These different activities can vary from day to day or even from minute to minute. Instead of devoting an entire workout to one particular exercise, like stair climbing, blend in several exercises during the session. Devote 15 minutes to the treadmill, perhaps another 15 on the exercise bike, indulge in light weight training for another 15 minutes, and then take on an aerobics class. That's cross-training. The possibilities, the combinations, are endless.

Along with cross-training comes a slew of fitness benefits. The variation you throw into your workouts should trigger faster, more satisfying results. When you're partaking in the same, old exercises day in and day out, you're body becomes accustomed to the regular routine. Thus, the gains will come to a standstill.

Cross training aptly initiates the change-up that your workouts may need by shocking your body with new, foreign exercises. If you're used to swimming five days a week and suddenly, you substitute a swim for a jog through the park, your body will recognize the difference.

Also, cross-training may be a better option for avoiding injuries. While a constant strain is put on certain joints if you're running every day, other joints will be used in specific exercises like weight training or say, rock climbing.

Then again, there's one more useful function of cross-training.

It'll kill the boredom.