Use a cable machine or resistance band. Rotate your torso diagonally, pulling the cable or band from high to low or vice versa.

Hang from a pull-up bar with your arms extended. Lift your legs towards the ceiling, keeping them straight.

Lie on your back with legs straight. Lift your legs towards the ceiling, keeping them straight, then lower them without touching the floor.

Lie on your back with knees bent and feet flat on the floor. Place hands behind your head, and lift your upper body towards your knees.

Start in a push-up position with your arms straight. Lower onto your forearms and hold your body in a straight line from head to heels.

Lie on your back, raise your legs and upper body off the ground, forming a "banana" shape. Keep your lower back pressed into the floor.

Sit on the floor, place your hands beside you, lift your legs and body off the ground, forming an "L" shape with your body.

Start in a plank position. Bring your right knee toward your right elbow, then return to the plank position. Repeat on the left side.

Lie on your back with arms extended toward the ceiling and legs raised. Lower your right arm and left leg toward the floor, keeping them hovering above the ground. Return to the starting position and switch sides.

Lie on your side with your elbow directly beneath your shoulder. Lift your hips, forming a straight line from head to heels.

Lie on your back with knees bent. Lift your hips off the ground by contracting your lower abs.

Lie on your back with hands behind your head. Bring your right elbow and left knee towards each other while straightening the right leg.

Start in a plank position. Alternately bring your knees towards your chest in a running motion.

Sit on the floor, lean back slightly, and lift your feet off the ground. Rotate your torso, touching the floor beside you with your hands.