Post-workout shakes, or "PWO shakes" as they are commonly referred to around internet forums, refer to the drinks that many gymrats will consume after some sort of workout in which resistance has been overcome. Generally, these are high-protein content shakes made from whey protein and some sort of solvent, usually water or low-fat milk. I've used everything from those bottled Starbucks frappuccinos to various fruit juices, depending on the situation.

During intense workouts involving resistance training, the body interprets overcoming a lot of heavy resistance as a stressor. Cortisol is released into the blood stream, causing a break down of body tissue - including muscle - in order to increase blood-sugar levels. This puts the body in a catabolic state, or a metabolic state in which tissue is broken down into smaller units for energy. This trend continues for several hours after resistance training has been completed. This is obviously the single most undesirable effect for someone lifting weights with the intention of building muscle.

Consuming food, particularly high-protein foods, immediately or shortly after training reverses this trend. Cortisol, among other things, causes the breakdown of muscle protein. Bringing an outside source of protein into the body aids in the rebuilding of muscle tissue after a catabolic workout, swinging the body's metabolism back to anabolic - or, a state in which body tissue (muscle) is being built from smaller units. PWO shakes make this process much more convenient. Most protein powders are made almost specifically to serve as a post-workout restorative in that they are fast-absorbing and pass into the blood stream very quickly. Whey protein's peak absorption occurs something like an hour after consumption.

Ideally, PWO shakes don't serve as the primary inducer for an anabolic state, merely as a fast way to stop or minimize catabolic effects until you can actually get real food into your body and start rebuilding tissue.

Depending on the intent of the consumer, PWO shakes can also include large amounts of carbohydrates to induce a stronger insulin response (insulin is an anabolic hormone, in that it signals the body to send nutrients into the liver and muscles), "healthy fats" like omega-9 fatty acids (found in olive oil), or calorie-dense foodstuffs, such as peanut butter, to aid in developing mass. Some of the real die hard folks I'm sure put electrolytes and extra vitamins in there to get an extra restorative kick out of their post-workout nutrition.

PWO shakes aren't just for people looking to build muscle. People wanting to lose or maintain weight and/or lose fat should also consume some sort of post-workout drink because 1.) catabolism results in the breakdown of both fat and muscle tissue, meaning that while food-deprivation post-workout might result in fat loss, it will also result in significant muscle loss which defeats the purpose of weight-training, and 2.) calorie intake is the primary controller of weight, and it's entirely feasible to make a low-calorie PWO shake. Most whey protein contains something around 100 calories plus or minus per serving.

There are some folks who put whey protein shakes in the same category as like, anabolic steroids, but I don't think they realize that whey protein doesn't introduce exogenous hormones or chemical signals into the body to induce some kind of "unnatural" physiological effect. I mean I guess since it's obviously a processed dietary supplement, some die hard whole foods-only types might not be too hot on it, but from a macronutrient standpoint, consuming whey protein is pretty much like eating a 10oz steak without the fat, the 500 calories, or the chewing.

sources:

- gymratting around

- there are about eight quadrillion billion thousand articles floating around everywhere that at least correlate high-protein diets to muscle building and while i love e2 and believe that high standards should be held for factual - ok fuck it, here's one: Paul GL. Dietary protein requirements of physically active individuals. Sports Med 1989; 8:154-176.

- Human Anatomy & Physiology. Marieb, Elaine N. 7th ed. Benjamin Cummings, 2006.

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