One way that weight training enhances muscle growth is by stimulating the release of various anabolic hormones, such as testosterone and growth hormone. Along with another potentially anabolic hormone, insulin, they are profoundly affected by nutrition. For example, low-protein diets adversely affect the synthesis and release of insulinlike growth factor 1 (IGF-1), the active anabolic product of growth hormone. Without a large supply of amino acids, insulin has no anabolic activity at all. Conversely, the combination of high blood amino acids and insulin is quite anabolic.
The latter effect has led to the development of postworkout recovery drinks consisting of a fast-acting protein, such as whey, and a rapidly absorbed source of carbohydrate. That nutrient combination provides the greatest release of insulin following training and promotes amino acid entry into muscle. It also promotes the rate-limiting enzyme required for glycogen, the main fuel in muscle that powers anaerobic exercise such as weight training. Glycogen itself is produced from carbohydrates, which is another reason to include simple carbs in a postworkout drink. Glycogen can also be synthesized from other sources, such as lactate or even protein, but the process isn’t nearly as efficient as it is with carbs.
While the notion of taking a postworkout protein-and-carb drink is widely accepted by scientists as an efficient anabolic-response modifier in muscle, studies show that a preworkout protein-and-carb drink may work just as well or even better because of the increased blood flow into muscles that results from exercise. On the other hand, a pure protein drink may produce hypoglycemia, or low blood glucose, because of a heightened insulin release.
Taking in protein and carbs before training may also increase cortisol levels. Cortisol is a catabolic hormone released from the adrenal glands that is most often associated with muscle breakdown (although higher postworkout cortisol levels have a reverse effect in helping to supply energy for muscle recovery).
The precise effects on anabolic hormones of having a protein drink prior to weight training remained speculative until recently.1 Ten men, average age 23, all with at least five years of training experience, who’d taken no drugs or any supplements that would influence release of any type of anabolic hormone during exercise, participated in the study. Thirty minutes before training, one group took a protein drink containing 25 grams of whey and casein, and the other got a placebo. They all did sets of heavy one-rep squats, sets of 10-rep squats and four sets of 10-rep leg presses. They rested between sets two to three minutes.
Both groups had a protein-and-carb recovery drink following the workout. The workout began three hours after the subjects ate a 500-calorie breakfast of 21 percent protein, 66 percent carb and 13 percent fat. The postworkout drink contained the same 25 grams of milk-derived protein as the preworkout drink, but it also included 50 grams of carbohydrate.
The protein group showed lower levels of both GH and testosterone than the placebo group. The protein group, however, had higher blood insulin levels, but only during the first half of the workout, with a steady decline afterward until the subjects got the postworkout drink. The authors note that the elevated insulin produced by the preworkout protein drink likely led to decreased muscle breakdown and increased amino acid entry into muscle—in other words, a potent anabolic effect. The protein drink increased insulin to levels that would produce a maximal protein synthesis rate in muscle. The rapid release of amino acids from whey probably enhanced insulin’s anabolic activity.
The lack of growth hormone response in the protein group isn’t surprising; past studies show that you get the highest release of GH during a preexercise fasting state. Any nutrients in the blood blunt the release of exercise-induced growth hormone. Milk proteins are rich in branched-chain amino acids and glutamate, both of which have potent GH-suppressing effects during exercise.
The lower testosterone levels in the protein group were also expected. A high-protein diet is linked to lower levels of both total and free testosterone, as well as a decreased test response during exercise. That may result from a decreased testosterone synthesis, lowered secretion or increased clearance from the blood through its increased breakdown in the liver. On the other hand, since weight training promotes postworkout muscle protein synthesis, the lowered test level may merely reflect increased uptake into muscle, where the anabolic action is.
Research shows that weight training enhances increased androgen cell receptors in muscle, and testosterone interacts with those receptors, explaining the relative paucity of the hormone in the blood after exercise. Postexercise nutrients may also divert blood from the muscles to the gastrointestinal tract, masking or diminishing testosterone blood levels. The preworkout protein drink, by increasing insulin release, promotes the activity of androgen muscle receptors.
Other effects of the preworkout protein drink included a heightened postworkout energy expenditure that’s likely related to the higher energy requirements of muscle protein synthesis after the workout—which, by the way, is powered mainly by fat. The increased metabolic effect is also reflected in a higher resting energy expenditure two hours after the workout in the protein group. On the other hand, the lack of GH, coupled with the increased insulin release, also lowered postworkout fat oxidation.
What it all points to is that a preworkout protein drink increases insulin levels during the workout, which in turn results in less muscle breakdown, higher amino acid entry into muscle and possibly greater testosterone uptake into muscle—in short, an anabolic environment conducive to muscular growth.
©,2012, Jerry Brainum.Any reprinting in any type of media, including electronic and foreign is expressly prohibited.
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