A physicist wired his hamster's wheel into Strava — Mollie runs nearly 10 km a night

An MRI physicist in the Netherlands has turned his pet hamster's nightly exercise into a full Strava training log. Thijs de Buck, who is based in Utrecht, posted on Reddit that he built a speed and distance tracker for his hamster's wheel, with the data uploaded automatically to Mollie's own Strava account. The ten-month-old hamster now logs runs with distance, pace and time: one recent activity showed 6.06 miles in 4 hours and 37 minutes, and the following night Mollie recorded 5.55 miles in 3 hours and 56 minutes.

From a cheap bike computer to an ESP32

De Buck's first goal was simply to find out how far Mollie travelled after dark. "I bought a very cheap bicycle computer pretty much right away," he told Runner's World. The device used a magnet and sensor, but the sensor switched to standby when the wheel stopped for more than five minutes: "So if Mollie would take a lunch break at 1 a.m., we'd have no idea how far he'd have run after that," he said.

The finished rig is simple in principle. A magnet on the wheel passes a hall sensor that detects each rotation, and an ESP32 — a small programmable computer — collects the data overnight. In the morning, a script on de Buck's laptop turns it into a Strava-compatible .FIT file and uploads the activity through the Strava API. "All that remains is for me to manually add a photo of Mollie, and for Mollie to do the actual hard work during the night," he said.

Records and a Premium account

The build goes beyond uploads: a tiny OLED display shows Mollie's live speed, and the setup includes code for automated personal-best tracking plus more than 100 possible run titles. Automatic uploads required a paid plan, so the hamster ended up with Strava Premium. According to de Buck, Mollie averages almost 10 kilometres a night, with a record of 10.8 kilometres after the first week of tracking. Over one seven-day stretch the hamster started running within the same ten-minute window on five nights, between 9:54 and 10:04 p.m.

The account drew thousands of likes, more than 1,200 kudos and over 600 followers within a week, and Mollie completed Strava's August 400-minute challenge on day two.

What comes next

De Buck is a marathon runner himself and is currently nursing a minor injury, which gave him extra time for the build. "When I get back, I think it'll be a nice challenge to try to match Mollie's weekly running distance," he said. "I don't normally hit 70km a week!" The next milestone is Mollie's 20th run, when Strava should start offering race predictions. "I can't wait to see his estimated 5K and marathon times," de Buck said, adding that he is slightly worried the hamster may end up with the better marathon time.