The popular idea of an “anabolic window” — a crucial period of time before/after training during which protein must be ingested to maximize muscular adaptations — has been called into question. Indeed, the largest determinant of gains in muscle strength and hypertrophy seems to be total protein intake throughout the day (and a well-structured resistance training program), rather than nutrient timing per se.[1]
But protein timing may not be inconsequential; exercise does have a “sensitizing” effect on muscles, and consuming protein in close proximity to a workout can ensure that one maximizes this anabolic sensitivity. Furthermore, exercising on an empty stomach can put the body into a negative protein balance; reupping on protein afterward helps maintain a positive protein balance to promote muscle protein synthesis instead of breakdown, and seems to be better than eating a protein-containing meal before or a few hours after working out.[2]