Effects of intermittent high-intensity exercise and carbohydrate supplementation on IGF-1 and glycogen of Wistar rats

Objective: The aim of this study was to analyze the association between glucose infusion during intermittent physical exercise and its metabolic effects on rats. Design: Forty male rats were divided into eight groups based on training (intermittent), exercise and carbohydrate intake (glucose 20%): TEC (trained exercised with carbohydrate). TES (trained exercised without carbohydrate). TNC (trained non-exercised with carbohydrate). TNS (trained non-exercised without carbohydrate). UEC (untrained exercised with carbohydrate). UES (untrained exercised without carbohydrate). UNC (untrained non-exercised with carbohydrate) and UNS (untrained non-exercised without carbohydrate). The training and/or exercise protocol consisted of the rats running on a treadmill for 1 min above the lactate threshold, or running below the lactate threshold for 30 s, intermittently for 30 min. Blood was analyzed for glycemia, lactate and IGF-1. Muscle and liver glycogen were measured (T2). Results: Glycemia was found to be different in T2 compared to T1 in the TEC, TNC, UEC and UNC groups. Lactate was higher in T2 than in T1, but remained within the lactate threshold. Glycogen showed higher concentrations in the trained groups and, whether trained or not, in the supplemented groups. IGF-1 levels were higher in exercised rats independent of supplementation or glycogen levels. Trained rats showed lower IGF-1 when exercising than did the untrained animals. Conclusions: We conclude that intermittent exercise is beneficial in preventing a trained lactate pool, and that, in association with glucose supplementation, intemittent exercise will be efficient both in preventing a trained lactate pool and in maintaining sufficient glycemia levels. Exercise raises IGF-1 levels, whereas training inverts this relationship. (C) 2008 Elsevier Ltd. All rights reserved.