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.
Admittedly I was looking around the room to see who else was on the verge of giving up (so it would make me feel less bad about collapsing on the floor).
But what was evident was that none of us had the same body type.
We ranged from super slim to super toned, some women had chiselled muscles and some had perfectly average bodies. What was really interesting is the women you'd expect to wobble first - for instance the super slim and those with less than Amazonian bodies - were some of the strongest, both in endurance and punches.
It made me feel slightly ashamed in assuming they weren't going to be the fittest, but after that dissipated, it also made me feel better about myself. In that, I could actually see how becoming as fit as them was an achievable goal.
I'm not saying that competitiveness is why I do fitness. It has to do with a lot of reasons from finding it calming to getting a lot of satisfaction from physical strength.
But I'd be lying if I didn't say that I don't look at other women in the gym as a barometer of where I should be. And most of the women in my non-boxing gym fit that very standardised ideal of fitness - slim and slightly muscular.
It didn't occur to me that they probably were working to a fitness program that gave them that body type, rather than their body being an example of what every fit person should look like.
The same thing happened to me at a kayaking induction course in a swimming pool last week.
We had to prove that we could roll under water and be able to pull ourselves back up. It was hideous, I got bruised flailing around but the people who did really well did not have bodies that indicated hours in the gym.
And perhaps here is a hidden weapon in the body image arsenal via the medium of sport.
Clare Balding earlier this year commented on how impressed she was by the variety and shapes and sizes of the women at the Women's Boat Race as they lined up to be weighed ahead of the race.
It was a very clear, visual reminder that physical fitness and strength isn't a one size fits all. In fact, we're peddled this nonsense by the diet and fitness industry from when we were teenagers.
Measuring yourself by another person's body is a losing game, in any case.
It doesn't account for big bums, broader shoulders, skinny legs. So you could spend a lifetime running (literally) towards a body image goal that only focusses on your shortcomings, not your body's incredible strengths.
And this is why campaigns like Sport England's #ThisGirlCan is really important, because taking part in group sport is a fantastic reminder of how diverse we women are in the body department.
It's inspirational, even, and I'll certainly remember that the next time the ladies and I are throwing it down in the boxing ring.
If you haven't read much of HuffPost UK Lifestyle's Fitspiration campaign in July, then catch up on what we've been trying to espouse here.