Not long ago a reputable coach referred to the plank as an exercise for “stamp collectors.” Obviously, this coach had not done his GOOGLE search. Had he done so he would have learned a lot of research back in 2006 demonstrating that plank holds and side planks actually out performed squats and deadlifts on EMG measurements. Sign me up for stamp collecting 101.

By placing yourself in the plank position you actually strengthen the muscles for their purpose, which is to hold the spinal column in extension. Strong muscles of the core help to maintain a healthy spine.”

source:againfaster.com