The Anabolic Window – that special place where all your gains come true.
The anabolic window describes the supposed 30-minute window that opens up immediately after the completion of a workout.
During this time the body is said to be in an optimal state to accept essential nutrients and shuttle them into the muscle tissue, enhancing recovery, improving our capacity to build muscle, and ultimately bringing with it all sorts of gains.
As a result, it has been thought to be absolutely imperative for the advanced and beginner lifter alike to smash a protein shake immediately after their session (unless they want that entire session wasted, of course…).
But is there actually any truth behind the anabolic window?
The Anabolic Window
The anabolic window has been long supported by the suggestion that after an intense weight training session, muscle fibers are damaged and the glycogen stores within those muscle tissues are depleted (all of which holds some truth).
It was then thought that by consuming some quick release protein (eg. Whey protein powder) and a high GI carbohydrate (eg. Dextrose) immediately after a workout, you could take advantage of the body's energy depleted state, and rapidly provide the muscle tissue with much needed nutrients (AKA protein and glucose).
This was said to improve the rate at which muscle tissue recovers, increasing muscle protein synthesis, refilling muscle glycogen stores, and maximizing muscle hypertrophy and strength gains.
And in all honesty, on face validity, this sounds like a solid suggestion (which likely explains why it was so easily accepted within the health and fitness industry).
Unfortunately, the human body does not work on face validity.
The two key benefits suggested to come from consuming carbs and protein post workout (and as such taking advantage of the anabolic window) are to prevent the breakdown of muscle tissue and increase muscle protein synthesis.
The ingestion of carbohydrates is said to create a large insulin response, which in turn was suggested to prevent the breakdown of muscle tissue, while the ingestion of protein was said to increase the synthesis of new muscle tissue.
Now while there is no question that to build muscle tissue, muscle protein synthesis needs to be higher than the rate at which muscle protein breakdown occurs. Post workout nutrition will not contribute to this.
Firstly, the breakdown of muscle tissue is only slightly elevated after an intense weight training workout – unless you are training fasted, in which case it is further elevated slightly1.
This suggests that there is no reason to fear muscle breakdown after a workout, unless you are training in a fasted state (which I believe anyone with half a brain would avoid if possible – we need energy to fuel a workout)
Secondly, the immediate consumption of proteins and carbohydrates after a workout has not shown to influence the rate at which muscle tissue recovers, or the rate of muscle protein synthesis at all2.
In fact, it has been shown that consuming a mix of protein and carbohydrates at either 1 hour or 3 hours post exercise elicits the same response in regards to muscle protein synthesis3, completely dispelling the suggestion that there is an anabolic window lasting only 30 minutes.
And while there may be some merit in consuming carbohydrates post workout as a means to refill muscle glycogen stores, it is important to note that weight training does not actually deplete energy stores all that significantly2.
This suggestion holds merit after extremely long duration aerobic exercise (AKA 6 hours and above), as that would provide enough glycogen depletion to warrant an immediate need to refuel, but does not when discussing a 90 minute weight training session.
So what is important?
So if consuming protein and carbohydrates immediately after a workout is not important, what is?
The first thing (and hands down the most important) is to hit your individual, daily macronutrient requirements.
This obviously means eating enough carbohydrates to fuel your workouts, and eating enough protein to keep your rate of muscle protein synthesis high, providing enough nutrients to build and repair muscle tissue.
Your macronutrients should be spread evenly throughout the day, preferably around your workouts to a certain degree – consuming a meal that has a good mix of both protein and carbohydrates 2-3 hours before your workout will provide more than enough energy to allow you to complete your workout at a high intensity.
And considering the slow rate at which protein is digested, doing so will provide a sustained release of amino acids into the bloodstream throughout the duration of your workout2.
Post workout nutrition still holds some importance, but is certainly not required immediately as once suggested.
Similar to our pre workout meal, a meal containing a good mix of protein, carbohydrates, and fats should be consumed 2-4 hours after the completion of a workout as means to provide continued release of amino acids into the blood, while also providing the body with other essential nutrients to aid in recovery3.
By meeting these requirements your body will ultimately receive the nutritional content required to both provide energy for high intensity exercise, then refill the stores of energy lost during that exercise (no matter how minimal), AND recover and build new muscle tissue.
Now, there are a couple of necessary factors to point out.
Obviously, if you are trying to build muscle mass, you need to be eating in a calorie surplus. If you are in an energy deficit, your ability to recover and build new muscle tissue will be limited – even if you hit those two key meals above.
If you are trying to lose fat and maintain muscle mass, meeting the pre and post workout criteria outlined above should be enough to allow you to maintain muscle mass and keep your workout intensity high (despite being in an calorie deficit) – although it will limit your ability to build any new muscle tissue and recovery may be slowed slightly (due to the energy deficit).
Should we keep drinking our post workout shakes?
Look, although the anabolic window has been proven false, it does not mean that you should discard your post workout shake. They still have some merit.
Firstly, it is not always easy to hit our macronutrient requirements through food alone, and protein requirements are arguably the most difficult to achieve. A protein shake provides a simple and easy (and often tasty) way to bump up our daily protein intake without causing a large increase in our daily energy intake.
Secondly, for those of us who supplement with creatine monohydrate, protein shakes can provide an easy way to mask its flavor either pre or post workout without consuming something that has a high sugar content such as fruit juice (which is often recommended).
Finally, if you are someone who does happen to train fasted (for whatever reason), or is unable to get in a decent meal within 4 hours post workout (you may train on your lunch break etc.) then a post workout shake may be a beneficial way to guarantee your body has the nutrients required to recover effectively after a solid training session.
The research suggests that the anabolic window does not really exist, and by eating well balanced meals throughout the day, we can provide our body with enough nutrients required to both perform at our best and recover effectively.
Ideally consuming a well balanced meal containing both protein and carbohydrates 2-3 hours before a workout, and a meal containing protein, carbohydrates and fats 2-4 hours after a workout, we can guarantee our body has nutrients to fuel a solid training session and recover adequately, allowing us to repair and build muscle tissue.
Despite the anabolic window being a proven myth, a post workout shake may still have merit as an easy way to reach our daily protein requirements, provide a good way to supplement with creatine, and provide post workout nutrition to those who are unable to eat after a workout, or train in a fasted state.
- Pitkanen, H. T., et al. "Free amino acid pool and muscle protein balance after resistance exercise." Medicine and science in sports and exercise 35.5 (2003): 784-792.
- Aragon, Alan Albert, and Brad Jon Schoenfeld. "Nutrient timing revisited: is there a post-exercise anabolic window?." Journal of the international society of sports nutrition 10.1 (2013): 1.
- Levenhagen, Deanna K., et al. "Postexercise nutrient intake timing in humans is critical to recovery of leg glucose and protein homeostasis." American Journal of Physiology-Endocrinology And Metabolism 280.6 (2001): E982-E993.