Posture Hinge

Why this matters

Trunk Forward Lean tells you how much the trunk leans, but not where the lean comes from. Two runners can show the same trunk angle for very different reasons:

• Leaning from the ankles — the whole body tips forward as one unit, keeping a straight line from the ankle through the hip to the shoulder (~180°). This is the efficient pattern.
• Bending at the hips — the runner folds at the waist, so the trunk leans while the legs stay vertical (a smaller hip angle). This shifts load to the lower back and reduces propulsion.

Posture Hinge measures that hip angle so you can tell the two apart.

What good looks like

Lateral view at initial contact. The ankle, hip, and shoulder sit close to a straight line (165°–180°) — the forward lean is coming from the ankles.

Common faults

• Slight hip hinge (155°–165°) — some of the lean is coming from the waist. Often linked to anterior pelvic tilt or a weak posterior chain.
• Marked hip hinge (<155°) — the runner is folding at the waist. Loads the lower back and cuts propulsion.

Coaching cues

• "Lean the whole body from the ankles" — the same cue that fixes over-leaning trunk posture.
• Anterior pelvic tilt / hip-flexor mobility — tight hip flexors pull the pelvis into a tilt that forces a hip hinge.
• Glute and core strengthening — to hold an ankle-based lean under load.

Related measurements

• Trunk Forward Lean — read the two together: the trunk angle is how much, the hinge is from where.
• Hip Extension — anterior pelvic tilt affects both.