Pay a visit to your local gym, observe the grimacing patrons as they pound the treadmill or march in place on the StairMaster, and you might conclude that exercise is no fun. But it doesn’t have to be that way, according to Kelly McGonigal, who lectures at Stanford, teaches dance classes, and wrote “The Joy of Movement: How Exercise Helps Us Find Happiness, Hope, Connection, and Courage.” Today, she explains how exercise — of all kinds and in all doses — can strengthen your mind, elevate your mood, and deepen your social connections.