WASHINGTON — At last, the secret to first lady Michelle Obama's sculpted arms? Tricep pushdowns and hammer curls.So says Cornell McClellan, Mrs. Obama's longtime personal trainer, who described the workout routine of his famous client in the October issue of Women's Health magazine. She began working with McClellan in 1997 at his Chicago fitness studio. "She's truly committed herself to the importance of health and fitness," he says. McClellan said that at the end of an intense routine of cardio workouts and weight training, Mrs. Obama finishes with the "arm-shaping superset" of tricep pushdowns and hammer curls to tone one...