Alteration Of Muscle Fibers For Athletic Performance

Athletic Performance Conditioning and Training

Are you a better distance runner than a sprinter? There is a strong belief that having more slow and fast twitch muscle fibers may determine what athletes excel at and how they respond to athletic performance conditioning and training.

muscle fibersSkeletal muscle has two different fibers. Slow twitch (Type I) muscle fibers and fast twitch (Type II) muscle fibers. Fast twitch fibers can be further categorized into Type IIa and Type IIb fibers. These bundles of individual muscle fibers called myocytes contain many myofibrils, which are strands of proteins (myosin and actin) that can grab on to each other and pull. This muscle contraction can shorten the muscle.

Influence How Muscles Respond to Training

Each fiber type has a unique ability to contract in a certain way to and influence how muscles respond to training and create a metabolic response. Human muscles contain a genetically determined 50% mixture of both slow twitch and fast fiber types in most of the muscles used for movement.

(Type I) Slow Twitch

The slow muscles are the most efficient at using oxygen to generate more fuel (known as ATP) for continuous, extended muscle contractions over a long period of time. Firing more slowly than fast twitch fibers, they can go for a long time before they fatigue. Therefore, helping athletes run marathons and cycle for hours.

(Type II) Fast Twitch

Fast twitch fibers are much better at generating short bursts of strength or speed than slow muscles because they use anaerobic metabolism to create fuel, but they fatigue more quickly. Fast twitch fibers fire more rapidly than slow muscles and share same amount of force per contraction. A sprinter needs more fast twitch fibers to quickly generate a lot of force.

(Type IIa) Muscle Fibers

Also known as intermediate fast twitch fibers, Type lla fibres can use both aerobic and anaerobic metabolism almost equally to create energy. When doing so, they are a combination of Type I and Type II muscle fibers.

(Type IIb) Muscle Fibers

These “classic” fast twitch muscle fibers excel at producing quick, powerful bursts of speed and use anaerobic metabolism to create energy. These muscle fibers have the highest rate of (rapid firing) contraction of all the muscle fiber types. They also have a much faster rate of fatigue.

What Sports We Are Naturally Good At

Performance and muscle fiber types influence what sports we are naturally good at or whether we are strong or fast. Typically Olympic athletes fall into sports that match their genetic makeup; in fact, Olympic sprinters possess about 80% fast twitch fibers, while marathon runners tend to have 80% slow twitch muscle fibers.

Can Specialized Conditioning Change Fiber Type?

Can personal training with specialized conditioning change muscle fiber type? Although this is not entirely understood, there is research showing that human skeletal muscle may switch muscle fiber types from “fast” to “slow” due to high intensity interval training.

When improving your performance, know that genetics lead the elite levels of athletic performance. Following the principles from an elite personal trainer can dramatically improve the personal performance of a typical athlete. With consistent endurance training, high intensity interval training, more muscle fibers develop and improve athletic performance and the athletes’ ability to cope with stress of exercise.

Fiber Type is Only Part of a Athlete’s Success

There are many other factors that go into determining athleticism, including mental preparedness, proper nutrition and hydration, rest and having appropriate equipment and conditioning. Fiber type is part of a great athlete’s success, but it alone is a poor predictor of athletic performance. Research shows that all athletes in any given competition share certain physiologic characteristics. It was once thought that in order to be an Olympic competitor, you would have to be born tailored to your sport. However, with this new research, we have learned that our body’s muscle is adaptable, and can be shaped by proper professional training. Maybe there is an Olympic champion somewhere inside each of us…

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