If you’ve ever walked across a carpet cluttered with toys, there’s a good chance you’ve had the misfortune of stepping on this agony-inducing object: a LEGO® brick. But why does it hurt so much? Science has the answer.

Have you ever walked across a carpet covered with toys? Then there’s a good chance you’ve had the bad luck of stepping on this painful object. It’s a LEGO^® brick. But why does stepping on it hurt so much? Science has the answer.

One reason it’s so painful when you step on a LEGO piece is that they’re made from a strong plastic called acrylonitrile butadiene styrene (ABS). “You can hit a LEGO brick with a hammer, and it won’t break,” says Frankie Wood-Black, a chemical physicist from Northern Oklahoma College. Because ABS doesn’t bend or snap under pressure, there’s no give when your foot lands on one of the toys.

LEGO bricks also have a lot of sharp edges. All the force from the weight of your body pressing down becomes concentrated on these areas when you step on a LEGO piece. If the same amount of force were spread over a larger area of your foot, you wouldn’t feel as much pain, explains Wood-Black.

One reason for all the pain is the material LEGO bricks are made from. It’s a strong plastic called acrylonitrile butadiene styrene (ABS). “You can hit a LEGO brick with a hammer, and it won’t break,” says Frankie Wood-Black. She’s a chemical physicist from Northern Oklahoma College. ABS doesn’t bend or snap under pressure. So it doesn’t give when your foot lands on one of the toys.

LEGO bricks also have a lot of sharp edges. When you step on a LEGO piece, your body’s weight presses down on these areas. All of that force becomes focused there. It’s different if the same amount of force is spread over a larger area of your foot. Then you won’t feel as much pain, explains Wood-Black.

Another reason treading on a LEGO brick hurts “has a lot to do with the concentration of nerves on the bottom of your foot,” says Dr. Lauren Geaney. She’s a foot specialist at UConn Health in Connecticut. Nerve cells send messages throughout the body, including telling the brain when something is painful (see How You Feel Pain). The sole of the foot has about 200,000 nerves. That’s 10 to 20 times more nerves than in the skin on your leg. All those nerves magnify the sensations felt on the bottom of the foot, says Geaney.

Both Geaney and Wood-Black agree that classic, rectangular LEGO bricks are the worst to step on. Because they’re thick, their edges dig farther into your foot, agitating loads of nerve endings. OUCH!

Stepping on a LEGO brick also hurts for another reason. It “has a lot to do with the concentration of nerves on the bottom of your foot,” says Dr. Lauren Geaney. She’s a foot specialist at UConn Health in Connecticut. Nerve cells send messages throughout the body. Some messages tell the brain when something is painful (see How You Feel Pain). The bottom of the foot has about 200,000 nerves. That’s 10 to 20 times more nerves than in the skin on your leg. All those nerves increase the feeling on the bottom of the foot, says Geaney.

What are the worst LEGO bricks to step on? Geaney and Wood-Black agree that classic, rectangular ones are the worst. They’re thick, so their edges dig farther into your foot. That triggers loads of nerve endings. OUCH!