If I sew sitting down, my back freezes up.....years ago we put my machines on high tables and I sew & serge standing up.....the secret is to be sure they are high enough that you are standing up straight (same goes for ironing board)..and if my legs feel tired there is a daybed in the sewing room, the secret is to lay down not sit down. I am sure it would look funny if anyone ever saw, but hand sewing bindings and applique can be done laying down with a lap tray holding the project and sewing with your arms supported at the elbows with the mattress or pillows if needed
Yesterday I was at the LQS for a class "Picture Piecing" with Cynthia England, it was wonderful...I have admired her work since the mid 90's ....anyone who has not seen 'Piece and Quiet' should check her website. My back was so bad that I had to do the surefire back cure......3-4 inches of really warm water in the tub and lay down with your back flat to the bottom of the tub (legs bent or up the wall(good for ankles)...yes it messes up your hair-do but it sure straightens out the muscles of the back.
ok, sorry so wordy today, off to sew now !