Science 8th grade
UNIT 4: Respiration 4.4 Keeping fit
Science 8th grade
UNIT 4: Respiration 4.4 Keeping fit
How fit are you? A fit person can do moderate exercise casily, without getting too tired too quickly.
For most of us, we just need to be able to run for a bus, to go for a cycle ride or to climb a few flights of stairs. A professional athlete - such as a footballer, tennis player or racing car driver-has to be fit enough to do really vigorous exercise for a long time.
Energy for muscles
When you are exercising, your muscles need energy. Inside the muscle cells, energy is released from glucose, by respiration. The energy is transferred to movement energy in the muscles.
The harder your muscles work, the faster they respire. So hard-working muscles need really good supplies of the two reactants in respiration -glucose and oxygen.
Glucose and oxygen are brought to the muscles in the blood. This is why your heart beats faster when you exercise. The heart pumps blood more quickly to the muscles.
You also breathe faster when you exercise. Faster breathing moves air in and out of the lungs more quickly. This means that more oxygen can get into the blood from the air sacs each minute
Activity 4-4 (Investigating the effect of exercise on breathing rate)
SE: Plan and carry out an experiment to find out how a person's breathing rate changes when they do exercise.
You could use Activity 3.2 on page 35 to give you some ideas.
Check your plan with your teacher before you do your experiment.
Record your results in a results table. Display your results as a graph.
Write a short conclusion for your experiment.
Diet and fitness
Doing regular exercise will help you to keep fit. Exercise helps your heart and breathing muscles to get strong, so they can work hard for you when you need them to. Exercise also strengthens your muscles.
What you eat also affects your fitness. If someone cats too much and gets very overweight, they will become unfit because:
• the extra mass of their body means that more energy is needed to move it around.
• the heart has to work much harder to push blood around the larger body
• the space inside the arteries may get narrower, because fat deposits build up inside them.
Questions
1) Explain why each of the effects described in the bullet points above would make it more difficult to do energetic exercise.
2) Explain why a professional sportsperson often has a dict that contains:
a: plenty of protein on most days
b: carbohydrate (such as rice or pasta) just before a competition.