Your lungs shrink as you get older - a physical change that has far-reaching health consequences. But if you can increase your lung capacity, you'll be able to oppose and successfully reverse this biological result of aging.
To restore some of the lost lung volume of your youth, you need to create an "oxygen debt" by making your body ask for more oxygen than your lungs can currently provide. You do it by exerting yourself to the point where you have to pant and catch your breath.
Now, it would be dangerous for you to go out and sprint or shovel snow if you're not used to it. But it's not dangerous to challenge your lungs a little bit at a time. I originally developed my PACE (Progressively Accelerating Cardiopulmonary Exertion) exercise program to allow you to do just that.
My recommendation is to use an exercise machine that can read your heart rate - like a stair-stepper, elliptical machine, treadmill, or stationary bicycle. Warm up for two minutes at a leisurely pace. Increase your speed to 75 percent of a full sprint for two minutes. Then immediately go to a 90 percent sprint for 30 seconds.
Note your heart rate when you stop. If it continues to climb a few more beats per minute after your sprint, during the "recovery" period, you have successfully created an oxygen debt. Now you can hit the shower! You have sent your body the message to get to work building you a bigger lung capacity - while you rest.