Prudent personal trainers know that both training stimuli and nutrient consumption affect hypertrophy gains. Training increases protein synthesis, but it may also activate muscle protein degradation. In the absence of properly-timed quality nutrition, these two can potentially cancel each other. Let’s explore this key physiological equation: Net Protein Balance (skeletal muscle mass) = Muscle Protein Synthesis – Muscle Protein Breakdown and how meal timing plays a role.
Training, Muscle Mass and Amino Acids
Training intensely plus proper nutritional intake will always encourage synthesis over degradation. Protein intake remains key in maintaining the quality and quantity of skeletal muscle mass, helping individuals remain strong throughout life. The performance of acute exercise enhances muscle protein remodeling by stimulating protein synthesis rates for several hours after each bout, further enhanced by consuming protein during the post-exercise recovery period.
Several reports have shown that amino acid utilization increases during exercise. As a result, whether resistance-based and aerobic in nature, exercise appears to temporarily depress muscle protein synthesis (MPS). Positive nitrogen balance occurs only when the body perceives an uptick in amino acid availability, at which point MPS significantly increases. Disagreements among professionals still exist as to whether amino acid feeding before or after resistance exercise promotes MPS optimally. Exercise training studies report that the stimulation in MPS seems better and more effective when the athlete consumes protein immediately after the exercise rather than several hours later. However, not every research study concurs…
The Leucine Link
The dual interaction between resistance exercise and dietary-protein-derived amino acid availability on the stimulation of MPS rates strongly correlates with the essential amino acid content of the ingested protein source. The branched-chain amino acid leucine figures prominently. The leucine content of a protein source causes the greatest impact on protein synthesis and muscle hypertrophy. Consumption of 3–4 g of leucine seems to promote maximum protein synthesis. This theory earned the nickname of the leucine threshold or trigger hypothesis, suggesting that the peak amplitude of blood leucine concentrations after protein ingestion holds the primary role in determining a powerful post-meal MPS response.
Leucine alone cannot modulate protein synthesis quite as effectively without the presence of insulin; adding the consumption of a simple carbohydrate source will elicit the slight insulin spike required. Consuming this combined supplement immediately post-workout (or within a 45-minute window following exercise) most effectively increases muscle protein synthesis and thus greater muscle hypertrophy and strength.
Isolated Proteins versus Whole-Food Meals
To date, the majority of the evidence regarding protein intake geared to accelerate and encourage MPS rates, including the aforementioned data on the leucine threshold, relates mainly to isolated protein sources. However, most athletes ingest whole food sources of protein along with other macronutrients post-workout. Emerging evidence demonstrates a promising role for the ingestion of whole foods – ideally a combination of lean protein and simple carbohydrates — as an effective nutritional strategy towards supporting muscle protein remodeling and recovery following intense exercise.
Consider Simple, Convenient Dairy
Milk consumption after exercise stands out as an easy and effective vehicle for attenuating the exercise-induced muscle damage associated with regular workouts. Surprisingly, milk offers excellent post-exercise rehydration, with an electrolyte panel similar to a majority of sports drinks currently on the market.
Similar findings have been made with chocolate milk, proven as an excellent choice for reducing muscle soreness and sustaining performance energy during. The beneficial effect of consuming chocolate milk largely relates to its blend of protein (8 grams/cup) and carbohydrates (12 grams/cup). This 2-prong approach enhances glycogen refueling as it supports muscle protein synthesis. For non-dairy consumers, simply bear in mind that ideal supplementation following resistance exercise should contain whey, or any other easily digestible protein source boasting at least 3 g of leucine per serving, paired with a fast-acting carbohydrate source such as maltodextrin or glucose.
How Critical is the Post-Workout Supplement Window?
The majority of serious weightlifters rank post-exercise intake as the most critical aspect of training; many athletes adhere to an anabolic “window of opportunity”, the limited time after training when proper protein-carb intake can optimize muscular adaptations. However, this cookie-cutter plan may not suit each and every body.
Naysayers offer plenty of science-based details which challenge this view on timing nutritional support towards ideal muscular development. Glycolysis, a process whereby enzymes anaerobically break down the glucose in our bodies to produce energy, creates close to 80% of the body’s ATP production for physical output (energy demands).
However, it appears to some professionals that the sense of immediacy of intake can apparently get tempered without the athlete losing much ground. Dr. Berardi and his team found that following a 60-minute cycle class, an appropriate protein-carb supply continued to effectively replenish glycogen stores even 2 hours later.
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Differences Within Exercise Formats
We must take into account the type of exercise in which an individual engages when attempting to perfectly identify timing of post-workout intake. Endurance sports lasting several hours, such as running a half-marathon, definitely demand immediate refueling. However, when engaging in a weightlifting program consisting of multiple sets of higher volume/frequency, returning the body to pre-training glycogen levels less than 100% would not leave the athlete depleted.
There’s some merit to these claims. According to Dr. Erin Glynn and her researchers, muscle protein synthesis increases in response to strength training much more than the concomitant muscle breakdown. They believe that, given the net protein balance equation referenced above, refueling quickly may not hold as much importance as once believed.
Science makes an exception when exercising from a fasted state. For those of your early-morning strength-training clients who choose to exercise on an empty stomach, refueling as soon as possible takes on more importance. Having not eaten (i.e., replaced glycogen availability) since last night’s dinner promotes a highly elevated rate of muscle breakdown, thereby stressing the importance of eating promptly following the gym session.
Given the dirth of inconsistent and also limited data on this debate (some culled from poorly-constructed experimentation), the ideal time frame for a post-exercise meal remains elusive. The choice rests with you and/or your clients. Differing opinions on this subject may never find scientific resolution. We do recognize how muscle tissue responds differently to each mode of exercise performed, as well as the uniqueness of each individual’s body/metabolism. Take these ideas into consideration, then enjoy your post-workout protein-carb meal when it best suits you. Whichever way you decide, strength training always works in our favor!!
Tell us about your experience with varying the time of post-exercise consumption. Has one method worked best for you?
References
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Cathleen Kronemer is an NFPT CEC writer and a member of the NFPT Certification Council Board. Cathleen is an AFAA-Certified Group Exercise Instructor, NSCA-Certified Personal Trainer, ACE-Certified Health Coach, former competitive bodybuilder and freelance writer. She is employed at the Jewish Community Center in St. Louis, MO. Cathleen has been involved in the fitness industry for over three decades. Feel free to contact her at trainhard@kronemer.com. She welcomes your feedback and your comments!
