It's become ubiquitous. Anytime you see a person jogging, there's always a cord flapping in the breeze and on closer look, you'll see their earphones. They're having an endorphin rush, zoning out to their favorite tunes. But - you have to wonder - can earphones designed for the rigors of exercise really sound okay? And more important, how safe are they to wear?

People who work out regularly enjoy listening to music. It's hard to say why it's so motivating (though scientists are trying to quantify it), but a good playlist can make an hour in the gym fly by. More and more earphone manufacturers are recognizing this market and are cashing in with some rather impressive products, perfectly suited for gym rats, swim fans, cyclists, or any outdoor enthusiasts.

Polk just released a line of four new earphones designed for athletes. Since they're from Polk, the sound quality is quite good. And they include various features important to athletic people, such as moisture resistance and reflective safety bands. They also claim to have moderate noise reduction. More on that later.

Sennheiser has a line of earphones produced in association with Adidas. The lineup features water resistant products that are also sweat resistant (all that icky salt plays havoc on electronics) and more. The MX 680i earphones add a unique fin that helps secure it in the ear, and use Kevlar reinforced cables to add durability. Having recently ripped apart a pair of earphones during a workout, this writer can attest to the need for added durability. Also, I've used the MX 680i's extensively and they sound quite good.

Westone is a earphone company that you might not know about, but their athletic models were on exhibit at the US Pro Cycling Challenge this summer in Colorado, in a booth strategically placed among others selling electrolyte drink powders and chamois creams. Their earphones use a custom fit for a really secure acoustic seal, and even their universal fits feel great. Looking into the company's background, you can see why they were at this bicycle race. They sponsor two pro cycling teams, and helped create the custom radio communication equipment used by the teams in races. It also doesn't hurt that the CEO is an active mountain biker.  

Yes, outdoor earphones can offer good sound quality, durability, and acoustic isolation. But are features such as isolation and noise reduction really good things when you're out playing in traffic? The Polks, for example, come with a variety of tips to ensure a snug, sound-isolating fit that improves bass response while blocking outside ambient sounds. But what if one of those sounds is a car tooting a warning honk? Or a cyclist about to zoom by? Westone suggests their earphones be used in the gym or on a mountain bike trail - far away from traffic. Nevertheless, many cyclists do wear earphones on the road - and not everybody's happy about that.

State laws vary on the issue of earphones (no one has yet followed the example of Quebec in outlawing headphone use on the bike, though there has been some movement in that direction on the municipal level). In most cases, bicycles are considered vehicles and most states require that one ear must remain unobstructed by earphones. Few states address the question of earphones while jogging. Clearly, acoustic isolation on the commuter train is great, but out in a bike lane or jogging path, being oblivious to your surroundings can be deadly. The most important feature in any earphone is your own common sense situated between the earphones. Isolation, noise reduction, and high listening levels must be used wisely.

Seriously, leave the critical listening for the safety of your home or the gym, and when outside, use one earphone (or two wrapped around your bicycle helmet straps, but out of the ear). You'll hear the music, get motivated by the beat, but can also hear the world around you. Stay fit. Enjoy music. Avoid becoming roadkill.