Question 1

What is the difference between isotonic and isometric contractions?

Accepted Answer

Isotonic contractions involve a change in muscle length and joint movement, while isometric contractions involve no change in muscle length or joint movement. Isotonic contractions can be concentric (muscle shortens) or eccentric (muscle lengthens under tension). For example, lifting a weight in a bicep curl is a concentric contraction, lowering it is eccentric, and holding the weight still is isometric.

Question 2

How do antagonistic muscle pairs work?

Accepted Answer

Antagonistic pairs consist of an agonist (prime mover) that contracts to produce movement, and an antagonist that relaxes to allow the movement. For example, during elbow flexion, the biceps brachii (agonist) contracts while the triceps brachii (antagonist) relaxes. During elbow extension, the roles reverse. This coordinated action ensures smooth, controlled movement.

Question 3

What are the main muscles used in sprinting?

Accepted Answer

Sprinting primarily uses the quadriceps (knee extension), hamstrings (knee flexion and hip extension), gluteals (hip extension), and calf muscles (gastrocnemius and soleus for ankle plantarflexion). The hip flexors (iliopsoas) are also important for lifting the thigh. Additionally, the core muscles (abdominals and erector spinae) stabilise the trunk.

Question 4

Why do muscles work in pairs?

Accepted Answer

Muscles work in pairs because they can only pull, not push. To produce movement in opposite directions, two muscles are needed: one to pull the bone one way (agonist) and another to pull it back (antagonist). This pairing allows for controlled, bidirectional movement at joints.

Question 5

What is the role of a fixator muscle?

Accepted Answer

A fixator muscle stabilises a joint or body part to allow the agonist to work effectively. For example, during a bicep curl, the shoulder muscles (e.g., deltoid and rotator cuff) act as fixators to keep the shoulder joint stable, so the biceps can focus on flexing the elbow.

Question 6

How do muscle fibre types affect athletic performance?

Accepted Answer

Slow-twitch fibres (Type I) are fatigue-resistant and suited for endurance activities like long-distance running. Fast-twitch fibres (Type IIa and IIb) generate more force but fatigue quickly, making them ideal for explosive activities like sprinting or weightlifting. Athletes in different sports have varying proportions of these fibres, which influences their performance and training needs.

The structure and function of the muscular system

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Related Topics in OCR GCSE Physical Education

Aerobic and anaerobic exercise

Applied anatomy and physiology

Applying the principles of training

Characteristics of skilful movement

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