Across the world of fitness, it is widely accepted that nutrition plays a key role in the success of any body transformation plan, whether it is to gain muscle or lose fat. Of particular interest is the post-workout period, often referred to as the "anabolic window" or the "window of opportunity."

Both supplement companies and scientific studies concentrate on the intake of nutrients after the completion of a workout. The actual dimensions of this window are under constant construction, with some arguing that immediate feeding is imperative, while others claim that waiting a certain amount of time is preferable.

With all this fuss about the post-workout period, though, it almost seems as if no other meal matters. This is an assumption that can have costly consequences. The body recovers and builds muscle around the clock, not just during an effervescent window of anabolism directly following a workout. In fact, several studies have suggested that pre-workout nutrition may even be more important than post.

In a study that featured a mix of healthy young men and women, researchers compared the effects of whey protein supplementation either immediately before exercise or after the workout. While one of the popular justifications for the importance of post-workout nutrition is the insulin spike that supposedly drives protein into muscle cells, the researchers found there was not a significant difference between insulin levels of the pre-workout group and the post-workout group (1).

But that wasn't the only myth of post-workout nutrition superiority busted in this study. The researchers also investigated the anabolic response in each of the groups. Contrary to what most might expect, the anabolic response to the whey protein ingestion did not differ significantly between the groups. Additionally, intra-cellular amino acid concentrations and amino acid uptake levels did not suggest an advantage to either of the ingestion periods (1).

In effect, the study suggests that in regard to pertinent factors, consuming protein during the "anabolic window" is not the be-all and end-all of workout nutrition. However, it should be noted that the study did not indicate that post-workout nutrition was not beneficial.

For many, eating post-workout provides a valuable source of calories to contribute to the surplus needed for muscle growth. Additionally, data from this study showed that amino acid delivery was higher compared to rest for in both pre- and post-workout groups (1), so it is unlikely that a post-workout feeding is going to do more harm than good.

SOURCES:

Tipton, Kevin D., et al. Stimulation of Net Muscle Protein Synthesis by Whey Protein Ingestion Before and After Exercise. American Journal of Physiology - Endocrinology and Metabolism, 2007; 292: 71-76