I've realised that I am just like the most inflexible person ever. I was just wondering about the effects of the quality of some workouts. For example, in a lot of ab workouts, I cannot for the life of me lie on my back and put my feet straight in the air, or in deadlifts, I can't keep a straight enough back in order to feel anything in my legs. Is there any way of improving this? Or am I just naturally born this way?