In reply to Ollie Keynes:
perhaps...
Stable Static: using muscles to maintain posture only (Standing; sitting)
Unstable Static: Muscle activity required to maintain contact (holding a hold to maintain position; feet not flat on surface) (thinking about this, standing might be seen as belonging to next category)
Stable Movement: Changing position, but can stop at any time and reverse
Active Dynamic Movement: A dyno, jumping (including down),
Passive Dynamic movement: Falling (planned, unplanned), abseiling, dropping/sliding