A great personal trainer can be invaluable: Plenty of us wouldn't get to the gym without a guy there rooting for us, and we often depend on trainers to demonstrate good exercise form. The reality for most men, though, is that they can't justify the expense or commit to showing up at a certain time and place several times a week. But that doesn't mean you can't get the same kind of workout: It's easier than you might think to build your own professional training program. Although the lifting and running that a trainer puts you through may seem like a mysterious science, it's not. In fact, most trainers stick to simple formulas to help you build strength and endurance. We tapped some of the best trainers in the country and researched the best fitness books you should have on your shelf to uncover the secrets to getting a proper workout – all by yourself.