Why Ice Skaters Turn Faster with Their Arms In

An ice skater turns around with both arms out. Then the skater brings the arms close to the chest and turns faster. There is no new push against the ice. Why does this happen?

Imagine a line through the skater's body, from head to foot. The body turns around this line. With the arms out, the hands and arms are farther from it. Bringing the arms in moves them closer. The skater does not become heavier or lighter.

When more of the body is far from this line, it is harder to change how fast the body turns. When there is very little pushing or pulling from outside to change the turn, bringing the arms closer makes the skater turn faster. Moving the arms out again slows the turn.

Turning faster still takes energy. The skater must use the muscles in the arms to pull them in. This adds energy to the turn. Air and contact with the ice slowly take energy away, so the turn cannot last forever.

People jumping into water use the same idea. They bring their arms and legs close to turn faster in the air. They open their bodies to slow the turn before entering the water.

Sport is not just about being strong. Body shape matters too.