Grades K–2 · Organisms
Why do you get warm when you play?
On a cool day, a running child can feel warm without the Sun getting any brighter. The warmth is coming from inside the body. Working muscles make heat as they help the child move.
Food supplies energy that the body can use. Muscles use some of that energy to pull on bones and move arms and legs. Some becomes heat. More busy muscles usually make more heat than resting muscles.
Working muscles use energy from food; both movement and heat result.
Blood carries warmth away from those busy places. Warmth can then leave through the skin. Sweat can help too: when liquid sweat changes into water in the air, it takes heat with it.
A coat does not make the same kind of heat as a muscle. It slows heat leaving the body. That is why playing in a thick coat can feel very different from sitting still in it. Your body is making warmth, and your clothes change how quickly that warmth escapes.
About this explanation
Schematic relationships are emphasized; sizes and timing are not to scale.
Starting knowledge: Notice movement, warmth and familiar body parts.
Sources
- OpenStax — Anatomy and Physiology: Skeletal Muscle
- OpenStax — Anatomy and Physiology: Energy and Heat Balance