Protein turnover and physical fitness in man

The whole-body flux and protein-synthesis rates were determined in two groups of adult males aged 20-30 years who were matched for height and weight. [¹⁵N]Glycine was used as a tracer. Flux and synthesis rates were calculated from the urinary ammonia ¹⁵N excretion enrichment. Group I consisted of international competition level oarsmen, while Group II engaged in no exercise program. Measurement of the urinary nitrogen excretion rate showed that the oarsmen excreted more than twice as much nitrogen as the control group (P < 0.05). Results: flux and synthesis were 21.3 ± 3.2 gN 9 hr and 188.7 ± 59.9 g protein/day for the oarsmen and 16.4 ± 2.1 g N 9 hr and 201.7 ± 33.0 g protein/day for the controls. Data are ± 1 SD for the eight oarsmen and eight controls. The flux values were different at the P < 0.05 level. We concluded that (i) an exercise program does not lead to an increase in the basal protein turnover rate in adequately nourished individuals.