Why doesn't my high jumper's back arch over the bar?
A flat clearance over the bar usually starts well before the bar, in a plant and a shoulder position that never gave the arch anywhere to happen.
A flop jumper who clears the bar flat, hips barely arching, shoulders and knees close to the same height as the hips, is usually not lacking flexibility. They are usually arriving at the bar in a position the arch was never going to be possible from.
What the arch is actually doing
Arching the back over the bar lets the hips clear at their highest point while the head, shoulders and legs are still below it, effectively letting the body's centre of mass pass under the bar even though the body itself goes over. A flat clearance forces the whole body, including the hips, to clear the bar as one straight-ish line, which needs more total height than the arch does for the same bar.
Where a flat clearance actually comes from
- A plant that is too far under the bar rather than out from it, which leaves no room to lay back before the shoulders arrive.
- Shoulders that stay square to the bar on takeoff instead of starting to rotate, so there is nothing for the back to arch against.
- An athlete bailing out and looking down at the bar mid-flight, which pulls the chin to the chest and the hips down with it, the opposite of the position an arch needs.
- Simple unfamiliarity: an athlete new to the flop who has not yet been taught to actively push the hips up and back rather than just jump and hope the shape happens.
What the Film Room measures here, and what it does not
The high jump analysis reports hip rise as a share of body height, takeoff angle, and knee fold and extension, all read from the plant. If hip rise and takeoff angle both look reasonable and the clearance is still flat, the plant did its job and the fault is in what happens after it, in the air, which the app was never built to read.
A single 2D camera has no way to measure spinal arch. The skeleton it tracks is a set of joint points, shoulders, hips, knees and so on, not a curve along the spine, and even a perfect side-on clip only shows the arch in silhouette rather than as a number. Watch this one with your own eyes, ideally from directly side-on and at slow motion, and use the hip rise and takeoff angle numbers only to rule the plant in or out first.
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Related
Why does my high jumper clear the bar without their hips getting above it?
It is usually the arch working the way it is supposed to, and it is also the exact moment the Film Room already admits it cannot measure well.
Read →Why your high jumper knocks the bar off on the way down
Legs taking the bar after the hips have cleared is a timing fault at the top, and usually a takeoff point that drifted before it.
Read →Why does your high jumper's plant foot never land in the same spot?
A side-on camera reads the vertical arc of a jump well and has no idea where the plant foot actually landed on the ground, which is usually the real question.
Read →