Occasionally I focus on my workout, monitoring intensity of effort, breathing, speed, foot strike, arm carriage, or pedal rotation on a bike. I like listening to music behind the wheel of a car, but I find it very distracting during a normal workout.

Unfortunately, I may be in the minority. Not long ago, a popular running website published an article featuring the benefits of listening to music while running. It took me a while to realize that this particular piece was actually a paid advertisement sponsored by a well-known company that makes portable music devices.

By coincidence or not, this cleverly disguised ad just happened to appear shortly following a well-publicized story linking hearing impairment to use of portable music devices.

According to the American Speech-Language Hearing Association, the prevalence of hearing loss in the U.S. has doubled in the last 30 years, affecting more than 28 million Americans. Clinical audiology professor Robert Novak of Purdue University believes a big reason for the increase in Noise Induced Hearing Loss (NIHL) is the use of portable music devices, which were introduced in 1979. Recently he has been randomly examining college students and finding a level of hearing loss normally seen in middle-age adults.

The extent of NIHL depends on loudness, pitch, and length of exposure to sound. Lawnmowers, motorcycles, jet skis, snowmobiles, power tools, guns, many toys, and loud music pumped through headphones can all affect hearing. The problem is, once you damage your hearing, the impairment becomes permanent.

Sound that is projected through speakers is required to travel through distance and has a chance to dissipate. MP3 players, on the other hand, are made to blast music directly into the ear canal with very little leakage of sound.

Listening to music on MP3s or other portable devices for hours each day has become a trend amoung teens. If and when hearing problems develop, they just turn up the volume to compensate.

This practice worries hearing experts such as Professor Novak, who claims to be seeing more and more patients with older ears on younger bodies.

To protect your hearing, wear earplugs anytime you are exposed to loud noises, and by all means tone it down when you listen to music through headphones. Cut back on the time you spend listening and give your ears an occasional break.

Hearing experts from Boston Childrens Hospital say it is safe to listen to your MP3 player or iPod at 60% volume for 1 hour a day.

Take my advice. Learn to run without music, and let your mind work on something else to avoid boredom. If you must listen to music while you run or workout, keep the volume as low as possible.

Hearing is something you want to preserve for a lifetime.