The Ever-Popular Anabolic Window, Explained
The so-called “anabolic window” refers to a short period of time following workouts, during which exercisers need to consume protein for muscles to properly recover, grow and become stronger. It revolves around the concept that muscles are more sensitive to protein and therefore more likely to absorb and use protein immediately after exercise than they are later throughout the day.
“The ‘anabolic window’ implies that delaying protein intake by one hour or more after exercise will reduce or, worse still, prevent muscle anabolism [growth] during recovery,” explains Oliver Witard, Ph.D., a protein metabolism researcher and senior lecturer at the University of Stirling in Scotland.
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To understand why that’s important, you’ll need a quick biology lesson: Exercise, especially tough workouts, create microscopic damage within the worked muscles’ cells, which are composed of proteins. So, the protein you eat supplies the building blocks that make up your muscles. These building blocks, or amino acids, help repair damaged muscle proteins and form new ones, with the ultimate goal of creating stronger, bigger and fitter muscles, Witard says.
Simply put, consuming protein is vital to workout recovery and results, with current research showing that for optimal muscle health, people need about double the amount of protein that experts once thought. For example, the current recommended daily allowance of protein, which represents the minimum required for good health, is 0.8 grams of daily protein per kilogram of body mass. For a 150-pound adult, that works out to 55 grams of protein per day. However, the National Strength and Conditioning Association recommends 1.5 to 2 grams of daily protein per kilogram of body mass per day for optimal muscle growth. For the same 150-pound adult, that equates to 102 to 136 grams of protein per day.
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So Do You Need Protein After a Workout, After All?
But here’s the thing: Research also shows that you don’t have to immediately cram in all that protein after a workout. “High-quality and short-term muscle biopsy studies report similar muscle anabolism after consuming an essential amino acid mix one, two or even three hours post-exercise,” Witard says, citing 2014 research from his team, published in Applied Physiology, Nutrition, and Metabolism, as well as previous research from the University of Texas.
Meanwhile, a 2017 Medicine & Science in Sport & Exercise study found that when men drank 22 grams of protein after a workout, they didn’t build more muscle than those who didn’t. But here’s the catch: All of the study’s subjects were already eating roughly 1.3 grams of protein per kilogram of their body mass per day.
“Taken together, this research clearly demonstrates that skeletal muscle remains responsive to protein ingestion during time periods outside the limits usually defined by the ‘anabolic window,'” Witard says. “Indeed, it appears that this ‘anabolic window’ extends to 24 hours post-workout, or perhaps even longer.”
“If there’s any benefit to getting protein within a half hour and 45 minutes of your workout as opposed to a few hours later, and I’m not convinced there is, it would be very narrow,” says exercise researcher Brad Schoenfeld, Ph.D., C.S.C.S., C.P.T., who has studied post-workout protein timing in exercisers. So do you need protein after a workout? “As long as you hit daily protein intake, you can build muscle,” he says.
Spread Out Your Protein Intake for Greater Muscle Gains
Even if the anabolic window is 24 hours or longer, there’s still good reason to space out your protein intake within that time frame.
“Recent efforts have focused on understanding the muscle building response over an entire day after consuming multiple protein-containing meals,” Witard says.
For example, in one study in The Journal of Physiology, men performed resistance exercise and followed up their workout by consuming 80 grams of protein over the next 12 hours. They either consumed 20 grams every three hours, 10 grams of protein every one-and-a-half hours or 40 grams of protein every six hours. It turned out that the men who consumed 20 grams of protein after a workout, for every three hours, had significantly higher rates of muscle protein synthesis.
Schoenfeld’s 2018 research, published in the Journal of the International Society of Sports Nutrition, suggests that for optimal muscle growth, people should consume between 0.4 and 0.55 grams of protein per kilogram of their body mass four times per day. For a 180-pound adult, regardless of sex, that works out to eating 33 to 45 grams of protein four times per day.
A previous 2015 review concluded that most adults need to eat 25 to 35 grams of protein at every meal for optimal muscle health. Lean meats, fish, eggs, dairy, legumes and soy are all rich in protein and can help exercisers hit their protein goals at every meal.
Practically speaking, if you eat sufficient protein at every regular meal, you are going to get in all of the protein you need around your workouts, Schoenfeld says. No extra post-workout protein shakes required.