14 Aug Does the Anabolic Window Truly Exist?
RESEARCH TEAM QUESTIONS #2
Anabolic Window…. (1-hour, 2-hours, None at all?)
Attempting to research and or decipher research centered around nutrition and it’s measurable significance when related to athletic performance can be difficult and some what ambiguous. The trouble with nutritional data is that the factors affecting the results can be so vague and limiting that the data can be skewed in truly any direction the researchers see fit. Hence the plethora of privately funded research that takes place in the dietary supplement industry. This issue has led to hundreds of “fad” diets backed by poorly designed research studies providing highly subjective information while attempting to seclude actual facts (i.e. much of the vitamins and mineral supplementation we see available today). Apologies for the overly opinionated comments I am merely trying to elude to how difficult nutrition can be to study. Even when all intentions are positive and the researchers concern are grounded in desire for investigating the truth; there still lies the inevitable factor that the intake of nutrients can effect each individual grossly different than the next.
The question we were posed was,
“Does an anabolic window really exist?”
Perhaps the most prominent question in the world of athletic performance with regard to macronutrient manipulation is the critical understanding of pre and post competition and or workout nutrition?
This question is spurred from a general consensus or belief in the idea that an “anabolic window” exists post workout. In addressing these topics I will attempt to answer (a) what is the anabolic window, (b) does it actually exist, (c) if it does how long does the window last, (d) and how important is pre-exercise nutritional intake.
WHAT IS THIS “ANABOLIC WINDOW?”
Macro and micronutrient timing has been widely researched and reviewed over the past two decades, especially when concerned with their intake surrounding a conditioning or competition event. Several researchers (3,5,9) have suggested or made reference to an idea of an “anabolic window” following a workout or competition event. These references are made with regard to the goal of maximizing an athlete’s exercise-induced muscular adaptations post workout (7). Some even suggest that this introduction of nutrients immediately following a training event can maximize improvements in body composition when related to lean-body mass (6). However, this topic has provide much controversy in the nutritional world and has led to many conflicting and disputing research studies.
The true issue with deciphering the relevance, timing, and or length of the “anabolic window” is that most case studies involving its relevance were conducted under the assumption that exercise or competition is performed in a fasted state (1). Thus, because in a fasted state muscle protein breakdown can be higher than norms, the addition of resistance exercise will likely increase these decremented levels. Therefore, exercise performed in a fasted state would absolutely need post-nutrient intake to combat the current catabolic state (8).
With such conflicting research and evidence some researchers have begun to suggest that pre-workout dietary practices maybe equally or even more important that post workout consumption (13). In addition Burd, Tang, Moore, and Phillips (2009) and Yang et. al., 2012 suggested that age and training level greatly affect the absorption and breakdown of protein and glycogen pre and post exercise bouts (2, 14).
LET’S TAKE A STEP BACK THOUGH…WHY IS NUTRIENT
INTAKE SO IMPORTANT PRE AND POST WORKOUT?
During exercise or competition there is generally a huge need for energy and musculature activation. Due to these two necessities both the bodies energy stores as well as it’s muscular tissue become depleted and damaged (primarily through the hydrolysis and oxidation of glycogen and amino acids). This intense event must be circumvented or combatted with an ingestion of proper nutrient values following and sometimes even during it’s existence. Therefore, post workout dietary requirements have become the main focus of many research studies with the ultimate goal of understanding how and when to attempt to restore energy store levels and begin the rebuilding of musculature tissues. Researchers believe that there is a distinct period post workout or competition in which the body will replenish and restore in a super compensated fashion in an attempt to enhance both body composition and future exercise performance (1).
Hence, the inception of the idea of an “anabolic window.”
Lambert and Flynn (2012) found that glycogen was responsible for approximately 80% of ATP production during a resistance training event (10). In addition, Macdougal et. al., (1999) and Robergs et. al., (1991) found that exercise intensity directly affected a reduction in glycogen stores (11, 12). Thus, suggesting a grave need for post workout replenishment of glucose and or protein nutrients (i.e. the anabolic window). However, as mentioned earlier Tipton et.al., (2007) found significant evidence that pre-workout consumption of 20g of whey protein greatly increased (4.4 times the normal levels) muscular protein synthesis (MPS) and that these pre-exercise levels did not fall back to normal levels for 3 hours following an hour of resistance training (13). Furthermore, Kumar, Atherton, Smith and Rennie (2009), found that exercising in a fasted stated presented elevated pre-exercise levels of muscle protein breakdown (i.e. a catabolic state (degradation or breakdown state)) (8). This rise elevated greatly throughout the workout and remained significantly raised for approximately 200 minutes post workout. Thus suggesting further research needs to be conducted into the importance of pre-exercise consumption and the resulting effect on post workout consumption.
The furthering of athletic performance (i.e. hypertrophy or muscular growth) is dependent on the body being in an anabolic state (growth state). One of the main limiting factors of remaining in an anabolic state is a rise in AMP-activated protein kinase (AMPK) as it attempts to limit anabolic pathways (i.e. protein synthesis) by stimulating the need for energy producing pathways such at glucose transport (1). Creer et. al., (2005) suggested that the phosphorylation of protein kinase is largely dependent on pre-exercise levels of glycogen (4). Again, this may suggest the ability to impair or even refute the existence of an anabolic window with proper pre-exercise dietary practices.
OK…… SO, THE “ANABOLIC WINDOW” MIGHT EXIST? WHAT ABOUT PRE- WORKOUT INTAKE?
So, we now know that main limiting factors affecting the existence, length, and significance of an “anabolic window,” will likely be an athletes age, training level, workout intensity and the most important being their pre-workout consumption.
Aragon and Shoenfeld (2013) provide much evidence suggesting that pre-workout consumption of both a fast absorbing carbohydrate and protein substrate would elicit elevated levels of muscular protein synthesis during and post workout (1). While this data would also need further research is does suggest the idea that pre-workout dietary practices maybe just as important if not more important than post-workout practices.
It would be my suggestion that to follow the advice of Aragon and Sheonfeld (2013) and minimize the gap between dietary intake to no longer than 2-3 hours apart surrounding your workout. With this practice it would be the hope that your pre and post workout muscle protein synthesis and glycogen levels should remain high. Until more research is available it will likely be wise to consume both pre and post a fast absorbing carbohydrate and protein substrate. According to research the recommended dose for hypertrophy is .8-2.0 g/kg of bodyweight for protein and as high as 4g/kg of carbohydrate (1).
1. Aragon, A. A., & Schoenfeld, B. J. (2013). Nutrient timing revisited: is there a post exercise anabolic window? The Journal of the International Society of Sports Nutrition, 10(5), 1-12.
2. Burd NA, Tang JE, Moore DR, Phillips SM: Exercise training and protein metabolism: influences of contraction, protein intake, and sex-based differences. J Appl Physiol 2009, 106(5):1692-701.
3. Candow DG, Chilibeck PD: Timing of creatine or protein supplementation and resistance training in the elderly. Appl Physiol Nutr Metab 2008, 33(1):184-90
4. Creer A, Gallagher P, Slivka D, Jemiolo B, Fink W, Trappe S: Influence of muscle glycogen availability on ERK1/2 and Akt signaling after resistance exercise in human skeletal muscle. J Appl Physiol 2005, 99(3):950-6.
5. Hulmi JJ, Lockwood CM, Stout JR: Effect of protein/essential amino acids and resistance training on skeletal muscle hypertrophy: A case for whey protein. Nutr Metab (Lond). 2010, 7:51.
6. Ivy J, Portman R: Nutrient Timing: The Future of Sports Nutrition. North Bergen, NJ: Basic Health Publications; 2004.
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8. Kumar V, Atherton P, Smith K, Rennie MJ: Human muscle protein synthesis and breakdown during and after exercise. J Appl Physiol 2009, 106(6):2026-39
9. Kukuljan S, Nowson CA, Sanders K, Daly RM: Effects of resistance exercise and fortified milk on skeletal muscle mass, muscle size, and functional performance in middle-aged and older men: an 18-mo randomized controlled trial. J Appl Physiol 2009, 107(6):1864-73.
10. Lambert CP, Flynn MG: Fatigue during high-intensity intermittent exercise: application to bodybuilding. Sports Med. 2002, 32(8):511-22.
11. MacDougall JD, Ray S, Sale DG, McCartney N, Lee P, Garner S: Muscle substrate utilization and lactate production. Can J Appl Physiol 1999, 24(3):209-15.
12. Robergs RA, Pearson DR, Costill DL, Fink WJ, Pascoe DD, Benedict MA, Lambert CP, Zachweija JJ: Muscle glycogenolysis during differing intensities of weight-resistance exercise. J Appl Physiol 1991, 70(4):1700-6.
13. Tipton KD, Elliott TA, Cree MG, Aarsland AA, Sanford AP, Wolfe RR: Stimulation of net muscle protein synthesis by whey protein ingestion before and after exercise. Am J Physiol Endocrinol Metab 2007, 292(1):E71-6
14. Yang Y, Breen L, Burd NA, Hector AJ, Churchward-Venne TA, Josse AR, Tarnopolsky MA, Phillips SM: Resistance exercise enhances myofibrillar protein synthesis with graded intakes of whey protein in older men. Br J Nutr 2012, 108(10):1780-8