What is the Anabolic Window?

You've probably noticed more than one person concerned about taking protein right after their workout. Chances are, they do this because they've heard that taking protein immediately post-workout is essential for muscle recovery and to enhance muscle mass gain.

Some even believe that skipping this step renders their workout ineffective, having missed out on the so-called "anabolic window."

So, what exactly is this anabolic window? Should we actually be concerned about it? Keep reading to find out.

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Key Points

Strength training promotes an anabolic state in the body, as it increases muscle protein synthesis. However, it also increases muscle protein breakdown (the opposite process).

Making muscle protein synthesis greater than degradation is crucial for building muscle mass. This requires a sufficient availability of amino acids, which is achieved through optimal protein consumption in your diet.

However, protein intake is not only important in the immediate minutes post-workout but throughout the entire day, as the increase in muscle protein synthesis remains elevated for 24-48 hours after a workout session.

Evidence indicates that consuming protein immediately post-workout does not provide additional benefits for muscle mass increase compared to simply meeting daily protein requirements in 4-5 meals a day (every 4-6 hours).

Consuming protein shortly after a workout may be beneficial in certain scenarios. For example, when training is done on an empty stomach or after not eating for many hours, or for advanced athletes.

What is the anabolic window?

Some studies have referred to the "anabolic window" as the brief period after a strength training sessiong when muscle mass gain can be maximized through nutrition (1).

 However, the exact duration of this period has not been clearly defined.

Typically, it's mentioned as being 1 hour post-workout or less (1,2). Furthermore, proteins are the nutrients that seem to be most critical during this period (1,2,3).

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How does the anabolic window work?

To understand it,  it's essential to grasp a few preliminary concepts:

1. Strength training induces numerous physiological changes. One of the most important for muscle mass creation is the increase in muscle protein turnover (4,5,6). Protein turnover is the cyclic process of protein degradation (destruction) and synthesis (creation) that occurs naturally and constantly in all our cells. During this process, existing proteins are broken down into amino acids and then new proteins are created (as needed) using these amino acids and those obtained from the diet. Thus, strength training increases both the synthesis and degradation of proteins in the muscles.
2. To build muscle mass, the rate of muscle protein synthesis needs to be greater than the rate of protein degradation (4). You need to create more than you break down.
3. This can only be achieved with an adequate availability of amino acids. Without sufficient materials, you couldn't produce more product. How do you ensure you have enough amino acids? By consuming enough protein in your diet.

Once we establish this as our baseline, we can understand the logic of the anabolic window:

After strength training, the potential to build muscle mass is higer (since muscle protein synthesis increases), but this potential can only be harnessed if enough protein is consumed (as enough amino acids are needed to exceed muscle protein degradation). Therefore, it's logical to think that we need to consume protein right after training to achieve a positive balance between synthesis and degradation of proteins in the muscles, thereby gaining more muscle mass.

Up to a certain point, this seems to make a lot of sense, as it aligns with what we've previously explained. However, there's an element that still seems to lack an explanation: timing.

Why is it necessary to consume protein right after finishing a workout? If I don't consume them within this first hour post-workout, will they no longer be effective? This is where the concept of the anabolic window begins to falter.

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What does science say about the anabolic window?

Various studies have attempted to pinpoint the optimal time around a workout to consume protein to boost protein synthesis.

However, the findings don't seem to provide a conclusive answer. For example:

One study compared the effect on muscle mass, strength and power in 33 experienced men when they consumed protein supplements (2 shakes of 42 g protein each) at different times. One group consumed the proteins immediately before and after training, while another group consumed the proteins early in the morning and at night. The results found no significant differences in the amount of muscle mass gained between the different supplementation schedules (7).

Another study compared the effect of consuming a solution of amino acids and carbohydrates immediately before or immediately after a training session. The results showed that protein synthesis post-exercise was higher when the solution was consumed before training (8).

In a very similar study, 21 individuals were subjected to the same training and nutritional plan for 10 weeks. These subjects were divided into 2 groups, with the only difference being that one consumed a shake with 25 grams of whey protein before training and the other afterwards. After the 10 weeks, changes in muscle mass, fat, and strength were equivalent in both groups (9)

Therefore, to date, there is no solid evidence to show that consuming proteins immediately after the training session is superior to consuming them 2 or 3 hours later, or even before (1,7,8,9,10).

In fact, a meta-analysis on the topic examined whether consuming proteins within a 2-hour window before or after training had a beneficial effect on muscle hypertrophy compared to not consuming anything during that same period. The analysis found a small to moderate effect on muscle mass gain.

However, when a sub-analysis was conducted, it was shown that the total amount of protein consumed throughout the day was responsible for the effect, not the timing of its consumption (13).

The explanation probably lies in two very important factors:

After strength training, the increase in protein synthesis is not only elevated for 1 hour, but can remain elevated for up to 48 hours after a training session (1,6).

The anabolic potential (the ability to increase protein synthesis) of a protein-rich meal can extend up to 4-6 hours after consumption (11,12).

This means that:

It would be more important to consume protein consistently throughout the entire day and every day, to maintain amino acid availability during the entire period that protein synthesis is increased.

The true duration of the "anabolic window" would be considerably longer than just 1 hour and could last between 4-5 hours depending on when you ate before training.

Even the pre-workout meal can continue to provide sufficient amino acids to increase protein synthesis.

So, do you have to rush to get protein? The answer is: not necessarily. If you meet your requirement throughout the day and consume a post-workout meaal within the first 5 hours after training (depending on when your last meal was), you will be meeting the proper conditions for muscle gain. 

However, there are no adverse effect from doing so, and there may be some circumstances where it is convenient. For example, if you have trained on an empty stomach, your amino acid availability will be low, as your last meal would have been many hours ago. In this case, it would be wise to consume a good amount of protein as soon as possible to replenish that availability.

On the other hand, if you are highly experienced in strength training (like a bodybuilder), you might need to pay more attention to details such as the timing of your protein consumption.

Practical Recommendations to Enhance Muscle Mass Gain

First and foremost, make sure to meet your daily protein requirement. It won't be very beneficial to have a protein-rich meal right after training if you don't meet your total daily requirement. Remember, protein synthesis is not limited to just 1 hour. Aim to consume between 0.7 - 1.0 g/lb (1.6 - 2.2 g/kg) of body weight if you're engaged in strength training.

Distribute your meals in ranges of up to 6 hours to ensure a sustained protein intake throughout the day. For example, if you consumed your pre-workout meal 1 hour before training and then trained for another hour, you would have up to 3-4 hours to have your next meal. On the other hand, if you ate 4 hours before training and trained for 1 hour, then you should eat during the first hour post-workout.
Distribute your total protein requirement as evenly as possible so that most of your meals contribute to this nutrient intake. That is, if you need 120 grams of protein per day, try to ensure that each meal provides you with approximately 20-40 grams of protein.

Create a pre-workout and post-workout plan including nutrients that fit your current needs.

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