With FM, my shin and thigh muscles are especially "tight" feeling and my left shin (the leading foot in hiking) has an easy tendency to cramp and this cramp lasts well overnight and requires tizanidine (which works best on actual spasms).
Could be something about calf muscles themselves or the connective tissues. Has it been studied in other mammals?
Now at 75 years old and with FM of long duration and its peripheral and central nerve abnormalities, my thighs (left one especially) feels heavy and rather painful before I start out for a gentle 20 min total walking time (but an hour's duration because of constant rests) in the woods, no more than an occasional 30-45 degree incline, twice a week.
Even that restriction leads to a persistent rather severe ache not well relieved by tizanidine (though a hot microwave pack is soothing while it's in contact), that lasts well into the next day and with less severity when walking around the block on subsequent days, as well as finding the stairs painful and difficult.
I don't have peripheral vascular disease that I know of. Good leg muscle development until after age 70.
Prior to my lastest walk, I pre-medicated with half strength ibuprofen/acetominophen and could feel a certain lightness in the muscle. I implemented an OT-like reform of my walk: a I slowed down my pace, rested standing every few paces and sat down aplenty. I almost completely avoided any uphill walking. Nothing more than a necessary 20% incline for 30 yards, twice.
This careful plan worked so far. No thigh pain during or after the walk. I am using the handrail to help haul myself up the stairs.