And fitness a deux doesn't have to mean a high-impact sport or monumental goal, like training for a marathon (though it might!). "Bowling, yoga or even horseback riding are great…anything that allows time for interaction," says Kaiser. The key is making the commitment together, and sticking with it. Below, three couples who are fit and happy share their workout secrets:
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Couple #1: The Knockouts
Glynis and Adam
Age: early 30s
Location: New York, NY
Glynis and Adam began their routine in the ring long before they exchanged rings: Each week the couple, now approaching their third wedding anniversary, dons boxing gloves to spar against each other. "It relieves the week's stresses," says Glynis, a PR executive. "But it also brought this whole other dimension to the relationship. If you learn to trust your partner in the ring, that moves throughout your whole life." Another unexpected upshot: Trading blows bettered their sex life. "The training brings more passion to the relationship," explains Glynis. "We always have more energy afterward."
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Couple #2: The Charity Cases
Katie Sloan and Frank Sweet
Age: Late 20s
Location: Birmingham, MI
If a better bod or a stronger relationship isn’t enough motivation to get off the couch, how about sweating for a cause bigger than the two of you? Last summer, Katie and her boyfriend Frank took part in a three-day, 300-mile charity bike marathon for the Make-A-Wish Foundation of Detroit, where they teamed up in honor of a child. "It's exhilarating and rewarding," says Katie. "We raised $3,000 between the two of us!" Altogether, their team of 30 bikers raised over $200,000. The couple, who have been dating for three years, have even started to volunteer at other charity marathons as a result. Kaiser applauds twosomes who take on this "triple hit," as she puts it. "It's companionship, charity, and a workout all in one," she says.