There's the standard plank exercise, the tougher one-arm plank, and then there's this, one of the toughest variations in existence.
In the video, NFL linemen Fernando Velasco and Cordy Glenn do this deceptively difficult drill to prepare their bodies for the physical demands of the brutal season.
Notice the subtle form adjustments we make to ensure maximum tension to the core and maintain good spinal alignment. Most will want to cheat the single-arm plank by creating cervical hyper-extension and tilting their heads up. This not only strains the neck, but it places excessive tension on the lumbar spine by causing the hips to sag.
Focus on keeping a tall and elongated neck throughout rather than tilting the head up or down.