Gabriel Valencia, founder of NYC's Focus Fitness and trainer to some of Manhattan's busiest power players, shares an office, home, or hotel-room regimen that burns about 100 calories in 20 minutes.
60 seconds: Sprints up and down a flight of stairs, two steps at a time if you can.
60 seconds: High knees (like a fast, bouncy, knees-up-to-chest march-in-place).
60 seconds: Simulated jump rope.
40 seconds: Squats, then a 20-second rest.
40 seconds: Jumping jacks, followed by 20-second rest.
40 seconds: Push-ups, followed by 20-second rest.
40 seconds: Split squats (one foot in front of the other, about a foot apart; squeeze glutes and bend knees—back knee dips to floor), 20 seconds each side, then a 20-second rest.
40 seconds: Mountain climbers (bend over, place hands on floor a couple feet in front of you, put one foot in front of other, then jump up and land with opposite foot in front; switch at fast pace), then rest 20 seconds.
2 minutes: Rest (check your e-mail if you must!), then repeat.