Protein Timing, Does It Matter?

Protein Timing, Does It Matter?

Article Difficulty: Moderate

Do you have to consume protein immediately after a workout?⁠

Post-workout protein timing is a contentious topic, but one we're going to settle here today. If you're looking for the short answer to whether you have to consume protein immediately after a workout to maximize muscle growth, the answer is no. But hold on, why continue reading the rest of the article? Well, there's slightly more to it than a black-and-white yes or no. Understanding the factors that maximize muscle growth and recovery are crucial for anyone looking to get the most out of their time in the gym. So, with that being said, let's delve into the topic of protein timing!

Where does the idea come from?
Protein timing to optimize muscle growth is commonly referred to as 'the anabolic window of opportunity' and is a concept that has been around for a long time within the fitness community. If you've been in a gym locker room, you can likely attest to the many protein shakes being consumed immediately after a workout. But why is this such common practice? When we work out, we place stress on our muscles which causes a certain degree of catabolism known as muscle protein breakdown (MPB). During the recovery period between our workouts, our tissues repair and grow through an anabolic process known as muscle protein synthesis (MPS); dietary protein provides the building blocks that fuel this super-compensatory process. It has been proposed that our muscles are most sensitive to protein-induced anabolism for a narrow period of time post-workout. Hence, the concept of the post-anabolic window aims to minimize muscle breakdown (catabolism) and maximize muscle protein synthesis (anabolism) by promptly replenishing dietary protein during the period when our muscles are most receptive to protein. This concept appears logical on paper, which has prompted extensive research on the topic.

The reason this idea is believed by many is due to how people have interpreted the available scientific evidence. To be clear, there is empirical evidence supporting the anabolic window concept (2) (4) and some researchers have gone as far as to suggest that protein timing is more important than total daily protein intake (2). However, when looking at the methods and participants included in these studies, the results obtained are inapplicable to healthy individuals who regularly lift weights. Study 2 focused on untrained seniors, while 4 focused on cardio-respiratory training rather than weight training, and there are other studies of a clinical nature that are not valid for those seeking best practices for hypertrophy. Furthermore, certain studies supporting the concept have only looked at the short term effect of protein on MPS (4), rather than the effects on muscle growth or strength over time. The issue is that these studies get misconstrued and applied to a different population than the original studies set out to research. In order to have valid evidence, a study protocol must monitor the effects of protein timing on a large sample size of healthy participants that are undergoing ongoing consistent resistance training. To this end, the studies that have employed relevant experimental design methods have not demonstrated a significant effect from post-nutrient timing (1) (5). Of particular note is a recent randomized controlled trial (10) that was performed using resistance-trained men that were assigned to either a pre-exercise or post-exercise protein supplement. After 10 weeks of consistent strength training and timed protein consumption, both groups had similar changes in body composition and strength. These findings contrast the narrow anabolic window theory. Furthermore, this study also highlights the importance of pre-exercise protein, as this was equally effective as post-exercise protein at inducing muscle strength, growth, and recovery when from resistance training. The process of protein digestion and absorption takes place over time and can last many hours (15), therefore by consuming protein pre-workout, there is no need to adhere to a narrow anabolic window post-training as there is still a supply of amino acids from the previous serving of protein.

How narrow is the anabolic window?
The common belief is that the anabolic window diminishes after one-hour post-exercise, however, evidence has suggested that this window may be significantly longer (1) (6). Of particular interest is a 2018 research review that concluded that to induce maximal muscle hypertrophy, protein should be consumed pre-exercise and post-exercise within about 4 to 6 hours of each other (1). This would mean that if you consumed protein 2 hours before your workout, the anabolic window would span to 4 hours post-workout. However, while the study found that consuming protein servings within 6 hours of each other was optimal, the negative effects for being slightly over were not dramatically significant. Furthermore, as mentioned at the start of the article, exercise induces the breakdown of tissues and compounds (catabolism). In a well-fed individual, this catabolism is not significant because instead of breaking down tissues for energy, the body utilizes the available food sources. However, catabolism becomes more pronounced in states of fasting as food sources are not available. Therefore, practical advice from this research is to avoid prolonged fasting pre and post training if your goal is to maximize muscle growth and recovery. If you are fasting prior to exercise, then the post workout anabolic window becomes narrower as the body has little available dietary protein for anabolism. If you are an astute reader, you may have noticed that previously I mentioned a study that found post-workout protein had a significant effect on recovery from cardiorespiratory training (4). This is due to the same reason as just mentioned, less available food substrates for repair. Endurance exercise uses a greater amount of total energy therefore food substrates are burnt faster and if left unreplenished, our muscle tissues are catabolized for energy. Although more research is needed in this area, endurance training may actually have a far narrower window for optimal repair and recovery. In regards to muscle tissue only remaining sensitive to protein for a short period of time, research has shown that this is not true. A 2011 study (13) monitored the sensitivity of muscles to protein following resistance training and found that muscles remain sensitive to protein-induced anabolism for around 24 hours, far beyond the 1-hour myth.

Total daily protein intake is king
A recent meta-analysis by Schoenfeld, Aragon & Krieger (2013) (11) found that consuming protein within 1 hour post-resistance exercise had a small but significant effect on increasing muscle hypertrophy compared to delaying consumption by at least 2 hours. However, sub-analysis of these results revealed the effect all but disappeared after controlling for the total intake of protein. Therefore, if you are consuming adequate total protein intake, the exact timing becomes insignificant. If you’re interested in what the optimal levels of protein are, read our blog here.

Both muscle protein breakdown and muscle protein synthesis are constantly happening in a process known as muscle protein turnover. The balance between the rates of synthesis and breakdown of muscle proteins determines the amount of protein in that muscle (14). It is not the case that immediately consuming protein post-workout will turn a switch and stop MPB, instead, giving your body favorable conditions for muscle protein synthesis is what tips the scales in favor of MPS and muscle protein anabolism. To favor MPS, there are a few factors to consider and these include how well-fed you are, your total daily protein intake, your exercise modality, and the exercise session duration as well - it is these factors that dictate the length of your anabolic window of opportunity. There are also many other lifestyle factors that affect MPS such as sleep, general nutrition and stress.

To give some general and scientifically backed recommendations, the optimal anabolic window for resistance training seems to be somewhere around 4 hours post-workout, again this will depend on the session length and pre-workout nutrition. Longer sessions and fasting will induce far greater amounts of catabolism (12), therefore, for long-duration resistance training sessions or endurance exercises, refueling post-workout becomes a bigger priority.

If you are interested in learning more about this topic, I would highly recommend this paper by Schoenfeld et al. 2018 (1) as it covers a great deal of research and presents the most up-to-date findings on the topic of protein timing.

1. Schoenfeld, B. J., & Aragon, A. A. (2018). Is There a Postworkout Anabolic Window of Opportunity for Nutrient Consumption? Clearing up Controversies. The Journal of orthopaedic and sports physical therapy, 48(12), 911–914.

2. Esmarck, B., Andersen, J. L., Olsen, S., Richter, E. A., Mizuno, M., & Kjaer, M. (2001). Timing of postexercise protein intake is important for muscle hypertrophy with resistance training in elderly humans. The Journal of physiology, 535(Pt 1), 301–311.

3. Phillips, S. M., Tipton, K. D., Aarsland, A., Wolf, S. E., & Wolfe, R. R. (1997). Mixed muscle protein synthesis and breakdown after resistance exercise in humans. The American journal of physiology, 273(1 Pt 1), E99–E107.

4. Levenhagen, D. K., Gresham, J. D., Carlson, M. G., Maron, D. J., Borel, M. J., & Flakoll, P. J. (2001). Postexercise nutrient intake timing in humans is critical to recovery of leg glucose and protein homeostasis. American journal of physiology. Endocrinology and metabolism, 280(6), E982–E993.

5. Erskine, R. M., Fletcher, G., Hanson, B., & Folland, J. P. (2012). Whey protein does not enhance the adaptations to elbow flexor resistance training. Medicine and science in sports and exercise, 44(9),1791–1800.

6. Schoenfeld, B. J., Aragon, A. A., & Krieger, J. W. (2013). The effect of protein timing on muscle strength and hypertrophy: a meta-analysis. Journal of the International Society of Sports Nutrition, 10(1), 53.

7. Power, O., Hallihan, A., & Jakeman, P. (2009). Human insulinotropic response to oral ingestion of native and hydrolysed whey protein. Amino acids, 37(2), 333–339.

8. Tipton, K. D., Rasmussen, B. B., Miller, S. L., Wolf, S. E., Owens-Stovall, S. K., Petrini, B. E., & Wolfe, R. R. (2001). Timing of amino acid-carbohydrate ingestion alters anabolic response of muscle to resistance exercise. American journal of

9. Morton, R. W., Murphy, K. T., McKellar, S. R., Schoenfeld, B. J., Henselmans, M., Helms, E., Aragon, A. A.Devries, M. C., Banfield, L., Krieger, J. W., & Phillips, S. M. (2018). A systematic review, meta-analysis, and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. British journal of sports medicine, 52(6), 376–384.

10. Schoenfeld BJ, Aragon A, Wilborn C, Urbina SL, Hayward SE, Krieger J. Pre- versus post-exercise protein intake has similar effects on muscular adaptations.

11. Schoenfeld, Aragon & Krieger (2013) Schoenfeld BJ, Aragon AA, Krieger JW. The effect of protein timing on muscle strength and hypertrophy: a meta-analysis. Journal of the International Society of Sports Nutrition.

12 .Aragon AA, Schoenfeld BJ. Nutrient timing revisited: is there a post-exercise anabolic window? J Int Soc Sports Nutr. 2013 Jan 29;10(1):5.

13. Burd NA, West DW, Moore DR, Atherton PJ, Staples AW, Prior T, Tang JE, Rennie MJ, Baker SK, Phillips SM. Enhanced amino acid sensitivity of myofibrillar protein synthesis persists for up to 24 h after resistance exercise in young men. J Nutr. 2011 Apr

14. Tipton, K. D., Hamilton, D. L., & Gallagher, I. J. (2018). Assessing the Role of Muscle Protein Breakdown in Response to Nutrition and Exercise in Humans. Sports medicine (Auckland, N.Z.),

15. Bilsborough, S., & Mann, N. (2006). A review of issues of dietary protein intake in humans. International journal of sport nutrition and exercise metabolism.

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