Some workouts require more concentration than others. Obviously, if you are practicing yoga or martial arts, or if you are counting weightlifting sets or reps, you can't be reading or watching TV.
But for some cardio and strength workouts, listening to your favorite music while you run can keep you better motivated. Those 45 minutes may go by quicker when indulging in an intriguing book or trashy magazine on the stationary bike, or watching your favorite TV show from the elliptical trainer.
MP3 players have revolutionized portable workout entertainment; now you can design a mix of your favorite motivational music with a few clicks. Choose fast tunes for your interval workouts, and slower songs for rhythmic activities such as long, slow runs or lifting weights. But if you exercise outdoors with music, be sure to avoid tuning out so much that you are unaware of your surroundings. You still need to watch for cars, dogs, pedestrians or any other distractions.
And believe it or not, working out with a friend is entertaining, too. Carrying on a conversation about everything from world affairs to the World Series to your crazy relatives makes a 20-mile training run go by quickly. Even if you don't work out with a group, meeting a friend even once a week for a workout can make fitness more fun and help you stay motivated.