100 mile bike event - complimentary classes

[badgerread]

I'm doing a 100 mile cycle event in 4 months and have started doing 2 spin classes a week as well as getting out on a long ride at weekends. What other class could I do to compliment these for strength or should I just do some upper body weight training??

General fitness. Swimming is great to balance your muscles. Make sure you're stretching and using your hamstrings properly as it's easy for quads to get overdeveloped when cycling lots.

Agree with @designed swimming is excellent for strength training. I also find running is good for cardio fitness and build your leg muscles for those climbs!

You need to get out on your bike and do a ride with hills in the evening, plus a second ride at the weekend. Hours in the saddle really count.
And if you aren't used to riding in groups, then find a group to go out with at the weekend as the big cycle events have a lot of people to navigate around and you need to be used to it