# Explain how the length–tension relationship of a sarcomere determines the force a skeletal muscle can generate at different degrees of stretch.

> IB DP Biology Higher Level (2023 syllabus) — B3.3 Muscle and motility (HL only) · Explain · 4 marks

> Skeletal muscle generates maximum force only within a specific range of sarcomere lengths. When a muscle is either overstretched or compressed beyond this optimal range, force production declines.

## Mark scheme (4 marks)

1. At optimal sarcomere length, maximum overlap between actin and myosin filaments allows the greatest number of cross-bridges to form simultaneously, producing maximum force.
2. When a sarcomere is overstretched, actin and myosin filaments overlap less (or not at all), so fewer cross-bridges can form, reducing force production.
3. When a sarcomere is excessively shortened/compressed, actin filaments from opposite Z-discs overlap with each other (or myosin contacts Z-discs), sterically hindering cross-bridge cycling and reducing force.
4. The relationship is therefore described as an inverted U-curve (or bell-shaped curve): force is low at very short and very long lengths, with a plateau of maximum force at intermediate (resting/optimal) sarcomere lengths of approximately 2.0–2.4 µm in human skeletal muscle.

## Key terms

- [sarcomere](https://www.gradenine.co.uk/glossary/sarcomere)
- [length–tension relationship](https://www.gradenine.co.uk/glossary/length-tension-relationship)

## Related

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-length-tension-relationship-of-37b01d8c) · Published by Druglandscape Ltd.