Tempo is a problem for every guy. It's why we wear condoms and rarely hit the dance floor. But it's no less challenging at the gym—where just about everyone and their mother has a different idea about the speed at which exercises should be done. To do things right (at a speed that's safe and keeps muscles working at peak performance), you'll need to understand a principle called "time under tension."

Every exercise that you do has a prescribed tempo for maximum effect. For example, a bench press with a tempo of 321 would require you to lower the bar in three seconds, pause for two seconds, then lift it in one second. Figuring out the proper time code for a given exercise is simple. Research shows that if you lower and reverse the load in under four seconds, you're still using momentum to move the weight—that's bad. So the first two numbers of the tempo should add up to 4 or higher. The last number can vary, but you won't go wrong if you try to lift the weight as fast as you can while maintaining control of the bar. Calculating the number of reps is a bit harder, but the thinking goes like this: Our 321 press would strain the muscles for six seconds (just add the three numbers together). A full set should put your muscles under tension for between 40 and 60 seconds for maximum muscle gain. So for this move, you're going to want to perform 7–10 reps. Easy as, well, algebra. But for once, this math won't leave you looking like a nerd.