What did you injure? What did you do after thinking you were injured?
And now I'm a refugee and my running trails back home were in the zone russians dropped cluster munitions on. So it's not looking good for running going forward, lol.
Don't recall having plantar fasciitis or shin splints; but spent a lot of time on steps doing many many single leg heel raises, to work around achilles tendon and calf muscle pain.
Exercise finds our weaknesses.
The cardiac exercise research group in Norway have developed and tested an online maximum heart rate calculator.
https://www.ntnu.edu/cerg/hrmax
Check what that number is for you.
The interval training they recommend would be about 90% of maximum heart rate.
(For example, I'm in my early 60s and I'm supposed to push my heart rate into the range 150—165 bpm.)
Yes, I think C25K and the "just run" sentiment in general is missing half a dozen asterisks about this aspect. Like "except don't run on concrete for the first year", or "except do this progression of exercises for feet and tendons for 3 months before you start doing continuous 2-3k", or just "hire a trainer to get you started".
I've never been overweight, been active as a kid, was in increasingly good physical shape throughout my 3 attempts to start running over the years and got injured for months every time. By the last attempt I was taking multi-hour walks as a habit, lifting weights 5 days a week, watching my sleep and diet. And heart rate monitor has shown that I straight up didn't have this magical "easy run" heart rate zone available - brisk walk was well below 120 bpm and even jogging in place got me over 130.
C25K is great for what it is, but I feel what it is is not enough to start running safely.