Chapter 7 of 8

All 8 chapters
  1. 1The skeleton, readunderstood
  2. 2Joints, readunderstood
  3. 3Muscles move bones, readunderstood
  4. 4Teeth, readunderstood
  5. 5Food groups, readunderstood
  6. 6A balanced diet, readunderstood
  7. 7Exercise and rest, readunderstood
  8. 8Keeping food safe, readunderstood

S2.3.7 Chapter 7

Exercise and rest

Why does my heart beat faster when I run?

Your guess

Pick one before you read on. It is fine to be wrong.

Your guess

  • You picked A. Read on. At the end, the chapter comes back to your guess.

  • You picked B. Read on. At the end, the chapter comes back to your guess.

  • You picked C. Read on. At the end, the chapter comes back to your guess.

By the end you can

  • Count your pulse before and after running
  • Explain how exercise and sleep keep bones and muscles strong

Your heart pumps blood round your body. Each beat pushes blood along.

Your pulse is the beat you can feel in your wrist. It shows how fast your heart is beating.

Lay two fingers on the inside of your wrist. Use the thumb side. Press a little. Never use your thumb. It has a beat of its own.

The inside of a wrist. Two fingers lie side by side on the wrist, on the thumb side. A dot just past their tips marks the pulse. Labels: thumb side, two fingers, pulse.thumb sidepulsetwo fingers

Cannot find it? Move your fingers a little. Press a little harder or softer.

Count the beats for 15 seconds. Then multiply by 4. That gives the beats in one minute.

See it three ways

As a picture

Four boxes in a row. Each box holds the number 20 and has the label 15 sec under it. Below the row is the label 1 minute: 80 beats. Labels: 20, 15 sec, 1 minute: 80 beats.2015 sec2015 sec2015 sec2015 sec1 minute: 80 beats

In words

You count 20 beats in 15 seconds. Four times 15 seconds is one minute. So you multiply 20 by 4.

In symbols

20 × 4 = 80 beats in one minute

At rest, many young people have 70 to 100 beats a minute. After running it is much higher.

Draw it first

Draw what running does to your pulse

  1. Two bars stand on a line. The short bar has the number 80 above it and the label rest below it. The tall bar has the number 144 above it and the label after running below it. Beside the tall bar are the labels more blood and to muscles. Under both bars is the label beats in one minute. Labels: 80, rest, 144, after running, more blood, to muscles, beats in one minute.80restbeats in one minute

    1 Draw a line. Write beats in one minute under it. Draw a short bar. Write 80 above it and rest below it.

  2. Two bars stand on a line. The short bar has the number 80 above it and the label rest below it. The tall bar has the number 144 above it and the label after running below it. Beside the tall bar are the labels more blood and to muscles. Under both bars is the label beats in one minute. Labels: 80, rest, 144, after running, more blood, to muscles, beats in one minute.80rest144after runningbeats in one minute

    2 Draw a tall bar. Write 144 above it and after running below it.

  3. Two bars stand on a line. The short bar has the number 80 above it and the label rest below it. The tall bar has the number 144 above it and the label after running below it. Beside the tall bar are the labels more blood and to muscles. Under both bars is the label beats in one minute. Labels: 80, rest, 144, after running, more blood, to muscles, beats in one minute.80rest144after runningmore bloodto musclesbeats in one minute

    3 Beside the tall bar, write more blood to muscles.

When you run, your muscles work hard. They need more blood. So your heart beats faster to send it.

At rest. One arrow carries some blood from the heart to the muscles. The pulse is 80 beats a minute. Labels: heart, muscles, some blood, 80 beats a minute.heartmusclessome blood80 beats a minute
After running. Three thick arrows carry more blood from the heart to the muscles. The pulse is 144 beats a minute. Labels: heart, muscles, more blood, 144 beats a minute.heartmusclesmore blood144 beats a minute

Try it

Count your pulse before and after running

You need: a clock or watch, if you have one, or a string 25 cm long and a small stone, a friend to help with the string, open, flat ground, paper and a pencil.

Be safe: Run only on open ground, away from roads and holes. Stop at once if you feel ill or dizzy. Stop at once if your chest hurts. With a heart or breathing problem, ask a grown up first.

  1. No clock? A friend holds the string, 25 cm from hand to stone. They let the stone swing. Each return to their side takes about one second. They count 15 returns while you count beats.
  2. Sit still for two minutes. Find your pulse with two fingers.
  3. Count the beats for 15 seconds. Write the number. Multiply it by 4.
  4. Run on open ground for one minute.
  5. Stop. Find your pulse fast. Count for 15 seconds. Write it. Multiply by 4.
  6. Sit still for two minutes. Count again, and write it.

What you will see: Your pulse is much faster after running. After a rest it slows down again. Numbers differ from person to person, so compare your own.

If you cannot try it, this is what happens.
A table with three columns, When, 15 sec and 1 min. At rest: 20 beats in 15 seconds, 80 in a minute. After run: 36 and 144. Rest again: 24 and 96. Labels: When, 15 sec, 1 min, At rest, 20, 80, After run, 36, 144, Rest again, 24, 96.When15 sec1 minAt rest2080After run36144Rest again2496

Exercise is moving your body so that it works hard. Walking, running, jumping and games are exercise.

Bones are alive. Exercise that carries your weight makes bones stronger. It makes muscles stronger too.

Rest is stopping so your body can recover. Sleep is the best rest.

Hard work tires your muscles. They mend and grow while you rest and sleep. Most young people need 9 hours of sleep a night or more.

Three boxes one under the other, joined by arrows that point down. The first is exercise tires muscles. The second is rest and sleep. The third is muscles mend and grow. Labels: exercise tires muscles, rest and sleep, muscles mend and grow.exercise tires musclesrest and sleepmuscles mend and grow

A wrong idea many people have

You get stronger while you are exercising.

Why it feels right: Your muscles feel hard and strong while you use them.

The test that breaks it: Open and close one hand as fast as you can. Squeeze hard. Keep going for half a minute. Is your grip stronger or weaker at the end? It is weaker. Now rest for two minutes. Your grip comes back.

What is true: Exercise tires muscles. Most of the growing happens in the rest afterwards, and in sleep.

Key words

pulse
the beat of your heart, which you can feel in your wrist.
exercise
moving your body so that it works hard.
rest
stopping so your body can recover. Sleep is the best rest.

Back to your guess

The answer is C: Because my muscles need more blood.

Your muscles need more blood when they work hard. Your heart beats faster to send it.

Check yourself

Try each one before you look. A wrong answer tells you where to go next.

  1. Why does your pulse go faster when you run?

    Tap your answer.

    1. Not this one. A heart that beats faster is not weaker. It is working harder to send more blood. Try another.

    2. Yes, that is right. Working muscles need more blood. The heart beats faster to send it.

    3. Not this one. Warm air is not the reason. Your muscles need more blood to work hard. Try another.

    See the answer

    Your heart sends more blood to your hard working muscles.

    Working muscles need more blood. The heart beats faster to send it.

    • If you chose A: A heart that beats faster is not weaker. It is working harder to send more blood.
    • If you chose C: Warm air is not the reason. Your muscles need more blood to work hard.

  2. Kofi counts 22 beats in 15 seconds. How many beats is that in one minute?

    Tap your answer.

    1. Not this one. That is the count for 15 seconds. A minute is four times as long. Try another.

    2. Not this one. You added 15. To get one minute, multiply by 4. Try another.

    3. Not this one. You multiplied by 15. Fifteen seconds fits 4 times into a minute, so multiply by 4. Try another.

    4. Yes, that is right. 15 seconds fits 4 times into one minute. So 22 × 4 = 88 beats.

    See the answer

    88

    15 seconds fits 4 times into one minute. So 22 × 4 = 88 beats.

    • If you chose A: That is the count for 15 seconds. A minute is four times as long.
    • If you chose B: You added 15. To get one minute, multiply by 4.
    • If you chose C: You multiplied by 15. Fifteen seconds fits 4 times into a minute, so multiply by 4.

  3. Mei has a pulse of 96 beats in a minute. How many beats would she count in 15 seconds?

    See the answer

    24

    A minute is four times 15 seconds. So 96 ÷ 4 = 24.

  4. Which of these helps bones get stronger?

    Tap your answer.

    1. Not this one. Bones are alive. Like muscles, they get stronger when you use them. Try another.

    2. Not this one. Bones are alive. They grow stronger when they carry your weight as you move. Try another.

    3. Yes, that is right. Exercise that carries your weight makes bones stronger.

    See the answer

    Running and jumping games

    Exercise that carries your weight makes bones stronger.

    • If you chose A: Bones are alive. Like muscles, they get stronger when you use them.
    • If you chose B: Bones are alive. They grow stronger when they carry your weight as you move.

  5. When do your muscles mend and grow stronger?

    Tap your answer.

    1. Not this one. Running tires muscles. They mend and grow afterwards, in rest. Try another.

    2. Not this one. Muscles do change. They grow stronger with use and rest. Try another.

    3. Not this one. Food helps the body. Muscles mend and grow while you rest and sleep. Try another.

    4. Yes, that is right. Hard work tires muscles. They mend and grow while you rest and sleep.

    See the answer

    While you rest and sleep

    Hard work tires muscles. They mend and grow while you rest and sleep.

    • If you chose A: Running tires muscles. They mend and grow afterwards, in rest.
    • If you chose B: Muscles do change. They grow stronger with use and rest.
    • If you chose C: Food helps the body. Muscles mend and grow while you rest and sleep.

  6. From an earlier chapter

    When you run, your legs carry your weight. Which is the longest bone in your body?

    Tap your answer.

    1. Yes, that is right. Your thigh has one bone. It is the longest bone in your body.

    2. Not this one. The backbone is a stack of small bones, not one long bone. Go to S2.3.1. Try another.

    3. Not this one. Ribs are short curved bones round the chest. Go to S2.3.1. Try another.

    See the answer

    The thigh bone

    Your thigh has one bone. It is the longest bone in your body.

    • If you chose B: The backbone is a stack of small bones, not one long bone. Go to S2.3.1.
    • If you chose C: Ribs are short curved bones round the chest. Go to S2.3.1.

  7. Kofi is running and his chest starts to hurt. What should he do?

    Tap your answer.

    1. Not this one. Pain is a warning. Exercise should not hurt your chest. Stop at once. Try another.

    2. Not this one. Water does not fix chest pain. Stop at once and tell a grown up. Try another.

    3. Not this one. Chest pain needs a stop at once. Tell a grown up now. Try another.

    4. Yes, that is right. Never exercise through chest pain. Stop, rest and tell a grown up.

    See the answer

    Stop and rest, and tell a grown up.

    Never exercise through chest pain. Stop, rest and tell a grown up.

    • If you chose A: Pain is a warning. Exercise should not hurt your chest. Stop at once.
    • If you chose B: Water does not fix chest pain. Stop at once and tell a grown up.
    • If you chose C: Chest pain needs a stop at once. Tell a grown up now.

  8. Amina wants to feel her pulse. What should she do?

    Tap your answer.

    1. Not this one. The thumb has a beat of its own. Use two fingers. Try another.

    2. Not this one. Press only a little. A hard press can hide the beat. Try another.

    3. Yes, that is right. Use two fingers. Lay them on the inside of the wrist, on the thumb side.

    4. Not this one. The pulse is on the inside of the wrist. Use the thumb side. Try another.

    See the answer

    Lay two fingers on the inside of her wrist.

    Use two fingers. Lay them on the inside of the wrist, on the thumb side.

    • If you chose A: The thumb has a beat of its own. Use two fingers.
    • If you chose B: Press only a little. A hard press can hide the beat.
    • If you chose D: The pulse is on the inside of the wrist. Use the thumb side.

Keep it

Copy this into your exercise book.

Two fingers on your wrist find your pulse. Count for 15 seconds and multiply by 4. Running makes your heart beat faster. Games and running make bones and muscles stronger. Muscles mend and grow in rest and sleep.

Draw: Draw two bars: rest and after running. Make the second bar taller. Write pulse above them.

Reading with a child? A short page for the adult: what this chapter teaches and three questions to ask.

No internet tomorrow? Save the whole book as one file (704 KB). It opens on any phone.