The Air Squat is a great compound, bodyweight exercise that engages the quadriceps, hamstrings, and glutes. The Air Squat will also help improve your balance and prepares your body for heavier dumbbell and barbell squats if you so choose. To perform, start in a standing position and place your feet flat on the ground just outside of the width of your shoulders. Angle your toes to point outwards at 45-degree angles. Keep your spine and neck straight and your head facing forward. Keep your eyes looking forward and your chest upright.
Only your lower body should be engaged in movement. To maintain your balance, extend your arms out in front of you in line with the height of your shoulders while clasping your hands together in a 'prayer' like position. In a slow controlled movement and keeping your feet flat on the floor, bend your knees and lower your hips down until your thighs just break parallel with the ground. Your hips should be just highly lower than your knees. Do not let your knees extend forward past your toes- this can lead to injury.
Pause for a moment at the bottom, and then raise your body upwards to your same starting position while driving through the bottom of your heels. Bring your legs and upper body back up to an erect standing position before repeating the same movement again.