The problem with planks
Paper Boat Creative
A great thing happened in fitness about 20 or so years ago. People started to realize that crunches and sit-ups are good for strengthening core muscles, but they aren't exactly great for the neck, spine, back, etc. Instead, there was a movement to toss those exercises and strengthen the abs doing what you see this guy doing (above). Planks have become a popular alternative to traditional core-strengthening exercises such as crunches, but how effective are they? The answer: Well, there's an issue, says Ben Shear, Golf Digest's chief fitness advisor.
The problem with planks, in their traditional form, is that they require support from the muscles of the shoulders. When you first start doing them, everything is rosey, because your untrained abs give out before your shoulder muscles do. But the longer you train, the longer you can maintain the plank, and sooner or later, the shoulders will fatigue before your abs. It's just physiology.
Planks also suffer from the law of dimishing returns. You have to hold the pose longer and longer to make your abs stronger. At some point, taking a huge chunk out of your gym time to hold a plank isn't really an efficient way to get things done.
To be clear, no one is saying planks aren't a good exercise. For new gymgoers, they are an effective way to get ab strength up to par. For golfers, they're great because they put far less stress on the back than sit-ups and crunches. But if you really want to get more value out of them, switch to pillar-bridge planks (demonstrated by world-class trainer Mark Verstegen) and no-arm side planks (demonstrated by Golf Digest Top 50 Fitness Trainer Andrea Doddato).