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).