McGill sees this sets-and-reps approach as an improvement on the standard way of doing planks and other isometric exercises. His study focused on the benefits for athletes (half the subjects were experienced Muay Thai fighters), but there's another group that may gain even more.
"I've seen plank-related injury in people who're already back-pain sufferers," McGill says. "They just did inappropriate durations."
It's up to you to decide whether you like your planks short or extended. The key, as with any type of training, is to make it challenging. Ten-second holds sound easy until you do 5 sets of three different exercises. That's tough. And that two-minute plank Dan John advocates?
"From one minute to two minutes is the hard part," he says, especially if you've never tried going beyond 60 seconds. But two minutes and one second? "Absolutely no value at all."
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