i"m currently up to 2 minutes, on toes and elbows, hands under my chin, spine held rigidly straight. I can also go 2 minutes seated on the floor, fingers interlaced at my navel, knees locked straight and heels held 6" off of the floor. Not one right after the other, but, say, on alternate days. I can take any man's bare knuckle punch to the navel. I've been able to do this for decades now. Can you?