This approach is interesting because, if you ask people "do you go to the gym", you are faced with the fact that 90% of gym attenders actually do not train, but

This approach is interesting because, if you ask people "do you go to the gym", you are faced with the fact that 90% of gym attenders actually do not train, but pretend to train. So instead the treadmill test is a much better predictor I guess since it meters the results of your training as athletic performance.