What is the difference between fast-twitch and slow-twitch muscles?

National Athletic Trainers' Association

Fast-twitch muscles are used in quick, forceful muscle contractions such as sprinting or power lifting. Slow-twitch muscles are used in endurance activities such as long-distance running or biking.

(This answer provided for NATA by the Gustavus Adolphus College Athletic Training Education Program.)

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.

Functions of Muscles

Muscles keep your body moving by contracting and relaxing. In some cases, this movement is voluntary. You use your skeletal muscles to bend your arms or legs when you want. Smooth muscles, however, are part of the involuntary movement within your body. These muscles surround organs of the digestive tract as well as the arteries. You don't have to be aware of the process -- your brain controls the function! One of the most vital muscles is the cardiac muscle, or heart. Understanding the functions of muscles can help you keep them healthy or treat injury as needed.

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