2nd new concept: "critical contact surface" (ice & roller skating)

the "critical contact surface" is the 2nd new concept introduced, as intended & written (2/7/13)
(c.c.s. - conceptual approach, through cross industry knowledge)
it represents the blades'/rollers' minimal total surface area, in full contact with the
skating surface, at a certain moment during skating, beyond which the skater looses.
grip (slips & might fall) and eventually traction (often just partially).

attn: (r.s.) consider replacing the rollers on your skates, right away, if their surface appears
                pitted by craters (mm wide), particularly in speed skating, downhills and/or if you
                are overweight.
                from now on, we will call the rollers, with this type of wear: "pitted"
                (not the same as "pitting" - localized craters on a metal surface, associated always
                with corrosion.)
 the analogy for roller skating (not done 2/7/13), is to be added (using c.c.s.) here below: