"For less distant Sports such as Tennis, Beach Volleyball, Motocross, Inline Skating, and Boxing you can get away with using an 80-200mm f2.8 lens, since you are closer to the action.  The digital camera body provides another 1.5X magnification-factor so you may not need a tele-extender.  Try a 70-300mm f3.5 lens, (1.5X mag factor equals 105 to 450mm) to get in extra close, than change the ISO setting to recapture the lost shutter speeds."