i had similar experience as author. so run few times a week for 7 years.

i was run in pine forest(it produces air with antibiotics), sub zero, down to -20c(in light clothes and sneakers).

for simple throat and nose conditions it was immediately healing, body temperature under 38c.

there rule was - never stop. nor walk. only run(until get to shower). or will get ill. tested few times.

in hockey people does not seem to run all time

also, i was run on frozen randomized ice pieces, dirt and snow like things. i had to adapt my posture for that, basically it does not streess same joints same way, not like thread mill or flat city roads. it was good. rule was never walk. when i started to walk, slipped to ground fast.