souplesse

I first heard the word at a race in Belgium. Some sort of mystical ability that the top riders have? Loosely -- very loosely -- translated as suppleness, but so much more.

I've sensed it in the pedaling action of some of the super-fast pro track riders; got some feel of it in my own legs on late-night "twiddles" home on an extremely low gear after watching said riders. There's a sense of connected flow, as well as speed, relaxation, power and... well, suppleness.