When I trained for the 2 full marathons that I ran in 2007 and 2008, I trained with the National AIDS Marathon Training Program. It was a 6-month program that got us ready to run the 26.2 mile race in addition to raising funds to support the San Francisco AIDS Foundation. One of the coolest things about the program was that the coaches taught us a lot about running from every aspect, including nutrition for before, during, and after running.
During aerobic exercise, the body will use the most easily accessible energy it can. Our bodies are efficient (or perhaps lazy) in that way. Carbohydrates are much easier to break down than proteins or fat, so the carbs get utilized first.
The carbohydrates we eat are broken down by the body and one of the results is glucose, some of which is temporarily stored in the liver and muscles as glycogen. Only glycogen from the liver can be made available to other organs for energy. Once your body has used any available glucose that is in your bloodstream and liver from recent meals, it will look to other sources for fuel.
When we exercise for an extended period of time, and/or work out major muscle groups, the muscles involved will begin to use the glycogen stored there as fuel. Endurance athletes (such as marathoners, long-distance cyclers, competitive swimmers and the like) will eventually use up all the glycogen in the muscles and go into what is called "glycogen debt". Marathoners know this phenomenon well. We call it "hitting the wall" because the runner suddenly experiences great muscle fatigue and sometimes pain. It suddenly becomes excruciatingly hard to continue moving forward. The body is now in a state of hypoglycemia, which can become dangerous, and can be accompanied by diziness, weakness, and even hallucinations. This is why Olympic-level marathoners sometimes run with smelling salts.
At this point, the body may begin to cannibalize proteins from the muscles for fuel, and begin burning fat stores. Sounds good, right? Well, maybe not. I'd like to keep my lean muscle mass as opposed to using it for energy, wouldn't you? Adults tend to lose muscle mass over time anyway, as part of the aging process. I'd like it if my body could solely burn my accumulated fat stores (even after losing 80 pounds, I still have plenty). But it takes more energy to burn fat than it does to burn protein or carbs. It also requires more oxygen. After prolonged running, most runners are not able to consume enough oxygen to keep this anaerobic process going for long. Additionally, some experts believe that this type of stress on the body can be damaging to the immune system!
So what is the best way to keep from going into glycogen debt during exercise? Consuming carbohydrates before, during, and after exercise is the best way to prevent hitting the wall. Sporting goods stores, nutrition stores, and running stores offer a host of products that endurance athletes can consume easily while exercising in order to replenish the glucose that has been used.
Some of my favorite products to use during exercise are Gu Brand Energy gels, Clif Shot Bloks, Luna moons, and PowerBar Gel Blasts (especially the Cola flavor...just like a Coke Slurpee!)
Just as important as fueling DURING exercise is what you put into your body AFTER exercise. After intense and prolonged exercise (over an hour), the body will convert carbohydrates into glycogen to replace what was used up to 3 times faster than it does at normal times. This is called the "glycogen window". You want to take advantage of this period and get that glycogen back in there ASAP so you have it available for your next workout. If you don't, you will certainly notice the lack of readily available energy in the form of fatigue, sluggishness, and maybe even muscle pain.
In addition to consuming carbs after your hard workout, you also want to consume some protein to help repair any microscopic muscle tears. An ideal ratio has been suggested by nutritionists of 2:1 carbohydrate to protein ratio. If you have been sweating a lot, you will also want to consume some sodium, which is lost rapidly during prolonged exertion. Now, a big mistake that many people make is to eat a huge meal after working out. They justify their hard work as an excuse to consume huge amounts of calories. Regardless of your increased caloric burn after exercise, any EXCESS calories will still be stored in the body as fat, negating all the hard work you just did. And research has shown that most people tend to overestimate the amount of calories they burn during a workout.
So what are some healthy, great-tasting foods with a 2:1 carb to protein ratio that contain sodium and won't destroy your calorie budget for the day? Here are some great suggestions:
--A glass of chocolate milk, half a banana, and a piece of string cheese
--A hard-boiled egg, plus half a bagel with hummus
--Half of a peanut butter and jelly sandwich and a piece of fruit or glass of juice
--A Big handful of Trail mix (the type with nuts and raisins) and some sports drink
--A tuna sandwich with dill pickles
--An energy bar that contains protein, carbs, and some fiber, along with water or sports drink
Obviously, I am NOT a doctor or a nutritionist, so these ideas come solely from my own opinions and experience of what works for me personally.
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