Holding the standard plank for ten seconds or longer is useless according to Dr. Stuart McGill. Unfortunately, many people still try to do planks for time.
A better way to progress this core exercise? Make it harder. The cable plank press will help you take your core strength to the next level, and you'll even build some extra upper-body muscle.
With squats, fear is often the limiting factor. Part of us is afraid that a big weight will flatten us like a pancake and make people want to pour syrup onto us. Heavy Supports will cure that fear.