Thanks for your opinion, it may well be I have a problem but have not yet owned up to it?
One thing I do know however is that in order to get my 'pains,' as I experienced them on my last long hike in August, they develop, as on previous hikes, over a bit of time. Since then, I go out to the woods to run every day, possibly a 5-mile walk as well later in the afternoon, but never of course wearing a rucksack, and to date, I haven't experienced a twinge.