Interesting one this. Firstly, as I understand it, the kicks and punches that score in competition, do not have to land, ie contact does not have to be made. However, in using a sweep, to be effective it MUST contact with the opponents leg. The result of the contact could be several things. 1) The contact is ill-timed/poorly targeted and injury occurs from the delivery of the technique itself, or 2) the technique is successful and the opponent falls to the floor. The latter could result in injury dependant on how the opponent falls. However, most clubs teach very little in the way of "breakfalls" so the risk is probably increased. Having said that, it is karate we are doing, and we have all signed a form to acknowledge that karate carries a risk of injury. I would have thought the risk from being swept and falling is not really greater than other sports where contact is made. I don't believe the technique is dangerous, full contact would be far more dangerous, or targeting of vital areas. I'd like to see it kept in, as further attempts to "make it safe" seem to me to be self-defeating.
lloydie