I have one of the Varidesk models (that lets you easily stand & sit throughout the day). It was necessary for my back, as sitting for long periods contributes to the painful flare-ups in my lumbar/sacral area. Here is the website for them:
http://www.varidesk.com My employer actually bought mine for me, which was wonderful, but they are reasonably priced if you have to pay out of pocket for one.
Also, I keep my elliptical in my home office. If I'm on a conference call I'm only listening for awareness, I try to hop on the elliptical for a portion of the time. If I stay at my desk, I'm more likely to multi-task and not pay attention, whereas on the elliptical, I'm still focused on listening to the call. If you find yourself on a lot of calls, and have some where you're just listening, perhaps use that time to do some yoga or other physical activity near your phone so you can still hear but also keep the blood flowing. I do also get up and move around (go outside for a few mins here and there), have my desk positioned near a window so I can vary my vision focus throughout the day, etc.
People think WFH full time is some cake-walk; it's not. You just get to wear more comfy clothes.
