The main difference between fast twitch and slow twitch muscle fibers is that the fast-twitch muscle fibers (type II muscle fibers) contract quickly whereas the slow-twitch muscle fibers (type I muscle fibers) contract comparatively slowly. Furthermore, fast-twitch muscle fibers consume oxygen instantly while slow-twitch muscle fibers consume oxygen slowly, but in a very efficient manner.
Fast-twitch and slow-twitch muscle fibers are two types of skeletal muscle fibers that produce force and motion. Fast-twitch muscle fibers are also called type II muscle fibers while slow-twitch muscle fibers called type I muscle fibers.
Key Areas Covered
1. What are Fast Twitch Muscle Fibers
– Definition, Types, Characteristics
2. What are Slow Twitch Muscle Fibers
– Definition, Characteristic, Importance
3. What are the Similarities Between Fast Twitch and Slow Twitch Muscle Fibers
– Outline of Common Features
4. What is the Difference Between Fast Twitch and Slow Twitch Muscle Fibers
– Comparison of Key Differences
Key Terms
Fast Twitch Muscle Fibers, Fatigue, Power, Skeletal Muscle Fibers, Slow Twitch Muscle Fibers
What are Fast Twitch Muscle Fibers
Fast-twitch muscle fibers are one of the two main types of muscle fibers activated at the maximum exertion of the body. They are also called type II muscle fibers. The main characteristic feature of type II muscle fibers is being fatigued soon. The type II muscle fibers are further classified into two type IIa and type IIb.
- Type IIa – They exhibit long-term anaerobic activity with a maximum duration of less than 30 minutes. They produce medium power and have a considerable mitochondrial density.
- Type IIb – They exhibit short-term anaerobic activity with a maximum duration of less than 1 minute. They produce very high power for a very short time period.
Figure 1: Fast Twitch Muscle Fibers Structure
Fast-twitch muscle fibers have a fewer amount of myoglobin, which is the oxygen-binding protein found in muscle tissue. Due to this fewer amounts of myoglobin, fast-twitch muscle fibers are pale and called white fibers.
What are Slow Twitch Muscle Fibers
Slow-twitch muscle fibers are the bright red colored muscle fibers found in the muscles. They are red in color due to the presence of a higher amount of myoglobin. Also, the slow–twitch muscle fibers have a good vascular supply. This means these muscle fibers have a good oxygen supply. They consist of higher amounts of mitochondria inside the fibers as well. Therefore, these type of muscle fibers are the sites where an efficient breakdown of glucose takes place for the production of energy.
Figure 2: Slow Twitch Muscle Fibers Structure
The main characteristic feature of slow-twitching muscle fibers is their resistance to fatigue. They can generate energy continuously for a long period of time through aerobic respiration, producing a moderate power.
Similarities Between Fast Twitch and Slow Twitch Muscle Fibers
- Fast-twitch and slow-twitch muscle fibers are the two types of skeletal muscle fibers found in the body.
- They occur in equal amounts in a regular person.
- Both help in the production of force and motion.
- They affect the physical activities and training.
Difference Between Fast Twitch and Slow Twitch Muscle Fibers
Definition
Fast-twitch muscle fibers refer to any muscle fiber that contracts relatively rapidly, utilized especially in actions requiring a maximum effort of short duration, such as sprinting while slow-twitch muscle fibers refer to a muscle fiber that contracts relatively slowly and is resistant to fatigue.
Also Called
Fast-twitch muscle fibers are also called type II muscle fibers while slow-twitch muscle fibers called type I muscle fibers.
Speed of Action
The fast-twitch muscle fibers contract fast while the slow-twitch muscle fibers contract slowly.
Blood Supply
The fast-twitch muscle fibers have relatively poor blood supply while the slow-twitch muscle fibers have a good blood supply.
Amount of Mitochondria
Fast-twitch muscle fibers have a fewer amount of mitochondria while slow-twitch muscle fibers have a higher number of mitochondria.
Oxygen Consumption
Fast-twitch muscle fibers consume oxygen instantly while slow-twitch muscle fibers consume oxygen slowly.
Oxygen Consumption Efficiency
The fast-twitch muscle fibers consume oxygen less efficiently while the slow-twitch muscle fibers consume oxygen very efficiently.
Type of Respiration
The fast-twitch muscle fibers undergo both aerobic and anaerobic respiration while the slow-twitch muscle fibers mainly undergo aerobic respiration.
Amounts of Myoglobin
Fast-twitch muscle fibers contain a low amount of myoglobin while slow-twist muscle fibers contain a higher amount of myoglobin.
Preferred Fuel Source
Fats-twitch muscle fibers are better in fat burning while slow-twitch muscle fibers are good at glucose burning.
Color
The fast-twitch muscle fibers are pale in color while the slow-twitch muscle fibers are deep red in color. Furthermore, fast-twitch muscle fibers are called red fibers while slow-twitching muscle fibers are called white fibers.
Diameter
The fast-twitch muscle fibers have a large diameter while the slow-twitch muscle fibers have a small diameter.
Amount of Force Produced
Fast-twitch muscle fibers generate a greater force while slow-twitch muscle fibers generate comparatively weak force.
Hypertrophy or Growth Potential
Fast-twitch muscle fibers have a great hypertrophy while slow-twitch muscle fibers have a comparatively low hypertrophy.
Muscle Fatigue
Fatigue occurs quickly in fast-twitch muscle fibers while fatigue occurs slowly in slow-twitch muscle fibers.
Good for
The fast-twitch muscles are best suited for high-intensity but, short-duration activities while the slow-twitch muscle fibers are best suited for low amounts of force for long periods of time. Further, fast-twitch muscles are good for sprinters and lifting heavy weights while slow-twitch muscle fibers are good for marathon runners and cyclists.
Conclusion
Fast-twitch muscle fibers are the type II muscle fibers that can generate a high power for a short period of time. On the other hand, slow-twitch muscle fibers are the type I fibers that can generate a moderate power for a long period of time. They do not become fatigued soon. The main difference between fast twitch and slow twitch muscle fibers is their characteristics.
Reference:
1. “Muscle Fibre Types.” TeachPE.com, Available Here
2. “Type II Muscle Fiber.” Athlepedia, The Athletics Wiki, Available Here
Image Courtesy:
1. “keywords-running-athlete-men-sport-2438428” (CC0) via pixbay
2. “athlete-athletic-body-fit-fitness-2849220” (CC0) via pixbay
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