I have heard many times that it is counterproductive to exercise for more than 45 minutes (1 hour max), but I do not see how it is possible to spend less than 1 hour. Sure, assuming one does only one or two exercises, it is doable, but I think a moderate routine consists of at least 4 exercises. For example, here is what I do on Mondays.
2.5 minutes rest between sets, 5 minutes rest between exercises. Dips (4 sets), military press (4 sets), barbell curl (4 sets), upright row (4 sets). I start with a 10-minute warm-up. To complete this, it takes me 1.5 hours. So, who are these people that spend only 45 minutes or less in the gym? What am I missing?