My first foray in structured exercise -- Get in Shape, Girl! (GISG) cassette tapes. Mom, feeling bad I was barely fitting into my elasticized Pretty Plus jeans from Sears, invested in a kit of wrist and ankle weights with matching sweatbands and leg warmers and left me to it. After I would finish one of my GISG workouts, I'd wander to the kitchen feeling famished. Mom would call from the other room, "Don't spoil your hard work."
Now, if the myth that one should fast post-exercise or risk undoing all their hard work wasn't faulty enough, the notion that every exercise requires a protein smoothie chaser is equally misguided.
Students often express sudden desires for ice cream mid-workout. Their lustful eyes set on the distance as they dream of a post-workout cocktail. This isn't surprising. In fact, I'd be worried if my high intensity exercisers weren't hungry after a particularly grueling sweat session. Why?
Let's explore the science behind what happens during exercise --
The first thing to remember is that ANY muscle contraction/force exertion is due to a molecule called adenosine triphosphate (ATP). The ATP must always be produced, but how it is produced depends on the form of exercise being performed.
If we look at exercise on a spectrum. from one extreme, such as an explosive 3-foot box jump, to the other, a prolonged, leisurely stroll, the energy system varies.
There are three energy systems that produce ATP:
ATP-PC (high power, short duration),
Glycolytic (moderate power/short duration), and
Oxidative (low power/long duration).
All are available and will occur at the outset of any activity, but what dictates which one (or two) is relied upon the most is the effort required.
While an explosive, one-time movement such as a standing long jump or the aforementioned box jump requires maximal effort, you will not become fatigued from a single exertion. However, jump multiple times and eventually you will get tired. Going all out for as long as possible will deplete immediate ATP stores, then glycolytic stores. Continuing effort must be fueled by the oxidative system at a lower intensity, all other factors being equal. The most pure aerobic activity that exists is sleeping or lying comatose.
The oxidative system provides energy much more slowly than the other two systems, but has an almost unlimited supply (in the form of adipose -- that stuff you can pinch around your waistline). The oxidative system by itself is used primarily during complete rest and low-intensity activity. It can produce ATP through either fat (fatty acids) or carbohydrate (glucose). This is where the "fat-burning zone" myth comes from, but that's a post for another day.
If the form of exercise determines the energy system employed, it follows that it should also dictate the form of post-exercise nutrition required.
Generally, post-workout nutrition has three specific purposes:
Decrease protein breakdown; and
Increase protein synthesis.
In other words, your post-exercise nutrition should:
These points are important, because in the absence of proper nutrition muscles will be slow to heal, leading to prolonged soreness, increased risk of injury or strain, as well as contribute to decreased bone mass and suppressed immune function.
When we exercise intensely, we damage the muscle tissue at the micro-level (muscle protein breakdown) and use fuel via one or several of the systems described above. What makes us stronger and leaner through exercise is the process by which the muscle rebuilds -- muscle protein synthesis.
Muscle growth (hypertrophy) occurs when a positive protein balance can be established during recovery. In other words, when we make sure we have enough raw materials available for protein synthesis to occur post-exercise, so that it doesn’t lag behind.
But with all this talk of protein, it is important to remember that protein is not our only demand post-exercise. During intense exercise, the body becomes depleted of muscle glycogen, as well. Carbohydrates are therefore an equally important consideration to the composition of your post-exercise nutrition.
What you should know about post-exercise nutrition is:
Availability: the raw materials, or amino acids and simple carbohydrates, need to be present and readily available to the body for quick and easy consumption. Pair your lean protein with simple carbs, or if you must rely on protein shakes, incorporate the ones that have a balance between protein AND carbs, since we don't need just protein here (remembering the need for glucose mentioned previously). And I'm just going to say it now -- if you are going to eat a piece of cake, well you'd be better off eating it after intense exercise because of all those simple, quick-burning sugars.
Timing: Often referred to as the "window of opportunity," this is expressed as the time after exercise during which the muscles are primed (side note: primed suggests the muscles have been broken down, more on this to follow!) to accept nutrients to build and repair. Research suggests that while protein synthesis persists for at least 48 hours after exercise, it’s most important to get postworkout nutrition immediately, and within 2 hours afterwards.
Now, back to the topic of availability of raw materials. So what should you eat?
As mentioned, you should be seeking to balance protein to aid in protein sythesis with carbohydrates to replenish muscle glycogen and and to enhance the role of insulin in transporting nutrients into cells. Now, you could get that from a freshly prepared meal, but the odds that you have the time and appetite immediately following exercise are often low. Not to mention the speed at which you may be able to digest a complete meal is considerably lower than some of the more convenient, ready-to-drink options.
If you are incorporating a post-exercise shake or smoothie, look to include ones that have a balance of protein (e.g. concentrates, hydrolysates, isolates) with rapidly digesting carbohydrates (e.g. maltodextrin, dextrose, glucose). Such a blend will accelerate recovery by utilizing insulin for nutrient transport into cells, result in rapid absorption and digestion, and will be more easily tolerated post-exercise.
But ignore this notion that more is always more. Data indicate that it may only take about 20 grams of protein after a workout to maximally stimulate muscle protein synthesis.
Now, let's go back to the side note on when muscles are primed for post-exercise nutrition. In other words, which workouts qualify?
Save your post-exercise nutrition for instances where you are weight training, incorporating explosive plyometric exercise, doing interval work, or endurance training for periods of 45 minutes or longer. You do not need a post-exercise shake if you are walking the dog, putzing around in the yard, or riding your bicycle to a friend's house.
If, however, exercise is being done in the interest of promoting fat loss, go easy and invest in a BCAA (branched chain amino acid) supplement instead. In order for fat loss to occur, there needs to be some calorie deficit. Prioritize the consumption of healthy meals over elaborate post-exercise shakes. After all, the use of post-exercise nutrition is in the interest of enhancing performance and recovery between sessions.
To summarize and conclude:
You can either make your own post-workout drink or find a ready-to-drink option that contains rapidly digesting carbohydrates (e.g. maltodextrin, dextrose, glucose, etc) and proteins (e.g. protein concentrates, hydrolysates or isolates).
If priority #1 is to lose body fat, use only BCAAs as a workout drink, from 5 to 15 grams per hour of training according to bodyweight (200 pounds or more = closer to 15 grams, 200 pounds or less = closer to 5 grams).
Disclaimer: Fit Club is not a medical doctor and the information contained herein should not be taken as medical advice. These are not intended to diagnose, treat, cure or prevent any health problem. Recommendations by Fit Club are not intended to replace the advice of a physician or health professional. Please consult your physician or a health professional before beginning any diet or exercise program.