Swimming longer distances helps build lung capacity. Swim a brisk 100 meters, or four lengths of the pool. Rest two minutes and repeat. When this workout becomes routine, gradually work up to a 200-meter distance with the same two-minute rest in between sets, Runner's World advises.For more variety, change to a different stroke each time you start a new set.print 25 meters, the equivalent of one length of a standard pool. Rest 30 seconds, then repeat four to six times. Eventually increase your sprinting distance until you can do 50 meters six times, recommends Runner's World.. Finish each set with a few slow, easy laps of freestyle, backstroke or breaststroke.