I just took a very hilly ride (for me). The biggest climb is 2.4 miles long and climbs 800 feet. The grade is often 9%. I can do this without stopping at all. My legs don’t hurt or feel at their limit. My limiting muscles are in my lower back. I think they are the muscles I use when I do a dead lift. I know I need to do more. Does that sound right? I’m sure there are other abdominal exercises I should do. Any other advice?

Thank you.