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.
The heart is known as the cardiac muscle and never tires.
Voluntary muscles have fast twtch and slow twitch fibres:
FAST TWITCH FIBRES
- contract quickly
- don't use oxygen well
- tire quickly
SLOW TWITCH FIBRES
- contract slowly
- use oxygen well
- keep going for a long time
Sprinters have more fast twitch fibres which allows them to run fast over a short distance. Endurance runners have more slow twitch fibres which allows them to run over a long distance without tiring quickly.
Triceps: Extend the arm at the elbow
Biceps: Flex the arm at the elbow
Deltoids: Move the arm in all directions at the shoulder
Pectorals: Adduct the arm at the shoulder
Trapezius: Move head back and sideways, holds the shoulders in place
Gluteals: Adduct and extend leg at the hips
Quadriceps: Extend the leg at the knee
Hamstrings: Flex the leg at the knee
Gastrocnemius: Help to flex knee, pointing toes
Latissimus dorsi: Adduct and extend the arm at the shoulder
Abdominals: Flex the trun across the stomache
Muscles and Movement
Muscles contract when they work, when a muscle contracts to make movement it is called an isotonic contraction.
An isotonic contraction can be concentric or eccentric:
- muscle shortens as the fibres contract
- muscle lengthens as the fibres contract
When a muscle contracts and no movement is made its an isometric contraction.
Antagonistic pairs of muscles create movement when one muscle contracts and the other relaxes.
Examples of antagonistic muscles are:
- Hamstrings and quadriceps in the leg
- Biceps and triceps in the arm
When one muscle contracts the other relaxes and visa versa...
Muscle tone and posture
Muscle tone can be seen when 'tensed' or when ready for action. Regular training creates both good muscle tone and good posture.
Training will cause muscles to HYPERTROPHY (increase in size) and develop better ENDURANCE.
Muscle tone developed by regular training makes daily tasks much easier. It also helps to prevent injury as good posture reduces the strain on muscles, tendons and ligaments.
Good posture also makes people feel better about themselves, you can often tell someones self-confidence by their posture.