While many people may want to increase their muscle mass primarily to improve physical fitness, some are also after a more attractive physique.

Glutes, triceps, obliques and chest muscles are all desired. Biceps are, too. But often the most buzzed about muscle region that people are after is abdominal muscles. Men in particular frequently chase the chiseled six-pack, only to find that getting it is easier said than done.

Here's that the health and fitness pros say about the overall benefits of building a strong core and which exercises are most likely to yield the desired outcome.

Are abs a sign of good health?  

Though defined abdominal muscles aren't necessarily a definitive sign of overall good health (for some people, an obsession with a lean stomach can lead to or stem from an overly restrictive diet), having strong abs usually means achieving a level of physical fitness that benefits the whole body. 

That's especially likely because plenty of cardio often accompanies ab-toning workouts; and abs are only one part of the body’s core muscle group that are affected by abdominal exercise. "Many people overemphasize the importance of abs, which are important, but they are just one part of our overall core," says Dr. Shelby Johnson, a physical medicine and rehabilitation specialist at Mayo Clinic, Rochester.

Austin "Ozzie" Gontang, a licensed psychotherapist at Pacific Pearl of La Jolla and the director of the San Diego Marathon Clinic, agrees. He says that core muscles are fundamental to "maintaining good posture, preventing injuries, and enhancing overall physical performance." These core muscles include the internal and external obliques, the transverse abdominis ("the deepest abdominal muscle which wraps around the spine," Gontang says), the erector spinae, pelvic floor muscles (which form the base of the core), the diaphragm, gluteus muscles, and the rectus abdominis - which is "the muscle at the front of the abdomen that most people think of as the 'six-pack,'" says Gontang. 

"Each one of these muscles must work together to enhance the stability of the spine," explains Dr. Michael Fredericson, director of Physical Medicine and Rehabilitation and the co-director on Longevity at Stanford Medicine. He says these muscles are also important for improving breathing, aiding everyday movement, and are essential for providing balance and support. 

Is it hard to get abs?

As for actually strengthening these muscles and getting noticeably stronger abs, it's important to remember that a healthy diet usually needs to come first. "The old adage 'abs are made in the kitchen,' underscores the importance of nutrition in achieving a defined abdominal area," says Gontang. He explains that overall visibility of one's abs "are heavily influenced by body fat percentage;" so one must avoid fatty foods, be mindful of calories, and get plenty of healthy nutrients to maintain a healthy enough body for abdominal muscles to be visible.

After all, as Fredericson points out, getting abs isn't the objective "since we all have abs already." Rather, it's about having the kind of physique where abs can be seen, then activating and defining that group of muscles by making them stronger.

Beyond diet, other factors affect whether one's abs become readily visible. "Genetics play a role in how abs develop and appear," says Gontang. Different exercises and approaches will also lead to varying results in different people. "It's important to remember that no single exercise regimen works for everyone," he says. "The best results often come from a varied workout plan that keeps the body challenged."

How to get abs

Some exercises that are known to challenge the body this way and target abdominal muscles directly, include:

• Planks, because they are great for building endurance in the abs, back and stabilizer muscles. 
• Crunches and sit-ups are a traditional but effective movement that target the front of the stomach. "Variations like bicycle crunches and reverse crunches can also engage the obliques and deeper abdominal muscles," Gontang says. 
• Leg raises are effective at targeting the lower abdominal muscles especially. 
• Flutter kicks and scissor kicks similarly target lower abdominal muscles and also engage one's hip flexors.
• Mountain climbers are a "dynamic exercise that works the entire core and also provide a cardiovascular benefit," Gontang says. 
• Pilates and yoga are good for targeting, toning, and strengthening most core stomach muscles. 
• Stability ball exercises such as stability ball crunches, pikes, and rollouts "engage deep core muscles and improve balance," Gontang says.

For individuals with lower back pain or spine concerns, Frederickson cites the work of Dr. Stuart McGill, a well-known spine researcher, who has identified three specific exercises that most efficiently address one's core muscles without placing excessive stress on the back. He says this group of exercises has famously become known as ‘the big 3' and include the curl-up, the side plank, and the bird-dog. 

Each big 3 exercise is performed as follows:

• The curl-up looks like a sit-up, but different in that one leg remains bent at the knee (with the foot of that leg flat against the ground and the other leg straight) with your hands under your lower back to provide support. Then, lift your head 4-8 inches off the ground and hold it there for 10 seconds or so before resting and repeating the motion again. 
• The side plank is performed by laying on your side with the legs bent and your upper body supported by one extended elbow. Then, raise your hips off the ground slowly so only the side of your bent knee and your extended arm are supporting your upper body weight. Hold the pose for 10 seconds or so before returning to the former position. Then rest and lift again to repeat the motion. 
• The bird dog starts in the same position as a push-up, only on your knees instead of supporting your weight on the tips of your toes. Then, straighten and raise one leg while simultaneously extending one arm on the opposite side of the body. Hold the pose for 10 seconds or so before returning to your former position, resting, and resuming the pose with the opposite arm and leg. 

Regarding these movements and others, Johnson says that "different exercises target different parts of your core" and that the important thing is to make sure "a variety of exercises are used."