Well, 8:30 pace for the average person (including women) for about 28 mpw requires a good deal of effort. Remember, the average person can not knock down even a sub 20 5k.
strenuous joggers - people who ran faster than 7 mph for more than four hours a week; or who ran faster than 7 mph for more than 2.5 hours a week with a frequency of more than three times a week -
Since when is this the definition of "strenuous"?
I'm old now, but I could go sub 16 long ago on 50mpw. Now 28 mpw would be quite a feat for me. And I can still out run the average runner over 5k.