[Mechanism of the increased insulin sensitivity of rats following physical training]

A rise of sensitivity to insulin was noted in healthy rats living an inactive life in a vivarium as a result of regular physical exercises (swimming with load for 30 min. during one month). It was expressed in a drop of glycemia in response to insulin administration in the presence of glycogen load, in greater glucose consumption and glycogen accumulation by tissues during incubation with insulin, in a lesser rise of C-peptide and insulin levels after glycogen load. Muscular activity was shown to incorporate glucose consumption and oxidation mechanisms unrelated to insulin regulation. Physical exercise resulted in a rise of the activity of enzymes involved in oxidation of glucose metabolism intermediate products in the presence of a decrease in the insulin level. A conclusion has been made that physical exercises determine a decrease in a demand for insulin secretion in response to a rise of the glucose level in the blood resulting in decreased insulinemia and consequently in raising sensitivity to insulin.