When you want a total-body workout but don't have a lot of time, twofers -- combinations -- are the answer. Merging exercise modes saves time, adds balance and variety, boosts overall fitness and cuts down on overuse injuries.

Some combos balance body-awareness or stability work with more energetic or movement-oriented activity, notes Kymberly Williams-Evans, M.A., academic fitness adviser at the University of California, Santa Barbara. Others, like the ABC (Abs, Balance, Core) class offered there, blend complementary styles, such as dance, yoga, sports and strength training.

Look for combo classes at your gym or try these hybrids on your own:

Indoor cycling/power yoga
Yoga limbers up leg muscles that cycling tightens and adds upper-body work.

Step/total body circuit
Extends your cardio workout and balances upper- and lower-body conditioning.

Pilates/yoga
Provides a double dose of flexibility and core training.

Sports training/core conditioning
Increases core stability/strength for better athletic performance and injury prevention.