By Sarah Katz, Graduate Student in Dietetics, Coordinated Program
It is common practice to reach for a protein shake immediately after a workout, but do you know why?
Protein is necessary for muscle growth and recovery. Amino acids are the building blocks of protein that can be made in the body (i.e., non-essential amino acids) or consumed in the diet (i.e., essential amino acids). The essential amino acids, specifically, have been found to stimulate muscle protein synthesis, therefore, enhancing the benefits of resistance training.
So why does timing matter?
Nutrient timing is a strategy that individuals may use to optimize the effects of their training. Consuming nutrients at specific times is thought to improve performance, recovery, and adaptation to exercise stimuli. The post-workout period is often considered the most critical part of nutrient timing, and the “anabolic window” is a term that generally represents the 30-60 minutes after exercise that is suggested to be the optimal time to enhance muscular gains and recovery through nutrition. After a workout, muscle fibers are damaged and glycogen stores are low. Consuming protein and carbohydrates prevent further breakdown by initiating muscle protein synthesis and replenishing glycogen stores in the body. This association leads many people to suspect that consuming protein immediately after exercise is necessary to achieve maximal gains from the gym; however recent evidence suggests this may not be the case.
What do scientists say about the anabolic window?
We know that protein intake is beneficial to resistance training, but the specific timing of ingestion has remained a topic of debate. While the common belief is that the anabolic window ceases within one-hour post-exercise, evidence has suggested that this window may extend to the 5-6 hours surrounding training. The timing of post-exercise nutrition is largely dependent on what state the individual is training in. If exercise occurs in the fasted state, for example, the anabolic window gets much tighter compared to when someone trains in the fed state.
To further investigate this idea, a randomized controlled trial was performed in which resistance-trained men were assigned to either a pre-exercise or post-exercise protein supplement. After 10 weeks of consistent strength training and timely protein consumption, both groups had similar changes in body composition and strength. These findings contrast the narrow anabolic window theory, and instead, suggest that pre-exercise protein is equally effective in employing muscle strength, growth, and recovery when combined with substantial resistance training.
Though there is evidence that post-workout protein is important for muscle strength and growth, there is also evidence that pre-workout protein can eliminate the need for immediate post-exercise protein consumption. The findings suggest that protein ingestion can be based on other factors, such as preference, tolerance, convenience, and availability. The recommended amount of protein to consume surrounding training is 0.4-0.5 g/kg of lean body mass. For most individuals, 20-40 grams of protein is adequate. These needs can be met by consuming one serving of whey protein, four ounces of animal protein, or one cup of mixed plant proteins, such as rice and beans.
Overall, the evidence suggests that the anabolic window may not be as small as we once thought. The only time that post-workout nutrition is keenly important is when training is performed in the fasted state. If a pre-workout meal is consumed, post-workout nutrition does not need to occur as soon as you re-rack your weights. Though nutrient timing is important in some cases, total daily protein intake as well as usual protein intake are equally, if not more, important to muscular health. Nonetheless, there is little to no risk in consuming a protein shake immediately after a workout if daily protein intake is still in the acceptable range, so if you enjoy a shake post-workout, consume it, but for the taste and enjoyment of it rather than the perceived health benefits.