You don’t need to spend hours working out in order to drop those unwanted pounds. In fact, long workout periods don’t necessarily gain you more benefit. In order to get results from your workout, it’s important to find the optimum length of time and intensity needed to reach your goals. Exceeding the ideal workout time can actually decrease the effectiveness of your exercise and slow down progress toward your goal.

High-Intensity Interval Training (also called HIIT, or simply “interval training”) helps you burn fat continuously for up to 24 hours after your workout—whereas moderate-intensity workouts tend to burn glucose or sugar after your workout. It also improves muscle tone, firms up your skin and reduces wrinkles, boosts your energy and performance, slows down the aging process and—last but not least!—increases your sexual desire.

How Interval Training Works

Interval training is growing in popularity among professionals striving to meet aggressive health goals, but who find themselves pressed for time. Here’s the basic idea: you perform eight “burst training” exercises in succession. A burst training exercise involves pushing yourself to your anaerobic threshold—the level of intensity that causes you to run out of breath—followed by a period of low-intensity exercise or rest. One way to do interval training is to alternate between sprinting and walking.

Find Your Personal Intervals

Everyone is at a different level of physical fitness, so you have to experiment with different intervals until you find what works for you. Here’s a good place to start: try 30 seconds of intense (anaerobic) activity followed by 90 seconds of light activity or rest. If you can repeat this eight times in succession, you will raise your metabolic rate (by increasing human growth hormones) and can potentially continue to burn calories and fat for hours after your workout. If you find that these intervals do not challenge you, you might want to try 45 seconds of high-intensity and 75 seconds of low-intensity—or 60 seconds high and 60 seconds low.

Create Your Program

To incorporate interval training into your personal training regimen, you’ll need to decide on a schedule. Interval training works best in 20- to 30-minute exercise periods (including a warm up and a cool down), repeated two to three times per week. Many people find that exercising before breakfast is most effective for jump-starting their metabolism and getting the day started, but be careful if you’re more sensitive to changes in your blood sugar levels. You may find that it works better to eat something first. As with all aspects of diet, it’s important to pay attention to your body’s response.

Forms of exercise can include running, biking or circuit training (pushups, rest, squats, rest, jump rope, rest and repeat). If you’re just starting to exercise, you can go easy on yourself by alternating between walking and fast walking for 4-8 intervals.