Whether it's biking, running, or any other activity, safety should be a pre-requisite. In my case, I was contemplating running another marathon. I ran one about 20-years ago. After getting up to about 10-miles, my back would be hurting. Long-story, short, I backed off the idea of running another marathon.
No doubt, for health, a marathon is not necessary. So, whatever activity you are involved with, be sure to do it safely.