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Defining the anabolic window of opportunity
Is protein intake immediately post resistance exercise critically important for muscle growth?

corresponding

OLIVER C. WITARD*, KEVIN D. TIPTON
*Corresponding author
Health and Exercise Science Research Group, School of Sport, University of Stirling, Stirling, FK9 4LA, Scotland

Abstract

The anabolic response of muscle to resistance exercise and protein feeding is influenced by multiple factors, including the timing of protein feeding. A common perception is that a 45-60 min post-exercise ‘anabolic window of opportunity’ time frame exists, within which dietary protein must be consumed to achieve muscle anabolism (and ultimately muscle growth). In this review, we argue the importance of feeding protein immediately following exercise is not as critical as has been espoused. Indeed, muscle remains responsive to protein ingestion for at least 24 h post-exercise. On the other hand, given that feeding protein immediately post-exercise is unlikely to impair the muscle anabolic response, and could improve it, from a practical standpoint, we recommend athletes and exercisers consume some protein, as a meal or supplement, in the immediate period following resistance exercise.


INTRODUCTION

Recent nutrition interest has focussed on nutrient timing for recovery from resistance-type exercise, in particular for maximising skeletal muscle hypertrophy. The focus of interest has been primarily on the timing of dietary protein intake. Seemingly, the most prevalent opinion is that a source of dietary protein should be consumed immediately, or as close as possible, post exercise (1-4). The belief is that the anabolic response of skeletal muscle will be impaired – or even alleviated - if a source of dietary protein is not ingested within as little as 45-60 min following resistance exercise (1-4). This time period has been coined the “anabolic window of opportunity” (1-4). In this review, we critically examine the importance of post-exercis