Another factor to take into consideration is the potential for over-training that can lead to injury. Many of us that run and walk have other fitness programs incorporated into our daily lives. Lifting weights at the gym, Spin classes, Yoga studio sessions, Bootcamp are some of the many activities put on hold. It's natural for us to pick up the miles as a way to offset the loss of those activities. That where it gets tricky.
I typically run 2-3 times a week while doing strength training and core workouts 4-5 times a week. My body has adapted to that routine. The mileage for my runs can and does vary but even if I add some additional miles to a particular run, I have my non-running days to recover. With my gym being temporarily closed, aside from some basic stuff I can do at home, that balance is gone. I can now see myself running a LOT more and that has some risks.
Endurance athletes live the axiom "if some is good, more is better" and why not? Building up a training program with a particular race in mind or wanting to shed a few pounds by adding extra miles are positive goals. The mental and emotional benefits of exercise keep us grounded and focused in these times of stress. With the reduction of so many life and work related activities, who isn't worried about gaining weight? I say go for it but do so with caution.
Do an honest assessment of your running/walking norm. Assuming you're injury free, this is what your body is comfortable handling. Gradually increasing the frequency, distance and pace is fine but do so with a plan and make sure it includes recovery. We all know the basics of exercise, pushing ourselves just a little bit harder than is comfortable and then allowing ourselves to recover. The recovery allows us to strengthen ourselves for the next workout. When we omit rest and recovery, we don't allow our bodies to catch up and when that happens, we get hurt. Being injured is never good but being injured now would really stink.
As the saying goes, we're all in this together and we'll get through it together. Run and walk safely, better days lie ahead.