I've heard this referred to whole bunch of times in different ways. Even as a sale pitch for bike frames, helmets or wheels; however I've never really thought about it. I think as triathletes we really get caught up in viewing triathlon as 3 separate sports when it is not... or at least I do. For example, the fastest bike split theoretically will be done ( engine aside ) from the most aerodynamic setup but it is not practical. I guess there is give and take where the weight of benefit is greater than the drawback. Wearing an aero helmet will make you sweat more, and heat up your body but the time savings depending on length of course is worth it.

So getting back to my question, what should be considered during swimming and cycling to improve run performance?