Types of Muscle Fibers

September 20, 2009

Did you know that every athlete has several different types of muscle fibers throughout their body? Depending on what type and combination of muscle fiber you have in your body will help to determine your aerobic and anaerobic capacity.

Slow Twitch Muscle Fibers

Type I

These types of fibers contain large numbers of oxidative enzymes and are surrounded by more capillaries that any of the other fibers. This means that people with these types of fibers will have a large capacity for aerobic activity and a high resistance to fatigue. Athletes that usually have a large number of Type I fibers usually compete in long activities such as biking, running, swimming (Ironman, Ultra-marathon, marathons, etc). Athletes with a large percentage of type I fibers are not able to generate as much strength and power as these types of fibers produce lower specific tension in comparison.

Fast Twitch Muscle Fibers

Type IIx

These types of fibers contain relatively small numbers of mitchondria and have a limited capacity for aerobic activity. These fibers are also rich in glycolytic enzymes which in turn provide them with a high anaerobic threshold. Essentially this means that athletes with a large number of Type IIx fibers excel at power sports such as sprinting, hockey, football, powerlifting, BMX racing, etc). Athletes that have a large percentage of Type IIx fibers will have a very minimal aerobic threshold.

Type IIa

This type of fiber can also be referred to the intermediate fibers or fast-oxidative glycolytic fibers. With this being the intermediate fiber it contain both characteristics of the Type I and Type IIx fibers. This type of fiber is very adaptable and can easily take the form of it counterparts. Through specific athletic training the body can easily convert Type IIa fibers into I or IIx. This is great news for athletes looking to improve their strength or aerobic capacity. Training does have benefits as you can enhance your body's type of muscle fibers dependent on your sport and the training that you do.

Typical Muscle Fiber Composition in Elite Runners

    Distance Runners
    70-80% (Slow Twitch Type I)
    20-30% (Fast Fibers Type IIx and IIa)

    Track Sprinters
    25-30% (Slow Twitch Type I)
    70-75% (Fast Fibers Type IIx and IIa)

    Non-athletes
    47-53% (Slow Twitch Type I)
    47-53% (Fast Fibers Type IIx and IIa)

What does this all mean?

Essentially our bodies consist of three types of fibers. Depending on your body's combination you might see more success in certain athletic events. If your body is made up of 90% fast muscle fibers you will probably excel as a power-lifter and struggle as a marathon runner. On the other hand if you are made up of 80% slow-twitch fibers might not be very strong but you will be able to run, bike or swim long distances with ease. There is hope as recent research proves that through specific training we are able to convert our fibers from one type to another. Depending on your sport the right training program will to enhance your muscle fiber combinations. Sport performance is dependant of various factors and just looking at your types of muscle fibers may not be the best indication of success. "An individual's muscle fiber composition in not the only variable that determines success in athletic events. In fact, it is generally believed that success in athletic performance is due to a complex interaction of psychological, biochemical, neurological, cardiopulmonary and biomechanical factors."

References

Powers,Howley: Exercise Physiology-Theory and Application to Fitness and Performance, Fifth Edition, 2004
Baechle, Earle: Essentials of Strength and Conditioning, NSCA, Third Edition,2008

Nutrition "Eat Right, Train Right"

June 6, 2009

When you are training at an intense level you must make sure that you continue to eat healthy and do not justify eating bad food just because you worked out that day. In order to be in top shape you must eat, sleep and train right. A diet rich in fruits, vegetables, low fat meats, whole grain carbohydrates, low-fat dairy will help you body reach its optimal performance level. If you need more assistance with your nutrition just ask and we can work on this for you.

How much protein do I need?

Protein is important in the repair of muscle tissue and is needed to maintain optimal performance. When you are training you need approximately 2.0 grams of protein per kilogram of body weight. If you intake too much protein your body will not be able to absorb all of it therefore your kidneys will have to work extra hard to get rid of the excess. To determine how much protein you need please fill in the formula.

Current weight (lbs) / 2.2 = weight in kilograms x 2.0 = How many grams of protein you need when training at a high intensity.

How many carbohydrates do I need?

Carbohydrates are very important when you training, as they are your primary source of energy. When you train at an intense level you must replenish what you have used during your workout. If you do not refuel your body immediately after a workout you will find that you will not have as much energy in future workouts. Make sure that when eating carbohydrates that you avoid simple carbohydrates such as table sugar, candy, pop, etc and rather that you opt for complex carbohydrates such as whole wheat breads, whole wheat pastas, etc. When you are training you should have 6 grams/KG of body weight.

Current weight (lbs) / 2.2 = weight in kilograms x 6.0 = How many grams of Carbohydrates needed per day.

How much water per day do I need?

Water is an essential nutrient and it is needed to maintain proper function in the body. It is important in preventing muscle cramping and helping the body control its temperature. When you are training at a high intensity you will lose more water than the average individual who does not exercise, so you must make sure that you are taking in more water compared to the average person. On a daily basis you should be taking in any where form 2-5 litres of water a day (8-20 cups). If you allow your body to become too dehydrated you decrease performance on a rather significant level. Do not wait until you are thirsty as this means you are already dehydrated. Drink throughout the day and this will ensure that you are hydrated. If you do not like the taste of water you can have powerade or Gatorade in a very diluted form.

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