How to Make the Obliques Curve Inward Like an Hourglass

In the quest for a fit and toned body, you may hit the gym several times each week, faithfully perform cardio and closely monitor your diet. Countless crunches may have even granted you the enviable six-pack abdominal definition that so many pursue. However, if your waist is thicker or wider than you would like, it could be that you are overlooking two crucial muscle regions in your fitness training. Use your workouts to tighten the muscles that have the physiological function of narrowing your midsection. All body types possess these muscles, so even if you are not naturally wasp-waisted, you can still see improvement with time and effort. Toning these muscles pulls in the waist like a natural corset or girdle and creates more of an hourglass silhouette.

Performing regular crunches is a familiar part of working out for most people. Unfortunately, standard crunches focus mainly on the rectus abdominis, or the vertical bands of muscle fibers that extend from the sternum -- breastbone -- to the front of the pelvis while ignoring the internal and external obliques on the sides of the waist, and the transverse abdominis, which encircles it. To effectively trim and tighten the midsection, these muscles must be targeted directly during your workouts.

Employ exercises that involve the controlled rotation of the torso to activate the internal and external oblique muscles with the transverse abdominis. You may use the rotary torso machine at the gym or use an inflatable ball to perform a simple version of a torso rotation. You can do this by sitting on an exercise mat with your knees bent and feet flat on the floor. Hold the ball between your palms with your back straight and your abs pulled in to protect your spine. Keep your knees together and your legs still as you rotate your upper body as far as you can first to one side, pause, return to center and then repeat in the other direction. Twist your upper body in a slow and steady movement as far as you can. Perform up to 25 rotations on each side.

Hold a dumbbell in each hand with your palms facing your body, with your arms down at your sides. Lean to the side as far as you can without leaning forward. You should feel a stretch on the opposite side. Contract the muscles that are being stretched as you return to your starting position. Repeat the movement leaning to the opposite side. Use light dumbbells that are just heavy enough for you to feel a moderate, tightening contraction when performing this exercise. Heavier weights may encourage the development of a thick waist. Do three sets of 12 repetitions for each side.

Perform cardio exercise at least three times each week to burn excess fat that would otherwise obscure your muscles and include protein and whole-grain carbs at each meal to assist with muscle growth and repair. Spot reduction is not possible, so to reduce body fat around your waist, lower your body's total fat percentage. Snack on fresh fruits, nuts, vegetables and dips that include healthy fats like hummus and avocado. Drink up to 16 ounces of water with each meal and during workouts to stay hydrated and avoid the bloating from water retention that could make your muscles look less defined.