The tricky part here is that the pains from being too stretched out are much the same as those from being too bunched up. In Tierstein's case, an article in a cycling magazine alerted her to the problem by pointing out that men's bike frames don't always accommodate women, who typically have shorter torsos. My back felt better, and I could go longer. Then the seat problem manifested itself. Which reveals an unfortunate truth - any adjustment in one area can cause a problem to another.
Some shops can accomplish roughly the same thing with a yardstick, a level and a plumb bob.
While you're fine-tuning, start with a short ride and build up, so problems can reveal themselves gradually. Keep a detailed record of any changes, in a log or on the bike itself, as racers do, says Callan. Some riders mark the original position of a seat post or handlebar stem with tape, so they can restore the original position if need be. Even though there is a basic best position, there are still individual differences for which there is no accounting. This is especially true when it comes to saddles, a prime candidate for a comfort upgrade, and the most researched and modified cycling product over the last two years.