Muscle Fibers - Type I

Also known as:  Red Muscle Fibers;  Slow-Twitch Muscle Fibers

Type 1 Muscle Fibers are slow contracting Muscle Fibers that contain large amounts of Myoglobin.  The physical appearance of Type I Muscle Fibers is red.

Musculoskeletal System

       Type I Muscle Fibers are used during endurance Exercise and respond to Exercise by becoming more efficient, (rather than growing to become larger):

 They are very resistant to Fatigue and contact slowly.  They work aerobically and perform when a weak contraction is required.

Prescribed Medications

 Clenbuterol causes some Type I Muscle Fibers to convert to Type II Muscle Fibers.