15-30% Increase in Protein Synthesis if Protein is Ingested After Exercise

What common sense already told us has now been proven again in a scientific study published by the American Society for Nutrition (Pennings. 2010). Protein synthesis is greater if protein is consumed after exercise. And these results hold true for both, young and old.

As a marker of protein synthethis, the scientists investigated the response of exogenous phenylalanine on a 20-g bolus of intrinsically l-[1-¹³C]phenylalanine-labeled protein which was administered either at rest or after exercise:

[...] Muscle protein synthesis rates calculated from the oral tracer were 0.0620 ± 0.0065%/h and 0.0560 ± 0.0039%/h for the rest condition and 0.0719 ± 0.0057%/h and 0.0727 ± 0.0040%/h for the exercise condition in young and elderly men, respectively (age effect: P = 0.62; exercise effect: P < 0.05; interaction of age and exercise: P = 0.52).

So overall, this is a non-negligible increase in the calculated protein synthesis rate by 15% and 28% in the young and old subjects, respectively. It does however not answer the question, whether administration of the same 20g of marked protein right before exercise would not have increased protein synthesis to an even greater extent. Personally, I feel that for people on an everyday exercise regimen keeping protein intake high 24/7 will certainly be the best solution, even if it is just via an occasional protein shake at work (and thus probably "before workout).