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NAME:____________________________________________ PERIOD:_______ S3.H9.L2- Identifies the structure of a skeletal muscle and fiber types as they relate to muscle development Muscle Fiber Types Within skeletal muscle there are three types of fiber. Type 1= Slow twitch muscle fiber, type 2A= fast twitch muscle fiber and type 2B= fast twitch muscle. Each fiber type has different qualities in the way they perform and how quickly they fatigue. Type I Type I fibers are also known as slow twitch fibers. Slow- twitch (Type I) fibers are identified by a slow contraction time and a high resistance to fatigue. They are red in color due to the presence of large volumes of myoglobin (hemoglobin of muscle- oxygen carrying pigment=red & conveys oxygen to the muscle), oxygen and high numbers of Mitochondria (energy production). They are capable of producing repeated low-level contractions by producing large amounts of ATP (adenosine triphosphate) through an aerobic metabolic cycle. Functionally, ST fibers are used for aerobic activities requiring low-level force production, such as walking and maintaining posture. Most activities of daily living use ST fibers. Athletes with a high number of ST muscle fibers would include distance runners, swimmers, cyclists, etc. Type 2A Type 2A fibers are also sometimes known as fast oxidative fibers and are a hybrid of type I and 2 fibers. These fibers are also red in color due to the fact they contain a large number of mitochondria and myoglobin. They manufacture and split ATP at a fast rate by utilizing both aerobic and anaerobic metabolism and so produce fast, strong muscle contractions, although they are more prone to fatigue than type I fibers. Resistance training can turn type 2B fibers into type 2A due to an increase in the ability to utilize the oxidative cycle. Functionally, they are used for prolonged anaerobic activities with a relatively high force output, such as racing 400 meters. Type 2B Often known as fast glycolytic fibers Type 2B muscle fibers are white in color due to the fact they have a low level of myoglobin and few mitochondria. They produce ATP at a slow rate by anaerobic metabolism and break it down very quickly. Therefore, they are very sensitive to fatigue and are used for short anaerobic, high force production activities, such as sprinting, hurdling, jumping, and shot put. These fibers are also capable of producing more power than ST fibers Fiber Type Color Contraction Time Resistance to Fatigue Activity used for Metabolic cycle used Force Production Sport/athletic example Characteristics of Three Muscles Fiber Types Type 1- Slow Twitch Type 2A- Fast Twitch Red Red Slow Fast High Medium/Intermediate Aerobic Long Term Anaerobic Aerobic Aerobic & Anaerobic Low High Distance Runner 400-800 M sprinter Type 2B- Fast Twitch White Very Fast Low Short Term Anaerobic Anaerobic Very High 100 Sprinter/Hurdler Determining Muscle Fiber Type The only way to directly determine the fiber-type composition in an athlete is to perform an invasive muscle biopsy test (in which a needle is stuck into the muscle and a few fibers are plucked out to be examined under a microscope), Indirect methods include 1 Rep Max and many reps at 80% of the athletes 1 Rep Max or for younger athletes or people new to sports, try different events. Their dominant fiber type will soon become evident based on their success in certain events https://www.youtube.com/watch?v=3L9JUfzh66I https://www.youtube.com/watch?v=Uxwh2IIg_Z0 – sprinter vs. marathoner http://www.coachr.org/fiber.htm www.teachpe.com Muscle Fiber Types QUIZ Circle how many questions out of 5 that you answered correct? 1 2 Write the correct answers for each of the questions below: 1.____Slow Twitch______ 2___Mitochondira & Myoglobin____ 3.___Fast Glycolitic__ (the quiz online says the right answer is slow anabolic but that is INCORRECT) 4.____2B & 2A_________________________ 5. _____Type 1____________________ 3 4 5