Why does my runner's shoulders rotate opposite to their hips when they run?
It looks like a fault. In a normal running stride, the shoulders and hips are supposed to counter-rotate against each other.
A coach watches a runner from behind, sees the shoulders twisting one way while the hips twist the other, and the instinct is to call it a flaw. For most runners, that counter-rotation is not the problem. It is the system working the way it is built to.
Why the opposite rotation exists
Every stride rotates the pelvis slightly as one leg drives forward and the other extends back. Left unchecked, that rotation would spin the whole body around with each step. The upper body counters it: as the right hip rotates forward, the left shoulder and arm swing forward to cancel it out, and the two halves of the body twist against each other in opposite directions at the same rate. That cancelling action is what lets a runner's head and eyes stay pointed straight ahead instead of swinging side to side with every stride.
When it actually is a problem
- When the rotation is so large that the whole trunk visibly twists, rather than just the shoulders and arms.
- When one side rotates noticeably more than the other, instead of the two sides matching.
- When the arms cross the midline of the body instead of swinging straight forward and back.
The question worth asking from behind is not whether the shoulders and hips rotate opposite each other. They are meant to. It is whether the amount of rotation on each side matches, and whether it stays controlled rather than growing as the runner fatigues.
A clip filmed from behind can show whether the rotation is even side to side and whether it grows late in a run. It cannot measure the rotation in degrees the way the Film Room measures trunk lean and elbow angle from the side, because counter-rotation happens across a plane a side-on camera cannot see at all.
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Related
Why does my runner sway side to side instead of running in a straight line?
A trunk that rocks left and right with every stride usually starts at the hip, not the shoulders, and it is the one running fault a side-on camera cannot see at all.
Read →Why does my sprinter's knee cross toward the other leg instead of driving straight?
A knee that drifts inward on the recovery leg is a different fault from arms crossing the body, and it is one a side-on camera is poorly placed to catch at all.
Read →Why does my runner's feet cross an imaginary line down the middle when they run?
Crossover gait is a sideways fault, which is exactly why a side-on video of it so often looks fine.
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