Reaction time is the least important part of a start

Commentators read the numbers off the screen as though they decide the race, and they account for almost none of the difference.

The graphic comes up after every sprint final. Reaction times to three decimal places, lane by lane, presented as though we have just been shown why somebody won.

Consider what those numbers actually contain. The spread across a top-class field is usually a few hundredths at most, and much of that is choice rather than ability, because athletes deliberately sit back from the threshold to avoid a disqualification. Meanwhile the race itself is decided by differences in acceleration and top speed measured over ten seconds. A few hundredths at the gun is real. It is also the smallest lever available.

Worse, a fast reaction and a good start are not the same thing and are frequently in tension. An athlete who is primed to leave early tends to be tense in the set position, and tension makes the first push worse. I would rather have a sprinter who reacts unremarkably and clears the blocks in a strong, patient, forward line than one who is first to move and upright by the fourth step. The second one wins the graphic and loses the race.

There is one context where I will concede the point entirely, and it is the sixty metres indoors. Over a distance that short, with no time for the field to sort itself out, the gun genuinely matters more, and specialists in that event train the response separately and are right to.

But outdoors, the obsession does damage. Young athletes practise reacting rather than practising pushing. Coaches buy timing systems before they buy anything useful. And an entire viewing public has been trained to believe that the fastest man out of the blocks is losing the race through some later failure of nerve, rather than simply being the third or fourth best accelerator in the field, which is what he usually is.

The starts that look explosive on television are mostly athletes with high force output in the first three contacts. That is a strength quality built over years, not a nervous system trick.

So when the graphic appears and somebody says he was slow away, look at where he is at thirty metres instead. That is the number nobody puts on screen, and it is the one that would tell you something.