Should a sprinter dip at the finish line?
A dip gets the torso across sooner only if it is timed to the very last stride, and the same forward lean that wins a close finish can also cost a whole stride of speed if it starts too early.
A close finish and a coach will usually tell the athlete afterward to lean, or dip, next time. It is good advice, badly timed advice, or occasionally no advice an athlete needed at all, depending on how close the race actually was and when the dip happened.
What a dip actually buys
Placing is decided by the torso, not the head, an arm or a leg reaching forward. A forward dip through the hips on the very last stride gets the torso across the line a few hundredths of a second sooner than running tall through it would. That is a real, usable gap in a race decided by hundredths, and it is why sprinters are taught to do it at all.
What it costs when it is early
The same lean, started a stride or two too soon, slows the athlete down before the line rather than at it. A dip is a controlled loss of balance, and an athlete cannot keep driving at full speed while falling forward, so the earlier it starts, the more ground speed it trades away for a lean that has not reached the line yet to cash in.
- Dip from the hips, not the head or shoulders, since reaching the head forward does nothing for a result decided by the torso.
- Time it to the last stride, which has to be drilled at speed, not just explained standing still.
- Skip it entirely in a race that is not close, where the risk of stumbling costs more than a dip could ever gain.
Where this runs into how a phone reads the line
StatLap's finish line is a plane you set on screen, and it stops the clock on whatever crosses it first inside that frame. Set the line to catch the torso and a clean dip is exactly the case it is built for. Set it badly, too high or angled across one side of the track, and it can just as easily trip on an arm flung out ahead of the body, which looks like a fast finish on the clock and is not one by the actual rule.
A single 2D camera can tell you which body part crossed a line first. It cannot tell you whether a given dip gained more than it cost, because that needs the same athlete's splits from several reps compared against each other, not one frame of a finish.
Time your next meet with the phones you already have
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Related
How far forward should a sprinter lean?
A lot out of the blocks, very little at top speed, and never by bending at the waist, which is the version that gets taught by accident.
Read →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 →Which foot goes in front in the starting blocks?
The popular rules of thumb contradict each other, which is why the only answer worth trusting is a timed one.
Read →