Adjust the machine lever to fit your height and lie face down on the leg curl machine with the pad of the lever on the back of your legs.
Keeping your body flat on the bench, ensure your legs are fully stretched and grab the side handles of the machine. Position your toes straight
As you exhale, curl your legs up as far as possible without lifting the upper legs from the pad. Once you hit the fully contracted position, hold it for a second.
Bring the legs back to the initial position.
Caution: Do not ever use so much weight on the exercise that you start using swinging and jerking as you can risk both lower back injury and also a hamstring injury.