Picture a fairly ordinary Tuesday. You sit down at your desk with a coffee around half eight, and apart from a couple of quick laps to the kitchen, you’re more or less in that chair until five. Then it’s the drive home, dinner, and an hour on the couch with the phone. Add it up and you’ve spent the better part of twelve hours sitting. It’s completely normal, and it’s exactly the kind of day that leaves a lot of people stiff and sore without quite knowing why.