Urinary nitrogen excretion as influenced by muscle-building exercise program and protein intake variation

Abstract

Four groups of college men consumed two levels of protein (approximately .8g or 2.4g/kg body weight) for 28 days as controls or subjects engaged in a progressive resistance exercise program. Average caloric intakes were 50 and 68 at .8g/kg for controls and 52 and 62 at 2.4g/kg for exercise groups. Average total weight gain for exercising subjects was 3.2kg. Mean urinary nitrogen values (U-N) expressed as percentages of intake (I-N) were significantly different for controls and exercising subjects. Decreased urinary nitrogen for exercising subjects may be a result of higher caloric intake, higher weight gain, or increased sweat losses. Exercise is usually reported to increase urinary nitrogen. The study showed that during muscle building exercise associated with modest, deliberate weight gain, U-N is significantly decreased