This is just for lifting (I have no idea about for endurance athletes). It's pretty common practice for lifters to time protein intake around workouts (the so-called anabolic window around workouts). mainly leads to pre and post workout protein intake. Unfortunately, it doesn't look the empirical evidence supports the practice. There a could be a benefit, but it's small. Here is a reasonable meta-study (of like 15 protein timing experiments):
The effect of protein timing on muscle strength and hypertrophy: a meta-analysis.
http://www.ncbi.nlm.nih.gov/pubmed/24299050
First, no evidence that it increases strength (notice how the overall is insignificant):
Second, these experiments did show an increase in muscle size (hypertrophy):
However, there is a problem. Many of the experiment didn't control for the fact that treatment group (doin protein timing) also increased overall protein intake. If you control for overall protein intake the effect is no longer significant:
High protein intake helps with muscle hypertrophy for lifters (we know this from other studies), but the timing of the protein around workouts doesn't appear to be very important.
The effect of protein timing on muscle strength and hypertrophy: a meta-analysis.
http://www.ncbi.nlm.nih.gov/pubmed/24299050
First, no evidence that it increases strength (notice how the overall is insignificant):
Second, these experiments did show an increase in muscle size (hypertrophy):
However, there is a problem. Many of the experiment didn't control for the fact that treatment group (doin protein timing) also increased overall protein intake. If you control for overall protein intake the effect is no longer significant:
High protein intake helps with muscle hypertrophy for lifters (we know this from other studies), but the timing of the protein around workouts doesn't appear to be very important.
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