SCIENCE BEHIND THE 30-MINUTE WINDOW
Supporting optimum recovery from intense exercise (whether it is endurance or strength training) is one of the most important nutritional goals that we all face. The exact quantity of nutrients to consume all depends on how hard your previous exercise session was and of course, the time at which your next training session or competition is(1). Nonetheless, we should all take advantage of the “30 minute recovery window”, the immediate 30 minutes after exercise when our muscles are “primed” to recover our muscle glycogen stores as well as support muscle protein synthesis.
Recovery of muscle glycogen stores
One of the fundamental goals of recovery nutrition is to promote the recovery of muscle glycogen stores so that we can replenish the energy that we have just used and ensure we are ready to perform to our best in the next training session. The transport of glucose from the blood stream into our muscles is facilitated by a transport protein called GLUT4 and is also regulated by the hormone insulin. Fortunately, intense exercise primes GLUT4 to be active so that glucose transport into the muscle is increased in the immediate post-exercise period. Additionally, exercise increases our sensitivity to insulin thus meaning that more glucose can be transported into our muscles for the same dose of insulin. Collectively, the priming effects of prior exercise as well as high rates of muscle blood flow all ensure that our muscles have an enhanced capacity to replenish muscle glycogen in the initial 2 hour period post-exercise. Indeed, studies have shown that consuming carbohydrate within 30 minutes post-exercise enhances muscle glycogen resynthesis rates by almost 50% when compared with delaying carbohydrate feeding by 2 hours. The take home message is to consume at least 1.2 g/kg body mass of carbohydrate within 30-60 minutes of post-exercise(2).
Muscle protein synthesis
In addition to recovery of glycogen stores, it is also advised to consume high quality protein (especially leucine rich protein) within 30 minutes post-exercise. Indeed, intense exercise (whether it is endurance or strength) causes the proteins in our muscle to breakdown (i.e. protein degradation) essentially inducing a “catabolic state”(3). In contrast, consuming protein in the recovery period increases muscle protein synthesis so that it exceeds protein degradation therefore creating a positive protein balance. It is this positive protein balance that provides the conditions for our muscles to adapt to training. Delaying protein feeding by several hours post-exercise therefore induces a prolonged negative protein balance, conditions that can impair recovery and training adaptations(4). From a dosing perspective, protein feeding should be in the range of 20-40 g and liquid feeding can deliver amino acids to muscles quicker than solid foods(5).
Take Home Messages
- Muscles are most receptive to storing nutrients in the first 2 hours post-exercise. This is because prior exercise increases muscle blood flow, activates key transport proteins (e.g. GLUT4) and enhances our sensitivity to insulin.
- To take advantage of the recovery window, it is advised to consume 1.2 g/kg of carbohydrate and 20-40 g protein so as to maximise rates of muscle glycogen resynthesis and promote muscle protein synthesis. Delaying feeding by several hours can reduce rates of glycogen resynthesis and induce a negative protein balance, conditions that can impair your next performance attenuate training adaptations.
- Consuming carbohydrate and protein in fluid form is likely superior to solid sources as it can deliver amino acids to muscles quicker than solid foods and of course, fluid can also promote rehydration.
- Moore, D. R. (2015). Nutrition to support recovery from endurance exercise: optimal carbohydrate and protein replacement. Current Sports Medicine Reports, 14(4), 294-300.
- Ivy, J. L., Katz, A. L., Cutler, C. L., Sherman, W. M., & Coyle, E. F. (1988). Muscle glycogen synthesis after exercise: effect of time of carbohydrate ingestion. Journal of Applied Physiology, 64(4), 1480-1485.
- Rowlands, D. S., Nelson, A. R., Phillips, S. M., Faulkner, J. A., Clarke, J., Burd, N. A., & Stellingwerff, T. (2015). Protein-leucine fed dose effects on muscle protein synthesis after endurance exercise. Medicine & Science in Sports & Exercise, 47(3), 547-555.
- Levenhagen, D. K., Gresham, J. D., Carlson, M. G., Maron, D. J., Borel, M. J., & Flakoll, P. J. (2001). Post-exercise nutrient intake timing in humans is critical to recovery of leg glucose and protein homeostasis. American Journal of Physiology-Endocrinology And Metabolism, 280(6), 982-993.
- Macnaughton, L. S., Wardle, S. L., Witard, O. C., McGlory, C., Hamilton, D. L., Jeromson, S., & Tipton, K. D. (2016). The response of muscle protein synthesis following whole‐body resistance exercise is greater following 40 g than 20 g of ingested whey protein. Physiological Reports, 4(15), e12893.