Apologies that this isn't completely cycling related, but I'm frustrated, and have received very helpful advice on this forum before, so I thought I'd throw my problem out there.

The facts:
45-year-old
Sedentary desk job in home office = many hours sitting
Ride 6-8 hours per week (and enjoy it greatly)

The situation:
I spent 5 hours working on a railing for my front porch on Sunday, and my hamstrings are still killing me today, on Tuesday. I did a lot of squatting and bending over while cutting the wood (mitre saw positioned on the ground) and screwing spindles onto the rails. I've still got half the job to finish, but have decided I'm going to have to wait until this coming Saturday before resuming it, as past experience has taught me that I'll need at least three more days of rest before my hamstrings are in any shape to do any more work.

I've noticed this before over the past few years. An afternoon spent weeding in the garden results in hamstring suffering for at least three days afterward. Which is frustrating and annoying, because it seems like I can't ever do more intensive physical labour-type work for more than one day at a time.

Does anyone else have problematic hamstrings? What do you do? Is there some sort of regimen I should follow to keep them limber? And yes, I know I'm far too sedentary for my own good, but I am trying my best to get up from my desk every hour or so to run around and do some weight-lifting for about 10 minutes. Though some days get really busy and the good intentions, well...

Any suggestions?