Sitting all day can predispose you to injury, both inside and outside the gym. It can cause you to have weak abs and glutes, as well as tight hamstrings. Exercises that work the glutes and abs can help fix this. Planks in particular often reduce hamstring tightness, make you more stable while lifting, and improve the range of motion in your hips. When doing them, focus on squeezing your glutes as hard as possible. If you hold a plank until you feel the contraction more in your lower back rather than your abs and glutes, stop the plank and rest before doing another one. Emphasize doing quality planks rather than holding them for as long as possible.