Automatic Litterbox Central

ok so this week we moved the two cats (both 8 years old sister and brother) into my larger apartment. They seem very comfortable except for one thing. I turned my treadmil on to run on it and the second it started moving the cats freaked and now refuse to go anywhere near it. The cats had been playing with me in my living room for two days, but now they won't leave the back of the apartment because the treadmil sits in the middle of the living room/kitchen/dining room area in the front of the apartment. I enjoy the company of the cats, but now they refuse to come join me in the living room. Does anyone have any suggestions?