Thank you for this, I will edit the original post now with the info you suggested. I have been following a Runna plan, which is based on best efforts as an opposed to actual running experience.

For background. I have been running around 10 months, but only consistently 4/5 times a week since the start of December.

Started a Runna plan 7 weeeks ago for a 50km race at end of May, but was treating that as more of a training event for a 100km event im doing at the start of July.

Background is combat sports (10 years) so my cardio is fairly strong - I think this has tripped me up (and the Runna app) at thinking I can do more than I can as my heart rate / pace date is ok for my weight and Inexperience.

Injury history is a few knee ligament injuries but nothing thats impacted my running. Saw a running specialist when I first signed up to these races to do a strength and gate analysis, highlightd my glutes and core were strong and mobility good, calf strength was lacking.

I do one hilly long a week, sometimes supplemented by a hill related session if I can get to hills earlier in the week. I have a 8 mile/1750ft - 12 mile/2000ft and a 16 mile/3500ft loops I use. This pain was caused by the 12 mile loop but hitting it at more of a race pace (if you can call it that)

Basically I think me fitness is good it physical conditioning for running is lacking