Metabolic Window – Myth or Reality?

Metabolic Window – Myth or Reality? Does it really exist? Is it useful for us to use this time period? When Does it start and end? In this post I’m going to show you what is the metabolic window and whether we can really use it and get a real benefit from it.

What is the Metabolic Window?

The metabolic window is a term used in strength training to describe the period after exercise during which nutrition can shift the body from a catabolic state to an anabolic one. Specifically, it is during this period that the intake of protein and carbohydrates can aid in the increase of muscle mass.

Commonly, it was believed that the 30 mins period after the training session were very important in order to maintain an anabolic body environment. It can’t be further from the truth though. Researches show that this timing after working out could be between 2 and 6 hours (1), which is also far from definitive. Let’s see why.

Let’s talk in terms of macronutrients:

Protein synthesis

It’s been known that, after a workout, the muscular protein synthesis increases due to the damage induced to the muscle for a period of 36h (5). It’s true than athletes protein requirement are higher that those for normal population (I already talked about that in this post) So, we might think that a post workout meal could be needed if we want to avoid this catabolism induced in the training session. I have to disagree…

One study (4) shows how a pre-workout meal has the same effect than a post-workout one in terms of body composition, maximal strength and muscle thickness.

Another study (6) also compares the ingestion of amino acids versus whole proteins and shows non significant different between the 2 groups. However, when we talk about a fasting training session, there seems to be some differences and in this case, the post workout metabolic window seems to have some effects (6). But in my opinion, it would be due to the lack of amino acids resulting after the fasting period.

It leads to think that what really matter is the total daily protein intake (2).

Glycogen synthesis

The common belief is that our glycogen stores get depleted after a training session and we must immediately refill them. It is due to the main source of ATP production comes from the glycolysis. Thinking on this way, it’s normal to believe that we must eat right after our workout. Well, it is partially true and will depend on our goals.

First, let’s talk about how “depleted” we are after a training routine. A few studies (7, 8) demonstrate that high volume training with multiples exercises would deplete almost all the local glycogen stores. But, do we need to refill them immediately after the training session? It will depend on the frequency of our training. If you train more than once per day, then you will need to refill them immediately after the session. If we use to train once per day, having a healthy diet will refill these stores (9, 10). But even if you train more than once per day, a couple of studies (9, 10) show that there is no difference in our glycogen stores after a 24h period.

Conclusion

Due to the lack of evidence, we don’t really know whether the most important one is the pre or post workout meal. But all lead me to think that the metabolic window is not important. What’s really matter is to have a good diet that adapts to our necessities and help us to achieve our goals.

Total intake is the real important matter, not the timing!

I hope you have enjoyed it and don’t forget to leave your comment! See you in the next one!

Sources

  1. Nutrient timing revisited: is there a post-exercise anabolic window?
    Alan Albert Aragon and Brad Jon Schoenfeld
  2. The effect of protein timing on muscle strength and hypertrophy: a meta-analysis
    Brad Jon Schoenfeld, Alan Albert Aragon and James W Krieger
  3. Glycogen resynthesis after exercise: effect of carbohydrate intake.
    Ivy JL
  4. Pre- versus post-exercise protein intake has similar effects on muscular adaptations.Schoenfeld BJ, Aragon A, Wilborn C, Urbina SL, Hayward SE, Krieger J.
  5. The time course for elevated muscle protein synthesis following heavy resistance exercise.MacDougall JD, Gibala MJ, Tarnopolsky MA, MacDonald JR, Interisano SA, Yarasheski K
  6. The role of protein and amino acid supplements in the athlete’s diet: does type or timing of ingestion matter?Lemon PW, Berardi JM, Noreen EE
  7. Muscle substrate utilization and lactate production.MacDougall JD, Ray S, Sale DG, McCartney N, Lee P, Garner S
  8. Muscle glycogenolysis during differing intensities of weight-resistance exercise.Robergs RA, Pearson DR, Costill DL, Fink WJ, Pascoe DD, Benedict MA, Lambert CP, Zachweija JJ
  9. Muscle glycogen storage following prolonged exercise: effect of timing of ingestion of high glycemic index food.Parkin JA, Carey MF, Martin IK, Stojanovska L, Febbraio MA
  10. Adding fat calories to meals after exercise does not alter glucose tolerance.Fox AK, Kaufman AE, Horowitz JF

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