A recent study shows that turning up the volume on your i-pod while you exercise pushes you to work out harder. When women listened to their favorite workout songs at four different volumes, they worked harder when the music was the loudest. Researchers believe that this is kind of like the flight-or-fight response. The brain thinks the loud music is a threat, so it responds by increasing adrenaline levels in the blood, which then sends more glucose to the muscles, giving them more fuel during an intense exercise session.
Most people can attest that they can work out longer, run farther, or lift heavier when listening to music, as music can be motivating, uplifting, or at the very least, a distraction. Make sure to program your music player with high-energy, up-tempo songs when you need to push yourself, and some slower-paced mellow tunes for cooling down and post-workout stretching.
Be careful, though, as loud noise, especially over a long period of time, can damage your hearing. Think of the last time you went to concert and left feeling like you had cotton balls in your ears. The happy medium is to keep the volume just loud enough that you get the full sound in your ears, but not so loud that the person next to you can hear it. If you need a boost in the last few minutes, turn it up a bit and finish strong.