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Impact of Caffeine and Protein on Postexercise Muscle Glycogen Synthesis


Medicine & Science in Sports & Exercise: April 2012 - Volume 44 - Issue 4 - p 692–700
doi: 10.1249/MSS.0b013e31823a40ef
Applied Sciences

Background: Both protein and caffeine coingestion with CHO have been suggested to represent effective dietary strategies to further accelerate postexercise muscle glycogen synthesis in athletes.

Purpose: This study aimed to assess the effect of protein or caffeine coingestion on postexercise muscle glycogen synthesis rates when optimal amounts of CHO are ingested.

Methods: Fourteen male cyclists were studied on three different test days. Each test day started with a glycogen-depleting exercise session. This was followed by a 6-h recovery period, during which subjects received 1.2 g·kg−1·h−1 CHO, the same amount of CHO with 0.3 g·kg−1·h−1 of a protein plus leucine mixture (CHO + PRO), or 1.7 mg·kg−1·h−1 caffeine (CHO + CAF). All drinks were enriched with [U-13C6]-labeled glucose to assess potential differences in the appearance rate of ingested glucose from the gut. Muscle biopsies were collected immediately after cessation of exercise and after 6 h of postexercise recovery.

Results: The plasma insulin response was higher in CHO + PRO compared with CHO and CHO + CAF (P < 0.01). Plasma glucose responses and glucose appearance rates did not differ between experiments. Muscle glycogen synthesis rates averaged 31 ± 4, 34 ± 4, and 31 ± 4 mmol·kg−1 dry weight·h−1 in CHO, CHO + PRO, and CHO + CAF, respectively (P = NS). In accordance, histochemical analyses did not show any differences between net changes in Type I and Type II muscle fiber glycogen content between experiments.

Conclusions: Coingestion of protein or caffeine does not further accelerate postexercise muscle glycogen synthesis when ample amounts of CHO (1.2 g·kg−1·h−1) are ingested.

Department of Human Movement Sciences, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, Maastricht, THE NETHERLANDS

Address for correspondence: Luc J. C. van Loon, Ph.D., Department of Human Movement Sciences, Maastricht University Medical Centre, P.O. Box 616, 6200 MD Maastricht, The Netherlands; E-mail:

Submitted for publication January 2011.

Accepted for publication September 2011.

©2012The American College of Sports Medicine