The Heave-Ho Club

A 3D tour of the muscles for children about five to eight. The muscles glow soft red over the skeleton of a see-through child: a message from the brain makes the biceps pull and the arm bend, the biceps and triceps take turns, tendons tug the bones, and the heart and tummy muscles work all by themselves. Then it looks inside the biceps, at its bundles of tiny fibres all pulling together. Free, with no ads and no sign-ups.

What your child will learn

• Muscles make you move. You have more than 600 of them, and they pull on your bones. Tendons, strong cords, tie them on.
• Your brain tells your muscles what to do: a message goes down the spinal cord and along a nerve, and the muscle contracts, getting shorter and pulling. The muscles you move when you want to are voluntary.
• Muscles can pull, but they can't push, so they work in pairs: the biceps bends the elbow and the triceps straightens it; the quadriceps straighten the knee and the hamstrings bend it. When one pulls, the other relaxes.
• Inside, a muscle is made of thousands of tiny fibres, bundled together, that all get shorter at once.
• Some muscles work all by themselves: the heart muscle (cardiac muscle) beats day and night, and smooth muscles in the stomach squeeze food along.
• Muscles keep you going: when you're cold they shiver, making heat to warm you up, and moving and playing, in the ways you can, make them and the heart stronger.

How it works

Story. An emu tells it in nine short chapters (emus have long, powerful legs). It starts with what a child can feel (make a muscle, smile), then follows a ringed message from the brain to the biceps, which pulls and bends the arm, and the chapter waits for it. The page turns to a close-up, the biceps cut open lengthways and drawn big and simple: a message comes down the nerve, every fibre tightens together, and the tendon tugs the bone; the chapter waits for the muscle to relax. The wallaby drops in as the heart beats. Then the snow falls and the muscles shiver, the emu and the child run, and the child plays. Every word is spoken and shown.

Explore. Turn the child round, peek inside (the skin fades away to show the muscles), or tap any muscle to hear its name and what it does. Tap the biceps with the skin peeled away to see the close-up. Four buttons: Lift (the arms lift and lower, the biceps and triceps taking turns), Run (running on the spot, the leg muscles working in turn), Beat (the heart muscle beats, faster, then calms) and Shiver (snow, and the muscles shiver to warm you). Follow a message takes a message from the brain to the biceps, again and again, and What's this? shows the parts one at a time, including the close-up.

Quiz. Six picture questions, read aloud, so it works before your child can read. A wrong answer greys out and they have another go; nothing is ever lost. Finishing brings a new animal for their My mob book, and a card of the words they now know.

The real words it teaches

The tour uses the real names for the parts, and says what each one means the first time. These are on the card at the end, and a tap on each says what it means. Cardiac muscle, the Achilles tendon, the quadriceps and hamstrings and the bundles are named in the story, and more muscles (the deltoid, pectorals, abdominals, glutes, calf and shin muscles) in Explore, but kept off the card.

• Muscle: it pulls on your bones to make you move.
• Tendon: a strong cord that ties a muscle to a bone.
• Biceps: the muscle on the front of your upper arm. It bends your arm.
• Triceps: the muscle on the back of your upper arm. It straightens your arm.
• Contract: when a muscle gets shorter and pulls.
• Fibre: one of the thousands of tiny threads a muscle is made of.
• Heart muscle: the muscle that makes your heart beat, all by itself.
• Voluntary: a muscle you move when you want to, like your biceps.

For grown-ups: the muscles, in detail

The muscles are drawn simply, and the close-up much bigger than real. What it shows, cartoon but true:

1. Three kinds of muscle. Skeletal muscle moves the skeleton and is under voluntary control; it looks striped (striated) under a microscope. Cardiac muscle, in the heart, is striated too, but beats by itself, set going by the heart's own pacemaker. Smooth muscle, in the walls of the stomach, gut, blood vessels and bladder, isn't striped and works without our thinking about it.
2. Inside a skeletal muscle: the whole muscle is wrapped in connective tissue (the epimysium); inside, its fibres (long muscle cells, each with many nuclei) are grouped in bundles called fascicles, each wrapped too (the perimysium). Each fibre is packed with myofibrils, made of repeating units (sarcomeres) of the proteins actin and myosin, which slide past each other to shorten the fibre. The close-up shows the bundles and fibres, but not the threads inside.
3. The message: a motor neuron carries a signal from the brain and spinal cord to the muscle. At each fibre it releases a chemical messenger (acetylcholine), and the fibre contracts. One neuron and the fibres it serves are a motor unit; more units working means a stronger pull. Muscles are richly supplied with blood vessels, bringing oxygen and nutrients.
4. Pairs: muscles can only pull. Around a joint, one muscle (the agonist, such as the biceps) contracts while its partner (the antagonist, the triceps) relaxes and lengthens; then they swap. Tendons join muscle to bone; ligaments join bone to bone. The Achilles tendon joins the calf muscles to the heel bone.
5. Shivering is quick, involuntary contractions of skeletal muscle, switched on by the hypothalamus in the brain when the body is cold; the work makes heat. Exercise makes muscle fibres bigger and better supplied with blood, and makes the heart pump more strongly; children build strength and coordination through active play.

Also left out: tendon sheaths, the many small muscles of the hands, feet and face by name, and the chemistry of a contraction (calcium, ATP).

What it practises

• My body. How the body works, and the real names of its parts: the heart's atria and ventricles, arteries and veins (the Lub-Dub Club).
  AC9S1U01 (Science, Year 1); AC9HPFM03 (Health and Physical Education, Foundation)

The codes are from the Australian Curriculum v9 (Foundation to Year 1). Each links to the official wording.

Things to try together

• Make a muscle, and feel the biceps get hard. Now straighten the arm and feel the triceps on the back.
• Feel the back of your foot just above the heel: the Achilles tendon. Stand on tiptoe and feel the calf work.
• Put a hand on your chest and feel your heart beat. Move about for a minute and feel it again.
• Make funny faces in a mirror: lots of little face muscles at work.
• The sheet to print has muscles to label, pull partners to join, and a place to draw a muscle and count heartbeats.

For every child, and every body

Moving and playing help keep muscles strong "in the ways you can", and "wheeling" is named alongside running, swimming, dancing and climbing, so a child who uses a wheelchair, or moves differently, is included. The tour never compares bodies: nothing is big or small, strong or weak, and there are no six-packs, weights or body shapes. It says nothing about muscle conditions, cramps or injuries, and shivering is shown as the body warming itself, with a warm jumper to help. On the sheet, heartbeats are counted "after moving about", in any way the child likes, and there's no right number.

• Every word is spoken and written, so it works with the sound on or off.
• It works with a keyboard: the arrow keys turn the child in Explore, and What's this? steps through the parts.
• The hero has its own shape as well as colour: a message is a glowing zap in an orange ring; in the close-up the fibres are long striped rods, the tendon a shiny cord, heat wavy lines and snow six-pointed flakes.
• If your device asks for less motion, the camera cuts instead of flying, the page turns without the iris, the run becomes a slow march, the shiver has no trembling, and nothing spins or wobbles.

What's simplified, and why

• The muscles are drawn as about 20 smooth shapes rather than more than 600, over the Click-Clack Club's simple skeleton; the tummy muscles are one smooth sheet down each side, and the smile muscles are two little straps in the cheeks.
• Only one nerve is drawn, from the spinal cord in the neck to the right biceps, and the message is shown as one zap; really, nerves reach every muscle, and the arm's nerves leave the spinal cord from the neck.
• The heart and the stomach are the hub's simple shapes, faint. The heart's beat and the stomach's squeeze are drawn as the whole shape swelling and squashing.
• When a muscle works, it's drawn bunching up and glowing, bigger than a real muscle would bulge, so it's easy to see which one is pulling.
• The close-up is one drawing of the biceps, cut open lengthways, with five bundles of four fibres each (really, thousands of fibres), one nerve branch to each bundle, and one blood vessel in and one out. When the message arrives, every fibre tightens at once and the muscle gets shorter and fatter; the tiny threads inside the fibres (actin and myosin) aren't drawn.
• Shivering is drawn as quick little pulls all over, with snow and heat lines; the brain's part (the hypothalamus turning shivering on) is left to the guide.
• Running on the spot is drawn with the thigh and calf muscles taking turns; really, many more muscles work together.

Where the facts come from

Every fact the tour states was checked against the page linked beside it.

• "the legs are long and powerful"
  In the tour: Hello! I'm Emu. My long, strong legs help me run! (and: My leg muscles are big and strong.)
  Australian Museum — Emu
• "Did you know you have more than 600 muscles in your body?"; "Skeletal muscles are held to the bones with the help of tendons"; "the skeletal muscles work with your bones to give your body power and strength"
  In the tour: These are your muscles. They make you move! You have more than 600 of them, from your head to your toes. (Tap: Your muscles: more than 600 of them. They pull on your bones to make you move.)
  KidsHealth (kids) — Your Muscles
• "Facial muscles don't all attach directly to bone like they do in the rest of the body. Instead, many of them attach under the skin. This allows you to contract your facial muscles just a tiny bit and make dozens of different kinds of faces."
  In the tour: Smile, and your smile muscles are working! (Tap: Your smile muscles, in your face. Your face muscles help you make lots of different faces. Smile!)
  KidsHealth (kids) — Your Muscles
• "When you make a muscle in your arm, you tense your biceps muscle"; "opposing pairs such as the biceps and triceps on the front and back of the upper arm" (Better Health Channel)
  In the tour: Can you make a muscle? Bend your arm and squeeze! That bump is your biceps, on the front of your upper arm.
  KidsHealth (kids) — Your Muscles
• "Muscles get their signals to contract and relax from the brain"; the spinal cord and nerves "let messages flow back and forth between the brain and body" (KidsHealth, Your Brain & Nervous System)
  In the tour: Your brain sends a message, down your spinal cord and along a nerve. (Follow a message; Tap: Your brain. It sends messages to your muscles to tell them what to do. A nerve. It carries messages from your brain to your muscles.)
  KidsHealth (kids) — Your Muscles
• the spinal cord: "a long bundle of nerves inside your spinal column, the vertebrae that protect it"; the nervous system lets "messages flow back and forth between the brain and body"; "If you're too cold, the hypothalamus gets you shivering."
  In the tour: Tap: Your spinal cord. It carries messages from your brain to the rest of your body.
  KidsHealth (kids) — Your Brain & Nervous System
• muscles "contract (tighten up) and relax"; "When you make a muscle in your arm, you tense your biceps muscle"
  In the tour: The muscle contracts: it gets shorter and pulls!
  KidsHealth (kids) — Your Muscles
• "Muscles can pull on bones, but they can't push them back to their original position, so the muscles work in pairs"; "The extensor muscle relaxes and stretches as the flexor muscle contracts"
  In the tour: Muscles can pull, but they can't push. So they work in pairs. When one pulls, the other relaxes.
  KidsHealth (kids) — Your Muscles
• the biceps: "Flex your arm at your elbow (bring your hand to your ear)"; the triceps: "Extend (straighten) your forearm at your elbow"
  In the tour: Your biceps pulls, and your arm bends. Your triceps, on the back, pulls it straight again. (Tap lines for the biceps and triceps; the Lift button.)
  Cleveland Clinic — Arm Muscles
• "Tendons are cords made of tough tissue, and they work as special connector pieces between bone and muscle"
  In the tour: Tendons: strong cords that tie your muscles to your bones. When your biceps pulls, its tendon tugs the bone, and up comes your arm! (Tap: A tendon: a strong cord that ties a muscle to a bone.)
  KidsHealth (kids) — Your Muscles
• "The Achilles tendon is a band of tough tissue on the back of the foot. It connects the heel bone to the calf muscles."
  In the tour: Feel the back of your foot, just above your heel. That's your Achilles tendon!
  KidsHealth (teens) — Achilles Tendonitis (what the Achilles tendon is)
• "Thousands, or even tens of thousands, of small fibers make up each muscle"; "A muscle is made up of thousands of elastic fibres bundled tightly together" (Better Health Channel)
  In the tour: A muscle is made of thousands of tiny fibres, bundled together. (Tap: Muscle fibres… There are thousands of them in a muscle.)
  KidsHealth (kids) — Your Muscles
• "Each muscle is wrapped in a sheath of dense, irregular connective tissue called the epimysium"; "muscle fibers are organized into bundles, called fascicles, surrounded by a middle layer of connective tissue called the perimysium"
  In the tour: Tap: A bundle: lots of muscle fibres, wrapped up together. The whole muscle has a wrapper too.
  OpenStax Anatomy & Physiology 2e (Oregon State) — Skeletal Muscle
• skeletal muscles are "sometimes called striated muscle because the light and dark parts of the muscle fibers make them look striped"
  In the tour: The close-up: the fibres drawn with faint stripes. (Tap: Muscle fibres: long, thin and stripy.)
  KidsHealth (kids) — Your Muscles
• "Every skeletal muscle is also richly supplied by blood vessels for nourishment, oxygen delivery, and waste removal. In addition, every muscle fiber in a skeletal muscle is supplied by the axon branch of a somatic motor neuron, which signals the fiber to contract."
  In the tour: When a message comes, they all get shorter together, and the muscle pulls! Then they relax, and get long again. (Tap: Blood vessels: tubes that bring the muscle blood, with the oxygen it needs.)
  OpenStax Anatomy & Physiology 2e (Oregon State) — Skeletal Muscle
• "The muscle that makes up the heart is called cardiac muscle"; "cardiac muscle works all by itself with no help from you"
  In the tour: Your heart is a muscle too. It's called cardiac muscle. It beats all by itself, day and night, with no help from you. (Tap: Your heart: a muscle that beats all by itself, day and night. The Beat button.)
  KidsHealth (kids) — Your Muscles
• smooth muscles: "In your stomach and digestive system, they contract and relax to allow food to make its journey through the body"
  In the tour: Muscles in your stomach squeeze your food along, all by themselves too. (Tap: Your stomach. Its muscles squeeze your food, all by themselves.)
  KidsHealth (kids) — Your Muscles
• "Shivering is the rapid contractions of our muscles over and over"; it "releases heat that helps to warm us up"
  In the tour: When you're cold, your muscles shiver: tiny, quick pulls, over and over. That makes heat, to warm you up! (The Shiver button.)
  The Conversation — Curious Kids: why do we shiver when we feel cold?
• "Some of the biggest and most powerful muscles are your calf and thigh muscles"
  In the tour: My leg muscles are big and strong. When you run, lots of your muscles work together. (The Run button.)
  KidsHealth (kids) — Your Muscles
• the quadriceps "work together to straighten the knee in activities such as kicking, jumping, squatting, and cycling"; the hamstrings "bend your knees"
  In the tour: Your quadriceps straighten your knee, and your hamstrings bend it. Another pair! (Tap lines for the quadriceps and hamstrings.)
  Hospital for Special Surgery — A Guide to Your Leg Muscles
• the calf "controls plantar flexing your foot" (pointing it, which lifts the heel); the tibialis anterior is "the main muscle used to raise the front of your foot upward toward your shin"; the gluteus maximus: "It's one of the muscles you use to climb a flight of stairs"
  In the tour: Tap: Your calf muscle… It helps you stand on tiptoe. Your shin muscle… It lifts the front of your foot up. Your glutes… You use them to climb the stairs.
  Hospital for Special Surgery — A Guide to Your Leg Muscles
• "Your deltoid muscles help you move your shoulders every which way"; "The pectoralis muscles are found on each side of your upper chest"; "Below these pectorals, down under your ribcage, are your rectus abdominus muscles, or abdominals"; "You'll be sitting on your gluteus maximus"
  In the tour: Tap: the deltoid, the pectorals, the tummy muscles (abdominals) and the glutes.
  KidsHealth (kids) — Your Muscles
• the forearm muscles: "Bend, flex and extend your wrist and fingers"
  In the tour: Tap: Your forearm muscles. They bend and straighten your wrist and your fingers.
  Cleveland Clinic — Arm Muscles
• "When you exercise, you make your body stronger"; running and jumping "can make your leg and arm muscles stronger"; "Your heart is a muscle. It works hard, pumping blood every day. Help your heart get stronger by doing aerobic… exercise"
  In the tour: Running and jumping make your leg muscles stronger. Moving and playing, in the ways you can, help keep your muscles strong. Your heart gets stronger as you play, too.
  KidsHealth (kids) — Why Exercise Is Wise

Every word it says

The whole script, for reading along, or for a child who'd rather read than listen.

1. Heave, ho!

• Hello! I'm Emu. My long, strong legs help me run!
• These are your muscles. They make you move!
• You have more than 600 of them, from your head to your toes.
• Smile, and your smile muscles are working!

2. Make a muscle

• Can you make a muscle? Bend your arm and squeeze!
• That bump is your biceps, on the front of your upper arm.
• Your brain sends a message, down your spinal cord and along a nerve.
• The muscle contracts: it gets shorter and pulls!

3. Pull, don't push

• Muscles can pull, but they can't push.
• So they work in pairs. Your biceps pulls, and your arm bends.
• Your triceps, on the back, pulls it straight again.
• When one pulls, the other relaxes. Heave, ho!

4. Tied on tight

• Tendons: strong cords that tie your muscles to your bones.
• When your biceps pulls, its tendon tugs the bone, and up comes your arm!
• Feel the back of your foot, just above your heel. That's your Achilles tendon!

5. Inside a muscle

• Let's look inside your biceps!
• A muscle is made of thousands of tiny fibres, bundled together.
• When a message comes, they all get shorter together, and the muscle pulls!
• Then they relax, and get long again.

6. All by itself

• Hello, Wallaby! Boing!
• Your heart is a muscle too. It's called cardiac muscle.
• It beats all by itself, day and night, with no help from you.
• Muscles in your stomach squeeze your food along, all by themselves too.

7. Brrr! Shiver

• Brrr, it's snowing!
• When you're cold, your muscles shiver: tiny, quick pulls, over and over.
• That makes heat, to warm you up!
• And a warm jumper helps too.

8. Run, Emu, run!

• My leg muscles are big and strong. Watch me run!
• When you run, lots of your muscles work together.
• Your quadriceps straighten your knee, and your hamstrings bend it. Another pair!
• Running and jumping make your leg muscles stronger.

9. Strong muscles

• Moving and playing, in the ways you can, help keep your muscles strong.
• Running, swimming, dancing, wheeling, climbing: they all count!
• Your heart gets stronger as you play, too.
• Welcome to the Heave-Ho Club!

The quiz

Quiz time! Let's see what you remember. The right answers are in bold.

1. About how many muscles do you have? (More than 600 / 6 / 2)
2. What tells your muscles what to do? (Your toes / Your brain / Your hair)
3. What do muscles do? (Push / Sing / Pull)
4. What ties a muscle to a bone? (A tendon / A shoelace / A hair)
5. Which muscle beats all by itself? (Your biceps / Your heart / Your smile)
6. Why do you shiver when you're cold? (To make you sneeze / To cool you down / To warm you up)

What it needs, and what we collect

A recent browser on a phone, tablet or computer. The first visit downloads about 12 MB, and after that it keeps working with no signal. Nothing about your child is collected: the My mob card and the sound setting are kept on your own device. The privacy page has the whole story.

More in the series: What Makes Me, with the Lub-Dub Club, the Huff-Puff Club, the Munch-Crunch Club, the Mix-Fix Club, the Zip-Zap Club, the Drip-Drop Club, the Five-Alive Club, the Tickle-Prickle Club and the Click-Clack Club.