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Skeletal Muscle Fiber Types
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Skeletal Muscle Fiber Types
Muscle Fiber Types
Types of Muscle Fibers
Introduction to the types of muscle fibers
Type 1 and type 2 muscle fibers Muscular-skeletal system physiology NCLEX-RN Khan Academy
https://www.youtube.com/watch?v=l5yMz2lFgx0
Muscle Fiber Types
Intro
Our skeletal muscles contain two types of muscle fibers - fast twitch and slow twitch
Type 1 - slow twitch
Type 2 - fast twitch
Type 2 is broken down into:
Type 2a
Type 2x
Type 1
50% of fibers in an average muscle
Type 1
Type 1 muscle fibers are durable, have a high resistance to fatigue and contract slow.
Type 1 muscle fibers are mostly used for lower intensity activities such as walking or jogging
https://www.elitefts.com/education/muscle-fiber-types-and-training/
Characteristics
High oxidative capacity fibers
Characteristics
- Maintain longer, slower contractions which is important for stabilization and posture
- Strong muscles
- Peak tension in 110 ms
- High concentration of mitochondria and myoglobin
- Surrounded by more capillaries than type 2
- These muscle fibers appear red
- These muscles fibers are high in fatigue resistance
- Low glycolytic capacity
Function
Slow twitch fibers
Function
- A person running a marathon will use type 1 muscle fibers
- Maintaining exercise for a long period of time
- Low intensity exercises
- More efficient than type 2 because require less energy - oxygen is required for ATP production - less
- Efficiently produce ATP from fats and carbohydrates - energy stored in triglycerides
Type 2
Type 2a - 25% of fibers in an average muscle
Type 2x - 25% of fibers in an average muscle
Type 2
There are two types of fast twitch muscles, 2a and 2x. These muscle fibers are larger in size than type 1, therefore, produce quicker and greater power. This power only lasts for a short period of time.
https://buildingmuscle.org/muscle-fibers-explained-type-1-and-type-2/
Type 2a
Short, high intensity endurance events
Type 2a
- Fast twitch oxidative
- Generate more force than slow twitch but quicker to fatigue
- Contract quickly to generate quick bursts of explosive speed
- Main source of energy comes from creatine phosphate and glycogen
- 2a muscle fibers can recover quicker than 2x because of the amount of oxygen taken in by the muscle
- Running an 800 - 1600 meter race
Type 2x
short, explosive sprints
Type 2x
- Fast twitch glycolytic
- White in color
- Very high fatigue rate and do not recover quickly because these fibers do not use oxygen
- Use creatine phospate and glycogen as fuel - no energy from natural sources like oxygen
- Contract very quickly and generate the most force
- Running short sprints (100m)
- Least efficient - more energy used
- When these type of muscle fibers are out of energy and can no longer contract, we turn to type 2a fibers
Type 1 vs Type 2
Know the difference!
Type 1 vs Type 2
Picture
Chart
Questions
1. What is the best way to target type 1 muscle fibers when training athletes? Give some examples of exercises.
2. How may an athlete may use both type 1 and type 2 muscle fibers during exercise? Explain.
3. Why are type 1 muscles fatigue resistant? Explain.