3 ms·

Running a marathon is risky because of the load on muscles and joints. That's specific to running. Doesn't have anything to do with extreme aerobic exercise. I

• alecst 9y ago
  > If you replace running with equivalent amount of cycling then there are no ill effects. You can easily cycle at a recreational level for 8 hours a day and see no ill effects. Muscle structure will be quite similar to distance runners. They just don't wear out as much. I once thought this too, but I have come to think that this is a myth. It's what my doctors and physical therapists (and friends) say -- if you're injured running, pick up cycling. I injured my knee cycling and haven't been able to do it in years. It's a chronic pain that starts when I hop on my bike, and only then. (I have had the full fit, bike sizing, and all that.) I began running instead and have never felt better. I do it barefoot, but I don't know if that's relevant. It's now hard for me to accept that cycling is easy on one's joints. Maybe it is true, but if it is true, it's not obvious. Our bodies are very good at running and walking. There is no reason to think they are good at cycling. A bike is a rather unusual and modern invention. I can speculate that maybe it's the shoes that are contributing to injuries in distance runners. I am not sure. Feel free to reply if you feel I am wildly off.