Physical Education

Muscles and movement

The heart is made of a unique muscle type known as cardiac and it never tires. But the body also has many other paired muscles, some voluntary that are attached to the skeleton and help the body move, some involuntary that work the internal organs and cannot be controlled. Muscles and posture also go hand in hand, where regular exercise tones muscle and improves your posture to reduce strain on other parts of the body.

Muscle types

sprinter in the starting blocks

Sprinters have more fast twitch fibres

Cardiac muscle is unique to the heart. It never tires.

The body's involuntary muscles work our internal organs. They are outside our control.

Voluntary muscles make the body move. They are attached to the skeleton and can be controlled.

Voluntary muscles have fast twitch and slow twitch fibres. Fast twitch fibres contract quickly, but do not use oxygen well and tire quickly. Slow twitch fibres contract slowly, but use oxygen well and keep going for a long time. Top sprinters have more 'fast twitch' fibres. Endurance athletes tend to have more 'slow twitch' fibres.

Voluntary muscles

The key voluntary muscles used in sport are shown in the illustration.

Name of muscleFunctionExample in sport
TricepsExtend the arm at the elbowPress-up, throwing a javelin
BicepsFlex the arm at the elbowPull-up, drawing a bow in archery
DeltoidsMove the arm in all directions at the shoulderBowling a cricket ball
PectoralsAdduct the arm at the shoulderForehand drive in tennis
TrapeziusHold the shoulders in place, move head back and sidewaysHolding head up in rugby scrum
GlutealsAdduct and extend leg at the hipsPulling back leg before kicking a ball
QuadricepsExtend the leg at the kneeKicking a ball jumping upwards
HamstringsFlex the leg at the kneeBending knee before kicking a ball
GastrocnemiusPointing the toes, help to flex the kneeRunning
Latissimus dorsiAdduct and extend the arm at the shoulderButterfly stroke in swimming
AbdominalsFlex the trunk across the stomachPulling the body down when hurdling
A female archer draws her bow

Drawing a bow uses the biceps. Photo courtesy of BBC Sport

Origin and insertion of muscles (AQA only) The origin is the end of a muscle which is attached to a fixed bone. The insertion is the end of the muscle that is attached to the bone which moves.

Muscles and movement

A tug of war

In a tug of war muscles contract isometrically

Muscles contract [Contract: A muscle tenses as fibres shorten. ] when they work. If a muscle contracts to create movement, it is called an isotonic contraction.

An isotonic contraction can be concentric, which is where the muscle shortens as the fibres contract or eccentric, where the fibres contract as the muscle lengthens.

When a muscle contracts with no resulting movement, it is an isometric contraction.

Muscle pairs

Antagonistic pairs of muscles create movement when one (the prime mover) contracts and the other (the antagonist) relaxes. Examples of antagonistic pairs working are:

  • the quadriceps and hamstrings in the leg
  • the biceps and triceps in the arm

Muscle tone and posture

Muscle tone can be seen when muscles are in a state of slight tension and they are ready for action. Regular training tones muscles and helps to create good posture [Posture: The way you hold your body in position. ]. In addition, muscles will hypertrophy (increase in size) and develop better endurance [Endurance: The ability to work hard for long periods of time. ].

Muscle tone developed by regular exercise makes daily tasks such as shopping and gardening easier. It also helps to prevent injury as good posture reduces the strain on muscles, tendons and ligaments.

A tennis player hits a forehand shot

Good posture is important to tennis players. Photo courtesy of David Wuertele

Good posture helps with sporting performance as special positions are often crucial to success, eg the position throughout the golf swing.

People with good posture also feel better about themselves. An upright body position is often a sign of self confidence. People who are less confident will sometimes show this in their body language, for example by adopting a slouched posture.

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