Front
Back
Major muscle: quadriceps
Front thigh muscles that extend the knee.
Major muscle: hamstrings
Back thigh muscles that flex the knee and extend the hip.
Major muscle: tibialis anterior
Shin muscle that dorsiflexes the ankle.
Major muscle: gastrocnemius
Calf muscle that plantar flexes the ankle and assists knee flexion.
Type I muscle fibres / slow twitch
Fibres that contract slowly, resist fatigue well, and are suited to aerobic endurance work.
Characteristics of Type I fibres
High fatigue resistance, lower force, many mitochondria, high myoglobin content, strong aerobic capacity.
Type IIa muscle fibres
Fast fibres with a mix of aerobic and anaerobic qualities; suited to repeated powerful efforts.
Characteristics of Type IIa fibres
Faster contraction, moderate fatigue resistance, moderate-to-high force production.
Type IIb muscle fibres
Very fast fibres suited to explosive anaerobic activity.
Characteristics of Type IIb fibres
High force, very fast contraction, fatigue quickly, low aerobic capacity.
Antagonistic muscle action
When muscles work in pairs to create movement.
Agonist / prime mover
The muscle mainly responsible for producing a movement.
Antagonist
The muscle that opposes the agonist and relaxes or lengthens during movement.
Fixator
A muscle that stabilises one part of the body so movement can occur elsewhere.
Synergist
A muscle that assists the agonist to produce movement.
