Effects of moderate exercise on metabolic responses and respiratory exchange ratio (RER).

To counteract insulin resistance, it is necessary to increase the utilization rate of fatty acids in blood and adipose tissue. The aim of the present study was to determine the relation between metabolic responses and exercise duration from changes in the respiratory exchange ratio (RER). The mean RER during 30 minutes of moderate exercise (mean pulse 115 beats/min) was 0.89 +/- 0.02, indicating no major change. Significant changes were observed in the levels of plasma glucose (PG), plasma free fatty acid (FFA), and plasma immunoreactive insulin (IRI) before and after exercise, demonstrating a decrease in PG and IRI, and an increase in FFA levels. However, the RER value indicated that carbohydrate was the dominant metabolic substrate; therefore, prolonged or repetitive brief and mild to moderate exercise is necessary to increase the utilization of fatty acids.