Exercise is – or at least should be – synonymous with good health.
It improves the physical body by preventing chronic disease and optimizing bodily function.
For many, exercise is a task in constantly setting the bar higher: to run faster, paddle harder or lift more weight. People reach for the latest and greatest “things” to help them achieve their goals faster.
But the Sports nutrition industry is an ugly monster. This shape-shifting giant is ready and eager to sell whatever they can convince people to buy; be it pills, protein powders or dietary regimes.
The Sports nutrition marketplace is very confusing, if not totally contradictory.
Much of the current focus in Sports nutrition is in post workout refuelling. This makes all too much sense, since exercise uses up a bunch of bodily substrate to power its activity, and you need to give it back in order to best reap the benefits.
Unfortunately, nearly every nutritional manufacturer has a different take on optimal refuelling, with the only real agreement being that consuming something other than pure water is preferable to consuming nothing.
But what truly is the ideal way in order to refuel the body? Why are most athletes now using post exercise protein powders? To answer these questions, one must first understand a bit about exercise and muscle physiology.
Muscle physiology
The fuel the body uses for energy comes from the foods people eat: carbohydrates, fat and protein.
During exercise, it is predominantly carbohydrates (glucose) that are utilized for energy, since fats and proteins are broken down too slowly to keep up with energetic demands.
The exception is low exertion exercise like walking, where some fats are used for energy.
Glucose is readily absorbed in to the blood stream upon eating. Insulin is released, and the glucose is stored in the liver (and to a lesser extent, the muscle) as glycogen.
When energy demands increase during exercise, the glycogen is broken down via the hormone glucagon, to liberate glucose once again for fuel.
The body has the ability to use glucose in two separate mechanisms:
– anaerobic cellular respiration: free glucose is converted to lactic acid, which is used by muscle for energy. This is done without the need for oxygen. This provides very short duration bursts of energy, and is used up within 60 to 120 seconds (i.e.- sprinting); and
– aerobic cellular respiration: free glucose is taken up by muscles cells and converted in to energy in the mitochondria through the addition of oxygen. This provides long-term energy (i.e.- running a marathon).
Muscle fatigue occurs mainly due to a combination of insufficient oxygen supply to the muscle, build-up of lactic acid and depletion of glycogen stores.
“Hitting the wall” is literally when the muscle has used up all of the available glucose, and can be thought of as synonymous to your car running out of gas.
As training improves, the body becomes more efficient: improved oxygen delivery, more mitochondria to produce energy, less net glycogen use, less lactic acid build-up, and an enhanced ability to oxidize some fat for energy.
Post-workout nutrient depletion
The post exercise individual is glycogen (carbohydrate) depleted. Their protein store is relatively untouched.
So why do so many people immediately grab a pure protein shake upon finishing exercise?
It likely comes down to effective marketing by protein powder manufacturers. Studies consistently reinforce that until glycogen stores are refilled, muscle recovery will not be completed.
Further, delayed glycogen recovery reduces the ability of the body to convert the hard work of exercise to something beneficial by causing a lesser extent of muscle building, slow muscle recovery and poor repair of damaged muscle (causes next day soreness).
The expensive protein powder taxes an already tired body by forcing it to convert protein to sugar in order to refill glycogen stores, when cheap sugar could have been ingested in the first place.
The evidence clearly shows that the majority of post exercise substrate should come from carbohydrates.
Carbohydrate-protein combinations
Protein alone does not promote good muscle recovery, but when ingested with carbohydrates it does.
In fact, a carbohydrate-protein combination is more effective at rapidly replenishing glycogen stores and promoting muscle recovery than carbohydrate alone.
It is important to note that most protein powders do not provide an effective combination of either macronutrient. They provide far too little (if any) carbohydrate, and far too much protein.
Ideal post-workout recovery
An effective post workout strategy follows an effective pre- and during workout strategy.
It is important to build a hydration and nutrition strategy leading in to and during activity to best optimize performance, but this is not discussed here.
The following only applies to post-exercise, and are the guidelines best associated with optimal recovery:
1. About 600ml of water for every pound lost during activity (weigh in before and after activity);
2. As soon as physical activity ends, consume 1.2 grams of high glycemic index carbohydrate per kg of body weight per hour of activity (i.e.- if you weigh 70 kg and exercised for 2 hours you should consume 1.2 grams x 70 kg x 2 hours = 168 grams); and
3. consume 0.2 grams of protein (whey) per kg of body weight (i.e. 70 kg person needs 0.2 grams x 70 kg = 14 grams). Compare this to your favorite protein powder.
This column was submitted by Dr. Michael Long, naturopathic doctor at Optimum Integrative Health Centre in Fergus.
