Fast then slow is the way to go

Love getting that runner's high? If so, why not try a runner's low ... followed by a runner's high ... and then another runner's low, etc.? Alternating between bursts of high-intensity and low-intensity activity -- commonly known as interval training -- is a proven way to quickly shed body fat and improve cardiovascular function.

In fact, numerous studies have revealed that interval training is more effective than working out at a constant, moderate pace. Not only does it challenge your body to train at a higher level of intensity than it is used to, but it also allows short periods of recovery, thereby allowing you to muster up the energy to blast through your workout without faltering toward the end.

Interval training can be applied to just about any form of cardio workout. Runners can try a 30-second sprint for every 3 to 5 minutes of lower-intensity jogging. Swimmers can try something similar; for every one lap (or half lap, depending upon your fitness level) at high-intensity, complete a few laps at a more measured pace. Whatever your exercise of choice happens to be, you can modify it so that it incorporates intervals.