Can AI give useful input on your running?

You have a setup you trust. The long run sits on Sunday, threshold work on Tuesday and Thursday. You know roughly what volume your body handles in November and what tends to break if you push October too hard.

So the question is not whether an app can write you a better plan. The question is whether AI can say anything useful about the plan you already have.

Short answer: yes, if it can see your workouts. What you get is not a new schedule but a second set of eyes on what you already do, and it gets more useful the longer it has followed you.

Coach Fartlek is our own app, so expect bias further down.

What AI sees that you miss

You evaluate your training in weeks. The patterns live in months.

The most common finding when someone reads ten consecutive weeks is that the easy runs have crept up. Four seconds per kilometre faster each week sounds like nothing, and six weeks later the easy days sit at a pace that costs you recovery without anyone deciding it should. Another one is calendar drift. The quality session lands the day after the long run every time work collides with the schedule, so the two hard days sit together and the rest of the week is too easy.

That kind of observation takes no intelligence. It takes something that reads the whole history every week and is willing to say the same thing again. Machines are good at that, and you are bad at it when you are in the middle of a build.

The requirement is that the workouts exist in structured form. Coach Fartlek reads them through Intervals.icu, which in turn pulls from Garmin, Coros, Polar and most other watches.

What it cannot do

It does not see how you feel.

That is the limitation that matters, and better models will not remove it. Your watch measures that HRV is below your average. Whether that is a cold coming on, a glass of wine with dinner, a night with a sick child or the build starting to bite is not in the data. An AI reading only numbers is guessing, and it guesses in the same confident tone whether or not it is right.

So the input becomes useful once you tell it things. Say you slept four hours three nights running and the answer changes. Leave it out and you get an answer that assumes the curve means training load.

It can also be wrong about the training itself. A model recognises patterns from how people usually train, and your setup may be unusual on purpose. If you run two threshold sessions a week because it has worked for three seasons, an objection to that is not a verdict. You get an argument to weigh, not an answer.

You do not have to hand over the planning

Most coaching apps are built on you letting go. Answer the questions, get the plan, follow it. If you already have a setup that works, that is the wrong deal, and it is probably why you have not downloaded any of them.

Coach Fartlek has a mode called self coached for exactly this. You write your training philosophy in your own words, that the long run is always Sunday and volume should stay around 80 km, for example. Then you build the weeks yourself in the calendar and push the workouts to your watch the usual way. The coach does not plan, it reviews. Before each new week it goes through what you have entered and sends a review where you approve or reject each suggestion separately, and nothing enters the calendar without your yes.

Workout analysis and zone corrections stay in place whichever mode you run. There is more on how it works on the self coached page.

The mode requires Elite at $20.99 a month, and it is built for a minority of runners. If you want to open the app and find the week done for you, the regular mode is the right one.

Is ChatGPT not enough?

For reasoning, often yes. It knows the training literature better than most runners do.

The difference is memory and data. A general chatbot only sees what you paste, and next time you ask, last week is gone unless you paste it again. That works for one question at a time and stops working when you want to follow a thread through a season. We have written more about where the line sits in ChatGPT as a running coach.

If you want to try it

Start with a question you actually wonder about. "Have my easy runs got too fast?" makes for a better conversation than "what do you think of my training", because the first one can be answered with your own numbers.

The free trial covers enough questions to see whether the answers tell you something you did not already know. The tiers are on the pricing page, and connecting your watch takes a few minutes through Intervals.icu.