And they won't refund your fee. Granted, you ARE a lust-crazed stalker. But there's no reason to be clumsy about it. Remember, you'll feel less guilty about a lazy, unproductive workout session if you know that you at least got some OK masturbation material out of it. To ease the mind-crushing boredom that exercise invariably entails, there are plenty of things you can do while at the gym to make your workout more enjoyable.
Nothing is more fun than feeling superior to another human being.
Look for people who are almost always there. Look at the people who are almost never there. When using one of the machines where you set the weight, it feels great when you have to increase the difficulty. That means you're stronger than the person who used it before you. Of course, this is a pleasure you will not get often.