Get the same strength results in 50 to 67 percent less time by doing just 1 set of strength-training moves. Recently revised guidelines from the American College of Sports Medicine (ACSM) recommend a single set of 8 to 12 strength reps (with enough weight that you can't do any more) instead of 2 or 3 sets. "Research shows that this gives similar results in terms of muscle strength and endurance as multiple sets," says Robert M. Otto, PhD, the guidelines' associate editor and director of Adelphi University's Human Performance Laboratory in Garden City, New York.
Time saved: 16 minutes if you normally do 2 sets; 32 minutes if you usually do 3 sets (based on eight exercises).
Build a pyramid
A pyramid approach to your cardio workout will save time over exerting the same effort throughout, says Keli Roberts, an ACSM-certified personal trainer and group-fitness manager at Equinox Pasadena. Here's how it works: You gradually move from low intensity for a longer time to high intensity for a shorter time, then back down again. For example, run for 5 minutes at 4 mph, then 3 minutes at 5 mph, 1 minute at 6 mph, 3 more minutes at 5 mph, then finally 5 more minutes at your original speed (4 mph); repeat.
Time saved: 4 minutes (off a regular 45-minute workout).
Mix it up
Try adding bursts of speed to your cardio routine to save time while burning the same number of calories (or maybe even a little more) and building your speed and endurance. Just ramp up to high intensity for 30- to 60-second bursts, do a few recovery minutes at a lower intensity, then repeat, Otto says.
Time saved: About 5 minutes (off a regular 45-minute workout).
Head for the hills
Take your usual walk, run, or bike ride up a hill. That'll increase workout intensity and calorie burnand shorten your session, Roberts says. If you use a treadmill, try bumping the incline by up to 10 percent.
Time saved: 25 minutes walking or 17 minutes running (off a regular 45-minute workout) if you do your whole routine on an incline.
Trim gym time by alternating upper- and lower-body strength exercises and skipping the rest periods in between. For example, instead of resting 60 seconds after a set of bicep curls, go straight to a set of lower-body moves like lunges, advises Len Kravitz, PhD, an exercise physiologist and University of New Mexico associate professor of exercise science. "This way, your upper body still gets a rest." You do your usual routine, but it's compressedand ultra-efficient.
Time saved: 8 minutes (based on eight exercises).