Although this may sound insane, hitting the gym is a lot more like visiting a comedy club than you might think. You need a good warm-up in both settings, there are plenty of fools to make fun of, and everyone you see is downing a drink of some type. But an even more important connection exists as well: "Like good comedy, when it comes to working out, timing is everything," says Joe Stankowski, C.P.T., a trainer in Wilmington, Del. "In other words, the amount of time you rest between sets can have a major impact on how the exercise you're doing affects your body." Rest too long and your workouts lose intensity; rest too little and you burn out too quickly. Luckily, we have expert advice on how to tailor your rest periods to any fitness goal.
Muscle gain: Studies have found that testosterone and growth hormone are produced in greater levels when you rest for short to moderate periods. The amount of time can vary a bit, depending on how many sets you're going for and how heavy the weight is, "but 60-90 seconds between sets is a good guideline," says Stankowski.
Fat loss: "There are two great approaches to losing fat in your training," says Stankowski, "and you should apply both in your program." The first method is simply to burn as many calories as possible, in which almost continuous exercise with little to no rest between sets (such as circuit training) is ideal. The other highly effective weight-loss strategy is to alternate sets of unrelated exercises (such as squats and rows) that work the entire body, while still allowing enough rest to build muscle. For circuit workouts or higher-calorie-burning programs, keep your resting time between sets to 30 seconds or less. For alternating sets, however, you can bump that time up to 30-90 seconds.
Strength gain: "Time is on your side when you're training for pure strength," says Stankowski. Both your muscles and central nervous system need time to recover from the effort of lifting very heavy weights, and failing to rest long enough will prevent you from lifting heavy on your next set-and even slow your recovery for your next workout. His advice: "Take three to five minutes of rest, then crank out another set."
To build more muscle and finish your workout in less time, try cutting back on your rest periods by five to 10 seconds every week (don't increase the weight). For instance, if you rested 60 seconds between sets this week, rest only 50-55 seconds next week. You'll find that in a few weeks you can accomplish the same amount of work in much less time, increasing your overall conditioning dramatically.