Why does my sprinter's head bob up and down when they run?
A visible bounce is usually the same fault as overstriding, seen from a different angle, and it is fixable with the same two drills.
Watch a sprinter from the side and a bobbing head is easy to spot: it rises and falls with every stride, sometimes enough that a coach standing still can see it from thirty metres away. It looks like effort. Mostly it is waste. A sprinter's job is to move forward, not up, and a head that bounces a visible amount is a sign that some of every stride's force went somewhere other than forward.
Where the bounce actually comes from
Almost every stride launches the body slightly upward as well as forward, that part is unavoidable, and the question is how much. Two things push that ratio the wrong way. An overstriding foot, landing well ahead of the hips, acts like a small ramp: the leg has to absorb that landing and then relaunch the body, and a lot of that relaunch goes up rather than out. And a stride with a long flight time relative to its ground contact time is a stride that spent more of its time in the air being pulled back down by gravity and less of it pushing the ground back, which is the trade a bobbing sprinter is making without meaning to.
- Check overstride first. A foot landing far in front of the hips is the single most common cause and the Film Room reports it directly.
- Compare flight time against ground contact time. A ratio that is high, long flight relative to short contact, tends to travel with a visible bounce.
- Watch whether the bounce gets worse late in a rep. A bounce that grows as the athlete tires is fatigue changing the mechanics, not a fixed fault.
What to do about it
The fix is rarely to tell an athlete to stop bobbing, which gives them nothing to actually do differently. It is the same cue and the same drills as overstriding: think push back, not up, and A-march into A-skip or a wall drill held in position, both of which teach the foot to land under the hip instead of reaching for the ground in front of it. Fixing the landing point tends to take the bounce with it, because the two are usually the same fault seen from different angles.
The Film Room reports flight time, ground contact time and overstride as numbers and a rhythm, and a change in that rhythm is real information. What it will not do is tell you how many centimetres the head actually rose, because turning a bounce on video into a real height needs a calibrated distance in the frame, and a side-on clip without one only has pixels to work with. The rhythm is trustworthy. The exact height of the bounce is not something a single uncalibrated camera can give you.
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Related
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A hip that dips every time one particular foot lands is a stability fault, and it happens in the one plane a side-on camera cannot see.
Read →Why does your sprinter's foot turn out when they run?
A side-on camera cannot see which way a foot points, and from where most coaches film, neither can you.
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