Publication Date

Spring 1984

Degree Type


Degree Name

Master of Arts (MA)


Human Performance


Carol Christensen

Subject Areas

Kinesiology; Human Performance


Initial muscle glycogen stores were altered to determine if subjects who exercised in a carbohydrate depleted state would use protein as an energy source. Six female subjects (23-30 yr) ran on a treadmill for 1 hr at 60% VO2 max after carbohydrate loading (CHOL) and carbohydrate depletion (CHOD). Serum urea nitrogen (N) and glucose were measured before exercise (ex), at 15 min ex, 60 min ex, 15 min recovery, and at 60 min recovery. Prior to the test period, each subject ran at 70-75% VO2 max for 1 hour and then maintained a CHOL or CHOD diet for 3 days or 1 day, respectively to insure appropriate initial muscle glycogen levels. Subjects then switched diets and repeated exercise periods. t-tests indicated there were no significant differences between oreexercise and exercise serum urea N. An increaae in serum urea N appeared at 15 min of recovery following CHOD (p < .01). At 15 min of ex there was an increase in glucose following CHOL. An increase in glucose occured at 60 min of recovery following CHOD. Significant differences were found between the serum urea N following the CHOL and CHOD diets at all sampling times. A Pearson Product Moment correlation coefficient showed weak to moderate relationships between glucose and serum urea N. It was concluded that serum urea N levels can be altered by diet, and that under certain conditions, such as low muscle glycogen, there appears to be an increase in the contribution of protein as an energy source. Also in addition to their role as fuel, amino acids may be involved in maintaining blood glucose levels during long-term exercise.