Have you ever played tug of war with a dog using a pull toy or a towel or some other garment?
It's a ton of fun.
They sink their teeth in and pull until the line between the 2 of you is taught. 
Then they keep inching back tightening and tightening the pulled object,straining it to the point where you surely believe either the dog's teeth will come out,you will lose your grip or the item rips apart.
When you or the dog lets up a bit, the line goes a little slack and then whammo, he tugs hard again and the tension continues.
Well that is exactly what the back of my thighs felt like all day yesterday!
It started with that initial bite, where the teeth just sank in and grabbed a hold of my glutes draining all of the strength from the rest of my legs.
Then when I would least expect it ,whammo, that tug as the teeth's grip on my buttocks and upper thighs sank deeper and deeper.
This went on literally all day long.
Needless to say, I was miserable.
Hence , no writing yesterday.
When I first got out of bed this morning, the only thing that had changed was that the death grip had increased. 
Disheartened barely describes how I was feeling.
I could barely walk.
I certainly could not bend.
I couldn't even reach over from the edge of my bed to the night stand to get a pair of socks out of the drawer.
I started to do some light stretching .
Little by little I regained some range of motion. 
After about 20 minutes, I was able to get dressed and make my way to my desk.
After another 15 minutes of sitting upright and gently extending my stretches, I was able to stand with relatively manageable discomfort.
As the morning has gone on, I have found that the "pain" is now an ache.
There is absolutely a difference between an ache and a pain!
I guess the dog that was biting at my butt has found another play toy for now.
I was able to drive the bus, go shopping at the grocery, put up dinner and now write to you.
Hopefully that mutt will be as accommodating for the rest of the day.
I can use the break!