Contact time is the only number I trust in the last thirty metres

Speed traces and stride counts both mislead at the end of a sprint; ground contact is the one measure that shows fatigue honestly.

Watch the closing stages of a sprint on a velocity trace and you will see decline. Everybody declines. The trace tells you it happened and refuses to tell you why, which is the part a coach needs.

Ground contact time tells you why.

The mechanism is simple enough to explain in a sentence. At top speed the athlete is airborne for most of the stride and on the ground for roughly a tenth of a second, and everything that determines whether the next stride is as fast as the last one has to be done inside that window. When an athlete fatigues, the window opens. The foot stays down a little longer because the leg is no longer stiff enough to reverse quickly, the hip drops fractionally on each contact, and the athlete sinks. Speed falls not because the push got weak but because the push got slow.

That distinction changes the training response entirely. An athlete whose contacts stay short while speed falls is running out of fuel or coordination, and the answer is conditioning or race modelling. An athlete whose contacts stretch out is losing elastic quality, and the answer is different: shorter maximal exposures, more reactive work, and probably less accumulated volume before the fast running.

Two athletes with identical splits. Two completely different problems.

I like contact time also because it resists the athlete's opinion. A sprinter can tell you they felt strong and be wrong; they cannot make a hundredth of a second appear on a timing mat. It is the sort of measure that punishes the flattering interpretation, which is what a good measure should do.

There is one honest objection. Contact times at speed are short enough that a lot of measurement methods are simply not accurate at the level of difference that matters, and comparing across systems is a waste of everyone's afternoon. Fine. Compare within a system, on the same surface, in the same shoes, and only ever look at the shape across the run rather than the absolute value.

Do that and you will get an argument you can win. When someone tells you an athlete needs more strength for the last thirty metres, you can show them the contacts stretching from the sixty and ask which strength exactly, and how it will be expressed in a tenth of a second by a leg that is already too slow to catch itself.