Muscles and movement
For movement of the body to take place, muscles need to work in pairs – one muscle pulls in one way while the other muscle relaxes.
Muscles can be separated into four categories that relate to the specific movements they cause – these are:
- Flexors - these muscles cause a limb (arm, leg) to bend at a joint by contracting.
- Extensors - these muscles work with and against the flexor muscles and they contract to straighten a limb at a joint.
- Adductors - these muscles cause a limb to move towards the body.
- Abductors - these muscles work with and against the adductor muscles and they cause a limb to move away from the body.
Click on the links below to see some examples of muscle movement.
Biceps and triceps
This muscle pair is mainly involved in any movements of the arms, especially bending at the elbow. For example, throwing a ball or swinging a tennis racket will use these muscles.
When you bend your arm at the elbow, the bicep muscle is working as the flexor. Then, when you straighten your arm, the tricep muscle is working as the extensor.
Hamstrings and quadriceps
This muscle pair is involved in movements of the legs – for example, running or kicking a ball.
When you bend your leg at the knee, the hamstring muscle is working as the flexor. Then, when you straighten your leg, the quadricep muscle is working as the extensor.