The Anabolic Window: Facts & Myths

Is it really T-minus 30 minutes or all is lost?

For those in the pursuit of muscle gain, a quick flick through fitness magazines, or search through Google, and you will no doubt come across the ‘anabolic window’. 

The ‘anabolic window’ is a time period of great notoriety.

The Anabolic Window

Particularly amongst resistance training individuals, where the timing of protein pre and post-training is considered immediately necessary for super-compensated muscular repair and remodelling.

This is based upon a common held belief that you can only take advantage of this anabolic opportunity for a short period of time, with 30-60 minute timeframe typically suggested.

This often leads to confusion, and individuals doubting whether the efforts in their previous gym session disappear if they don’t throw down some post-training protein.

Should we really be that worried?

Nutrient timing is a strategy put forward to optimise performance or the adaptation response to training. 

This strategy has been of great interest when it comes to carbohydrate and performance and recovery, particularly within endurance and intermittent bout activities. 

Although the consumption of protein following resistance training is beneficial for growth and repair, is there such a narrow window in which to take advantage of the anabolic response?

Protein and resistance training

First, let us set the scene regarding training and muscle. 

When at rest in a fasted state the rate of muscle protein breakdown (MPB) is greater than muscle protein synthesis (MPS) resulting in a negative net protein balance. 

However, when protein is consumed there is a transient increase in MPS above rates of MPB, which brings about a positive net protein balance. 

Following resistance exercise, MPS rates are primed for an increased sensitivity to protein feeding. 

Following resistance training the elevated rates of muscle protein synthesis remain above resting levels for 48hrs within non-resistance trained individuals, whilst persisting for up to 24hrs in resistance trained individuals. 

It is the repeated accumulation of resistance training, protein feeding and periods of positive protein balance over time that leads to muscle hypertrophy (increase in muscle size). 

The increased sensitivity of MPS to protein feeding following resistance training highlights that protein feeding following resistance training is of importance to those with goals regarding increased muscle mass. 

However, such a narrow window of anabolic opportunity is not as narrow as a 30 to 60 minute window.

Protein timing

A meta-analysis conducted in 2013 was the first to specifically look at the effect of protein consumption timing upon muscle hypertrophy following a long-term resistance training programme. 

Upon reviewing the relevant research studies, consuming protein within 1 hour post-resistance training offered a small, but significant, advantage for increasing muscle mass gains in comparison  to delaying protein intake by at least 2 hours. 

A win for the 60 minute ‘anabolic window’? 

Well, not exactly.

Further analysis indicated that the small to moderate effect was found to occur due to a discrepancy in the matching of total protein intake between studies (1.7g per kg of body mass vs. 1.3g per kg of body mass). 

Such beneficial findings for protein timing were therefore due to greater total protein intake rather than the timing of protein consumption. 

For those engaging in regular resistance training, particularly those with muscle gain goals, research suggests an approximate daily protein intake of 1.6 to 2.2g per kg of body mass. 

This study was therefore a comparison of sufficient protein intake vs insufficient protein intake.

However, it is important to consider the limitations of the current body of literature regarding protein timing.

Especially where such equivocal findings have been found due to methodological design differences, with issues such as the use of a small sample sizes, non-matched protein or essential amino acid content and a variation in the age, gender and training status of participants. 

Protein: is more better?

A common misconception when it comes to protein timing is that more is better. 

Some people are of the belief that continually consuming protein will continually stimulate MPS and lead to continued muscle mass gains. 

However, the ‘muscle full effect’ suggests that in the face of continued protein feeding the muscle will eventually become refractory once maximally stimulated, with excess protein either oxidised for energy or utilised for other roles within the body.

Typically, following the consumption of a saturable dose of protein, a 30 minute lag follows before a large increase in MPS, which peaks at around 90 minutes before returning to baseline at roughly by 120mins, which highlights the transient nature of MPS.

As an analogy, let’s take a light bulb. 

Once the light bulb is turned on and reaches its maximal brightness, you cannot make it any brighter. 

The same can be said for MPS – once maximally stimulated you cannot enhance the response by continued protein feeding. This is where the basis for protein feeding every 3-4 hours has been suggested in order to maximally stimulate rates of MPS .

The anabolic window: fact or myth?

Interestingly, a recent study conducted amongst resistance trained individuals investigated muscle adaptations in response to an equal dose of protein (25g) consumed either immediately pre or post-resistance exercise, with total protein intake (1.8g/kg) controlled. 

The pre-training group didn’t consume protein until 3 hours after training, whereas the post-training group refrained from consuming protein for at least 3 hours before training. 

After the 10 week intervention, no significant effect on upon muscle thickness, body composition (fat mass or fat-free mass) or maximal strength was found. 

This therefore suggests that there is not a narrow anabolic window of opportunity to maximise muscle adaptation following resistance training.

However, it’s also important to acknowledge any potential limitations with this study, such as the small sample size, a free-living design (harder to control subjects), and the risk of underreporting of dietary intake due to self-reporting. 

Although not planned, subjects were found to be within an energy deficit during the intervention, although this could be due to underreporting of dietary consumption.

Protein timing

Based upon the above research it has been put forward that the timing and contents of the pre-workout meal dictate the timing needs of the next protein feeding due to the time course of digestion and absorption. 

The closer the meal is consumed to the training bout, the longer the time needed for post-training protein consumption due to the sustained delivery of amino acids. 

Based upon the above findings of muscle protein stimulation every 3-4 hours, and the typical resistance training bout of most individuals lasting 60 minutes, individuals wishing to optimise their muscle gain efforts may wish to consume protein 90 minutes pre-training, and ensure protein intake within 90 minutes following training. 

This can be adjusted based upon personal preference with regards to how close or far away you wish to consume a protein dose pre-training.

Individuals opting for a large mixed meal (containing both protein and carbohydrate) should be aware that this may be digested and absorbed over a longer period of time (roughly up to around 5-6 hours). 

This may further decrease the necessity for immediate post-training protein consumption if consuming a meal a couple of hours before training. 

For example, again based upon a 60 minute training session, if consuming a decent sized mixed meal 2 hours pre-training, one would look to consume protein within 2-3 hours following training. 

The wrap

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To your lean, healthy, optimised future,

Josh & the Optimised personal training team

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