It’s a scenario most working fitness buffs have experienced: You unexpectedly have time for a 20-minute workout, and you’d love to cram some exercise in. But is 20 minutes really long enough to get a decent workout? And if it is, should you try to work up a quick sweat on the elliptical, treadmill or other cardio machine, or bang out as many reps as possible in the weight room? The answer, says U.S. Olympic Silver Medalist and traveling personal trainer Kim Glass, is yes…and neither. “It’s absolutely possible to squeeze a quick workout into a sliver of your day, and you can maximize your time by performing a series of exercises back-to-back using weights—both free weights as well as your body weight,” Glass says. Doing this will elevate your heart rate and metabolism while boosting strength and endurance. “You’ll build muscle, which torches fat and burns calories long after you’ve finished your workout, which doesn’t happen with steady state cardio.” (I.e. slogging away on the elliptical while you watch the news on T.V.) Aubre Winters, an Equinox-certified Group Fitness Instructor who frequently partners with the W Los Angeles – West Beverly Hills to offer quick fitness bursts during meetings and group breakout sessions, seconds that notion. “Try a high intensity interval training-style workout that incorporates moves like burpees, squat jumps, alternating lunges and abdominal work,” Winters suggests. Spend one minute on each movement before switching to the next, and set aside three minutes or so at the end to stretch, “so your body can fully recover before going on with your day.” Winters says her No. 1 tip for travelers who want to slip in a workout, but who have minimal space, equipment and time, can be summed up in two words: Get creative.