An AI triathlon coach that reads every leg

A triathlon on an Apple Watch is one workout with five parts: the swim, the first transition, the bike, the second transition, the run. The watch records each one with its own sport, distance and heart rate, and Apple Health keeps them together. That structure is the whole point of a race: where you lost time, and what the swim cost the bike.

It is also the first thing most tools lose. Strava, for one, receives an Apple Watch triathlon as a single generic workout with no distance; splitting it back into a swim, a ride and a run is a job you do by hand, and the transitions don't survive it. An AI coach reading either version can't tell you much about your race, because the race isn't there any more.

An AI reading all five legs

My first triathlon was the Ventouxman sprint, in September: a 750 m open-water swim, 20 km on the bike, and a run the watch measured at 4.6 km. The watch recorded it in multisport mode. Here's what Claude said when it could read the workout whole:

Four things in there that no summary screen gave me:

• The swim distance is wrong, and it said so. In open water the watch's distance is an estimate, and mine said 984 m for a 750 m course. An AI that knows the course length corrects it instead of praising a fast swim that wasn't. Oddly, the GPS track itself measures 769 m: more on that in the GPX article.
• The transitions are time. 2:47 in T1 against 1:17 in T2: a minute and a half, for free, by practising the wetsuit and the helmet.
• The bike didn't fade. Faster and at a lower heart rate in the second half means the course or the wind, not a pacing mistake. Without the halves, a 150 bpm average says nothing either way.
• The run built. Heart rate rising from 147 to 159 while the pace improved is a negative split, not a collapse.

Between races, it reads three sports at once

Triathlon training is where an assistant that reads everything earns its place. A running app sees your runs; a cycling app your rides. Neither knows that Tuesday's flat legs come from Sunday's long ride. Ask an assistant connected to your Apple Watch about your week, and it adds up the swims, rides and runs together, with their heart rate, before it answers.

Questions that work well for triathletes:

• "How were my training hours split between swim, bike and run over the last four weeks?"
• "How even were my 50s in yesterday's swim?" A pool swim arrives length by length.
• "Compare my run off the bike in my last brick with my usual easy runs."
• "Where did I lose time in my race: swim, transitions, bike or run?"

Where it stops

The watch measures heart rate everywhere, but cycling power only with a power meter paired to it, and open-water distance only roughly. An AI can't read what wasn't recorded; a good one says so rather than filling the gap. And it doesn't know the course, the wind or the water temperature unless you tell it: say "the swim was 750 m" and the answer gets better.

If you're choosing where your assistant should read your races from, I compared the Strava connector and Apple Health on this exact triathlon. Only one of them still had the race in one piece.