UNITED STATES – Two months ago, I uploaded more than a decade’s worth of running data into the artificial intelligence (AI) chatbot Claude and asked for help writing a half-marathon training plan. “The good news,” it told me, “is your engine is enormous.”

This is the kind of flattery AI is known for. I’m not even in my run club’s fast group. Still, watching Claude scan the GPS (global positoning system) files I had logged on the fitness app Strava and identify the highlights – a marathon personal best, a rugged ultra-distance trail run – felt nice.

Then, things took a turn. “The honest news,” it continued, “is where you’re starting from right now.”

My mileage had fallen off a cliff. A standing Friday morning run with a friend was my only consistent workout. I was risking injury if I tried serious training too soon.

The reality check stung, but it also made me think the AI might be worth listening to. It then asked about my goals, my current fitness and workouts I had enjoyed. Minutes later, I had a custom plan based loosely on the teachings of running coach Jack Daniels. Soon, I was checking in with my AI coach after workouts and even adjusting my pace mid-run to earn its approval.

AI has rapidly flooded the fitness world.

One industry survey from December found that two-thirds of gymgoers had used AI-powered fitness software in 2025. In 2024, Strava added an AI workout summary for subscribers. The fitness app has also acquired the automated coaching programme Runna, which uses some AI to modify human-written plans.

In 2025, exercise equipment company Peloton introduced an AI system that can count reps and give feedback on form using a built-in camera.

But many people are simply asking general-purpose AI models...