A hunched back, forward-slouching shoulders and a forward-protruding head are signs that youre either perfecting your Mr. Burns impression or you need to work on your core strength.

But dont feel singled out -- we all have to work on our core strength continually, from the most sedentary office worker to the regular exerciser to the athlete, according to Chris Kolba, a sports medicine physical therapist at the Ohio State University Wexner Medical Center.

Most people need to work on their core strength, Kolba said. Strength is not something thats stored -- you continually have to work to maintain it.

Having a strong core can improve your posture, protect you from back pain and help you lift, push and pull things more easily. But because of the mostly sedentary lifestyle we live, sitting at a desk for work, in our cars and watching TV, our core muscles are not as strong as they should be.

Over time, weak core muscles can lead to back pain, spinal injury, bad posture and difficulty doing simple movements like walking, bending over, lifting or carrying things.

For core strength, think beyond crunches

Before you roll out your yoga mat and get on the floor for some crunches, realize that the core encompasses more muscles beyond the abdominal six-pack." Your core muscle group includes anything that helps stabilize the trunk and pelvis, says Kara Radzak, an associate professor with the Kinesiology and Nutrition Sciences department at the University of Nevada, Las Vegas.

In addition to your abs, this includes back muscles like the transverse abdominis, which lies under your obliques and wraps around the spine, the erector spinae muscles that run along the spine, and the muscles surrounding your pelvis, which include the gluteus maximus and gluteus medius.

Because of the number of different muscles involved in having a strong, stable core, crunches alone will not produce the results you want, Radzak explains. She advocates doing regular weight lifting exercises, like a squat or an overhead press, with an eye toward engaging the core muscles.

One of the often overlooked things in developing good core strength is using the core muscles in all the other exercises that you do, she said. If youre working out in general doing any type of strength training activity and youre not engaging your entire core, then youre not really gaining the [full] benefit of all those other exercises. In practice, this means concentrating on good posture and drawing your bellybutton in toward your spine while lifting weights, so that your abdomen feels tightly pulled in.

But if you want more ideas for exercises that specifically strengthen the core, Kolba highlights four of his favorites in the list below.

Four exercises for a stronger core:

1. Farmers Carry

For beginners, start off by carrying hand weights in each hand and walk for 15 to 20 yards. Do two to three sets of this walk, and as time goes on you can either extend the distance or increase the weight. This functional exercise trains you to carry heavy grocery bags or suitcases short distances. The amount of weight you use depends on your strength and coordination, but Kolba estimated that a healthy 145-pound woman might be able to start with ten pounds in each hand.

This is going to create a downward load that your body is going to have to work against, says Kolba. "You have a little bit of time on a single leg so it has really been shown to recruit your lateral hip muscles and your core muscles and it doesn't create a lot of excessive rotation, flexing or bending on the spine."

2. Resistance training with split legs

Pushing or pulling weight while standing with split legs is a safe, effective exercise for the core, says Kolba. The exercise mimics everyday movements in which you have to maintain your balance while pushing or pulling something heavy.

"Stand with one foot in front of the other so you have a little bit better ability to stabilize when you're pushing or pulling something," he advises.

3. Planks

Lay face down on a mat and then prop up your body in a straight line on your toes and elbows. Keeping your core engaged, your spine straight and your pelvis drawn toward your front, try to remain in this position for 30 seconds at the beginning and then repeat two or three times. Ultimately, you want to try to get up to one minute in the plank position.

4. Side planks