Have you ever wondered why some people are able to run longer distances or seem to have better luck building body mass? The reason could be the difference between fast twitch vs. slow twitch muscles. These two types of muscles perform very different functions, and can affect how well you perform cardiovascular and strength training activities. Here are some things you should know about the different muscle types.
Slow Twitch Muscles
Slow twitch or Type 1 muscles take longer to reach peak contraction, requiring around 110 milliseconds to do so. These muscles also make up the smallest cross-sectional area, which is one reason they do not hypertrophy as much. Type 1 muscles have a higher aerobic capacity and a lower anaerobic capacity than fast twitch or type 2 muscles do. This makes them more efficient at synthesizing oxygen to generate fuel, enabling them to be used for longer periods of time without suffering fatigue. As such, they are primarily used in endurance activities such as running, swimming, or biking.
Fast Twitch Muscles
Fast twitch muscles are further broken down into Type IIa, which are “intermediate fast” fibers and Type IIb, which are “extremely fast” ones. Type IIa fibers can reach peak tension in about 50 milliseconds, whereas Type 11b fibers require only 25 milliseconds. Fast twitch fibers also generate more force, which means they are perfect for providing short bursts of energy such as during weight lifting. They give out quickly, meaning they will provide you with little assistance during activities that require a great deal of physical endurance.
Personal Genetic Makeup
The average person’s muscles are about half slow-twitch and half fast-pitch fibers; however, you may have more of one particular type based upon your genetic makeup. If you are able to run faster or jump higher than others your same size and age, but are generally lean and have a hard time building muscle, chances are you are fast twitch dominant. On the other hand, if you have difficulty running or jumping, but find strength training easy, chances are very good that you are slow twitch dominant.
Effect on Aging
In his book “Bending the Aging Curve”, Dr. Joseph Signorile claims that most of the muscle decline people experience after age 40 occurs in the fast twitch muscles. This is one reason why a person’s overall strength declines during middle age. On the other hand, the slow twitch endurance fibers tend to be maintained longer, even in those who are relatively untrained. Dr. Signorile claims that resistance and interval training will keep those fast twitch fibers healthy and vibrant, making it less likely people will slow down as they grow older.
When it comes to fast twitch vs. slow twitch muscles, knowing which one is dominant in your body can better help you develop a training program. This information is especially helpful to athletes who need to improve their overall speed and strength in order to excel.