Honor's humanoid ran the fastest half-marathon: how did they do it?

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Honor's humanoid ran the fastest half-marathon: how did they do it?<br>Engineering isn't magic, it's a matter of tradeoffs

Avik De<br>Apr 22, 2026

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Robotics headlines over the past week have been dominated by the news that the Honor Lightning humanoid robot has beaten the human half marathon world record for the first time. It’s important to remember that machines and humans have very different capabilities and constraints, so why should we ever have expected the half marathon time for a robot and human to be related? Down the line, I don’t expect this particular comparison of human to machine to be very relevant. Nevertheless, it’s still an important milestone for engineering, just like Deep Blue’s 1997 defeat of Garry Kasparov in chess. From a human standpoint, I hope we can resist comparing the accomplishments of machines to the well-earned and deserved achievements of humans… maybe the chess model is a reasonable one here. Also as in the chess case, where Deep Blue couldn’t physically move the pieces, the Honor robot’s capabilities are much more narrow than a human running elbow-to-elbow with other runners, effortlessly navigating the course without GPS, etc. Comparing the robot runner to a human runner is just an apples to oranges comparison.<br>What is a good comparison is this performance to last year’s, when the best robot time was over 160 minutes, or more than 3x this year’s time. That’s a remarkable improvement in one year. My doctoral thesis involved building and controlling hopping and running robots, and since then I’ve tried to design and build efficient commercial legged robots, giving me a decent idea of the constraints involved. So, in this article I wanted to try and examine — how did they do it? Is there some magical technology or technique that unlocked this performance? How did they beat the significantly better-known Unitree (who reportedly had to supply an ice pack backpack to try and complete the race without overheating)? Could a western robot have won?<br>Thanks for reading min{power}! Subscribe for free to receive new posts and support my work.

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This publication and this post contain the author’s personal thoughts and opinions only, and do not reflect the views of any companies or institutions.<br>The basic physics of hopping and running

Hopping, very simply, consists of alternating phases of a leg pushing against the ground (“stance phase”) and the body flying through the air (“aerial phase”).<br>In aerial phase, the body simply free-falls (constant acceleration due to gravity). You can think of this as losing vertical momentum. In stance phase, the job of the leg is to push against the ground to reverse this vertical momentum. The job of the “knee” actuator is primarily to generate this force in stance phase.<br>The other basic leg function is repositioning for the next foothold. In bipedal running, while one leg is pushing against the ground, the other leg is swinging to reposition for the next step. The job of the “hip” actuator is primarily to swing the leg forward.<br>Bipedal running is simply these two functions alternating in the two legs — while the left leg pushes against the ground, the right leg swings forward, and vice versa. Of course, this is an oversimplification in many ways, but it still captures the main effects that contribute to running energetics. Namely, it becomes clear that:<br>the knee actuator must produce enough torque to reverse the entire robot momentum in the stance duration Ts

the hip actuator must product enough power to accelerate the leg forward in the swing duration Tsw

The way a robot runs faster is that it increases its stride length and/or shortens the stance duration.

A depiction of a single-leg hopper’s stance phase showing the reversal of vertical momentum and the maintenance of horizontal momentum, as well as the stride length and the stance duration. Source: “Legged Robots That Balance”.<br>Shortening the stance duration requires a higher amount of knee torque to be needed to accomplish the same momentum reversal. Swinging the leg faster, and covering a longer stride length requires more torque and power from the hip actuator.<br>And just like that, with very basic physics, we’ve recovered the dependence of running speed on the torque and power produced by the actuators.<br>The basic physics of motors

Electric motors dissipate energy in an exact relation to the amount of torque they produce, and these quantities are related by an appropriately-named constant termed the motor constant, Km. If τ is the torque produced by the motor and Q is the heat it produces,<br>\(K_m := \frac{\tau}{\sqrt{Q}}\)

In the “New Motor Models” section in my thesis (2017) I described how a Km scaling relation can be approximated from rough first-principles geometry arguments. In particular, for a fixed length scale, Km scales with the square root of motor mass √m. In a recent...