Running

Thrilling running update:
I started running again recently, after a long period of just riding my bike again- pretty much since the duathlon in Norway.
Initially I was feeling very strong, minimum run distance (even when I went out for a 5k) was 12k, which I did a couple of times a week.
I ran a half marathon distance the Sunday before last and had no stiffness or pain afterward.
What I did have was a hard start- from initially going out the door and being "on it" at once at the start of returning to running, to on the half marathon almost bailing at the 4k mark due to lower leg pain.
Once I had run through it everything was fine, but the warmup phase was getting harder and harder.
This reached a peak last week when I couldn't run through the warmup and bailed at just under three miles.
I started doing a minimum of 300 calf raises that same day, which my physio had previously recommeneded doing, and went out for a 5k last night- ended up running 9k.
I still had the warmup, but it was done under 2k, after which I felt 100%.
What was interesting was that I could feel the (what I think to be) Tibialis (long muscle down the front of the shin) rapidly reaching a point where it was overloaded from absorbing the impact of foot on pavement, at which point the soleus/calf took over and everything smoothed out.
Now my understanding is that the role of the soleus in running is to absorb the impact, but due to my innate oddness (and cycling) mine didn't really develop so the anterior tibialis ended up doing the job.
I now have impressive, chiselled Soleus muscles, but it would seem that they don't actually start working until the tibialis gives in- how can I "re-prioritise" the muscles?
TL:DR, I know, I know.