Muscular Development|August 2020
Brad Schoenfield
For many years, the concept of a “postworkout anabolic window of opportunity” has been taken as gospel by those in the bodybuilding community. Simply stated, the “anabolic window” hypothesis postulates that a limited time exists after training to optimize training-related muscular adaptations – generally believed to be less than an hour after completion of an exercise bout.2,4,5 According to popular belief, consuming the proper ratio of nutrients during this critical time period not only facilitates muscle protein accretion, but it does so in a supercompensated fashion that maximizes the hypertrophic response to lifting – delaying protein intake by a matter of minutes after this time period is purported to seriously compromise muscular gains. Some researchers have proposed that the timing of nutritional intake is even more important to muscle growth than the absolute daily consumption of nutrients.2 Bold claims indeed!

To get a handle on the topic, let’s see what research says on the topic.

There is some evidence showing superior increases in muscle protein synthesis when amino acids are ingested in close proximity to the conclusion of exercise as opposed to delaying consumption. One such study found significantly greater acute protein accretion when beagle dogs consumed amino acids immediately following 150 minutes of treadmill running compared to two hours post-exercise.9 Although intriguing, we need to take these findings with a large grain of salt; an animal trial using aerobic training is not exactly indicative of the anabolic response of hard training lifters.

Another study carried out in human subjects by Levenhagen et al.7 showed that lower body and whole-body protein synthesis was increased significantly more when protein was ingested immediately versus three hours after exercise. Problem is, the training involved moderate intensity, long-duration aerobic exercise. This raises the distinct possibility that results were attributed to greater mitochondrial and/or sarcoplasmic protein fractions as opposed to synthesis of contractile elements. Let’s face it, long-duration aerobic exercise is not much of a muscle-building activity. Conversely, Rasmussen et al.10 investigated the acute impact of protein timing after resistance training – without question, a better indicator of synthesis of muscle contractile elements. In this study, no significant differences were seen in the protein synthetic response after consuming nutrients one versus three hours post-exercise. It should be noted that measures of acute muscle protein synthesis do not necessarily correlate with muscular gains achieved from consistent lifting8, so results from these studies need to be interpreted with caution. Ideally, the effects of protein timing can best be determined by long-term training studies that measure actual muscle growth.


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August 2020