fuel, we usually don’t push the patient, especially the over 70 crowd, too far. To do otherwise is to use the “test to destruction” principle. This principle, while interesting to observe, tends to interfere with the smooth practice of medicine.
Once you’ve seen the runner stumble, and go down on the treadmill, you do not want to see it again. Unlike George Jetson, the patient does not go 'round and 'round on the treadmill. Generally he just gets sucked underneath it, where he remains until physically removed. And treadmills are heavy to lift. And the paperwork afterwards is time consuming.
Old marathon runners can generally hit their predicted target, as can young ones. And even marathon runners cannot beat the treadmill. Keep in mind, the treadmill goes faster up a steeper grade every 3 minutes. At 28 minutes into the protocol, the testee is going 12 miles an hour up a 28% grade. I never had a patient reach 28 minutes. I think my longest testee was about 25 and a half minutes. And this was a guy that ran 3 marathons a year.