How does gravity affect an athletes performance?

Answer 1

Compared to everyone else, it doesn't. Since gravity is a constant force on our planet, it will not help or harm you relative to the performance of another athlete. However, if you were to hypothetically compete on another planet, your weight would change (as weight is relative to gravity...your mass however, would remain constant).

Answer 2

The weaker gravity on the moon would mean you cold kick and throw things much higher and much farther. Running, however, would be very difficult.