That's a good question. I've worn compression pieces that make me feel like I'm suffocating, which doesn't do much to enhance my performance. Ideally compression tops and tights are designed to increase blood circulation throughout your body, provide greater muscle stability, and help prevent injury. But there's a fine line—add too much pressure and compression clothing can be way too constricting. Provide too little pressure and there are no real benefits. So, the trick is finding a garment with just the right amount of compression pressure in just the right places. And take note: medical-grade compression clothing is for serious ailments like lymphedema—a blockage of the lymph vessels that causes fluid retention—and provides pressure levels that would be unhealthy for active athletes, so it's not a good idea to wear these garments while competing in a triathlon.
Australian company 2XU has been experimenting with compression fabrics since 2005 and is a front-runner in developing compression clothing worn by a spectrum of world champion-level athletes, from cricketers to snowboarders to runners. For spring, try their Women's Elite Compression ¾ Tights ($90; 2xu.com, be sure to click on the American flag at the top right corner for proper U.S. prices). Made from 50-denier Lycra fiber with antibacterial elements and UPF-50 protection, the tights offer comforting support to your quads and knees, cutting way down on fatigue. Cyclists will want to check out the Compression Cycle Shorts ($189); or if you're not sold on the concept of compression, try their Compression Recovery Sock ($49) on a long flight. You'll be a convert.
Sugoi's Piston 140 LS compression top comes in a long- and short-sleeve version ($80/$70; sugoi.com). The crew-necked, raglan-sleeved shirt has mesh inserts for ample ventilation where you don't need as much support, flat seams to reduce friction and add comfort, and it comes in pretty hot pink as well as black.