Two Weeks in Cambridge (England), practicing sport in group

In January, I am going to be in Cambridge for 2 weeks to attend a school to improve my English skills. I'm searching for things to do during the weekends, and since my goal is to improve my English, I'd like to do activities involving groups.

I like sport and wild activities, so it would be fun to find a good organization that organises sport or walking events during the week.

Any other ideas are welcome :)