The hip flexors are a group muscles located at the front of the hip joint and thigh. These muscles work together to bring your upper leg toward your chest and vice versa. The major hip flexors include the iliacus, psoas major, rectus femoris and sartorius muscles. The pectineus and tensor fasciae latae also aid hip flexion.
Hip flexors enable you to lift your leg toward your chest, whether you are standing, sitting or lying down. The iliacus and psoas major are the strongest of the hip flexor muscles. Walking, running, jumping, kicking, stair climbing, cycling and countless other activities rely on the leg-lifting work of your hip flexors. Rest your hand on your thigh and lift your leg to feel your hip flexors in action.
Your hip flexors also pull your torso toward your thighs. To demonstrate this action, sit on the floor with your legs straight in front of you. Place your hands on your thighs and lean forward. You will notice your hip flexors tense as they pull your upper body forward. This hip flexor function comes into play when you perform situps. Although many people think of situps as primarily an abdominal muscle exercise, the hip flexors perform a significant portion of the work.
Leg and Spine Rotation
Muscles commonly support more than one type of movement, and this is the case with the hip flexors. Some hip flexors rotate the leg at the hip joint, meaning they turn the leg inward or outward. The sartorius rotates your leg outward; the tensor fasciae latae rotates it inward. Your psoas major muscles work with several chest and abdominal muscles to rotate the spine, allowing you to turn your torso.
The pectineus is a short muscle that runs between the front of your pelvis and the inner aspect of your upper thigh bone. In addition to flexing the hip, it works with other leg muscles called adductors to pull your leg inward and allow you to bring one leg in front of the other. The sartorius and tensor fasciae latae work with an opposing group of leg muscles, the abductors, to pull your leg outward.
The hip flexors become tight if you sit for several hours each day and don't stretch them. This may cause forward tilting of your pelvis and low back pain. Hip flexor stretches work well to alleviate this problem. The American Council on Exercise describes a kneeling hip-flexor stretch: Kneel on one knee with the other knee out in front of you, foot flat on the floor. With your back straight, lean your torso forward; you should feel the stretch in the front part of the thigh of your kneeling leg. Hold your position for 30 to 45 seconds before releasing. Repeat two to five times with each leg, trying to lean further into the stretch with each repetition. Talk with your doctor if you have persistent back pain.