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6.1 DIFFERENT KINDS OF MUSCLE

All muscles work by shortening or contracting. There are three different types in the human body…

Attached to bones

Work whenever you want them to

Also called skeletal muscle because of attachment to bones

OR Striated (striped) muscle because of it’s striped appearance under a microscope

Found in walls of internal organs: Stomach, gut, bladder and blood vessels.

Work on their own-you can’t control their movement.

Also called smooth muscle-no stripes.

Also involuntary, forms the walls of the heart.

Works non-stop without tiring.

Striated like voluntary muscle

Each contraction is a heart beat and pumps blood out of the heart and around your body.

In voluntary muscle… A signal from your brain- nervous system-voluntary muscles required- Muscle contraction = MOVEMENT

They form the red meat around your bones. They give shape to your body. Approximately 40% of your weight is voluntary muscle. With training we can adapt our muscles to help us to increase muscular strength, muscular endurance and flexibility.

Further information on voluntary muscle…

MUSCLE FIBRES

Contract quickly with a lot of force.

They also tire quickly and more easily.

Suited to anaerobic type events requiring short, sharp bursts of power.

Examples are sprinting or weightlifting.

Contract slowly, without significant force.

Do not tire easily and can keep working for long periods of time.

Suited to activities requiring more endurance like jogging, swimming and cycling long distances.

Fast twitch (White) Fibres

Slow twitch (Red) fibres

Muscles are made up of cells called fibres. Muscles contract or shorten because the fibres do. The number contracting at any one time depends on the amount of force needed. There are two types:

The mixture of muscle fibres in each muscle is different. Eg your gastrocnemius (calf) muscle contains a lot of fast twitch fibres.

Each individual has a different muscle fibre make up. Some distance runners would have up to 80% slow twitch fibres while body builders may have up to 80% fast twitch.

Red and white fibres cannot change from one to the other, even with training. Research has suggested however that there is a third type of muscle fibre, grey fibres, which can be trained either way.

Your muscle fibre make up is dependant on genetics. You inherited your mix of fast and slow twitch fibres from your parents.