Ageing takes your top speed long before your engine

Masters results show endurance holding up far better than sprinting, and the reason sits in which fibres disappear first.

Look at masters age-group records and something odd jumps out. The marathon curve declines gently for decades. The hundred metres curve falls off a cliff.

The usual explanation is that endurance athletes keep training and sprinters retire, and there is something in that, but it is not the main thing. The main thing is that ageing muscle does not shrink evenly. The largest, fastest motor units are the ones that are lost, and the fibres they controlled are either lost with them or reinnervated by slower nerves and effectively converted. A seventy-year-old with an excellent aerobic system may have almost no fast tissue left to recruit, and no amount of willingness fixes that.

You can see it in the shape of a masters sprint. The acceleration phase is respectable. Top speed is dramatically reduced, and top speed is what the event is measuring. Meanwhile the aerobic machinery, capillaries, mitochondria, the ability to use oxygen efficiently, responds to training at almost any age, which is why a well-trained sixty-year-old distance runner is closer to their younger self than a sprinter of the same age could dream of being.

The uncomfortable conclusion is that the sport we tell older people to take up is exactly backwards. Everyone is nudged toward slow steady jogging, the thing they will lose least of anyway, and steered away from anything explosive on the grounds that it is risky.

I would flip it. The tissue that disappears is the tissue that keeps you upright when you trip, that gets you out of a chair, that reacts. Preserving it needs work that is fast or heavy, done regularly, scaled sensibly. Hill sprints of six seconds. Proper resistance training with real load. Jumping, in small doses, on a surface that forgives.

Masters sprinters understand this and are treated as an eccentric fringe by the running world, which is a shame, because they are running the experiment everyone else will need the results of.

The decline is real and nobody is beating it. But there is a large difference between losing the fast fibres at the rate biology sets and losing them faster because you spent twenty years being careful.