Take off your shoes and sit flat on the floor. Place your feet against the Sit and Reach box and make sure your legs are straight and remain so. Now reach forward with both hands and try to reach over the measuring line as far as possible.
It is important that your legs remain stretched and that both hands are reaching evenly. There should not be any reaching with a single hand. Bouncing should also not occur. The distance should be reached in a single movement.