Both legs down

I saw something I've never seen before on my commute this morning: a chap who was cruising with both legs down - and both crank arms in the same direction, towards the ground. I caught up to him at the lights and he said something about a bearing in the crank arm - being able to slip it, and reengage it, and that it helps with training - but quite frankly I didn't get it really!

WHAT IS THIS SORCERY?!

Probably something like PowerCranks
https://www.powercranks.com/

Does indeed sound like a tool of the devil

The idea behind Powercranks is that with them you need to pull up on the back part of the pedal stroke otherwise both cranks slip.

They train you to put in power the whole way round your pedal stroke, thus improving total power output. Hurts lots of muscles you haven't trained properly until you get them built up. Talking crap, nevermind.

Each crank has a clutch so that it is independent. You have to use your legs to pull the crank through the upstroke and round helping to develop a smoother pedalling technique.

Almost bought a pair of them years ago but never got around to it (the tax rebate money was required elsewhere). Occasionally I keep an eye out for a second hand pair on eBay but none have gone for a good enough price.

Eh? Your not meant to pull up so why train that bit?
http://www.bicycling.com/training/fitness/perfect-pedal-stroke

See not so stealth edit.