It is good that you are taking the time to research it properly to make sure you provide the best programme to clients. Too often many PTs give the same programme to people regardless of goal. Although you can always learn from other sports and bodybuilding etc, an athletes needs will differ. For example the typical 3 x 10 reps on things like leg extension, curls, cable rows I was given when I first went into a gym was a shocking programme given what I know now. Then I remember a strength and conditioning coach telling rowers to do db curls standing on 1 leg on a balance ball thingy. It was just utterly ridiculous.
Typhoons advice is really solid. One thing I have noticed when I do occasionally go for a swim is my shoulders tire really quickly compared to when I was 11 and trained for competition. Apart from lack of muscle memory, I think a lot of this is due to the weight and bulk I now have, although I agree with Typhoon that strength training in particular helps sprinters. Mark Foster said he wish he had started some form of weight training earlier in his career in one thing I read.