The anabolic window: does it exist?

The anabolic window (also known as the metabolic window or protein window) supposedly lasts for 30 minutes after a workout. It's touted as the most helpful time post-workout to consume protein and carbs to build muscle.

A 30-minute golden period where your body is primed to convert your workout into gains. So, smash that protein shake straight away. Right? Well, perhaps not. Yes, the window exists, to some extent, but instead of a fleeting golden period it more likely spans the entire day. Let’s break down the science. 

How the body builds muscle

To build muscle, your body must be in an anabolic state. The anabolic state is one where the body builds and repairs muscle (as opposed to the catabolic state where muscle is broken down).

Your body builds muscle by first damaging the muscle fibres. You do this through exercise. The heavier the weight, the more you’re likely to cause tiny tears. The muscle fibres repair themselves but because your body now realises it needs to lift heavier things, it tries to rebuild the fibres stronger than before. This means more fibres and hence your muscles grow. 

For this to happen, you need the building blocks of muscle: protein and carbohydrates. 

Here’s the theory:

Strength training ➔ muscle damage ➔ increased muscle production ➔ nutrition required for muscle repair and growth ➔ ideally taken within 30 minutes. 

But this theory is somewhat flawed. We can debunk this. 

Muscle remodelling

Muscle remodelling is an incredibly complex process and reducing it to such a simplistic narrative is a disservice to the amazing wonder that is your body. For example, does resistance training break down muscle? Undoubtedly. But, to a greater extent, resistance training increases muscle synthesis independent of muscle breakdown. 

When it comes to muscle remodelling, we know that age is a factor. Older people need more nutrition for the same effect as younger people. Training matters too. Most of the research has been carried out on non-athletes who often show rapid, marked changes in muscle mass. However, many people — including some of you reading this article — will be regular strength trainers in whom body adaptations result in slightly different muscle modelling outcomes and more of a plateau effect. 

The fact of the matter is that muscle metabolism is so complex that we still don’t fully understand it. And as for the window being thirty minutes, no one knows where that came from! 

So, let’s strain out the scientific fact from the myth. What do we know that’s useful? 

Four top tips for muscle repair and growth

There are ways you can push your body into the anabolic state. It primarily comes down to progressive overload, sufficient and balanced nutrition, and plenty of rest.

Here are our four top tips for muscle repair and growth: 

1. Do three to six days of resistance training

You want to be doing three to six days per week, having at least one full rest day and avoiding working out the same muscle groups two days in a row.

2. Eat your carbs and protein 

You must have proteins and carbs to build muscle. But you probably don’t need it within thirty minutes of finishing your workout. The research varies but having a meal containing both proteins and a small amount of good-quality carbs two to six hours before or after exercise seems sufficient to do the trick. 

How much food? Well, here’s another myth to bust. Your body can only really absorb so much protein — the body excretes the rest. Lots of people who frequently have protein shakes sometimes complain of an odd smell in the urine. That’s the area from all the protein being excreted that you don’t use.

If you want to build muscle, you probably need no more than roughly double the recommended daily intake for the average person. That’s 1.2-1.7 grams per kilogram. Having more than that won’t add much (apart from extra trips to the toilet). For a muscly 90kg person, that would be equivalent to: 

• 1 chicken breast 
• 2 salmon fillets
• 1.5 tins of kidney beans

Probably less than you may have thought, right?  

3. Try eating before exercising 

If you’re eating well, you should be able to build muscle. It seems the exception is if you’ve fasted before exercise (12-24 hours). In this case, your body will have gone into a fasting state and won’t be inclined to build muscle. So, if you fast, it’s probably a good idea to have something before or immediately after exercising.  

4. Optimise your recovery

Optimisation for strength training is so much more than just adequate nutrition. The same concepts apply to any other athlete:

• Make sure your nutrition is well-balanced and adequate. Not just protein, you need the right amounts of carbs and fats as well. High-quality whole foods are best. Our Ultimate Performance Blood Test gives an indication of your nutrition including important vitamins, minerals, and proteins. 
• Make sure you get sufficient periods of rest to avoid overtraining.
• Sleep well to encourage muscle healing and growth. Find out how sleep affects your overall health. 
• Cut down on alcohol and stop smoking.
• Keep stress levels low — the stress hormone cortisol can have negative effects on muscle growth. Keep an eye on your cortisol levels and inflammatory markers with our Ultimate Performance Blood Test, specifically designed for athletes. 

Does the anabolic window exist?

The anabolic window doesn’t exist in the way you may have heard about it.

Provided you have a nutritious meal a few hours before your workout and you’re meeting your overall nutritional requirements throughout the day, the need to have a protein-rich meal immediately after a workout becomes much less important. The exception to this is people who do fasted workouts, for example, in the morning. So, if this is you, you may want to consider eating after exercise. 

The key is balanced nutrition, appropriate recovery time, and listening to your body.

References

1. 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 vol. 10,1 5. 29 Jan. 2013
2. Tipton, Kevin D et al. “Assessing the Role of Muscle Protein Breakdown in Response to Nutrition and Exercise in Humans.” Sports medicine (Auckland, N.Z.) vol. 48,Suppl 1 (2018): 53-64. 
3. 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. Vol 292, no.1 (2007)
4. Schoenfeld, Brad Jon et al. “The effect of protein timing on muscle strength and hypertrophy: a meta-analysis.” Journal of the International Society of Sports Nutrition vol. 10,1 53. 3 Dec. 2013
5. Kumar, V et al. “Human muscle protein synthesis and breakdown during and after exercise” Journal of Applied Physiology. Vo1 106, no.6 (2009)
6. Glynn, E et al. “Muscle protein breakdown has a minor role in the protein anabolic response to essential amino acid and carbohydrate intake following resistance exercise” American Journal of Physiology-Regulatory, Integrative and Comparative PhysiologyVol. 299, No. 2 (2010)
7. Arent, Shawn M et al. “Nutrient Timing: A Garage Door of Opportunity?.” Nutrients vol. 12,7 1948. 30 Jun. 2020
8. Cintineo, Harry P et al. “Effects of Protein Supplementation on Performance and Recovery in Resistance and Endurance Training.” Frontiers in nutrition vol. 5 83. 11 Sep. 2018
9. Fabre, Marina et al. “Effects of Postexercise Protein Intake on Muscle Mass and Strength During Resistance Training: Is There an Optimal Ratio Between Fast and Slow Proteins?.” International journal of sport nutrition and exercise metabolism vol. 27,5 (2017): 448-457
10. Kerksick, Chad M et al. “International society of sports nutrition position stand: nutrient timing.” Journal of the International Society of Sports Nutrition vol. 14 33. 29 Aug. 2017
11. ACSM 2015, Protein Intake for Optimal Muscle Maintenance. Position Statement. American College of Sports Medicine. 2015. https://www.acsm.org/docs/default-source/files-for-resource-library/protein-intake-for-optimal-muscle-maintenance.pdf