An MRI physicist in Utrecht has built a connected exercise tracker that automatically posts his hamster's nightly wheel sessions to Strava. The project gives Mollie, a 10-month-old hamster, records of distance, pace and duration much like those produced by a human athlete's wearable.
Thijs de Buck began with a basic bicycle computer because he wanted to know how far Mollie traveled after dark. Its magnet-and-sensor mechanism could count rotations, but it went into standby whenever the hamster stopped for longer than five minutes. A late-night break therefore interrupted the total, and the device offered distance without the richer session data de Buck wanted.
The replacement uses a magnet mounted on the wheel and a Hall sensor that detects each revolution. An ESP32 microcontroller records the data overnight. In the morning, a laptop script retrieves the measurements, converts them into a Strava-compatible FIT file and uploads the activity through Strava's API. De Buck manually adds a photograph afterward.
The system includes a small OLED display for live speed and software that tracks personal bests. It can also choose from more than 100 activity titles. Automated upload required a paid Strava account, so Mollie now has a Premium subscription.
Early data showed distances that would challenge many recreational runners. One activity covered 6.06 miles over four hours and 37 minutes, followed the next night by 5.55 miles in three hours and 56 minutes. De Buck said Mollie averaged close to 10 kilometers per night during the first tracking week and reached a record of 10.8 kilometers. The hamster tends to run in bursts, sometimes reaching an indicated four to five kilometers per hour before stopping for water.
The timing was also consistent. Across one seven-day period, Mollie began running within the same 10-minute window on five nights, starting between 9:54 and 10:04 p.m. De Buck described the broader routine as a cycle of sleeping, eating and running, with the hamster spending much of the daytime underground.
The account quickly found an audience. Within a week, de Buck said Mollie's profile had more than 600 followers and had collected over 1,200 kudos. The hamster completed Strava's August 400-minute challenge on its second day.
De Buck, himself a runner who enjoys detailed training statistics, developed the tracker while dealing with a minor injury. He hopes eventually to match Mollie's roughly 70-kilometer weekly recorded running distance. He is also waiting for the 20th recorded activity, when Strava's system is expected to begin offering race-time predictions for its unusually small athlete.
