Bending forwards ninety degrees with a straight back and legs is something most people can’t do without feeling a strong pull in their hamstrings. I had the sa

Bending forwards ninety degrees with a straight back and legs is something most people can’t do without feeling a strong pull in their hamstrings. I had the same back soreness after starting using a standing desk. I was also running every day and not doing other exercise (thanks lockdown). It didn’t seem to improve over time. When it was allowed, I switched to going to the gym and only doing weights (squats, deadlifts, pull ups). After a couple of months the soreness just vanished, even after standing all day.