You've seen the person who leaves their last set and goes straight to the locker for a shaker bottle, like something will go wrong if they don't drink it in the next few minutes. Maybe you've been that person. The idea behind it is simple. Training opens a short "anabolic window," the story goes, and protein eaten inside it builds muscle while protein eaten after it is partly wasted. Usually the window is said to be thirty minutes, sometimes an hour.
It's a good story. The problem is that people tested it.
What the studies found
The big review found a timing effect, and then found it was something else. In 2013, Schoenfeld, Aragon and Krieger pooled the protein-timing studies they could find. At first glance, protein close to training looked slightly better for muscle growth. But in most of those studies, the "timed" group was simply eating more protein in total than the comparison group, because the timed shake was added on top of their normal diet. Once the analysis accounted for total protein, the timing effect basically disappeared. What looked like a window was really a bigger daily total.
Then the same researchers tested the window head-on. In a 2017 study, 21 trained lifters took the same 25-gram protein dose either right before training or right after it. If the post-workout window mattered, the "after" group should have pulled ahead. Over ten weeks, the two groups gained muscle and strength about the same.
None of this means timing is irrelevant. The window exists. It's just measured in hours, not minutes, and how wide it is depends on when you last ate. A meal two or three hours before training is still being digested while you lift, so you're already covered. A review by two of the same researchers suggested the window after training may be as wide as five or six hours, depending on when you ate beforehand.
The number that matters more
If timing is a small effect, the big one is the daily total. A 2018 meta-analysis by Morton and colleagues pooled 49 trials and found that extra protein helped muscle growth up to about 1.6 grams per kilogram of body weight per day, and then the benefit flattened out. The authors note that some people may do better closer to 2.2, so 1.6 is a reasonable target, not a hard ceiling.
For an 80 kg lifter, that's around 130 grams a day. And here's the part the shaker-bottle ritual hides: most people who stress about the thirty minutes after training aren't anywhere near their daily total. A shake at the perfect moment on a 70-gram day is a precise answer to the wrong question.
Spreading it out helps a little. There's decent evidence that splitting protein across three or four meals of roughly 20 to 40 grams works better than one huge serving. That's the real, modest version of timing. It's about the whole day, not a countdown after your last set.
What to actually do
Hit the daily number first. Work out roughly what 1.6 g/kg is for you and check whether you get there on a normal day. Most people find this is where the real gap is.
Split it across your meals. Three or four servings with a decent amount of protein in each. Breakfast is the usual weak spot.
Eat something within a few hours either side of training. If you had a proper meal beforehand, you don't need to hurry afterward. If you train first thing in the morning on an empty stomach, that's the one case where eating soon after is worth doing, because your last meal was the night before.
Judge it over weeks, not by the hour. Protein shows up in your results slowly, as the weight on your lifts creeps up session after session. It doesn't show up in the mirror the next morning, and the swelling you see in the first few weeks isn't muscle anyway.
Where we come in
We build Flexion. It isn't a calorie counter, and it isn't trying to replace the food app you already use. It reads the log you already keep through Apple Health, and the coach compares your day's protein against a target that's set differently for training days and rest days. So the question it can answer is the one that matters here: not "did you drink the shake in time?" but "did you eat enough today, on the day you trained?"
A food app and a bit of arithmetic will tell you the same thing. Whichever you use, watch the daily total. The shake can wait.
