A robot dog covered the 42.195 km of a marathon alongside human runners without recharging its battery even once.
This feat took place in November 2024 during the Sangju Marathon in South Korea. Named RAIBO2, the robot crossed the finish line in 4 h 19 min 52 s. A study published in Nature in September 2026 now explains how its designers achieved such endurance.
RAIBO2 during the Sangju Marathon, which it completed entirely on a single battery charge.
Credit: KAIST, via DongA Science.
Running on four legs requires a machine to use a great deal of energy. Unlike a wheeled vehicle, it must constantly actuate its joints to support its weight. Each contact with the ground can also slow the movement. These small losses eventually drain the battery, beyond the energy needed simply to move forward.
Scientists at the Korean institute KAIST redesigned the legs, motors, and running method. By lightening certain parts, they reduced the effort required for each stride while retaining a structure strong enough to withstand impacts.
They also improved the circuits that power the motors. Some of the electricity consumed by a robot is needlessly converted into heat in its components. Circuits with less electrical resistance limit this loss. It is a barely visible saving, but one that matters when the same movement must be repeated for more than four hours.
RAIBO2 runs alongside participants during the Sangju Marathon in South Korea.
Credit: KAIST/RAI Lab, via Seoul Economic Daily.
The software also learned to conserve its strength. Through simulation-based training, the robot adopted movements that reduce impacts when its legs touch the ground. In particular, it avoids placing a foot down at too high a speed, which would waste energy.
During the marathon, RAIBO2 maintained an average speed of about 9.5 km/h despite changes in terrain and elevation. The researchers measured total energy consumption of 1,280 Wh for the run. The battery was not completely empty at the finish, even after covering the official distance.
According to their comparison, this approach delivered more than three times the range of previous quadruped robots.
The next goal goes beyond sporting competitions. Greater range could allow robots to inspect industrial sites, monitor facilities, or cross areas that are difficult to access. However, it remains to be determined how this endurance changes with a payload and obstacles.