The "science" of recovery

Here's a short primer on muscle metabolism.  If you were sitting in a human physiology lecture in medical school, your professor would explain that muscle contraction uses a ratcheting mechanism where myosin filaments attach, pull, detach, swivel, reattach, and then pull themselves again along the length of actin filaments.  This process causes shortening of the muscle fibers, contraction of the muscle, and movement of the limbs.  This cycle utilizes a currency of molecular energy called ATP (adenosine triphosphate) which is converted into a form called ADP (adenosine diphosphate) as the energy is used up.  Think of a battery going from a charged state (ATP) to a flat state (ADP).   In order for the muscle to fire again, ADP must be converted back into ATP, and this process requires energy.

Muscles are like diesel trucks.  They'll run on nearly anything.  You can feed them crap and they'll still fire.  While your muscles can use fat (in the form of lipids), creatine phosphate, amino acids, and carbohydrates to fuel the furnace, one of the most important stores of energy found inside the muscle cell is called glycogen.  Glycogen is like a glucose tree where individual glucose molecules can be picked off when needed.  In technical terms, it is branched biopolymer consisting of linear chains of glucose molecules with branch points at intervals of ten glucose molecules.  At the center of every unit of glycogen there is a protein core called glycogenin that helps to organize the structure and get the branching started. Here's a picture of what glycogen looks like:

Here's a picture of what glycogen looks like
There are basically two storage depots of glycogen in the human body -- the liver and muscle cells.  When you start exercising, your muscles start to deplete their intramuscular energy stores.  What type of energy gets used first and how long it lasts depends upon a lot of factors.  Type of exercise, duration, degree of fitness, hydration, and what you ate in the last 24 hours all play a role. 

After a short period of time, your muscles will burn through their internal stores and the liver will start to break glycogen down and release it into the bloodstream.  Your heart is pounding, most of your cardiac output is being shunted to actively contracting muscles, and all that glucose released by the liver is delivered to the correct neighboorhood. 

Once it gets there, glucose transporters on the surface of the muscle cell grab a hold of the glucose molecules and transport them actively into the cell.  This process is dependent upon insulin, and while the intracellular mechanics can be complicated the basic principle is that insulin binds to the insulin receptor on the surface of the working muscle and this turns on the glucose transporters so that glucose is actively sucked up from the bloodstream. 

Without insulin receptor activation, the glucose molecule would simply keep moving along and end up somewhere else in your body.  When your muscles are working, they are hungry, and insulin receptor activation is what makes sure that they get fed.

Once you've finished exercising, because you're exhausted, depleted, you reached the finish line, you caught enough waves, or you have to go to work, your muscle cells need to rebuild their stores of energy and repair the damage done during exercise -- especially if the form of exercise was resistance training or weight lifting.  If you don't give your muscles enough time and the right kind of material to repair the damage and replenish their intramuscular stores of energy, the result is fatigue, exhaustion, and delayed onset muscle soreness (DOMS -- in the scientific literature).  

This is where C12 Recovery comes in.  In the last 10 years or so, we've all heard tons of negative press about high glycemic index sugars.  Glycemia is a state of elevated blood sugar and high glycemic index sugars are rapidly absorbed and they result in a quick spike in blood sugar levels.  Think BIG GULP.  Most of the time, this is terrible for you.  Hyperglycemia is associated with all sort of negative side effects (like diabetes), especially in sedentary people, and that's why you are hearing about low glycemic diets, complex carbohydrates, and whole grains. 

When I was a kid, my mother used to refer to refined sugar as "the white death" and we've all seen little kids act like ants when they are around sugar.  Why?  Because there is a biological basis for why sugar tastes so good.  It's energy.  It's really fast energy, and if your body is depleted it is exactly what it needs.  

It turns out that if you consume high glycemic index sugars (along with a supply of easily digestible proteins) immediately after exercise you will replenish your intramuscular stores of energy faster.  The insulin receptor on the surface of the muscle cell stay active, and keep the glucose transporters working for 30 to 60 minutes after hard exercise.  During this phase, you can get a jump start on recovery if you can boost your blood sugar levels.

There is a lot of science out there for you to pick and choose from if you want to dig further into this topic, but the type of study that proves this hypothesis typically goes something like this: a group of trained athletes follows a carbohydrate restricted diet while another group supplements their diet with carbohydrates.  They exercise to exhaustion on the first day of the study, or they perform lifts to their maximum potential, and then repeat the same exercise a day later, or for multiple days in a row.  Typically, the carbohydrate restricted group will become exhausted faster and they will have significantly less strength when tasked with repeated exercise routines during a state of carbohydrate restriction.  In contrast, the group that is allowed carbohydrate supplementation will have improved exercise tolerance and greater strength on subsequent workouts.  Here is a link to a well written review on this subject from the Human Performance Laboratory at Midwestern State University: http://www.ncbi.nlm.nih.gov/pubmed/12580676

The biggest problem with post-exercise carbohydrate supplementation is availability.  During the first 30 to 60 minutes after exercise you are usually putting your bike away, taking off your wetsuit, showering, or heading home.  By the time you get to a food source, your muscles have switched to idle, the insulin receptors are no longer active, and any carbohydrate that you consume is now preferentially picked up by your liver.  So here's an experiment.  Take a look at your training schedule and pick a couple of weeks where you can experiment.  Week 1, restrict your carbohydrate intake after exercise.  Wait to eat or drink for at least an hour or two after you finish.  Week 2, drink a recovery supplement immediately after hard exercise.  Keep a journal.  Chances are, you'll see why carbohydrate supplementation immediately after exercise works.

- Dr. G
C12 Team

J Strength Cond Res. 2003 Feb;17(1):187-96.
Carbohydrate supplementation and resistance training.
Haff GG, Lehmkuhl MJ, McCoy LB, Stone MH.
Source
Human Performance Laboratory, Midwestern State University, Wichita Falls, Texas 76308, USA. haffgg@appstate.edu
Abstract
There is a growing body of evidence suggesting that the performance of resistance-training exercises can elicit a significant glycogenolytic effect that potentially could result in performance decrements. These decrements may result in less than optimal physiological adaptations to training. Currently some scientific evidence suggests that carbohydrate supplementation prior to and during high-volume resistance training results in the maintenance of muscle glycogen concentration, which potentially could result in the maintenance or increase of performance during a training bout. Some researchers suggest that ingesting carbohydrate supplements prior to and during resistance training may improve resistance-training performance. Additionally, the ingestion of carbohydrates following resistance exercise enhances the resynthesis of muscle glycogen, which may result in a faster time of recovery from resistance training, thus possibly allowing for a greater training volume. On the basis of the current scientific literature, it may be advisable for athletes who are performing high-volume resistance training to ingest carbohydrate supplements before, during, and immediately after resistance training.









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