I always felt that walking was more efficient intuitively but I'm happy to see it quantified in the article.

> First, even if you happen to hit exactly the minima of the walking cost of transport curve, you’ll be consuming nearly 80% of the energy per traveled distance as compared to running

the article says “walking 50km as fast as possible takes nearly double the work and energy than running a marathon, even though the distance is just 8km longer”