So first the definition:
Overtraining centers around a runner trying to achieve too much. This can be done through overzealous training, too many races in a short period of time, or some combination of both. Below is a short list of symptoms. Having just a few of these is a pretty strong indicator of overtraining.
- Generalized fatigue
- Recurrent headaches
- Loss of appetite sexually or for food or work
- Listlessness, irritable, miserable, anxious, ill-humored, depressed
- Generalized apathy: loss of joy, enthusiasm, drive, thirst or desire for training or competition
- Cold, flu, worsening allergies, or generalized swelling of lymph glands
- Early morning awakening or general inability to relax
- Impaired physical performance- inability to complete routine training sessions
- Heavy-leggedness for more than 24 hours after a workout
- Consistent muscle soreness, muscle and joint pains
- Slower recovery in heart rate after exertion, abnormal rise in heart rate upon standing or after a routine workout
How does this happen and how can we avoid it? Tim Noakes in Lore of Running sums it up particularly well. He says we simply cannot objectively assess our own performance capabilities. We won't accept that we are mortal and have limitations beyond which we are simply hurting ourselves. We can even interpret resulting poor performance as undertraining. Inadequate recovery and training monotonously with the same type and volume can also lead to overtraining.
Fortunately, we can also catch it early in addition to watching out for the precursors and early signs of the symptoms. The earliest stages include a fall in performance, a lessened drive or interest in training, apathy, and tired legs. These could be related to other factors, however, so its crucial to know one's own body and appropriate training. However, if these continue for more than a day or two for the motivated athlete or for several days or more for the casual runner something is up.
The more serious early signs, as described by Richard Brown, are a progressive loss of weight, increased fluid intake, progressively later bedtime each evening, decreased number of hours of sleep, and a persistent increase of 5 to 10 beats per minute in early morning pulse rate.
For more on overtraining (and everything else running, frankly), check out Tim Noakes' excellent book.