The hip flexors are a group of muscles on the front of the pelvis responsible for bringing the knee closer to the chest. Walking, kicking, running, and climbing the stairs rely heavily on these muscles, so you need a strong set for a fit and functional body.
Unfortunately, prolonged sitting and underuse can weaken these muscles.
"Prolonged and constant hip flexion from continuous sitting can result in the muscle group becoming restricted," according to the Southern California Hip Institute. "They may become chronically tight, which can prevent the leg from correctly traveling behind the body while running or walking. Other body parts need to compensate when this happens."
One of the best ways to combat this is to incorporate more regular movement into your day, including hip-strengthening exercises to keep these muscles from becoming tight and weak. This will reduce your risk of injury in this area and lessen the need for other muscles to compensate.