Translate / Tradutor

Friday, 13 September 2013

Anabolic Window, myth or true?


Anabolic window, myth or true?

Most people claim that building strategical meals and eating the right combinations of nutrients throughout the day may bring great results when it comes to body composition. That means having proper ratios of carbs and protein during certain times of the day, especially before and after an exercise session. It is believed that the post-workout period is probably one of the most critical when it comes to nutrient timing. Eating an appropriate amount of nutrients after that period not only starts the rebuilding of damaged muscle tissue and replenishment of energy stores, but also does a super-compensated fashion, which improves both body composition and exercise performance.
A lot of researchers have mentioned about the possible existence of an anabolic window of opportunity.
But what does anabolic window mean?
According to my research and just like the name says, anabolic window is defined as a window of opportunity, which supposedly exists during a limited time right after training to enhance training-related muscular adaptations.
Glycogen repletion
The main goal of traditional post-workout nutrient timing recommendations is to replenish glycogen stores, which is depleted after a training session. We all know that glycogen is indispensable to an optimal resistance training performance. Typical high volume bodybuilding-style workouts involving multiple exercises and sets for the same muscle group would deplete the majority of local glycogen stores. Glycogen availability also has been shown to mediate muscle protein breakdown.
Studies have shown a super-compensation of glycogen stores when carbohydrate is consumed right after an exercise session, and delaying its consumption by only 2 hours diminishes the rate of muscle glycogen re-synthesis by as much as 50%. There are also some indications that adding protein to a post-workout carb meal may enhance glycogen re-synthesis.
It is important to mention that the urgency of glycogen re-synthesis is greatly diminished when one is not doing high-intensity resistance training.
Protein breakdown
Another alleged benefit of post-workout nutrient timing is in regards to diminishing muscle protein breakdown. This is mainly achieved by spiking insulin levels, as contrary to increasing amino acid availability. Studies have shown that muscle protein breakdown is only slightly increased immediately post-exercise and then rapidly rises thereafter. In the fasted state, muscle protein breakdown is significantly heightened at 195 minutes following resistance exercise, resulting in a net negative protein balance. These values are increased as much as 50% at the 3 hour mark, and elevated proteolysis (or protein breakdown into amino acids) can persist for up to 24 hours of the post-workout period. Insulin has known anabolic properties; however, its primary impact post-exercise is believed to be anti-catabolic. Muscle hypertrophy is nothing but the difference between myofibrillar protein synthesis and proteolysis (protein breakdown). When protein breakdown is decreased, it would possibly improve accretion of contractile proteins and therefore, enable greater hypertrophy. With that being said, it seems logical to conclude that consuming a protein-carbohydrate supplement following exercise would promote the greatest reduction in proteolysis since the combination of the two nutrients has been shown to elevate insulin levels to a greater extent than carbohydrate alone.
Contradictions?
There is another aspect to be considered. The inclusion of carbs to a protein dose for instance, could cause insulin levels to peak higher and stay elevated even longer. Therefore, the recommendation for lifters to spike insulin post-exercise is somewhat questionable. The classical post-exercise goal to rapidly reverse catabolic processes to promote recovery and growth may only be applicable in the absence of a properly built pre-exercise meal.
In addition to that, there is evidence about the impact of protein breakdown on muscle protein accretion being exaggerated. Studies found that the post-exercise anabolic response linked to combined protein and carbohydrate consumption was mainly due to an elevation in muscle protein synthesis with only a minor influence from reduced muscle protein breakdown. These results were observed regardless of the amount of circulating insulin levels. Therefore, it remains questionable as to what, if any, positive effects are realized with respect to muscle growth from spiking insulin after resistance training.
“Despite claims that immediate post-exercise nutritional intake is essential to maximize hypertrophic gains, evidence-based support for such an ‘anabolic window of opportunity’ is far from definitive. The hypothesis is based largely on the pre-supposition that training is carried out in a fasted state. During fasted exercise, a concomitant increase in muscle protein breakdown causes the pre-exercise net negative amino acid balance to persist in the post-exercise period despite training-induced increases in muscle protein synthesis. Thus, in the case of resistance training after an overnight fast, it would make sense to provide immediate nutritional intervention–ideally in the form of a combination of protein and carbohydrate–for the purposes of promoting muscle protein synthesis and reducing proteolysis, thereby switching a net catabolic state into an anabolic one. Over a chronic period, this tactic could conceivably lead cumulatively to an increased rate of gains in muscle mass” (Aragon, A. & Schoenfeld, B.).
Health Uncut also posted a very interesting article about anabolic window, which concludes:
“A study investigated the consumption of 35g of sugar and 6g essential amino acids in liquid form immediately before or after resistance training. In the group consuming the liquid pre-training, it was found that amino acid delivery and uptake was far greater during training and for one hour after; the critical period when it comes to AMPK elevation. It is noteworthy that this study was conducted in a lab setting on fasting individuals. Thus, it is not evidence to support the need to consume supplement shakes immediately before training, but instead to illustrate the importance of ensuring the presence of nutrients in the blood to promote positive nitrogen balance and prevent the AMPK rise. With resistance training sessions usually limited to an hour or under, this is just as easily achieved by ingesting a carbohydrate and protein-containing-meal circa two hours before training. Switching from the lab to a real world setting this is aptly illustrated in a study of resistance trained individuals, which demonstrated that those already on a high protein diet who consume protein supplements directly before and after training see no extra benefit compared to those who took it morning and evening.
It appears that the anabolic window as it is traditionally perceived is fabled. It is, however, paramount to ensure you have ingested protein and carbohydrates in a timely manner before training. The timing of this consumption is important; giving long enough that the meal is ingested before commencing training and preventing stomach distress, yet, being close enough to ensure that the nutrients are still in the blood to prevent the exercise induced AMPK rise. Whether this is achieved through diet or supplements is the choice of the user.”

No comments:

Post a Comment