Physiology Friday #224: Does Protein Timing Matter for Gains in Strength and Hypertrophy?
Debunking the "anabolic window."
Greetings!
Welcome to the Physiology Friday newsletter.
ICYMI: I appeared as a guest on Siim Land’s podcast to chat about all things VO2 max. You can watch the YouTube video here.
Details about the sponsors of this newsletter including Examine.com and my book “VO2 Max Essentials” can be found at the end of the post!
Around age 13, I began to take a keen interest in health and fitness. This is around the same time I became a long-distance runner.
Like any aspiring athlete, I wanted to do everything I could to help my body perform, which inevitably guided me to nutrition. One of the main practices that I thought was essential to my performance and recovery was eating something immediately after every strength or endurance workout. I went so far as to pack protein bars in my backpack so that I’d have a readily available food source to eat after practice.
This is a time-honored strategy. The thinking goes that after a workout, there’s a “window of opportunity” where the body is most sensitive to protein (for muscle building) and carbohydrates (for glycogen replenishment) and that, if one misses this window (which is thought to be around 30–60 minutes in duration), they’ll be leaving valuable gains on the table.
The post-exercise window has been mostly associated with resistance training, and is therefore commonly known as the “anabolic window” which refers to a specific period following exercise during which the body is exceptionally primed to absorb nutrients and initiate muscle protein synthesis. This heightened state of nutrient sensitivity and anabolic potential is driven by several physiological mechanisms activated during and immediately after exercise, including elevated muscle protein synthesis from the prior resistance exercise, enhanced insulin sensitivity, and elevated nutrient transport.
The anabolic window refers to how the timing of protein intake after exercise influences training adaptations. There are two other factors regarding protein that are also important: total daily protein intake and the within-day protein distribution.
Some argue that these latter factors are more important than timing. It’s all about whether or not you’re eating enough protein during the day.
How much is enough? The current consensus is that to maximize gains in strength and hypertrophy, 1.6 grams of protein per kilogram of body weight is the threshold.
Furthermore, one should distribute this protein intake over 4–5 meals throughout the day, each of which contain at least 20–30 grams of protein.
So, we have somewhat of a consensus about “how much” protein you need and “how often” you need it. But research is still undecided on whether we should embrace the idea of the anabolic window.
A New study published in Frontiers in Nutrition helps advance our understanding.1
For the study, a total of 31 men (average age of 25) who were experienced with resistance training were randomized to one of two protein timing groups:
Delayed protein intake group: Consumed 25 grams of protein (concentrated and isolated whey) 3 hours before and 25 grams of protein 3 hours after each resistance training session.
Immediate protein intake group: Consumed 25 grams of protein immediately before and immediately after each resistance training session.
Both groups had the same relative total daily protein intake at 2.0 grams of protein per kilogram of body weight per day, all of which was obtained from foods other than on training days (when they consumed 50 grams from whey).
The participants trained 4 or 5 times per week (depending on experience) with 2 or 3 days of upper-body exercise and 2 days of lower-body training. All of the training sessions were supervised.
Before and at the end of the study, researchers assessed several outcomes related to health and performance, including:
Body composition: skeletal muscle mass, fat mass, and body mass index (using bioelectrical impedance analysis)
Leg press maximal strength
Leg press endurance (repetitions to failure at 75% of one-repetition maximum)
Chest press strength
Chest press endurance
Vertical jump height
Australian pull-ups (repetitions)
Biochemical measures: creatinine, urea, liver enzymes, HDL, LDL, and total cholesterol
Results
Both groups improved their skeletal muscle mass after training: by 1.07 kg in the delayed intake group and by 1.18 kg in the immediate intake group. There were no significant differences between the groups for skeletal muscle mass changes. Fat mass and body mass index were unchanged in both groups.
Regarding strength outcomes, there were improvements in both groups observed for leg press strength (+44 kg and +26 kg in the delayed and immediate intake groups, respectively), chest press strength (+9 kg and +12 kg in the delayed and immediate intake groups, respectively), and Australian pull-ups (+5 repetitions and +3 repetitions in the delayed and immediate intake groups, respectively). No differences in strength outcomes were observed between groups. Vertical jump, leg press endurance, and chest press endurance didn’t change in either group during the intervention.
Lastly, there were no changes observed in any of the biochemical outcomes assessed, with the exception of urea, which increased in the delayed intake group (by 5.75 mg/dL) and the immediate intake group (by 6.26 mg/dL).
Is this the nail in the coffin for the “anabolic window” theory? Have bodybuilders and strength and conditioning coaches been preaching the wrong message for decades?
Though this study is just one data point, it adds to a growing body of research suggesting that total daily protein intake is probably what you should really be worrying about. If it’s adequate, you’ll gain strength and size, so long as your training stimulus is enough.
When total daily protein intake is equal, the timing of protein in relation to exercise seems to have little impact on gains in strength and changes in body composition.
Does this mean you can’t or shouldn’t leverage the pre- and post-exercise nutrition windows? Not at all. Eating close to a workout is just one more way to fit in another dose of protein, which for people who are really trying to push their protein intake up, can be valuable. Eating something shortly after exercise (or before) definitely isn’t harmful.
Furthermore, we’re more insulin sensitive after a workout, and consuming protein along with carbohydrates is known to help expedite glycogen replenishment when compared to carbohydrate alone. And, if you’re training twice per day, you should definitely start your post-workout nutrition as soon as possible.
Som, I don’t think this study is telling us that when we consume protein is completely irrelevant. After all, if you’re waiting 3 hours after a workout to eat your protein (or your first meal), you might likely be compromising your total daily protein intake if it means skipping a feeding opportunity.
Nevertheless, you certainly shouldn’t feel anxiety or dread (like my 13-year-old self did) if you miss the “anabolic window after your workout — you can still achieve gains, as this study clearly illustrates.
Today’s study might be one of the few examples where “bro science” and common practice gets debunked by real science. Sometimes it’s the other way around.
Thanks for reading. See you next Friday.
~Brady~
The VO2 Max Essentials eBook is your comprehensive guide to aerobic fitness, how to improve it, and its importance for health, performance, and longevity. Get your copy today and use code SUBSTACK20 at checkout for a 20% discount. You can also grab the Kindle eBook, paperback, or hardcover version on Amazon.
Examine.com: Examine is the largest database of nutrition and supplement information on the internet.
That is good news! Those guys in the study were aged 25. Do you think this applies equally to a 66 year old and additionally, should we increase the protein quantity? Thanks.