Pushups. If you're going to pick just one exercise to do, this is the one to go for, Weil says, "for all the obvious reasons." If you can’t do basic training-quality pushups at first, start with wall presses (essentially pushups done against the wall), aiming for 3 sets of 12 to 15 repetitions. When you're ready, progress to knee pushups on the floor, making sure to keep your back straight (squeeze your butt and suck in your gut) while you slowly touch your nose to the ground. Once you're ready to kick it up a notch, progress to traditional hand-and-toe pushups.
Abdominals. Weil, director of the New York Obesity Research CenterWeight Loss Program at St. Luke's Roosevelt Hospital Center, says your abs are a critical sex-boosting body area to work on. "After all," he says, "you have to use your abdominal muscles during sex." Weil suggests starting your ab workout with good old-fashioned crunches. Lie on your back, hands supporting your neck, knees bent, and your feet on the floor. Then bring your body up just enough to get your shoulders off the ground. Do 3 to 5 sets of 15 to 20 repetitions.
For additional ab oomph, Weil suggests men and women also do bridges. Lying on your back, knees bent, feet on the floor, lift your hips up and down for 3 sets of 15 reps. Men can also try pelvic tilts. Standing up or lying down, straighten your lower back and pull your belly button in until your lower back touches the wall or floor. Women can try Kegels. Contract your pelvic muscles -- the ones you'd use to stop the flow of urine; squeeze the muscles tight for 3 seconds, then relax for 3 seconds. Do 10 to 15 repetitions three times a day.
see more: http://www.webmd.com/men/features/exercises-better-sex