A Healthy Body

1
A Healthy Body

• Lesson 4 Exercise and healthy muscles.

2
What muscles do

• All movement in the body is caused by muscles.
• Muscles cause movement by getting shorter.
• Getting shorter is called contracting.
• Muscles that move limbs work in pairs - one bends
  the limb, the other straightens it.

3
Example - bending and straightening the arm.
4
Muscle endurance (staying power).

• Muscles need oxygen to work.
• When they work hard, they need more.
• If they exercise hard or non-stop, they cant get
  enough oxygen and waste products build up.
• The muscles feel sore and tired. This is called
  muscle fatigue.
• The muscles may cramp and stop working
  altogether!
• Rest lets oxygen get to the muscles so that they
  can work again.

5
Exercising muscles

• Regular exercise (2 or 3 times a week) will make
  muscles stronger and able to keep working for
  longer.
• Exercise may make muscles bigger as well.
• Muscles that are not exercised become smaller,
  weaker and unable to work for long without rest.