Carbohydrate window after training – how to use it correctly?

The carbohydrate window theory dates back to 1988 when the first study was published showing that eating carbohydrates immediately after a workout resulted in a twofold increase in muscle glycogen stores (compared to eating carbohydrates two hours later).

Based on this study, sports nutrition manufacturers have introduced a whole range of products – from weight gainers to carbohydrate-protein bars. However, does the carb window really exist – or is it just a marketing myth?

Post-workout carb window

The logic of the carbohydrate window is based on the fact that in the 30-minute period after the end of physical training, the metabolism becomes significantly more receptive to incoming energy – using it mainly to restore muscle tissue (and build muscle).

Since the main source of energy for muscles is glycogen (a product of the processing of carbohydrates supplied with food), providing² up to 80% of the needs of the muscles in ATP, the body really needs carbohydrates for a full workout.

When performing strength exercises in a multi-rep mode (which is required to start muscle growth processes), glycogen stores in the body are noticeably depleted – on the basis of which it is concluded that they need to be replenished as quickly as possible during the carbohydrate window.

Truth or myth?

While the carbohydrate window theory no doubt sounds extremely plausible, in practice there are a number of factors to consider. First of all, the consumption of carbohydrates during the day – since it takes the body at least several hours to convert them into glycogen.

Positive results in the 1988 study were achieved by no nutrition at all (i.e., training on an empty stomach) – while it is clear that the presence of a carbohydrate meal a few hours before training is a key factor in replenishing glycogen.

Plus, this study was conducted on people with a low level of athletic performance – and later trials on professional athletes showed completely different results (virtually disproving the presence of any carbohydrate window).

Symptoms of low carbs

A typical beginner mistake is trying to lose fat and increase muscle mass at the same time. As a result, physical training is carried out on a low-calorie (or low-carbohydrate) diet – which leads to a sharp decrease in blood glucose levels.

This condition is called “hypoglycemia” – and can be expressed in dizziness, deterioration in the coordination of movements, and in a decrease in strength indicators. In simple terms, the body literally does not have enough carbohydrates to maintain muscle performance.

Training on an empty stomach – pros and cons

On the other hand, training at low blood glucose levels is really used by professional athletes for the purpose of burning fat and drawing muscle relief.

However, we are talking about either cardio or training with a fairly light weight and a high number of repetitions (12-15) – and not at all about heavy exercises with a barbell.

In addition, even in this case, it is correct to speak not about the carbohydrate window, but about the metabolic one (implying that after training it is necessary to consume both carbohydrates and proteins).

Carbohydrate window – how to use it?

The position of modern researchers comes down to the fact that the carbohydrate window must be closed not after training, but before it. On average, the body needs about 5-6 hours to digest food and fully assimilate it – and the maximum level of amino acids is observed after 3-4 hours.

First of all, in the period 3-4 hours before training, the muscles need a portion of food containing at least 25 g of complete protein – meaning that it should be animal protein (milk, eggs, meat), and not vegetable (which is absorbed worse and does not always contains a complete set of amino acids).

And, no doubt, the total amount of carbohydrates in the diet plays a role – since they are processed into glycogen and ensure the working capacity of the muscles. In the absence of carbohydrates, the body cannot function in an anabolic muscle-building mode.

Sports nutrition or regular food?

It is also important to understand that there is no reason to believe that the use of sports nutrition can provide a significantly more beneficial effect than a balanced diet.

Although whey protein and a weight gainer can replace meals (for example, during a long work or school day), in the end, the difference with regular food is minimal.

Final words

Unfortunately, newer studies in professional athletes have failed to support the theory of a post-workout carbohydrate window.

Although the balance of muscle protein was affected by the use of whey isolate (about 25 g) – an additional intake of 50 g of maltodextrin did not improve these indicators.

Despite this, scientists propose the term “metabolic window” – which includes not only carbohydrates, but also protein, and the period of action which begins before training.

The fact that there is a carbohydrate window has not been confirmed by modern scientific research – and initially, the data was obtained from non-athletic people exercising on an empty stomach. Only in this case, the intake of carbohydrates immediately after training showed a positive result on muscle synthesis.