In my ‘abs blast’ sessions at the gym we’ll hold a plank for 1 – 2 minutes, but over the course of the half hour session we’ll do about ten minutes of plank, whether it be straight plank, or a mix of straight plank, side planks, straight arm planks, planks with a leg raised or any other weird and wonderful version they can dream up. When I first started my abs blast classes – upto 3 classes a week, for the first two weeks by abs were ruined – sore, painful, but after that initial two week period the benefits started to come. Not sure how long I could hold one for now, 2 minutes is tough but I could go longer, maybe 4 minutes? Not sure I could do 5.