The concept of Anabolic Window as it is broadly known is that after resistance exercise, your body is in a heightened state of muscle-protein breakdown and synthesis. The theory claims that by consuming protein (and often carbohydrates) immediately post-workout, you can shift the balance toward muscle repair and growth more effectively.
However, a major meta-analysis study published in 2013 by Brad J. Schoenfeld PHD (an exercise science professor and fitness expert) analysed 23 studies involving 525 subjects (for hypertrophy) and 20 studies with 478 subjects (for strength).
The study looked at specific outcomes around Muscle Hypertrophy and Strength to measure progress and impact of timing of protein intake around the workout. Specifically, the study looked at changes in Fat-free mass, Lean body mass, cross-sectional area of muscle
The study concluded that total daily protein consumption, rather than the exact timing around workouts, best predicts muscle hypertrophy and strength gains.
In other words, if you hit your protein target for the day, when you have it becomes less critical.
Importantly, based on another study conducted in 2003, where muscle synthesis was compared between participants who were active vs in rested state. The study concluded that if you train fasted, it is important to incorporate protein in your meal within 3 hours post workout is necessary to support Muscle Protein Synthesis (MPS = the rate at which muscle repair in response to a stimulus)
Do Men and Women Differ in Protein Timing or Response?
When it comes to young, healthy adults, the research suggests that men and women respond very similarly to protein around resistance exercise.
In a study published in 2012 by Daniel W. D. West, PHD, an affiliate scientist at KITE institute, eight men (~20 yrs old) and eight women (~22 yrs old), in a fed state, performed high-intensity resistance exercise and consumed 25 g whey protein immediately after and ~26 hr later. The Muscle Protein Synthesis response ( over the first 1–5 h post-exercise was nearly identical (men ~2.3×, women ~2.7× baseline). Despite men having ~45-fold higher testosterone response, the MPS response did not differ
Takeaways:
Total Protein Matters Most. The Anabolic Window is less critical as long as you are able to consume enough protein throughout the day.
When trained fasted, an Anabolic Window is important but wider than previously believe
For active men and women, the same core timing and amount recommendations apply. Women do not necessarily need to rush the protein shake more than men.
References:
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(53).
Pitkänen, H. T., Nykanen, T., Knuutinen, J., Lahti, K., Keinanen, O., Komi, P. V., & Mero, A. A. (2003). Free amino acid pool and muscle protein balance after resistance exercise. Medicine & Science in Sports & Exercise, 35(5), 784–792.
West, D. W. D., Burd, N. A., Churchward-Venne, T. A., Camera, D. M., Mitchell, C. J., Baker, S. K., Hawley, J. A., Coffey, V. G., & Phillips, S. M. (2012). Sex-based comparisons of myofibrillar protein synthesis after resistance exercise in the fed state. Journal of Applied Physiology, 112(11), 1805–1813.
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