Effects Of Isocaloric Aerobic Training With Different Intensities Upon Fitness, Adiposity And Microcirculation In Rats

Abstract

BACKGROUND: The role of exercise intensity and volume within aerobic training to improve cardiovascular and metabolic markers remains unclear. PURPOSE: To investigate the effects of isocaloric aerobic training performed with different intensities upon body composition, cardiorespiratory fitness and endothelial-dependent vasodilation in eutrophic rats. METHODS: Wistar rats (n=30) were assigned into three groups: sedentary control (SC), high-intensity training (HI), and moderate-intensity training (MI). MI and HI groups performed treadmill running for 4 weeks at speeds corresponding to 50% and 80% oxygen uptake reserve (VO2R), respectively. The duration of exercise sessions was controlled through energy expenditure (MI=3.4±0.3, HI=3.2±0.3 kcal; P=0.61). At the end of intervention all groups had assessed the body composition (DEXA), cardiorespiratory fitness (VO2max), and endothelial-dependent vasodilation (intravital microscopy). RESULTS: Only HI presented lower fat mass (101.2±3.0 g vs. 124.8±2.0 g; P=0.01) and % fat (29.8±1.0% vs. 35.5±1.0%; P=0.03) compared to SC after training. The VO2max increased in both exercised groups vs. SC (P<0.001), but improvement was higher in HI over MI (P<0.001) (ΔSC= -3.7±3.0 ml.kg-1.min-1; ΔHI= 4.9±2.0 ml.kg-1.min-1; ΔMI= 2.5±3.0 ml.kg-1.min-1). Endothelial-dependent vasodilation in response to acetylcholine improved similarly in HI and MI (21.5% vs. 20.8%; P=0.73) vs. SC (P<0.05). CONCLUSION: Isocaloric aerobic training with high-intensity was more effective to improve adiposity and cardiorespiratory fitness in eutrophic rats. On the other hand, endothelial function improved similarly in both exercise groups, suggesting that energy expenditure would be more important than exercise intensity to enhance endothelial-dependent vasodilation. Supported by the Brazilian Council for the Technological and Research Development (CNPq) and Carlos Chagas Foundation for the Research Development in the State of Rio de Janeiro (FAPERJ).