More from Prevention: Best Lunchtime Workouts Come in a little early, leave a little late. For those of you griping under your breath that your “lunch break” consists of scarfing down a few bites as you wade through your overflowing inbox, hey—we get it. However, forcing yourself to step away from your desk 3 to 5 times a week will slash your stress levels, boost your mood, and even lessen your risk of coming down with a cold—all things that will help your job in the long run. Still feel guilty? Come in 10 to 15 minutes early or leave 10 to 15 minutes later than usual. Also, if you’re afraid your boss will come looking for you, let him or her know ahead of time that you’re starting a new routine. Don’t forget a change of undies. “Packing your workout clothes the night before makes it easy to just grab your gym bag and go in the morning,” says Vanessa McDonald, a private trainer at the Sports Club/LA-San Francisco. A few items not to forget: deodorant, face wipes, a bottle of water and a change of socks and underwear—because there’s no way you’ll want to wear your workout skivvies back to the office. A better move—invest in workout underwear, check out our list of The Best Underwear for Exercisers. Finally: Don’t leave your iPod behind. There’s nothing worse than working out without your favorite playlist. (What do exercise pros listen to? Check out their playlists.) Pack it in with circuits. “Circuit training is great for your skeletal/muscular system, but it’s also a great cardio workout and calorie-burner,” says Wayne Westcott, PhD, Prevention advisory board member and fitness research director at Quincy College. The best part: It doesn’t eat up a lot of time. “Do 20 minutes 3 times a week and you’ll see amazing results,” says Westcott. “If you move quickly from exercise to exercise, you’ll burn about 8 calories per minute, and roughly 160 calories in a 20-minute session. You’ll also burn another 40 calories or so in the following hour, just sitting at your desk.”  When combined with your 3-days a week circuit schedule, you could lose about 1.5 pounds of body fat each month, says Westcott. More from Prevention: Torch Calories In Less Time With Circuit Training Kick up the cardio. When you’re short on time, try alternating between short, high-intensity bursts of speed with bouts at a slower pace throughout a single workout. “It’s a quick way to get your heart rate up and burn calories at a higher rate,” says personal trainer and Prevention contributing editor Chris Freytag. So if you’re hitting the treadmill or elliptical, try this: Warm up at a slow pace for 3 to 4 minutes, then alternate between 1 minute at an all-out effort followed by 1 minute at a moderate pace, for a total of 20 minutes. Finish with 3 to 4 minutes at a slow pace to cool down. Or try one of these other Walking Workouts That Blast Fat and Boost Energy. Get in with a group. Need someone to push you through that midday slump? Many gyms and studios offer express group classes, such as 30-minute indoor cycling and power-hour yoga classes. “Let the instructor tell you what to do and get it done!” says Freytag. You’ll be in and out, and back to work in no time, and have more energy to finish off the workday. Find a new workout buddy, join the free Flat Belly Community. Take your work with you. While it’s way better to leave office stressors where they belong—at work—there may be occasions when it makes sense to take a few files or notes for that afternoon meeting with you, and read them while you’re sweating it out on the stationary bike or elliptical. Really pressed for time? “Invite a co-worker and conduct a walking meeting,” says Freytag. Even if it’s just a few laps around the block, a little movement is way better than none. Fuel up fast. If you’re using those precious minutes for exercise, pack a healthy lunch that you can eat at your desk when you return. Or, if a beverage is more convenient, opt for a protein shake. “It’s fast and easy on the go,” says Freytag. “Also, don’t forget the beauty of packaged string cheeses, hardboiled eggs, milk, and most other grocery items pre-made for you at the corner store near the office,” says McDonald. Check out these 6 Great Portable Proteins you can eat on the go. Say “sayonara” to warm-up stretches. “There’s no need for static stretches before your workout,” says Samantha Clayton, personal trainer and co-star of YouTube’s Be Fit In 90. “Instead, spend five minutes at the beginning of your session doing dynamic movements, like slow lunges, to warm up your muscles.” Make sure to stretch after your workout, though—even if that means doing a few stretches when you get back to your desk. Stick to standing. Try to avoid going from one chair to another. “Weight machines that require you to sit instead of stand don’t utilize as many muscles,” says McDonald. Instead, opt for exercises where you’re firing multiple muscle groups and constantly having to use your core to keep you stable, such as full-body movements like squats and hamstring curls. Or try one of these 7 Exercises Women Avoid—But Shouldn’t.