Lie on your back with your lower back pressed against the floor.
Lift and bend one leg so your hip and knee are at right angles. Float the other leg a few inches off the ground.
Place both hands on top of your bent knee, and press down as hard as you can, engaging your core and keeping your back flat on the ground.
To modify, stand upright and lift one leg with your knee bent. Press both hands just above your knee and hold, engaging your core and glutes, while balancing on one leg.
