Here's why you probably don't need to worry about cracking your post-workout protein shake open before you finish your workout.
What is the Anabolic Window?
The anabolic window refers to the time period after a training session, when it's supposedly a good idea to get in foods that help with recovery and building muscle.
The theory is solid –
You just spent an hour or so destroying yourself in the weights room, and in order to repair and recover, your muscles need nutrients.
If you're bulking and in a calorie surplus, you'll be looking to make the most of this window to aid your recovery and boost the growth of new muscle tissue, whereas if you're cutting and in a calorie deficit, the idea is to prevent muscle loss, and stop your strength, energy and performance from declining.
Those who promote the idea of the anabolic window usually suggest that you need two things post-workout –
The protein component is obvious. The amino acids that make up a protein molecule are building blocks. It's these that are responsible for cell regeneration, and so you want them in your system to aid growth.
Fast-digesting carbs supposedly help the muscle recovery process for two reasons. Firstly, when you train, your levels of glycogen (the stored carbohydrate in the muscle cells) decreases, and so you want to top this back up again, or you risk feeling fatigued and losing muscle mass.
Secondly, it's argued that fast-digesting carbs spike insulin levels.
Insulin is a storage hormone, and while that often gives it a bad rap in terms of storing body fat, it can help shuttle nutrients (and protein) to the muscle cells faster, getting the repair of damaged tissues started sooner.
It seems sound, so why is the anabolic window a complete myth?
There's a widespread thought that speed is of the essence in terms of getting in nutrients post-workout, but this isn't the case.
Digestion is a long and complex process, and even the most fast-digesting food sources will take a good 45 minutes to get from your mouth, through your digestive tract and your stomach before hitting the rest of your body and your muscle cells.
Therefore, if you've eaten pre-workout, you can be assured that there will still be circulating nutrients when you finish your last set.
A case could actually be made that pre-workout nutrition is more important than post, when you take this into account.
Additionally, the speed at which nutrients are delivered really doesn't matter too much.
Lifting weights spikes levels of muscle protein synthesis (MPS – the rate of protein turnover within a muscle cell,) so again, provided you had some protein before you hit the weights, your muscles are still being fuelled for optimal growth.
The Fast Carb Myth
This is another area where the theory is easy to believe.
This is it: to help raise insulin levels and re-stock glycogen as quickly as possible, you need a fast-digesting, or high-GI carb. (Think white rice, white bread, sugary sweets, etc. rather than slower-digesting sources such as oats, brown rice and berries.)
You need to remember though, that as discussed above, digestion speed isn't as simple as "eat something and it goes straight to the muscles."
Not just that, but post-training, your body is extra receptive to food anyway, so any type of carb (and even some non-carb-based foods such as whey protein) will create a big insulin spike. They don't need to be fast digesting.
Do You Train Twice a Day?
If you do, then actually, all the above might not apply to you. It's one of the few scenarios in which faster digesting carbs may actually have some benefit to slower digesting ones.
We've slightly bashed the anabolic window, as for most people, it's a small and insignificant 'detail'. However, if you do train twice a day (be that both weights sessions, or one weights and one cardio) then what you eat between sessions is likely to matter more.
If you are going to train for a second time in a day, then the faster you can replenish your glycogen stores, the more likely that second workout is going to be more productive. In this case, it makes sense to incorporate some of the faster digesting foods in your post-workout meal, so that you can properly attack your second session.
Another caveat is those who train fasted. While not for everyone, it may make sense to get nutrients into your system quickly after you train, given the fact your body has not eaten in hours when you consider the time you've been sleeping and training. This is where protein (particularly in liquid form) and fast-digesting carbs could be beneficial.
Making a Guess
People preach that you MUST get your post-workout meal in within 30 or 60 minutes of finishing, but this would indicate that at 31 or 61 minutes, depending on who you listen to, you are no longer primed to gain muscle and your workout's been a waste of time - which is logically not going to be the case.
The Bottom Line
By far and away the most important factor is hitting your daily macronutrient targets.
You can bang on about the anabolic window all you like, but if come the end of each day, your protein, carb and fat numbers aren't within 5% of what you're aiming for, you probably aren't going to be progressing optimally.
Aim to get a nutrient-dense mixed meal of protein, carbs and fats in around 1 to 3 hours before you train, and the same again afterwards.
Personal preference plays a big role here too.
You want a pre-workout meal that doesn't sit too heavy, and allows you to perform well, and a post-workout feed that fits your schedule and allows you to meet your macros and make progress.
Don't overcomplicate the dieting process. Consume adequate protein, eat a surplus to build muscle, a deficit to lose fat, and eat foods you love, when it suits you while satisfying said macro targets. If there was a secret to long term body composition improvement, that would be it.