The Post-Workout Nutrition Debate…Musings From Ben Greenfield

I’ve been doing a bit of forum posting and thinking about post-workout nutrition…I read an article over at Tri-Fuel. Here’s what the article said:

What do you think is the most crucial time of a training session?  Is it the first few minutes, the very end, the warm-up, or somewhere in the middle of your workout that is the most important?  It may surprise you to know the most important time is the 30 minutes directly after your workout is finished.

The time from your warm-up to the conclusion of your workout is obviously important.  Improper form, too low an intensity, too high an intensity, unsafe behavior, and other factors can ruin the effectiveness of a workout.  But even if do all of that perfectly, you can still negate the benefits of a workout by not using the 30 minute window to replenish nutrients lost during your training session.

During a training session you are taxing your body and using up its energy stores (glycogen).  Once your workout is finished, you must replenish what you lost in order for your body to begin the process of repair.  In the 30 minutes immediately following your workout, your insulin sensitivity is at its highest and when your body is in this state, whatever nutrients you take in will be easily transported directly to your muscles, liver, and wherever else it is needed.  You will suck it up like a sponge.

If you do not eat or drink the right things soon after your workout, the window of opportunity will close and it will take you much longer to replenish glycogen stores and other nutrients.  This will dramatically increase the time it takes for you to recover from that workout, decrease the performance benefit of the workout, and affect your next workouts.  The more recovery time between workouts, the fewer workouts you can do in a period of time.  Fewer and lower quality workouts means less opportunity for fitness gains and slower race times.  Can you see why post workout nutrition is so important?

Now you know why it’s important, but what should you eat or drink after a workout?

The three things you need to focus on replenishing after a workout are muscle glycogen, water, and electrolytes.  To replace muscle glycogen, you should consume something with easy to digest carbohydrates, about 1 – 1.2 grams per pound of body weight.  Simple to digest carbs include some fruits, sports drinks, white bread, simple sugar, etc.

To aid in the absorption rate of the glycogen and prevent muscle catabolism (breaking down muscle tissue for energy), 10-20 grams of easy to digest protein is ideal.  Stick with whey protein for this, or even better, hydrolyzed whey, which is already pre digested and made for easy absorption.  You can find whey protein at any nutrition store.

To replenish electrolytes, a sports drink is your best bet unless you are planning on eating a salty meal soon after your workout.  Electrolyte is basically a fancy word for sodium or salt.

You should continue the carb, protein, electrolyte consumption every two hours or so until your next major meal.  If I know I am eating an hour or two after my workout, I find that chocolate milk is a great post workout drink.  It has sugar in the milk and the chocolate to replace muscle glycogen and protein in the milk to aid in absorption.

You can get away with a bad warm-up, bad form, or improper intensity to some extent and still have a good workout, but failing to consume proper nutrition can make your workout a waste of time, and in some cases, even damaging.  Just remember the 30-minute window of opportunity and plan ahead to make sure you get proper nutrition in before the window closes.

So initially, here was my response:

After that, I received some questions about how and what *should* be eaten post-workout, after regular workouts, after distance workouts, etc…so I wanted to share with you my response to that.

First of all, let me begin by saying that David Warden will graciously be allowing me to guest host an episode of the Tri Talk podcast to discuss the post-workout feeding issue in more detail. So stay posted for that, along with some more talk about this on my podcast at http://www.bengreenfieldfitness.com.

An example of one of the first studies to investigate whether mixing carbohydrate and protein is better than having carbohydrate alone can be summarized as follows:

———————-

Tarnopolsky, M. A., M. Bosman, J. R. MacDonald, D. Vandeputte, J. Martin, and B. D. Roy. Postexercise protein-carbohydrate and carbohydrate supplements increase muscle glycogen in men and women. J. Appl. Physiol. 83(6): 1877-1883, 1997.We have previously demonstrated that women did not increase intramuscular glycogen in response to an increased percent of dietary carbohydrate (CHO) (from 60 to 75% of energy intake) (M. A. Tarnopolsky, S. A. Atkinson, S. M. Phillips, and J. D. MacDougall. J. Appl. Physiol. 78: 1360-1368, 1995). CHO and CHO-protein (Pro) supplementation postexercise can potentiate glycogen resynthesis compared with placebo (K. M. Zawadzki, B. B. Yaspelkis, and J. L. Ivy. J. Appl. Physiol. 72: 1854-1859, 1992). We studied the effect of isoenergetic CHO and CHO-Pro-Fat supplements on muscle glycogen resynthesis in the first 4 h after endurance exercise (90 min at 65% peak O2 consumption) in trained endurance athletes (men, n = 8; women, tested in midfollicular phase, n = 8). Each subject completed three sequential trials separated by 3 wk; a supplement was provided immediately and 1-h postexercise: 1) CHO (0.75 g/kg) + Pro (0.1 g/kg) + Fat (0.02 g/kg), 2) CHO (1 g/kg), and 3) placebo (Pl; artificial sweetener). Subjects were given prepackaged, isoenergetic, isonitrogenous diets, individualized to their habitual diet, for the day before and during the exercise trial. During exercise, women oxidized more lipid than did men (P < 0.05). Both of the supplement trials resulted in greater postexercise glucose and insulin compared with Pl (P < 0.01), with no gender differences. Similarly, both of these trials resulted in increased glycogen resynthesis (37.2 vs. 24.6 mmol · kg dry muscle1 · h1, CHO vs. CHO-Pro-Fat, respectively) compared with Pl (7.5 mmol · kg dry muscle1 · h1; P < 0.001) with no gender differences. We conclude that postexercise CHO and CHO-Pro-Fat nutritional supplements can increase glycogen resynthesis to a greater extent than Pl for both men and women.

———————-

This, and the studies that have been done since then (like this one that you geeks can read in full for free: http://www.ajcn.org/cgi/content/full/72/1/106), suggest primarily the reason that the carbohydrate will enhance protein uptake is due to the insulin response with the sugar intake. Insulin is an anabolic hormone that causes energy uptake and storage, and is essential to stimulate the uptake of amino acids.  There is also a vice-versa effect – protein can act as a “chaperone” to assist with the carb absorption.

The rub is this: MOST folks aren’t exercising hard enough or long enough to justify re-fueling when they already have enough amino acids and sugar on board from pre and during workout feeding.

You can figure out whether you need a post-workout meal pretty easily. Let’s start by estimating about how much storage carbohydrate energy you have on board to start with. Your maximal carbohydrate storage is approximately 15 grams per kilogram of body weight [15 grams per 2.2 pounds]. So a 175-pound athlete could store up to 1200 grams of carbohydrate [4,800 calories]; enough energy to fuel high intensity exercise for quite some time.

So let’s say this 175lb person eats a bowl of oatmeal with some peanut butter (~600 calories), then goes on a 2 hour bike ride at 600 calories per hour. They arrive home at a 600 calorie deficit. Meaning they have 4200 calories of storage carbohydrate STILL ON BOARD.

Now, they hear about this post-workout need, and rush off to eat so they can have a “good workout the next day”, but is that really necessary. Let’s look at how long it would take to replace glycogen, or storage carbohydrate.

Unfortunately, in the scientific literature, glycogen restoration rates are measured in funky units like glycosol per gram or mumol.g wet wt-1.h-1, or mmol/kg – tough to translate into actual real world numbers for us normal folks. But I’m going to try.

5mmol of glucose is 1 gram. Assuming the glycogen is cleanly broken down into glucose, then 5.5mmol of glycogen is 4 calories, since there’s 4 calories in a gram. Post-exercise glycogen re-synthesis rates fall right around the 10mmol/kg/hr range, which is 4.5mmol/lb/hr, so for a 175lb individual, you looking at 785mmol/hr, which is 157g/hr, which is 630 calories per hour.

In other words, a conservative rate of glycogen re-synthesis for you is 630 calories per hour, for up to 2 hours after exercise. So why the heck would you be trying to replace glycogen stores by shoving 800 calories of carbohydrate down the hatch just 20-30 minutes after exercise?

Your goal after a typical workout should instead be to A) re-hydrate and B) elevate amino acids to limit muscle catabolism by consuming 0.25g protein per lb of body weight, with a small amount of sugar to elevate insulin levels. So, for example, the 175lb person could eat about 45g of protein power mixed into  100-200 calories carbohydrate (i.e. a couple bananas with a couple scoops whey protein).

What about for a more serious, glycogen depleting workout, like a 100 mile bike ride, followed by a run later in the day? That’s when you can and should focus on maximizing carbohydrate restoration. Here’s a good rule to follow based on research:

Notice I said “based on research”. If you’re not a lab rat and can’t mow through a bottle of Gatorade every 15 minutes for 4 hours, then just figure out way to creatively consume 2000 calories of about 25% protein, 75% carbohydrate in the 4 hours following your workout, and try and finish that eating about 2 hours before you start your next workout. I’ll wager a bet that you can creatively figure out how to eat 2000 calories in 4 hours. And remember, that’s for “Ironman style” two-a-day workouts, so it’s mostly the pro triathlete that’s going to be worrying about this.

OK, I’m done ranting! Here’s where I do end with a shameless plug – you should read my book “Holistic Fueling For Ironman Triathletes” if you haven’t yet – so you can learn how to eat lots of calories without destroying your body.  It’s free inside your member’s area here at the Rock Star Triathlete Academy.