Many people hear the word core and think "six pack". While a six-pack is a great achievement, it shouldn't be mistaken for the core. So what is the core anyway? You actually have two cores: an inner and an outer core.  Your outer core is what everyone thinks of, the "six-pack" abs, obliques ("side abs"), and your low back muscles. Your inner core is all the muscles that surround the spine itself. 

 I've used an example similar to this before, but picture a radio tower.  You know, the kind that's a single tower bolted into the ground with cables coming out from it. Let's picture the cables coming out of the sides as the abs, obliques ("side abs"), and low back muscles.
 
Question: What would happen if one of the cables was pulled really tight (i.e. abs)?

 That's right. The tower would fall over. The same can be said with our bodies. The problem with just constantly doing different variations of crunches is the ab muscles are being worked way too much, and as a result, the abs become way too tight.

 In order to properly develop the outer core, you must develop the inner core; as with the radio tower, if the base of the tower isn't strong (i.e. inner core), then the tower will collapse. Developing the inner core means strengthening tiny muscles surrounding the spine as well as a layer of muscle that wraps around the abdominal and low back areas. This layer of muscle is called the transverse abdominus; it can really be considered your body's natural corset. If this muscle isn't kept strong, then it'll loosen up and contribute, among other things, to the belly hanging out.

 As you've probably already guessed, a lot of people are weak in this area. A huge contributor to this problem is laziness, or to be more precise, slouching; I can be a culprit of this one. By slouching in a chair, or while standing, the transverse abdominus, along with all the other inner core muscles, isn't being activated.

Why do you think about 80% of Americans suffer from low back pain?
By strengthening the inner core, you set yourself up for improvements in every other area of fitness. Just something to think about. As a result of not being activated, the inner core muscles weaken, and this leads to deteriorating balance/stability, quickness, low back problems, etc.
 
Here's something to observe; for those of you who're parents of young kids, this is easy. For those of you that aren't parents yet, whenever you're around little kids, I'm talking 5 years old or so, watch how they sit. Most sit nice and tall on the edge of their seat. I'm not a parent yet, but I observe this with my little nephews when they're watching Star Wars or Power Rangers or something. They're always sitting up straight. As kids, our inner core starts out strong because we need it to be strong in order to learn to walk. As we get older though, we become lazy with our posture, and in comes the low back pain.

 Now that we're all sitting up straight reading this, another benefit of keeping the inner core strong is it won't be a contributor to the outer core muscles becoming too stretched out; they'll be at the ideal length to develop properly. If the radio tower leans, the cables stretch and aren't in proper alignment, form, or strength.

 The moral of the story, work the inner core. 

Written By: Dan Falkenberg Taken from http://www.columbussports.com