Pairs are definitely in season. Witness the range of for-two workout programs launching at health clubs across the country. In Fit-a-sutra, a class at some New York Sports Clubs and Washington Sports Clubs, couples get physical with quirky core and flexibility exercises like

But not all couples make great workout partners, notes University of Washington sociologist Pepper Schwartz, PhD. Consider going solo if one of you is competitive, or if you consider exercise sacred "me time." On different fitness levels but still want to play together? Run side by side on treadmills, or jog while your partner bikes. (Just be sure to leave those matching sweat suits at home.)