Weeeel.
Taking the devils advocate position, I am unsure if the people in PACE actually did anything which would (from a classical exercise physiology point of view) condition them.
If during GET, you do not comply, or you offset other parts of your activity for the GET activities, then you can not in any manner be 'conditioned' from an exercise physiology POV, so the PACE trial is only useful for proving deconditioning is not a reasonable hypothesis to the extent you believe that the activities done during PACE should have conditioned patients.
Weeeel.
Of course I speak not having done GET, but should we not be distinguishing activity and exercise?
The activities done during PACE were intended to condition patients, even those doing nothing else at all, because these activities were forms of physical exercise and were being gradually increased throughout the programme.
I guess most members of the patient group who were working must have had sedentary jobs, so even if they had given those up right at the start in order to manage the GET exercise programme you would still expect to see an improvement in their physical condition. Same goes if they had not been working but had cut down on sedentary social activities in order to manage GET. Had there been improvement in condition, though, we would surely have been given measured results.
But it is unlikely in any case that patients would have given up other activities
immediately in order to cope with the expected pressures of the programme, because they had been promised it was going to make them well. It is not usual for deconditioned people starting to get fit to have to give up their jobs, seeing friends or doing the laundry. This is an abnormal sign.
But yes, I take your point that maybe the whole programme was so haphazardly conducted that it would be impossible to demonstrate scientifically that the patient group - or many of them - were incapable of improving their energy levels and capacity through exercise.