Rethinking the Post-Workout Protein Window

Research suggests the post-workout "protein window" might not be as narrow as you think.

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We’ve all heard it: get your dose of protein immediately after an exercise session (especially resistance training) within the post-workout “anabolic window.” The advice athletes are given time and again is to ingest high-quality protein as soon as possible after a workout to maximize strength gains. This post-exercise period has been promoted as a small critical anabolic period, causing almost every athlete to down a chocolate milk, shake up a recovery smoothie, or chow down on a protein bar in the parking lot. Whether it’s a long run, a short swim, or a gym session, we athletes are obsessed with getting our post-workout protein.

But does this narrow “anabolic window” of opportunity really exist? More recent research suggests that there may be more factors at play than trying to optimize one very specific opportunity for protein ingestion for maximum muscle protein synthesis (MPS).

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The concept of ideal nutrient timing has been around for approximately ten years, when a statement discussed one pillar of nutrient timing as post-exercise ingestion of essential amino acids. This position-stand advised active individuals to consume protein and carbohydrate in a three-hour timeframe following resistance training, based on several studies that suggested a decrease in muscle breakdown and an increase in anabolic response when compared to carbohydrate alone or a placebo. Research suggested the depletion of stored fuels, such as glycogen and amino acids, combined with the damage to muscle fibers caused by an exercise session, could be mitigated with the consumption of approximately 50-75 grams of carbohydrate and 20-75 grams of protein.

This has since been simplified into the easy advice of “eat protein immediately following any workout.” But as more researchers look at the concept of the post-workout protein “window” the best nutritional advice for athletes becomes much more nuanced.

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Protein for athletes: Timing, Amount

Schoenfeld et al. performed what’s called a meta-analysis—e.g., an analysis of a large number of studies on a particular topic—of long-term resistance-trained athletes, to determine whether protein timing is the best strategy for enhancing post-exercise muscular adaptations. Using a combined 478 subjects over 20 different students, the results indicate that there are no significant differences between those who consumed protein within this window post-exercise and those that did not in either area of strength or hypertrophy (i.e. bigger muscle size).

Most surprisingly, total daily protein intake was the strongest tie to the adaptive response to exercise. In 2017, the same author set out to test the results from his meta-analysis using a study of 21 resistance-trained men within a university setting. Subjects were divided them into two groups, one group of nine that consumed a supplement containing 25g of protein/1 gram of carbohydrate immediately prior to exercise (PRE-SUPP) and one group of 12 that consumed the same supplement immediately post-exercise (POST-SUPP). Both groups performed the same resistance training program three times per week for ten weeks and compared for muscle thickness, body composition changes, and maximal strength.

Results suggested the pre-and post-workout protein participants had similar effects on all variables measured refuting the idea of a narrow post-exercise anabolic window that allows for maximizing the muscular response. Further, they contended that the interval for protein intake around the workout may be several hours post-training, depending on the timing of the pre-workout meal.

While this study had several limitations, this study suggests that this window is not nearly as narrow as previously described and potentially exists on a continuum that must take into consideration the nutrient mix that was consumed prior to the training session. 

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Protein Before a Workout? After? Not at all?

Now that you are thoroughly confused, what does all of this mean in terms of your protein smoothie or glass of chocolate milk immediately post-workout session? With all of this considered in the real world of free-living athletes, what we do know is that muscles remain sensitized to protein consumed for at least 24 hours following resistance training and that protein needs range from 1.4–2.0 g protein/kg body weight/day, which is sometimes hard to achieve for busy athletes who are performing both endurance exercise and resistance training.

The importance of this immediate post-workout snack may depend on how long it has been since your last meal and if it contained adequate protein. If it has been longer than 3-4 hours since your last meal, making a post-workout snack with approximately 25-40grams of high-quality protein that contains essential amino acids and some carbohydrates certainly is prudent to maximize both gains and recovery. This can also help athletes meet daily protein needs that are critical to long-term muscle repair and overall recovery.

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The bottom line

The 2017 research of Schoenfeld et al. suggests the “anabolic window” may not be nearly as narrow as once proposed. From a practical standpoint, a smart athlete should strive to meet daily protein needs while also making sure one of those doses is approximately 0.4-0.5g/kg of lean body mass (which usually amounts to approximately 20-40 grams) both pre-exercise and post-exercise, within 4 to 6 hours of each other. This advice, though not as tidy as “eat protein immediately after a workout,” leaves plenty of latitudes to customize this dose based on individual factors including preference, tolerance, convenience, type, and availability.

If you are already struggling to meet your protein needs for the day and are in a heavy phase of training where recovery is paramount, then research suggests adding protein to carbohydrates (0.8g/kg/h) within two hours of completing a strenuous workout has been suggested to improve recovery. Whether you choose the pre- or post-workout protein dose, a smoothie made with fruit and 20g whey protein, a peanut butter and jelly sandwich with 16oz of chocolate milk, or beef stick with 4 oz. of cheese and crackers can fit the bill to replenish glycogen stores – all while providing the protein punch you need to PR the next day’s workout.

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Kim Schwabenbauer, PhD, RD, CSSD, LDN, is a former professional triathlete turned registered dietitian, professor, consultant, speaker and triathlon coach with an emphasis in overall health, wellness and sports nutrition.