You can strengthen your core by learning how to engage your tranverse abdominus (TA).
It isn't really an exercise or a workout; but the DVD to learn this technique or posture is called The 5 Minute Workout.
There are some exercises that work the TA but that isn't the same. The TA is supposed to be worked only slight to moderately (5 to 20% I think).
This muscle is like a natural girdle. It starts at one side of the spine and goes around your trunk to the other side of your spine. In the front, it runs from the pubic bone to the rib cage. Its the deepest muscle in your ab area. It may also be the largest too.
Learning to engage it throughtout your day can not only strengthen your core and improve posture but also increase calorie expenditure as you use this rarely used muscle. When engaged it makes your torso look longer and leaner.
If you learn to engage this muscle you strengthen your core and improve your workouts. You can also eliminate any muscle tension in the shoulders or neck. Not using this muscle causes the neck and shoulders muscles to pick up the slack created by the bad posture and alignment we can be prone to. If you rest your back on the back of a chair then you are not using your TA.
You only need to engage this muscle for a total of 5 minutes a day (as a start). Learning to use this muscle is not that easy because it is seriously neglected. But once you develop the habit of doing 5 minutes a day it can become almost second nature or a habit.
The DVD shows three different steps you do while sitting, standing or lying to know that you are engaging the TA.
http://www.the5minuteworkout.com/
I don't exactly understand how one would make a full dvd about a 5 minute workout. Looks like the site wants you to pay to learn about their '5 minute workout secret'; hence I am very skeptical. Is the idea you flex your core muscles through out the day?
yeah me neither. it actually doesn't work - sorry 4eva...
TA work was advocated back in the 90s by physiotherapists who would have you 'engage' your abs by sucking in your belly in order to get that close to your spine in the mistaken belief that it will strengthen the abs. this was later taken up by 'expert' fitness enthusiasts and marketed to people. it just doesn't work period, either for olympic gymnastics athletes or normal folk who have no desire to compete but just to do good, quality exercise and conditioning work.
if you want strong abs, get someone knowledgeable to teach you how to front and overhead squat. go on, i know you can do it!
the argument of 'do you want strong abs or a v shape' is meaningless. it brings up all sorts of other issues...
ive seen gym junkies who have fabulous looking abdominals and yet ive said to them, 'get on your stomach lying face down and outstretch with your feet together and your arms out in front stretched with your hands together'. now i ask them to jacknife up as high as possible and hardly anyone can do that with the exception of a couple of people. what about jacknifing up with 1 arm and the opposite leg? if someone can do that, then they have outstanding (not just core) but overall physical strength.
and what about some of the boxers who have no definition in their abs and yet can take powerful after powerful hits? these guys have fantastic abdominal strength.
why waste time? - get strong by doing the appropriate exercises that will get you strong abdominals. combine that with a decent diet and some quality strength endurance work (hello snatches!) and you'll be ripped in no time.