Michael Jensen, a researcher at the Mayo Clinic, in Rochester, Minnessota, is talking on the phone, but his voice is drowned out by what sounds like a vacuum cleaner. "I'm sorry," he says. "I'm on a treadmill."
David Dunstan, an Australian researcher, uses a speakerphone so he can walk around his office at the Baker IDI Heart and Diabetes Institute in Melbourne.
It's not that Jensen and Dunstan are hyperactive. Rather, both are exercise researchers looking into the link between sitting down and premature death. And what they have found is disturbing enough that they both make sure they spend most of the day on their feet.