Dry skin is hereditary, but certain activities exacerbate it. “When planking or kneeling in yoga, for example, the skin on your elbows and knees thickens to protect itself, just like the calluses do on your feet,” says Robyn Gmyrek, a dermatologist in New York City. Create a shield by opting for workout gear that covers these trouble spots. Other helpful hints: Go easy on the moisture-sapping A/C, or use a humidifier. And take lukewarm, not hot, showers. In the heat, wear full-coverage layers of thin fabrics (as opposed to bare skin) to seal in moisture.