Refine Your Abs
A flat stomach is as much about having a low percentage of body fat as it is about having lots of muscle tone. These five moves help you achieve both.

STABILITY-BALL CRUNCHES
A wobbly surface like a stability ball makes you recruit more muscle, so you get more from your crunches. With your back on the ball, keep feet flat on the floor, knees bent. Place your hands behind your head. Contract your abs, lifting your shoulder blades and upper back off the ball. DO: Two sets of 20 repetitions, two to three times a week.

MEDICINE-BALL CRUNCHES
Work all of your ab muscles by lying on your back (knees bent, feet flat on the floor) and having a partner throw a medicine ball to you in different directions — straight at you, to your left, to your right. Catch the ball by moving only your torso and arms. Toss the ball back to your partner. DO: Two sets of 20 repetitions, two to three times a week.

V-SITS
Lie on your back with knees bent, feet on the floor. Draw your knees toward you, keeping them bent at 90 degrees (hips at 45 degrees). Raise your upper body toward your lower until you're balancing on your butt (your body is making a V shape). Return to starting position. DO: Two sets of 20 repetitions, two to three times a week.

INTERVALS
Blast calories with bursts of high intensity.
Long: Push yourself to the highest effort level you can sustain for three minutes. Then, drop down to an effort level of 3 (out of 10) for three minutes. Repeat five times.
Short: Push yourself to an effort level of 9 for 30 seconds, then back off to 3 for one minute. Do this five to eight times. DO: One long- and one short-interval workout each week.

LONG, SLOW DISTANCE
This teaches your body to become good at burning fat for fuel. Run or bike at an intensity of 6.5 to 7 on a scale of 1 (easy) to 10 (almost impossible) for at least one hour, increasing the amount of time by 10 minutes each week. DO: One distance workout per week.

— Jason R. Karp, running/sports coach

Nix Your Underbutt
Manage beneath-the-swimsuit bulge with these four moves.

SQUATS
Place a barbell or body bar across the back of your shoulders; hold the bar slightly farther than shoulder-width apart. Stand with your feet just beyond hip-width — this activates your main butt muscle most effectively. Keep your spine straight and move your hips back as if you're about to sit in a chair. Bend your knees and squat until your thighs are slightly past parallel to the floor (if you can). Straighten your legs and return to the starting position. DO: Two sets of 20 repetitions; rest one minute between sets. Do this one to two times a week.

HIP EXTENSIONS
Stand in front of a cable machine and place the strap around your ankle (or, at home, wrap a stretch band around your ankle and something immobile). Keep your leg straight, slide it behind you, and lift your foot slightly off the floor so your butt contracts. DO: Two sets of 20 repetitions; rest one minute between sets. Do this one or two times per week.

ROWING MACHINE
Rowing isn't just about your arms; it's a powerful toner for your lower body, especially the largest muscle in your butt. DO: 30 minutes once a week at an intensity level of 7 or 7.5 on a scale of 1 to 10 (10 being exhaustion). Increase by 10 to 15 minutes every three weeks. Bored? Download iRow ($6.99, iTrain.com) to your iPod, and it's like having a coxswain guide your workout.

HILL RUNNING
Running on an incline not only burns calories like crazy, it works your glutes big-time. DO: 10 minutes of warm-up, then set the treadmill to a 10 percent grade. Run at a sprint for 20 seconds, then run/walk with a .5 percent grade for three minutes to recover. Repeat eight times. Do this workout once a week.

Avoid a Toning Plateau
When working on your abs or underbutt, the key to consistent progress is to do less every three weeks, not more. On the third week of your program, decrease the number of repetitions by a third. In the fourth and fifth weeks, increase the weight and take an extra 30 seconds of rest between sets (but keep the number of repetitions the same as week three). During the sixth week, drop the number of repetitions again (like you did in week three), and so on.

From RealAge.com: Build a Better Body With a Personalized Workout Plan

What Do You Think?