess if potential differences between two exercise paradigms are related to changes in mitochondrial function; and 3. determine if endurance athletes differ from nonendurance‐trained controls in their metabolic responses to the exercise paradigms. Methods Nine endurance athletes (END) and eight healthy nonendurance‐trained controls (CON) were studied. Oral glucose tolerance tests (OGTT) and mitochondrial function were assessed on three occasions: in the morning, 14 h after an overnight fast without prior exercise (RE), as well as after 3 h of prolonged continuous exercise at 65% of VO2max (PE) or 5 × 4 min at ~95% of VO2max (HIIT) on a cycle ergometer. Results Glucose tolerance was markedly reduced in END after PE compared with RE. END also exhibited elevated fasting serum FFA and ketones levels, reduced insulin sensitivity and glucose oxidation, and increased fat oxidation during the OGTT. CON showed insignificant changes in glucose tolerance and the aforementioned measurements compared with RE. HIIT did not alter glucose tolerance in either group. Neither PE nor HIIT affected mitochondrial function in either group. END also exhibited increased activity of 3‐hydroxyacyl‐CoA dehydrogenase activity in muscle extracts vs. CON. Conclusion Prolonged exercise reduces glucose tolerance and increases insulin resistance in endurance athletes the following day. These findings are associated with an increased lipid load, a high capacity to oxidize lipids, and increased fat oxidation.

Muscle physiology and its relations to the whole body in health and disease

“…These findings are associated with an increased lipid load, a high capacity to oxidize lipids, and increased fat oxidation. 12 Sedentary behavior is closely linked to muscle IR, but not to liver IR. Low levels of physical activity and behavior that is more sedentary have repeatedly been associated with (IR) and impaired glucose homeostasis.…”

Nutritional health

“…6,7 While exercise is recommended in all guidelines aimed at reducing the impact of overnutrition-associated pathologies, current data indicate a necessary finetuning of exercise regimens to individual metabolic responses. 8,9 In addition to its influence on glucose metabolism, exercise positively influences both organ crosstalk 10 and fatty acid perception and metabolism. 11 The circadian system is a major regulator of metabolic health.…”