This is the time of year that you should reduce your training session.
Race schedules tend to slow down with the coming of the holidays and it is time to give your body a chance to recover from any lingering injuries. Exercising before an injury has healed may not only worsen it, but may actually increase the chance of re-injury.
Runners who continue their same training sessions year-round will fall into the category called staleness, which can cause fatigue, loss of performance, and depression. When staleness persists with extreme fatigue, an iron deficiency is often present. However, iron deficiency can be present with being anemic.
Research has shown that runners in heavy continuous training tend to develop iron deficiency. In some cases, the blood count may be normal but the body can be completely out of iron stores, which are necessary for the body's cellular makeup to function properly. It takes at least two months of daily iron supplements to build up these stores back to normal. If you are not sure if you have an iron deficit, a serum ferrin blood test can be done. However, studies have shown that bone marrow aspiration is the only fool-proof method to evaluate low iron stores.
Overtraining can also bring on vitamin deficiencies. Therefore, a daily intake of Vitamin C, as well as a Vitamin B Complex, should be taken in heavy training sessions. There has also been found to be a decreased supply of potassium and magnesium in the blood levels when fatigue sets in during heavy training sessions; if this fatigue is allowed to continue, one may develop colds, a sore throat, or cough.
For the winter, take a week off or cut down your mileage and learn to keep in touch with your body. Listen to your body physically, mentally, and spiritually.