ACUTE AND CHRONIC RESISTIVE EXERCISE INCREASE URINARY CHROMIUM EXCRETION IN MEN AS MEASURED WITH AN ENRICHED CHROMIUM STABLE-ISOTOPE

Both exercise and chromium exert beneficial effects on insulin functio n. The mechanism by which exercise improves insulin response may invol ve an alteration in Cr metabolism. To determine the effects of acute a nd chronic resistive exercise on urinary Cr losses, we measured the ef fects of acute resistive exercise and 16 wk of resistive exercise trai ning 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 w ith a Cr content of 30 +/- 4 mu g/d. Sixteen weeks of resistive exerci se training led to similar to 40% increases in upper and lower body st rength, increases in fat-free mass and decreases in the percentage of body fat. An enriched stable isotope of Cr, Cr-53, was employed to dif ferentiate the exogenously administered Cr from the ;native endogenous Cr. Both acute and chronic resistive exercise increased Cr-53 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.