Pre-exercise nutrient availability alters acute metabolic responses to exercise, which could modulate training responsiveness
..exercise before versus after breakfast consumption increased net intramuscular lipid utilization in type I (net change: -3.44±2.63% versus 1.44±4.18% area lipid staining, p < 0.01) and type II fibres (-1.89±2.48% versus 1.83±1.92% area lipid staining, p < 0.05). Training Study – postprandial glycemia was not differentially affected by 6-weeks of exercise training performed before versus after carbohydrate intake (p>0.05). However, postprandial insulinemia was reduced with exercise training performed before, but not after carbohydrate ingestion (p=0.03). This resulted in increased oral glucose insulin sensitivity (25±38 vs -21±32 mL.min-1.m-2; p=0.01), associated with increased lipid utilization during exercise (r=0.50, p=0.02). Regular exercise before nutrient provision also augmented remodelling of skeletal muscle phospholipids and protein content of the glucose transport protein GLUT4 (p<0.05).
Experiments investigating exercise training and metabolic health should consider nutrient-exercise timing, and exercise performed before versus after nutrient intake (i.e., in the fasted state) may exert beneficial effects on lipid utilisation and reduce postprandial insulinemia.