Truffle can go into much more detail, I'm sure, but it's due to something called tapering. It's where the swimmers set their training regimines so they are at their strongest for the day of the race (or week in some cases). It's certainly not an accident or pure coincidence. yeah, generally a swimmer will only shave/taper for a couple of meets a year. they'll swim other meets, but they'll be swimming a lot more yardage in the days before those meets. basically you train through the minor meets - knowing that your times will be slower - to get into better shape for the one or two meets a year that you do shave/taper for. i can't speak for what phelps does, but in college we swam about 5000-7000 yards a day for single practices, and about 10,000 yards when we had morning and afternoon practice. we'd come down a little bit in yardage before some meets, but generally never below 3500. in early january we'd do our training trip, when we'd swim about 12,000 to 14,000 yards a day. by the end of that, you'd be in great shape, but your arms would be mush. from that point until our big meet (patriot league championships), we'd come down in yardage gradually. the week before the meet, we'd never do more than 3,000 yards. you're in good enough shape and strong enough from the work that you've done during the year that coming down in yardage doesn't result in you getting out of shape. my best times in season were 2:08 in 200 back, 2:28 in 200 breast, 2:07 in 200 IM, 59.5 in 100 back, 1:56 in 200 free. shaved and tapered, my best times were 2:02 in 200 back, 2:21 in 200 breast, 2:02 in 200 IM, 57.0 in 100 back, 1:51 in 200 free. obviously i'm not as good as phelps or anyone in the olympics, but it's the same idea - my fastest times came in the meet that I expected to swim fastest. Truffle, are Phelps and Co. doing any weight lifting? How about the university swim teams? What's a typical plan? Back in the mid- to late-80's when I was swimming competitively it was still frowned upon as something that would "tighten up your muscles and slow you down."