Every Tuesday, I go to a grotty old man's gym tucked underneath a railway bridge for a boxing class. It's gruelling. Most of us are there because it's an unrelenting class that makes us toned, strong and gives us a really positive sense of empowerment. Oh, and beating the living crap out of a boxing bag can be extremely therapeutic. But as I looked around at the women in my class, sweat pouring down my face, thinking murderous thoughts about our Bulgarian trainer bellowing the words 'press up tuck jump burpee!', I had a revelation about body image and assumptions.