[dspillett]

Also it talks about planking for 2 minutes. Several studies have suggested that for most people there is little point in this due to diminishing returns. Two one-minute planks with rest between, or four 30-second ones (and so on) if you can't do a full minute, are far more effective. A 20-second plank is far better than nothing. A 20-second plank done right is likely better than a 60+ second one done wrong (arching your back, etc.).