Planks are better for your belly than a million crunches.
Ok, that was dramatic. 'Tis true, though. Why, you ask?
- oh boy, oh boy, oh boy, I get to be a nerd -
Well (clearing my academic throat), planks call into action your core at its deepest, most functional level. You are working a glorious number of gorgeous stabilizing muscles, including (but not limited to) your latissimus dorsi, transversus abdominis, multifidus, serratus anterior, obliques, mid trapezius (oh man, I'll stop) ... And the reason this is so effective in planks is because you are also challenging these key core muscles in an extended position. Most traditional core exercises of yesteryear required a whole lot of flexion (think, crunches). The trouble with that is your spine needs to exist and be supported in extension, so it is essential that we start training our core to function and stabilize while in extension. BINGO BANGO!
Additionally, flexion exercises lead us to believe we are working out harder than we are, especially in comparison to the burn factor. What I mean is that you will probably feel your abs burning a whole lot more while doing crunches than you will anything burn while doing planks. All you know when you do a plank is that you get tired, right? You probably don't actually feel your lats burn. But, this burn factor is not an adequate measure of how hard you are working or how much good you are doing for your body. All it tells us is which muscles we're working. You see, when you do crunches you are working fast twitch muscle fibers, which are meant to do quick powerful movements predominantly and, thus, they burn out when we do a move over and over. THIS DOES INDICATE STRENGTH. The muscles you work while in a plank do not give you that same burn because they are slow twitch muscles, designed for stabilization. Their job is to keep your shit together for sustained periods of time and, thus, they don't burn out the same way but instead get fatigued.
Planks can do more for your core and for whittling your waist than any other core exercise because they demand that these deep, sustaining muscles get stronger while you are aligned in a functionally extended position - wrapping around your midsection like a tightly fastened life vest. This life vest pulls together all your more surface level muscles and help them operate with efficiency, which then results in toning, which results in that six pack you've been ever-wanting (over-rated, honestly).
So, drop the crunches. Do some planks. Oh, cuz I love ya. I'm giving you access to my Plank Tutorial, which usually only members get. I know. It's your lucky ass day.