South Korean 'robot dog' became first to run a marathon on a single battery charge — now we know how

A four-legged robot completed a full marathon on a single battery charge, covering 26.2 miles (42.2 kilometers) on a hilly public-road course in South Korea two years ago.

Now we know a lot more about how it achieved this record-breaking feat.

The dog-like robot, called RAIBO2, finished the 22nd annual Sangju Dried-Persimmon Marathon in just over 4 hours, 19 minutes.

The bot's developers say it's the first quadruped robot to have completed an official marathon-distance event without stopping to recharge.

They're commonly referred to as "robot dogs" because the movement of their joints in both front and hind legs resembles that of canines.

The scientists outlined their findings about the robot's feat, which it achieved Nov.

17, 2024, in a study published Sept.

23 in the journal Nature .

This achievement represented a new milestone in overcoming a critical limitation for quadruped robots: endurance.

Although four-legged robots can cross difficult terrain that wheeled machines struggle to traverse (like stairs and rugged trails), their endurance has been limited because powering multiple joints while repeatedly lifting and stabilizing the machine's body consumes huge amounts of energy.

"Unlike wheeled robots, quadrupeds continuously expend energy at their joints to support body weight and incur kinetic energy losses during intermittent foot-ground contact," the researchers wrote in the study.

RAIBO2's race was a demanding real-world trial.

It took place during the Sangju Dried-Persimmon Marathon, with the bot racing alongside human participants.

The route covered two 50-meter [164 feet] elevation climbs, with slopes of up to 10 degrees.