The skeletal muscles include different muscles that join the bones with the tendons. Two skeletal muscles are meant to help perform varied tasks: fast–twitch and slow-twitch muscles. Even these muscles comprise approximately 40% of the entire body mass.
Key Takeaways
- Fast-twitch muscles contract quickly and generate power, while slow-twitch muscles contract slowly and provide endurance.
- Fast-twitch muscles fatigue quickly, while slow-twitch muscles resist fatigue and support sustained activity.
- Sp sprinting and power sports athletes possess more fast-twitch muscles, while endurance athletes have a higher proportion of slow-twitch muscles.
Fast Twitch Muscles vs Slow Twitch Muscles
Fast twitch muscle fibres are characterized by their ability to contract rapidly and powerfully for high-intensity activities in a short period of time. Slow twitch muscle fibres, also known as Type I fibres, are characterized by their ability to contract for longer periods of time without fatigue.
The other name used for these types of muscles is – Type II muscle. These muscles get stressed very easily and are further bifurcated into the other two types – Type II a and Type II b.
The second name used for these types of muscles is – Type I muscle. These muscles appear bright red, contain a huge amount of myoglobin, and comprise almost 80% of the human body.
Comparison Table
| Parameters of Comparison | Fast Twitch Muscles | Slow Twitch Muscles |
|---|---|---|
| Definition | Required for extensive work but for a short time | Contracts at a slow pace and doesn’t get easily fatigued |
| Another Name | Type – II muscle | Type – I muscle |
| Speed of Action | Fast | Slow |
| Type of Respiration | Anaerobic and aerobic | Aerobic |
| Blood supply | Poor | Good |
| Consumption of Oxygen | Fast | Slow |
| Myoglobin Amount | Less | More |
| Mitochondria Amount | Less | More |
| Oxygen Consumption Efficiency | Less | More |
| Diameter | Large | Small |
| Color | Pale (or white fibres) | Deep Red (or red fibres) |
| Fuel Used | Burns the body fat | Burns the body glucose |
| Fatigue | Fast | Slow |
| Best for | Sprinting, heavy weight lifters, etc | Cycling, marathon runner, etc |
What are Fast Twitch Muscles?
Fast-twitch muscles are one of the types of skeletal muscles that are much needed for performing various activities of daily life. They are also known by a different name and that is – Type II muscles which are also bifurcated into two other types – Type II a and Type II b.
Type II a are the muscles that mainly perform anaerobic activities but for up to 30 minutes or less than it and contain a certain good number of mitochondrial cells. While Type II b are the muscles that also perform the anaerobic activity, the duration is limited to 1 minute or less.
The blood supply in the muscle fibres is very poor, because of which the appearance of the muscle fibres is very pale, and they are referred to as white muscle fibres.
What are Slow Twitch Muscles?
Slow-twitch muscles are also among the types of skeletal muscles that help perform various body activities for daily life. And another name used for the muscle fibres is commonly said to be – Type I muscle fibres.
These muscles are a great source of blood supply which makes them appear in deep red color which is why they are also referred to by the name red fibres. The amount of myoglobin and the number of mitochondrial cells in the muscle fibre is large.
On average, these slow-twitch fibres cover 80% of the human body as they connect the bone with tendons.
Main Differences Between Fast and Slow Twitch Muscles
- With continuous use of fast-twitch fibres, the individual easily gets fatigued, while with the use of slow-twitch fibres, the individual doesn’t get easily fatigued.
- The fast-twitch muscle is mainly good for the person lifting heavy weights, a sprinter, while the slow-twitch muscle is good for a marathon runner or a cyclist, etc.
- https://journals.lww.com/investigativeradiology/Abstract/2001/12000/Effects_of_Aging_on_Muscle_T2_Relaxation_Time_.3.aspx
- https://journals.physiology.org/doi/abs/10.1152/ajpcell.1992.263.3.C598
- https://journals.physiology.org/doi/abs/10.1152/ajpregu.1997.272.3.r849
- https://journals.physiology.org/doi/abs/10.1152/jappl.1979.47.2.263
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