Acute and chronic resistive exercise increase urinary chromium excretion in men as measured with an enriched chromium stable isotope

Abstract

Both exercise and chromium exert beneficial effects on insulin function. The mechanism by which exercise improves insulin response may involve an alteration in Cr metabolism. To determine the effects of acute and chronic resistive exercise on urinary Cr losses, we measured the effects of acute resistive exercise and 16 wk of resistive exercise training on urinary Cr losses of 10 men 53-63 y of age. Subjects consumed diets in compliance with the American Heart Association Phase I diet with a Cr content of 30 ± 4 μg/d. Sixteen weeks of resistive exercise training led to ~40% increases in upper and lower body strength, increases in fat-free mass and decreases in the percentage of body fat. An enriched stable isotope of Cr, 53Cr, was employed to differentiate the exogenously administered Cr from the native endogenous Cr. Both acute and chronic resistive exercise increased 53Cr losses. These data demonstrate that the improvements in body composition due to resistive exercise are associated with increased urinary Cr losses that are consistent with increased absorption.