Myth 4: Run Every Day
Running every day is not necessary; in fact it can be harmful and lead to overtraining, burnout and injury. Instead, incorporate cross-training (i.e., swimming, biking, elliptical machine, rowing) into your routine. Many athletes find that they perform best if they take at least one day off from training each week, while other athletes do better with two rest days each week. Experiment during training and see what works best for you.
Myth 5: Mileage is All That Matters
Many runners are only concerned with their weekly mileage and think that's the measure of a true runner. However, what you do with those miles is more important than the actual number of miles that you run. Running 6 miles a day at the same pace five days a week is fine, but to boost running performance, an athlete should alternate between hard days (tempo runs, hill work and speed work) and one long run each week. Varying the intensity and the mileage during your workouts will help you make greater performance gains than running at the same pace and distance every day.
Myth 6. You Can't Miss a Workout
Even experienced runners have a hard time with this one. As stated in myth four, many runners can benefit from at least one day off from activity each week. Outside of your regularly scheduled rest day, some common sense will go a long way in keeping you healthy and strong. For example, it can be beneficial to skip your planned workout for the day if you're tired, sick, or you feel any pain. A day off now could prevent having to take a week off later. Try to look at the big picture. One individual workout does not make or break your training.