How you refuel after a workout is important. After an exercise session, you need to replace muscle glycogen stores. That’s where carbohydrates come in. It’s also essential to get adequate protein after exercising to prevent protein breakdown and help muscles repair and grow. Without the raw materials (amino acids) muscle growth won’t take place. That’s not the only reason you need protein and carbs. Taking in protein and carbs after an exercise session stimulates the release of insulin. Insulin helps help ferry amino acids into muscle cells where they can use them to grow and repair. There’s also evidence that consuming protein after a workout helps with exercise recovery.
Some studies suggest there’s a “window period” after a workout where muscles are more responsive to dietary protein. Consuming protein during this period may boost muscle growth and reduce muscle damage more than taking in protein at other times of the day. This is the theory behind nutrient timing. By consuming carbs and protein within a certain time period after a workout, you can maximize muscle recovery and growth while maximally replenishing glycogen stores.
How Can You Use Nutrient Timing to Your Advantage?
To maximize the benefits of your workout, refuel as soon as possible after your workout is over. Some studies show when you consume carbohydrates immediately after a workout, you get the most muscle glycogen replacement. If you wait two hours, muscle glycogen synthesis is reduced by 50%. Why might this be? Right after a workout, enzymes that are involved in glycogen storage are higher and conditions are ripe for glycogen synthesis and storage. By getting carbs quickly, you can take advantage of this.
Carbohydrates aren’t the only macronutrient you need during the post-workout period to maximize glycogen replacement. Some, but not all research, shows consuming a combination of protein and carbohydrates after a workout maximizes glycogen replacement more than carbohydrates alone. Replenishing muscle glycogen stores are particularly important if you do a split workout, half in the morning and the rest later in the day. If your muscles are still glycogen depleted during your second session, you won’t be capable of working as hard.
Nutrient Timing: Post-Workout Nutrition for Muscle Recovery and Growth
We’ve already mentioned that a combination of protein and carbs enhances glycogen synthesis more than carbohydrates alone. According to some research, a protein-carb combination stimulates muscle protein synthesis more than consuming a protein meal alone. This makes sense since the protein-carb combination elicits a greater insulin response. This helps to get the amino acids from the protein into muscle cells quickly so they can be used to build new muscle tissue.
How much protein and carbohydrates should you get after a workout? According to research published by the Journal of the International Society of Sports Nutrition, a carb to protein ratio of about 3-4 to one is optimal. Guidelines recommend consuming 0.5 to 1 gram of carbohydrate per pound of body weight during the post-workout period. So, a 120-pound person would take in between 60 and 120 grams of carbs within the window period. Combine this with about a third that quantity of protein. For a 120 pound person, that would be between 20 and 40 grams of protein.
How long is the window period? Most research suggests refueling within 30 minutes to one hour of a workout is optimal.
Nutrient Timing: More Protein Isn’t Necessarily Better
You might think consuming more protein after a workout would enhance protein synthesis even more. Not necessarily. There may be a limit to how much protein your body can absorb and use at one time. Even if all the protein from a high-protein meal is digested, the amino acids have to be transported across the small intestines and enter your bloodstream to reach muscle cells. There are a limited number of amino acid transporters available to do this job. Some research suggests that we can’t absorb more than 20 to 40 grams of protein at one time. So, consuming more protein than this at one meal may be pointless.
Don’t assume you need to drink a protein drink to get protein to your muscles quickly. A high-protein snack with an appropriate amount of carbs will work. If you use a protein supplement, whey protein is absorbed more quickly than casein. Whey will reach your muscles more quickly while the amino acids from casein are absorbed more slowly into the bloodstream. There are advantages to delivering amino acids quickly to the muscles you’ve just worked. This gets them on board quickly to maximize protein synthesis.
Casein has its advantages too. Because casein is more slowly absorbed, it helps to reduce muscle breakdown after a workout. One way to get the advantages of both without using a supplement is to drink low-fat milk. A glass of low-fat milk supplies your body with around 28 grams of carbs and 8 grams of protein. The protein in milk is 80% casein and 20% whey. Maybe add a little whey protein to your low-fat milk?
The Bottom Line?
Post-workout nutrition is important for replenishing glycogen stores and for muscle repair, recovery and growth. Nutrient timing may also influence glycogen replenishment and muscle protein synthesis. Eat a protein-carbohydrate meal within 30 minutes to an hour after a workout. Wash it down with a glass of low-fat milk so you can benefit from both quick-absorbing whey and slower-absorbing casein. Remember, building the body you want has as much to do with nutrition (or more) as it does with exercise. So feed those tired muscles so they can recover and grow!
Phys Sportsmed. 2009 Jun;37(2):13-21. doi: 10.3810/psm.2009.06.1705.
Appl Physiol Nutr Metab. 2008 Feb;33(1):184-90. doi: 10.1139/H07-139.
National Strength and Conditioning Association. “Whey Protein vs Casein Protein and Optimal Recovery”
Journal of International Society of Sports Nutrition 5(15): 2008.
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