Share this article on:

Postexercise Whole-Body Protein Turnover Response to Three Levels of Protein Intake

GAINE, PATRICIA COURTNEY1; PIKOSKY, MATTHEW A.1; BOLSTER, DOUGLAS R.2; MARTIN, WILLIAM F.1; MARESH, CARL M.2; RODRIGUEZ, NANCY R.1

Medicine & Science in Sports & Exercise: March 2007 - Volume 39 - Issue 3 - p 480-486
doi: 10.1249/mss.0b013e31802d0be4
BASIC SCIENCES: Original Investigations

Purpose: This investigation examined the effect of variations in protein intake on whole-body protein turnover (WBPTO) after exercise in endurance-trained males.

Methods: Five male runners (21.3 ± 0.3 yr, 179 ± 2 cm, 70.6 ± 0.1 kg, 8.7 ± 0.4% body fat, 70.6 ± 0.1 V˙O2peak) participated in a randomized, crossover-design diet intervention, where they consumed either a low- (0.8 g·kg−1; LP), moderate- (1.8 g·kg−1; MP), or high-protein (3.6 g·kg−1; HP) diet for 4 wk. WBPTO (Ra, leucine rate of appearance; NOLD, nonoxidative leucine disposal; and Ox, leucine oxidation) were assessed after a 75-min run at 70% V˙O2peak after each diet-intervention period.

Results: Leucine Ra (indicator of protein breakdown) and leucine Ox were greater on the HP diet than on the LP diet (Ra, 123.4 ± 6.9 vs 97.9 ± 6.0 μmol·kg−1·h−1; Ox, 23.9 ± 0.5 vs 17.0 ± 0.8 μmol·kg−1·h−1, P < 0.05). No differences were noted in NOLD (an indicator of protein synthesis) across diets. Plasma branched chain amino acids (BCAA) at rest were greater for MP and HP than for LP, and nonessential amino acids (NEAA) were greater for LP than MP at rest and greater than MP and HP after exercise.

Conclusion: Findings from this study show that variations in protein intake can alter plasma amino acid levels and modulate rates of WBPTO after exercise. Additionally, a lower protein intake was associated with decreased rates of WBPTO after exercise.

1Departments of Nutritional Sciences and 2Kinesiology, University of Connecticut, Storrs, CT

Address for correspondence: Nancy R. Rodriguez, Ph.D., R.D., Department of Nutritional Sciences, U-4017, University of Connecticut, 3624 Horsebarn Hill Rd Ext, Storrs, CT 06269; E-mail: nancy.rodriguez@uconn.edu.

Submitted for publication January 2006.

Accepted for publication October 2006.

©2007The American College of Sports Medicine