How do you throw an under hand throw?

Even though I'm a baseball player, it is harder to hit it under hand when the pitches are thrown at equal reaction times. -When the softball is thrown under hand, its harder to adjust because the...

two feet on the ground hands and ball over head its one motion

it means if a left-handed person throws the ball it is called a "left-hand throw."

i think it's a force of gravity

Left hand.