Triathlon training really isn't just tacking together the training you would do for all three sports; this would be impossible. Instead, it is doing the same amount of training as you would do if you were doing one of the three sports exclusively. But in the same amount of training, you are training to perform three sports rather than one.
This necessarily means that a triathlete is not performing to his/her ability in any single sport. For example, a good time for the marathon portion of an Ironman is 2:40-2:50, but a competitive marathon time is 2:05 or faster. Just to add additional perspective, a good marathon time for an amateur runner is 2:30, faster than what a topnotch triathlete would be expected to pull off.
> Just to add additional perspective, a good marathon time for an amateur runner is 2:30...
That's not a good time for an amateur, it's an insanely good time for an amateur. The world record is currently 2:03:38. A 2:30 would have put you in 22nd place (out of 26,000!) in this year's Boston Marathon.
I am not thinking of dabblers; many people will do marathons after having barely trained. The goal for these people is just to finish.
I think 2:30 is achievable for a healthy, moderately talented man who is not merely dabbling: someone who is training correctly and has put in a few years of sustained, injury-free effort.
2:30 is still very much an amateur time. For example, I think that even though 2:15 or faster is professional-caliber it is still nowhere near being competitive.
Of course it's an amateur time: You're not going to win any serious marathons running a 2:30, and if you have no chance to win, you can't really be described as a "professional". But c'mon, 2:30 is an amazing time for an amateur. Obviously it's "achievable", since maybe a dozen "amateur" runners managed it in Boston this year, but it's well beyond "good", as you initially described it. It's well into the top 1% of amateur marathon runners.
This whole argument is slightly tangental, but I figured I needed to chime in ;) A 2:30 is a ridiculous time for an amateur. It'll easy put you in the top 0.5% of amateurs in the world. To put in this in perspective... a 2:30 marathon pace puts you at doing roughly 17m30s 5km's, 8 times in a row!
Haha, yes, I agree. 2:30 would probably be run at the pinnacle of one's amateur career -- a personal best rather than a typical time.
I do want to point out somewhat pedantically that it takes being in better-than-2:30 shape to run 2:30 on the Boston course, a notoriously slow course. There are runners who ran more slowly than 2:30 in Boston when they could have run 2:30 elsewhere.
This necessarily means that a triathlete is not performing to his/her ability in any single sport. For example, a good time for the marathon portion of an Ironman is 2:40-2:50, but a competitive marathon time is 2:05 or faster. Just to add additional perspective, a good marathon time for an amateur runner is 2:30, faster than what a topnotch triathlete would be expected to pull off.