Core training

I've come to understand that you need to do work off the bike in order to maximize the time you spend training. My coach has a quote in the training bible that I like.

Golf pros hit balls on the range, swimmers practice with wooden paddles on their hands, and athletes in other sports do other things that improve performance by enhancing muscle memory. Too many cyclists just ride their bikes.
MIKE KOLIN, cycling coach

I started core strength training last year when I started getting upper-back pain after three hours on the bike. It helped immediately, and the payback was huge. In this off-season, I'm not weightlifting since I don't feel confident enough in my form to avoid injury, and I don't have a physical trainer to help me out. So I'm using basic tools like a jump rope and some bodyweight exercises to work other parts of my body. This is a routine I've been doing:

1 minute jumprope
20 pushups
1 minute jumprope
10 pullups
1 minute jumprope
60 seconds plank
1 minute jump rope
30 Hindu Squats
1 minute jump rope
15 side holds/extensions

I usually repeat it twice.