Lesson 3Mechanics
The Rocket Booster & The Slime
How your calf fires and your joints glide
When you walk, your calf muscle fires like a rocket booster, yanking the Achilles cable, which lifts your heel, and the foot rolls forward. But none of that smooth motion would be possible without the slime — the slippery fluid that keeps your joints gliding.
Listen to Mr. Bones
0:000:44
Tap the parts of the launch system
Calf Muscle
aka The Rocket Booster
Two muscles (the gastrocnemius and the soleus) that sit on the back of your lower leg. When they fire, they pull the Achilles tendon, which lifts your heel and launches you forward.
The force pathway — step by step
Step 1 / 5
Step 1: Calf fires
Your calf muscle contracts, pulling the Achilles tendon tight.
Mr. Bones says: I'm a fictional skeleton, not a doctor! This is for learning and fun. If anything hurts, stop and tell a grown-up you trust.
Knowledge Check
1
What does the calf muscle do when you walk?
2
What is the 'slime' that helps your joints glide?
3
