One glance in the mirror tells it all: You look sallow and worn, the result of having caught every bug that's crossed your path. When your vitality wanes, it's time to strengthen your lungs. That's right, lungs. A primary source of qi, or life energy, strong lungs help you feel alive, according to Traditional Chinese Medicine. Weak lungs, conversely, can leave you fatigued -- and more susceptible to congestion and infections like colds.

"In TCM, the lungs are known as the 'prime minister' of the body because they control breath and the circulation of qi and blood," explains Laurie Steelsmith, N.D., L.AC., author of "Natural Choices for Women's Health." They also circulate a particular type of energy known as wei qi. That's your immune system's first line of defense, serving as a barrier to outside influences that can make you sick. "The lungs act as a bellows," Steelsmith says. "They fan the fires of the body and turn up the flame on your overall well-being."

To develop a program that gets your lungs working and your qi moving, we turned to Tiffany Chen, star of "Step-by-Step Tai Chi" and "The Kung Fu Kickboxing Workout" DVDs, as well as Max Strom, Oregon-based yoga teacher, breathing educator, and developer of the DVD "Learn to Breathe."

This interval routine, which takes about 30 minutes, alternates between spurts of lung-strengthening cardio developed by Chen and focus-enhancing breaths from Strom. It's challenging yet simple in design so you can concentrate on coordinating your movements with your breath. "Monitoring your breath as you work out makes exercise more restorative," says Strom. With strong lungs, you'll gain energy and boost your immunity -- keeping yourself healthy this season.