Hip Flexors

Hip Flexors: what are they?

Psoas major starts on the lumbar vertebrae, joins iliacus on the inner surface of the pelvis, and the two attach together on the lesser trochanter of the femur as iliopsoas. That path is unusual: the muscle passes from the spine, through the pelvis, to the leg, which is why it influences both hip position and lumbar posture. Around it, rectus femoris (also a quadriceps head), sartorius and tensor fasciae latae contribute to flexing the hip. In coaching conversations the hip flexors are usually blamed for a client's back pain and stretched daily. That is frequently the wrong response.

What they do

Hip flexion is bringing the thigh and the torso closer together, whether the leg moves towards the body or the body towards the leg. Every walking step, every stair, every sit-up and every knee drive in a sprint is hip flexion. Iliopsoas is the strongest contributor above about 90 degrees of flexion, which is why it dominates in a hanging knee raise once the thighs pass parallel.

The muscle also stabilizes. Because psoas attaches to the lumbar spine, it contributes to segmental stability there, and it works isometrically in single-leg stance to control the pelvis. It is a postural muscle as much as a mover, which is part of why it responds to sitting all day.

The tight hip flexor question

A client who sits for eight hours has their hip flexors in a shortened position for most of their waking day, and a genuine loss of hip extension range is common. But short is not the same as tight, and tight is not automatically the cause of back pain. Many clients who stretch their hip flexors daily for months feel exactly the same, because the limitation was never a passive length problem.

The more useful frame is this: can the client reach full hip extension, and can they control the range they have? The Thomas test tells you the first. Standing hip extension quality, and whether the client compensates by arching the lower back rather than extending the hip, tells you the second. Loaded work through range, hip thrusts, split squats with the rear hip extended, half-kneeling positions, tends to change both more reliably than passive stretching.

How to train the hip flexors

Almost nobody trains hip flexion above 90 degrees, and it is the range that matters most for sprinting and for knee-drive strength. Direct work is quick, needs no equipment for the first progressions, and is worth including for any running or field-sport client.

What goes wrong in practice

The first pattern is a client whose lower back arches every time they extend their hip. They do have the range, at the lumbar spine rather than the hip. Cueing a rib-down position and a glute squeeze in a half-kneeling stance shows them the difference in one session.

The second is back discomfort during leg raises. When the hip flexors pull on the lumbar spine and the abdominals cannot hold the pelvis, the low back arches under load. Regressing to a dead bug or a bent-knee raise, and building the anti-extension work first, resolves it far more often than stretching.

The third is the assumption that a foam roller on the front of the hip is treating psoas. It is not reaching it: psoas sits deep, behind the abdominal contents. Whatever benefit a client feels there is coming from more superficial tissue and from the nervous system, which is fine, but it is not a reason to skip the loaded work.