New Delhi, Aug. 18 -- Push-ups may seem like one of the simplest exercises: you go down, and you come up. However, that simplicity conceals a mistake that almost everyone makes-letting the hips sag. When your body loses its straight-line form, the push-up stops working the right muscles and starts putting unnecessary stress on your lower back. This not only makes the exercise less effective, but it also places dangerous stress on your lower back, increasing the risk of injury. The truth is, a sagging midsection means your core and glutes are not engaged like they should be. But the fix is simple. With a bit of focus and the help of exercises like planks and superman holds, you can build the strength and awareness to correct your form and ...