MTS Long Sleeve V-Crew
But the fact is, synthetic clothing has always had a bad rap when it comes to smell. That's because the chemical structure of the fabric actually allows it to bond chemically with stink molecules, so you have a shirt that consists of 99 percent synthetic fabric atoms and 1 percent odorous atoms. I may have the precise chemical proportions here wrong, but you get my drift. And once the stuff binds, it's very difficult to get rid of. You can always double-wash the clothing, if you want to take the trouble. Or, wash with an odor-killer such as Febreze Laundry Odor Eliminator.
Generally, modern synthetic clothing has less of a problem in this regard than the stuff used 20 years ago, but it's still an issue. For that reason some makers add an anti-microbial finish to their clothing. REI's Lightweight MTS Long Sleeve V-Crew ($28; www.rei.com) is one example of this. Mind you, that finish can wash out after extended use. Another solution is to purchase garments made with X-Static, a silver-based material that employs silver's natural anti-germ capabilities to fight bacteria buildup and the subsequent smell. Silver has the added benefit of lasting for the life of the garment. Salmon's Bio Tech-T Shirt ($40; www.salomonoutdoor.com) has mesh made with X-Static in the armpits, obviously a critical area.
Personally, I've found that Patagonia's Capilene underwear seems to resist odor buildup, particularly the silkweight stuff, which has a smoother finish than other underwear (www.patagonia.com). And natural fibers such as woolwhich of course are completely different, chemically, from syntheticsseem to all but eliminate the problem. So try something such as Icebreaker's Superfine Tech T (www.icebreaker.co.nz). True, it's $69, but for that you get a superb shirt. I have several Icebreaker pieces, from lightweight to midweight, and find they keep me more comfortable across a wide temperature range than most synthetics.
Read "When Base Layers Go Bad" from the Outside 2005 Buyer's Guide for more expert advice on keeping the stench from soiling your workout threads.