Post-exercise refuelling: all at once, or spread out?
We’ve all heard about the post-exercise “window” for refuelling to maximize recovery and adaption: you need to take in carbs and protein with 0.5-2 hours. But does the timing really matter for building muscle? A new study from Stuart Phillips’ group at McMaster University compared two tactics for post-workout protein intake. Once group took 25 grams of whey protein immediately after a set of leg-extension exercises; the other group received the same 25 grams of whey protein in 10 2.5-gram doses every 20 minutes for 200 minutes. They measured “muscle protein synthesis” — basically a very accurate way of assessing how well you’re stimulating muscle growth after a single bout rather than having to run the experiment for several months to actually see muscle growth — and found that it was much higher in the group that took their protein all at once. After six hours, protein synthesis was elevated by 193% in the single-shot group and just 121% in the prolonged group.
The question this study was seeking to answer actually relates to the difference between whey protein (which is absorbed quickly) and casein (which is absorbed more slowly: the 2.5 grams of whey every 20 minutes was chosen to mimic the absorption pattern of casein). The problem is that if you compare two different proteins in a study, then you’re changing a bunch of different factors at once — the absorption timing, but also factors like the amount of leucine, a branched-chain amino acid thought to be key for muscle growth. Since both groups received 25 grams of whey (and thus identical amounts of leucine), this shows that absorption rate is key.
Practical takeaway: this was a muscle protein synthesis study, not a training study, so you have take the results cautiously. But it does suggest that if you’re trying to build muscle, taking in a big dose (i.e. 25 grams) of protein as soon as possible is preferable to snacking over the course of a few hours. It also confirms previous findings suggesting that whey (found in dairy products) has some advantages over other protein sources.