A recent study of swimmers who tapered down on their training intensity before a major competition did it this way: Twenty one days before the meet, they began to swim shorter overall distances during each session. They kept doing interval sets and pushed themselves to do each one at race speed. But again, their total distance was less during the 21-day period. If you are unclear about how to do these sets or need more help, you may want to talk with a swimming coach or a strength and conditioning specialist. Most pools have swim clubs and a trained coach whose expertise could be tapped for free or a nominal fee at most.