When it comes to physical health, there are few things more important than “lung power.” Great martial artists like Bruce Lee knew physical strength and robust health depend on your lungs.

The strong men of my father’s era knew it too. Part of what gives you the capacity to live robustly is getting enough oxygen. But without your awareness, you are probably losing lung capacity. Your lungs tend to shrink with age.

Sooner or later, you get tired more quickly, you’re less virile, you get colds and the flu more often, and it takes longer to recover from illness.

I’ve proven that it doesn’t have to be that way. You can stop this loss of vitality by taking a few simple steps to build your lungs back.

By the time you reached 20, you stopped growing lung tissue and your lung capacity stabilized. This lasted for about 10 years. Then, around 30, your lungs started to decline. The alveoli that deliver oxygen to your blood began to die off. Slowly, most folks limit their daily activities so their lungs can keep up.

Unless you prevent it, you lose 20 percent of your vital lung capacity by about age 35. By 50, you’ve lost 40 percent of your breathing capacity and the decline continues for life.