Muscle Up with the “Protein Window”

2014-01-15T15:00:05+00:00 January 15th, 2014|Athlete Nutrition, Energy, Protein|
muscle arm

The right kind and right amount of protein after a workout supports maximal muscle synthesis.

You’ve just finished pushing yourself beyond your limits at the gym. It’s that euphoric time when you celebrate your victory over the voice inside your head that tempted you to abort mission on working out in the first place. You welcome the screaming after-burn from your decimated muscle because it represents one thing: change to your body that is sure to come, change for the better. But what if nutritional science offered you a way to take your hard-fought training to the max? Call it a short window of opportunity to make the most of your workout and boost muscle gains.

Enter the “protein window”—the 30 minutes following an intense bout of exercise is that short, sweet window of opportunity where you can capitalize on your hard work to the greatest degree. The tough part is done. Now to get the most bang for your bench sets, you need to feed your body. Getting the right protein in the right amount after a workout will maximize your muscle gain and recovery. After all, failing to take advantage of the protein window is like working a 40-hour week and never cashing your paycheck.

What happens during the “protein window”

In the short period following a workout, your body is extremely sensitive to nutrients. This is directly related to the energy demands of exercise and the force placed on contracting muscle (1). During a hard training session, the body is fueled by energy from fat as well as sugar stored around muscle (glycogen). As working muscle burns through glycogen reserves, the hormone cortisol is released. Cortisol acts as a messenger to tell your liver to start making sugar from protein. Most of the protein that is used to make sugar comes from muscle, which is broken down when cortisol is high. Cortisol is known as the “stress hormone” and it tends to run high during stressful periods of fuel shortage.

Because high cortisol causes muscle to break down, it is necessary to lower levels as quickly as possible following a workout. Eating fast-absorbing whey protein and carbohydrate (sugar) within 30 minutes of exercise is the best way to do this (1). During this time blood flow to muscle is still high, resulting in quick delivery of nutrients (2). The body senses repletion of these nutrients and rapidly changes from a state of breakdown to a state of rebuilding and replenishment. This is the main goal of post-workout nutrition. By eating protein along with a source of carbohydrate directly after exercise, cortisol and muscle breakdown stops and muscle growth, recovery, and glycogen repletion starts (1,3).

The right protein, the right amount

After exercise your body is like a sponge. The key to optimizing muscle synthesis and recovery is getting the right type of protein in the right amount during the protein window. A fast absorbing protein that’s high in branched-chain amino acids (BCAAs), particularly leucine, will maximally stimulate pathways that activate muscle synthesis. Whey protein absorbs faster than other sources of protein, making it quickly available to muscle (4). In addition, it’s rich in BCAAs and leucine, making it a superior trigger for muscle growth. By eating about 25 to 40 grams of whey protein after your workout, muscle synthesis can be maximized (2).

Eating carbohydrate after exercising is also important, as it will rapidly lower cortisol while refilling the glycogen tank. Not only is the body sensitive to protein after exercise, but it’s also sensitive to carbohydrate (3). The post-workout period is the perfect opportunity to refuel.

IsaPro: Your go-to post-workout protein

By eating quality whey protein within 30 minutes of a workout, you can take advantage of your hard work and gain more muscle, faster. IsaPro is the perfect post-training protein. By pairing IsaPro with a carb source such as fruit or oats, you will get the body you want and the energy you need.

What if IsaLean Pro has been your go-to after a workout during the protein window? You’re not causing any harm, that’s for sure. And there’s definitely some muscle-building benefit to this as well, but the lack of fat and fiber in IsaPro paired with a carb source means that the protein and carb get to your muscles faster and more efficiently. It may be a matter of personal preference, but if maximum muscle building is your goal, stick with the straight protein (IsaPro) and carb.


  1. Ivy J, & Portman, R. (2004). Nutrient timing: The future of sports nutrition. Laguna Beach, CA: Basic Health Publications, Inc
  2. Hulmi JJ et al. Effect of protein/essential amino acids and resistance training on skeletal muscle hypertrophy: A case for whey protein. Nutr Metab (Lond). 2010 Jun 17;7:51.
  3. 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. doi: 10.1186/1550-2783-10-5.
  4. Phillips SM et al. The role of milk- and soy-based protein in support of muscle protein synthesis and muscle protein accretion in young and elderly persons. J Am Coll Nutr. 2009 Aug;28(4):343-54.