impulsion

CONT: [...] la vitesse n'est qu'une expression de l'impulsion, elle ne doit pas pour autant être confondue avec elle.

CONT: The horse is at the alert, and under control of the rider with muscles concentrated in readiness for movement like a compressed spring. A horse in this condition is said to have impulsion.
CONT: During a movement with impulse the neck and head must remain extended ... do not confuse impulse with speed.