It isn't necessary, er, actually swimming is a rather good way of keeping fit because it's particularly excellent for erm all three of the S-Factors if you like, the strength, the suppleness and the stamina.

没必要，呃，实际上游泳是一种很好的保持健康的方式， 因为如果你愿意的话， 它对呃所有三个 S 因素特别好， 力量、柔软度和耐力。