Last night I did w1 r2 and found it much harder than r1 but I got the same smugness, elevated mood, calmness and - in addition, my usual arthritic knee, back and foot pain was gone for the rest of the night.
Today I was able to cut both my back and front lawns, sweep paths and do weeding before my back got really sore (normally it would be so sore after 10 minutes that I couldn't stand any more.)
Is the running doing all this? Is it possible to have such a quick improvement in pain and is it endorphins causing it or what do you think?
And does this response happen after most runs?