The mystery is over.
The secret to First Lady Michelle Obama's killer arms? Tricep pushdowns and hammer curls.
In the October issue of Women's Health, her longtime personal trainer Cornell McClellan speaks out for the first time, revealing Mrs. Obama's buzzed-about workout routine.
Perform one set of tricep pushdowns using a straight bar attached to the high pulley of a cable station and then, without resting, follow with a set of hammer curls using dumbbells, she advises.
Then, immediately repeat the entire process until two or three sets of both exercises have been completed, adds McClellan.
McClellan says that at the end of an intense routine of cardio workouts and weight training, Mrs. Obama, 45 -- known for her sleeveless outfits -- tones her arms by finishing with the "arm-shaping superset" of tricep pushdowns and hammer curls.
McClellan - who began working with Mrs. Obama in 1997 at his Chicago fitness studio - says the first lady is "truly committed herself to the importance of health and fitness."
Though President Barack Obama likes his occasional burger, Mrs. Obama says she has been trying to get her family to eliminate processed foods, cut back on sugary drinks and eat more fresh fruits and vegetables.
"But health and fitness and how we eat and thinking about it has become part of our lives, because of our kids," she tells Children's Health magazine of daughters, Sasha, 8, and Malia, 11. "We are their primary role models. And if they see me exercising and thinking about what I'm eating, if they see their father, as busy as he is, getting to the gym and playing sports, when they grow up they'll understand that this is a natural part of being an adult."