This exercise is simple enough and oh-so-effective when done regularly. Let's get to it!
Kneeling Leg Extensions
Come to an all 4s position (quadruped), shoulders over wrists and knees under hip bones.
Pull abs up and in, shift your weight to your right knee and reach your left leg behind you with toes touching the floor.
Lift leg up to your fullest potential while keeping your hips level to the floor. Perform 10 reps and switch sides.
*Try adding pulses and circles, or add a ball behind your knee.
*Try reaching your opposite arm out in front of you to challenge your core even more.