Before I start, I probably already know the answer to this. Even as I write, I know what I would write as a reply so consider this a vent and feel free to move on to he next post.
I'm not a stranger to running but I'd not run for years. I did C25K and, by the end of the excellent program, I was happy/comfortable to run just under 6km in 30 mins (not that it was ever about distance). I'd found my running mojo again, lost 35 lbs, and was loving the freedom of using my legs in this way again (broken back at end 2015 meant I lost feeling in my legs for about a month when nerves got pinched).
I was back, taking it easy, but progressing. I was following a plane to get myself back to half marathon distance. I eventually managed that distance and was regularly running 40 - 50km a week. I was happy and, like I say, comfortable. Now why do I need to vent?
A couple months ago I tweaked my left hamstring. I was sensible, I rested it. When I returned, I ran slow, I ran short distances. As I increased pace my right calf clamped and felt really tight (like a low down cramp). I was sensible, I rested it. I returned slowly, stretching, warming up, using a support for a few runs. All good. I started increasing the pace on my runs... My left calf did the same as my right had done previously. It clamped painfully. Repeat all the rest, recovery, and today was my first run, I say run.. it was barely faster than I walk. Talking of which, I have zero problem walking. I cover around 4 mph when I can walk 20km happily (sorry, I realise I'm mixing my speeds/distance measurements). So I was running/jogging, no problem. I went on an out and back route. I went out 5 mins very slow, 20 mins slow/comfortable. On the return my left calf, once again, has clamped. I can walk without issue but running just seems to pull or aggravate something. It's frustrating as hell. My warm up is some slight stretching followed by 5 min fast walk then, like I say, a 5 min slow jog. Nothing is done fast. I'm not even reaching 'race speed'. I was running about 1 min per km slower than race pace. Not really sure how to move forward with this. Right leg is now fine, left leg is the problem.
I'm thinking it may be my weight since I put 10 of the 35 lbs back on.
Anyway. Vent over. I'm sure it'll be fine. Worse things happen at sea, etc.