THE LONG HURDLES
The importance of learning to hurdle with the other leg can not be overemphasized. In the long hurdles, if you are using 15 strides between and because of fatigue have to increase the number after hurdle four, going to 17 strides would add 12 steps. By going to the other leg after four, you would have to lead with this leg on only three clearances. By doing this, you would use a 16-stride pattern and add only 6 strides. No other training will save you as much time. (In the 1992 US Olympic Trials, seven of the eight finalists in the men's long hurdles changed lead legs during the race.)
If at all possible, have someone record your touch-down times during a race. You should expect to see some normal slowing, but major changes can point toward the area where your skill/speed/strength needs improvement.