Yeah, the tire pellets really ARE indictors of motion in athetics!!! In NCAA of NFL or CFL-level North American football, on really hard "cuts" that running backs and receivers make, there is often a very definite "puff" that shows immediately past motion. Same thing on diving catches and fierce tackles--we can literally SEE the impact that JUST happened when elbows and stuff hit the turf. It really truly is kind of a new thing in sports photos...the pellets stay in the air maybe two- or three-tenths of a second I'd guess, so it's almost like, well..like the wake in waterskiing. Like that four-foot long skidmark and rooster-tail wake in Scott's second to last shot--that kicks a&& as far as showing that these fellows are sliding along, scrapin' the turf!