When you're focused on goal -- a personal best, an improved split time or a marathon under 3 hours -- it's all too easy to overtrain. You tell yourself, "My splits were 10 seconds off pace on my last long run; maybe if I run double the number of hills this week, I can improve my speed." If negative thinking can turn your mind against you, too much training combined with too little rest can turn your body against you. Don't wait until you roll your ankle or limp home on a stress fracture to conclude that you might be overdoing it.
There are over 130 physiological signs of overtraining, including elevated heart rate and colds that linger [source: Aschwanden]. Since you probably don't plan on taking daily blood samples, another way to monitor your health is to give yourself an attitude check. Are you unusually grumpy or short-tempered? If so, you might be overtraining.
In Marathon training, what you do when you aren't running can be just as important as the workouts themselves. Your body needs plenty of sleep and quality nutrition in order to recover properly. If you don't honor the rest and taper days on your schedule, you might end up injured and unable to complete your race.
Next up, we talk about the hallmark of marathon training: the long run.