A person on a bicycle is by far the most energy-efficient among animals and machines per distance traveled relative to body weight. The bicycle is magic.

https://www.jstor.org/stable/24923004

@davidho To be any use to me, the "magic" would have to include it being self-stabilising. My sense of balance just isn't good enough to keep a bike upright.
@MikeH I would imagine that a well designed tricycle isn’t too far behind bicycles in efficiency.
@tim1724 A bit bulky for storage though. If it wasn't for that little detail I'd investigate buying one.