Hiking or Sagging the Hips
About 45 seconds into a minute-long plank, you may be tempted to hike the hips to the ceiling or sag them toward the ground to give your abs a break. You may even be doing it without realizing it!
“Hiking the hips up to the ceiling is going to take the emphasis off your core and load it more onto your shoulders, making it a different exercise,” Whitney says. “To get the most out of a plank for your core, you’ll want to keep your hips in a straight line with your body, with the pelvis tucked under.”
The plank is a full-body exercise — that includes your legs and glutes. To keep your hips from hiking toward the ceiling or sagging toward the ground, contract your quads and squeeze your glutes, Whitney says. This will help level your hips and engage your core.