As mentioned last week, Dr. Bruce Craig, Ball State University, had a great little article that talked about fat burning and how it happens. The summary provided below is taken primarily from his material word for word, with occasional commentary inserted. Please contact me if you would like a copy of his original article as printed in the Strength and Conditioning Journal, October 2006, vol 28 number 5.
There are basically two types of fibers. Type I and Type II.
"Type I muscle fibers produce less force that Type II muscle fibers but are more fatigue-resistant. They have a slower chemistry than type II fibers. So, when the workload is lower, these are the fibers of choice. Type I fibers are classified as aerobic fibers and contain numerous mitochondria. Mitochondria contain a series of aerobic enzymes that represent a metabolic pathway called the Krebs cycle. "
The mitochondria are also known as powerhouses. Energy is produced here. "Type I fibers can metabolize either carbohydrates or fats, and are more involved when exercise intensity is at or below 70% of you maximal aerobic capacity (VO2 max)……If you perform resistance training, the nervous system recruits more anaerobic muscle fibers (type II), which produce more force and metabolize more carbohydrates."
The type II fibers don't have as many mitochondria as type I fibers, but they use glycogen (or carbs) as the main fuel source and aren't as dependent on oxygen.
What does all of this mean? It means that if you are really good at running or some other cardiovascular type activity, you have a lot of Type I muscle fibers. If you happen to be really good at weight lifting or strength/power based activities, you probably have more Type II muscle fibers. If you are a well rounded athlete, you may have the gift of being evenly endowed with both types. Think about it. Do you hate cardio? It's your least favorite part of your training? It's because it doesn't come naturally. It hurts. You get winded. You don't have lots of type I fibers! That's why you prefer to do anything involving strength……you get to use all of those type II's! The reverse is true as well. Some people dread the weight lifting. They would rather do cardio all day. They have more type II's!
When you are cross training, you want to consider what type of muscle fiber you need to train and to what degree. This is a great conversation to have with your coach or trainer. You also want to give consideration to your diet and make sure that you are eating the quality and quantity that is necessary for your training plan. It's the start of a new year, start yours off with the right tools. Train hard and eat right.
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