"I use a standard stool right on top of my treadmill deck - for about 30 minutes at a time - lunch time... and haven't noticed any issues with the deck - I wouldn't suggest one with wheels on the deck, but just a standard stool…"
Won a trekdesk on facebook over a year ago & have my work set up to only have me walking at the treadmill or standing at the trekdesk.
I love it and wouldn't have it any other way... I walk 5-6 miles a day while at work - when I plan out my workload correctly (not needing to stop to help others or get things from my file cabinets)