Usually these reading culprits hang around the stationary bikes or move slowly on the elliptical. (since the stairmaster and treadmill would make this action difficult.) While I’m a huge fan of reading, and actually read also while on those cardio machines - if I am not sweating or in my target heart range I stop and focus on the physical action. However, there are those who move very slowly, engaged in a novel, who probably haven’t seen physical results since they joined the gym. This isn’t a huge peeve - but it develops into one when they are also the people complaining that they don’t see physical results. Put the book down and train.