1. There's a whole closet drawer dedicated to Lycra.
2. You need to find room in the kitchen for the boat sized containers of recovery shake powder.
3. They take all the fun out of food by referring to it as 'fuel'.
4. The Strava app has a better idea of where your other half is at any given time than you do.
5. There's generally a pair of trainers dangling off the washing line being aired.
6. Underwear is now selected for how supportive it is, not how attractive it looks.
7. Nipple chaffing is now a real thing that can apparently be discussed in polite company.
8. Your lovely bubble baths are shoved out of the way in favour of Epsom Salts.
9. Your bedroom always smells faintly of Ralgex.
10. Going out clothes and proper shoes are forsaken in the holiday luggage in favour of running kit.
11. You can no longer walk past a sports shop without having to go in for 'a quick look'.
12. The most expensive footwear they own is a pair of trainers.
13. PB & Jelly now means 'personal best and an energy gel'.
14. Their legs are considerably browner than most people considering it's only spring.
15. You realise that the only way you're ever going to get to see New York/Paris/Sydney is if they get a place on the marathon there.
16. You can't find your best wine glasses because your cupboard's full of sports bottles.
17. There's random safety pins all over the house from holding race numbers onto their Tshirts.
18. They have a total meltdown if they can't find their earphones.
19. You now know it's not just horses who can give off steam.
20. They wear plasters on their nipples.
21. You've gone right off pasta.
Despite all this, and everything I say, I'm hugely proud of mine as he runs his first full marathon, the London Marathon this weekend. If you'd like to sponsor him you can find his Just Giving Page here - he's raising money for Oxfam.