The Hamstring Bungees
Three stretchy cords behind your thigh
Behind your thigh live three bungee cords â the hamstrings. They bend your knee, swing your leg back when you walk and run, and stretch like rubber bands every stride.
The three hamstring muscles
Real anatomy photo spot: biceps femoris, semitendinosus, semimembranosus at the back of the thigh
Meet the bungee team
The hamstrings are three muscles: the biceps femoris on the outside, and the semitendinosus and semimembranosus on the inside. They all start at your sit bone â the ischial tuberosity, the bone you sit on â and run down to cross behind your knee. Two attach on the fibula and one on the tibia.
Stretch and snap
When you walk, your leg swings forward and your hamstrings stretch â like a bungee cord being pulled. Then they snap back, bending your knee and helping push you off. This stretch-and-snap saves energy: your body stores elastic energy in the tendons, just like the plantar fascia in your foot from Lesson 2!
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.
