I have done about 6 cross fit session that someone at work is organizing. I was avoiding them at first, but then took the plunge.
After the first session, the next day I felt like I had been run over by a steamroller. Now at six sessions in I dont feel too bad the next day.
The thing I like about them is that you are pushing your own targets so it is equally as hard for the fit people (the ones who have been doing it a while ) as it is for the beginners. I have already seen a big improvement, in what I can manage in each session. It’s also been a good laugh.
Note: I wont be joining a cross fit gym at home as is fӣ$ expensive and you can do most of it at home without much trouble.
It also seems to get a lot of grief online, not sure why but I reckon it’s a good way to add some strength training for Mountain biking.