Planks have long been a popular core exercise. They're simple, require no equipment, and can be an effective way to improve core stability. (But not to reduce belly fat or get a six-pack. Just sayin'.)
But like all exercises, form counts. The Form Cop has talked about this before. I'd like to revisit it here with an easy way to check for proper plank form.
The key to a good plank is alignment. To get this, you need to squeeze your glutes and abs to lock in a strong neutral spine position. You can see this by drawing a line (mentally...don't go drawing on people doing planks) from the ankles to the shoulders. It should be straight. Here's an example of a pretty good plank position:
Ignore the glutes which can stick up on people with well-developed posteriors. Instead, look at the skeletal system: the lower leg bones, the knee, and the thigh bones then follow the spine position (the spine will be above the line) to the shoulders.
Here are a couple examples of a misaligned plank:
Notice how the angle changes at the hips. Elevating the hips makes the exercise easier. If you can't do a good plank, this isn't the way to regress it! Instead, try doing it on your palms (pushup position), and if that's still too hard put your hands on a bench.
Another example of a good plank:
Again, we ignore the butt and get a nice straight line. Sure, it's harder. That's the point! Better to do it right for less time than poorly for a longer time.
Another example of poor form, this time from the pushup position:
Less common, but at least as troublesome is a misalignment caused by sagging hips. This is mostly the result of not holding your abs tight enough. If you get lower back soreness in your plank, this is probably the cause.
The bad plank position often shows up when people try to progress their planks, that is, to make them harder. For example, by raising a hand or a foot or both (one hand and one foot...not both hands or both feet!). This turns up far too often with trainers trying to demonstrate...something. If you can't do the harder version, stick to the regular one until you're strong enough to progress. In other words, don't do this:
Stick to what you can do well, like this:
Another progressed version of the plank is the "renegade row" in which you pull up a weight (usually a dumbbell) from the pushup plank position. This often leads to bad form, either from using too much weight or just trying to do too advanced an exercise. Here's an example:
Even without the arrows drawn on, you can easily see the problem. Don't do this!
While doing planks with poor form may not cause any harm (at least with raised hips; sagging hips can mess up your back), it's not doing much good. Remember, the point of doing them is to strengthen the core, not reach some arbitrary hold time. Better to do one with strict form for 10 seconds than poor form for a minute. With training, you'll get to strict form for a minute, unless you progress it, which I recommend...why waste time on long planks? If you really want a tough plank workout in a short time, try the RKC plank:
Notice in that video, the straight line we look for in a good plank is there. (There are different versions of the RKC plank floating around...this is a good example.)
That's it. So when you see someone doing a plank, in person or online, look for the straight line. We can't really look at ourselves to check form (even a mirror doesn't cut it), so get a friend to check or video yourself to review. Ask any carpenter: a good plank is always straight.
Be seeing you.