From what I know, no. You cant just use radio waves to alter the setting of such a machine, unless of course, the treadmill features remote setting of some kind.
It is much more likely that the treadmills are set to a programme in which it simulates a hill or various terrain. In such a programme, it automatically adjusts incline, speed and a few other settings.
(why would an employee want to tamper with a treadmill, of all things, is the question...)
Hope it helps,
Michael.