How do the joints, muscles and fibre types produce and control movement in sport?
Joint types and movements, the antagonistic muscle action that produces them, muscle contraction types, and the three muscle fibre types with their roles in sport.
A focused answer to OCR A-Level PE on the skeletal and muscular systems: the synovial joints and their movements, antagonistic muscle action with agonist, antagonist and fixator, the three contraction types, and the structure and roles of the three muscle fibre types.
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What this dot point is asking
OCR wants you to identify the types of synovial joint and the movements they allow, explain the antagonistic muscle action that produces those movements (naming the agonist, antagonist and fixator), classify the type of contraction, and describe the three muscle fibre types and how they suit different sports.
Joints and their movements
A synovial joint is a freely movable joint enclosed in a capsule, with articular (hyaline) cartilage on the bone ends, synovial fluid to lubricate and nourish, ligaments joining bone to bone, and sometimes bursae to reduce friction. The shape of the joint sets which movements are possible.
The key movement terms are flexion (decreasing the joint angle), extension (increasing it), abduction (moving a limb away from the midline), adduction (towards the midline), rotation (turning about the long axis), plantar flexion and dorsiflexion at the ankle. Each links to a plane and axis, which you meet again in biomechanics.
Antagonistic muscle action
The roles swap depending on the movement. At the elbow, the biceps brachii is the agonist in flexion (the upward phase of a curl) and the triceps is the antagonist; in extension (a press-up upward phase) the triceps becomes the agonist and the biceps the antagonist. Learn the major muscle groups (quadriceps and hamstrings at the knee, gastrocnemius at the ankle, deltoid at the shoulder, gluteals at the hip, biceps and triceps at the elbow) so you can name the correct pair.
Types of muscle contraction
The three muscle fibre types
The proportion of each fibre type is largely inherited and helps explain why athletes specialise. A marathon runner is dominated by Type I fibres for fatigue resistance; a 100 m sprinter or weightlifter is dominated by Type IIx for explosive force; a 400 m or 800 m runner relies heavily on Type IIa. Endurance training can shift Type IIx fibres towards Type IIa characteristics (more mitochondria and capillaries), but it cannot turn a fast fibre into a true slow fibre, which is why elite sprinters and elite distance runners are rarely the same person.
Exam-style practice questions
Practice questions written in the style of OCR exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
OCR 20194 marksDuring the upward phase of a press-up, describe the joint action at the elbow and the antagonistic muscle action that produces it. Name the agonist, antagonist and the type of contraction.Show worked answer →
A Component 01 Section A application question. One mark each for the joint action, the agonist, the antagonist and the contraction type.
Award marks for: the elbow performs extension (the angle at the joint increases). The triceps brachii is the agonist (the muscle shortening to cause the movement) and the biceps brachii is the antagonist (relaxing and lengthening). Because the agonist shortens under tension to overcome the body weight, the contraction is concentric.
Markers reward naming the specific muscles, not just "arm muscles", and identifying the contraction as concentric because the muscle shortens while developing force.
OCR 20218 marksAnalyse how the proportion and characteristics of a performer's muscle fibre types suit them to either a 100 m sprint or a marathon.Show worked answer →
A Component 01 extended-response (levels of response) question. Markers reward accurate fibre characteristics (AO1), clear application to the named event (AO2) and a reasoned link to performance (AO3).
Award credit for: a marathon runner has a high proportion of Type I (slow oxidative) fibres, which contract slowly but resist fatigue, have many mitochondria and capillaries and a high aerobic capacity, so they sustain a steady pace for over two hours. A sprinter has a high proportion of Type IIx (fast glycolytic) fibres, which contract quickly and powerfully, have large stores of phosphocreatine and glycogen and a high anaerobic capacity, but fatigue within seconds, matching a race lasting about ten seconds. Type IIa (fast oxidative glycolytic) fibres sit between the two and can shift towards endurance with training.
A top-level answer links each characteristic to the demand of the event rather than listing fibre facts, and reaches a clear judgement on why the fibre profile suits that performer.
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Sources & how we know this
- OCR A Level Physical Education (H555) specification — OCR (2016)