The deep squat is an essential movement pattern that you'll lose if you don't perform it regularly. Do it at least once every day, with bodyweight, for 30 seconds.
Why it's a good idea: The deep squat will help you maintain your hip flexion mobility – the ability to squat all the way down – throughout life. The deep squat is commonplace in many Asian and Middle East countries and requires 95-130 degrees of hip flexion and 110-165 degrees of knee flexion, which is an extensive range of motion.
If you use this ability, you'll keep it. If you don't, you'll lose it. Dr. Stuart McGill started performing this drill daily and credits it for helping him retain his hip function and prevent hip replacement surgery. If you're a lifter or an athlete, you want to retain your deep squat ability. It's been shown to lead to greater vertical jump transfer, quadriceps and hamstring hypertrophy, glute activation, hip extension torque, postactivation potentiation, and deep squat strength as compared to shallower squatting.
What to do: You don't want to use extra loading on this drill, so no dumbbells, kettlebells, or barbells. Just squat as deep as you can go with your own body weight and remain flat-footed (don't come up onto the toes).
With loaded squatting, it's imperative that you prevent the lumbar spine from excessive rounding, but with the bodyweight deep squat, it's okay to relax and let the spine sink down into the stretch. Hang out in the deep squat position for 30 seconds and then rise back up.
How to step it up a notch: If the deep squat isn't enough to satisfy your appetite, consider performing a set of goblet squats each day. The goal isn't to max out or go to failure but to simply use good form with a moderate load. This will take your hips, knees, and ankles through a good range of motion while the core is stabilized.