Characteristic Slow-twitch (Type I) Fast-twitch (Type IIb) Speed of contraction Resistance to fatigue Main energy source Example sport The table below compa...
Question 1 Report
| Characteristic | Slow-twitch (Type I) | Fast-twitch (Type IIb) |
|---|---|---|
| Speed of contraction | ||
| Resistance to fatigue | ||
| Main energy source | ||
| Example sport |
The table below compares two types of muscle fibre found in the human body.
(a) Complete the table by filling in the missing information about each fibre type. [4]
Answer Details
(a) The completed table comparing slow-twitch and fast-twitch muscle fibres:
| Characteristic | Slow-twitch (Type I) | Fast-twitch (Type IIb) |
|---|---|---|
| Speed of contraction | Slow | Fast / Rapid |
| Resistance to fatigue | High | Low |
| Main energy source | Aerobic (using oxygen) | Anaerobic (without oxygen) |
| Example sport | Marathon running / long-distance cycling | 100 m sprint / shot put / weightlifting |
[1 mark per correct cell, 4 marks total]
Why these differences matter:
- Slow-twitch fibres are designed for sustained, low-intensity activity. They have a rich blood supply and many mitochondria, allowing them to produce energy aerobically for long periods without fatiguing. This makes them ideal for endurance events.
- Fast-twitch (Type IIb) fibres contract rapidly and generate high force, but they rely on anaerobic energy systems and fatigue quickly. They are suited to explosive, short-duration activities where maximum power is needed.
Most people have a roughly equal mix of both fibre types, but the proportion can vary. Elite sprinters tend to have a higher percentage of fast-twitch fibres, while elite endurance athletes tend to have more slow-twitch fibres.
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