Should You Take a Whey Protein Isolate Post-Workout?

Kris Gethin
Written By: Kris Gethin
December 21st, 2018
Updated: June 13th, 2020
Categories: Articles Supplements
13.7K Reads
Should You Take a Whey Protein Isolate Post-Workout?
Maximize your post-workout nutrition by ensuring you get your protein from a quality protein source. Learn what makes Whey Isolate one of the best sources.

Reaching for a protein shake immediately following their workout has been the habit of many athletes looking to take advantage of the “anabolic window”.

For years, the supplement industry has insisted that there is a short window of opportunity post-workout in which anabolism can be enhanced by drinking a protein shake.

While there is some truth to this, you should be aware of a few caveats in order to take full advantage of your training sessions.

This column will explain why whey protein isolate is of significant importance during the post-workout window – and how to utilize it optimally for progress.

Defining the Post-Workout Window

As the name suggests, the post-workout window starts as soon as your lifting session ends and lasts approximately one hour according to most industry standards, although some shorten this period to thirty minutes.

Related: What to Eat Before AND After Your Workout

In essence, the physiologic environment following a training session is one where amino acid levels are lower than usual, blood sugar levels may be depleted, cortisol levels are higher than normal, and muscle cells need to recover from the trauma they’ve endured.

The idea of the “anabolic window” theory is that the body is hypersensitive to nutrient intake at this point. This allows for “super compensation” in the event that the correct nutrients are consumed. To a point, there is truth in this idea, although a few more stipulations exist to be properly applied.

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Post-Workout Window Myths Debunked

The biggest myth about the post-workout window is that an abundance of carbohydrates is needed to stimulate insulin secretion for anabolic impact. Insulin is an anabolic storage hormone that supports nutrient transportation to muscle cells, which is an essential part of the recovery process. However, whey protein isolates are insulinogenic in their own right, meaning additional carbohydrates are not needed for this purpose.

The typical hour-long resistance training session does not significantly deplete muscle glycogen stores. Therefore, there isn’t an urgent need for stores to be replenished following a workout. Provided that your diet as a whole contains adequate carbohydrates, glycogen stores will be maintained across the day and will support your training sessions and recovery.

To summarize and contextualize this point, boosting insulin levels post-workout will help with nutrient uptake and muscle recovery. When a whey protein isolate is consumed, carbohydrates are not required for these purposes due to the insulinogenic properties of the isolate. It’s also important to note that muscle glycogen stores will not become depleted after an average weight training session, leaving no need for replenishment within a set time frame.

However, lengthy endurance-based training sessions will deplete muscle glycogen stores, making carbohydrates more advisable in this post-workout window, and potentially even during training.

How Whey Protein Isolate Helps

Whey protein isolate is one of the most bioavailable sources of protein, meaning the body can process and absorb the nutritional content rapidly. There are several considerations to be mindful of when looking at the post-workout window and the impact of a whey protein isolate product.

Firstly, cortisol spikes during an intense workout and remains high in the post-workout window. This spike puts stress on the gastrointestinal tract, impacting its function which makes digestion of solid, calorie dense foods more difficult for the body. Compounding this factor, there’s less blood available for digestion following training, as the blood has been sent to the muscles which have been working intensely.

Dumbbell Lateral Raise

With that said, whey protein isolate offers an easily digested alternative to solid food in this situation, allowing the muscles to benefit from amino acid replenishment without applying further stress to the gut.

During intense weight training sessions, muscle fibers are broken down, regardless of the fact of being in a calorie surplus or deficit. However, being in a deficit increases the risk of excessive catabolic impact due to the lack of protein sparing properties in the diet.

Consuming whey protein isolate after training quickly activates muscle protein synthesis, via the mTOR pathway, which facilitates muscle recovery and growth. Encouraging this to happen shortly after training is important for recovery and managing muscle soreness.

Related: Pumps & DOMs - Are They Important for Making Gains?

Whey protein isolate contains a full spectrum of amino acids including leucine, which is known to spark muscle protein synthesis. The presence of leucine, combined with the other essential aminos, is just another way a whey protein isolate product is beneficial following training sessions.

Finally, as already discussed, whey protein isolate drives an insulinogenic response which enhances nutrient transportation to the muscle cell following training. Insulin behaves as a storage hormone and spikes anabolic activity, an essential part of muscle recovery and growth.

Distinguishing the Differences Between Whey Protein Isolate Products

Like all sports nutrition supplements, there are good and bad products on the market. Quality should always be a priority when selecting a whey protein isolate, and there are a few factors to be aware of as a consumer.

Firstly, a high-quality product will not have “whey protein concentrate” listed in its ingredients. Including a concentrate is a common step which companies take to dilute the isolate, lowering the production cost to increase their profit margin. The issue with this is that by cutting corners, quality becomes compromised, leading to inferior results.

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Another factor to look for is the presence of any artificial colorings and flavorings - natural products are always best for purity and your health. Additionally, a product which contains digestive enzyme support is a benefit for improved absorption and gut health.

Beyond ingredients, how a product is processed is also a critical component for quality. Many whey protein isolates have been exposed to high temperatures during production which can denature the amino acid content.

To avoid this factor, which can lower the product’s quality, ensure cold-filtered processing methods have been utilized. Finally, a product which has been third-party tested is another element which marks a higher quality product. The ability for a product to advertise this hallmark gives an athlete peace of mind that harmful or banned substances haven’t been included, or that illegal ingredients haven't been used in the production process.


The benefits of using a whey protein isolate product after training have been known for many years with science consistently demonstrating that it can help with recovery and muscle growth.

Following a diet which is geared towards the same goal is essential for any supplement to have a maximal impact.

When shopping for a whey protein isolate, always consider product quality, otherwise, results could be limited.

Take advantage of your training sessions by optimizing your post-workout window with a high-quality whey protein isolate product.