During the past week, I haven't run in order to let the stress on my left knee reduce and the knee heal. I don't consider this stress a serious injury, because the knee improved in three or four days. However, I've been thinking about my future running, and here is my plan for that.
1. I'm going to be more diligent in stretching before or after I run/walk. I ran for 40 years with no injuries, because I stretched regularly and my body adjusted to the running. In recent months, I haven't stretched much, although I was stretching (but not enough) when my left knee reacted to the stress.
2. I'm going to start with a distance of half a mile and increase my distance every week or so by about 10%. This will, I hope, allow my body to adjust to the running and become stronger. When I was younger, my body adjusted more quickly, but now that I'm older, my body needs more time for adjustment.
3. I've been using a run/walk ratio of 60 seconds walking and 40 seconds running (actually more of a jog). That ratio seems good for my body, and I plan on keeping it.
4. I've been running/walking 2 to 3 times per week, and I plan on keeping that.
Time will tell if this plan works for me. The key to running without injuries is to keep the stress level below that which can be handled by ones body. Keeping the stress level low implies keeping the distance and pace below that which would cause injuries, and keeping increases in distance or pace to 10% or less. Also involved is recognition that ones body needs at least 48 hours of reduced stress between bouts of increased stress, thus the limit of running and walking to 2 to 3 times per week.