The article’s directed toward Track&Field athletes:
http://www.flotrack.org/articles/view/948-hormones-working-overtime-by-danny-mackey-ms
Here’s the really good part if you don’t want to follow the link:
So we are on the same page, we need to have a working definition of overtraining. What I think of is; athletes that have too much stress combined with too little time for regeneration. As an athlete, I had coaches tell me running poorly is mental. Just “get tough” and you will be fine. Well, mental aspects are a part of the overall equation, as alterations in mood are an affect of overtraining. But, research has found significant decreases of maximal power output, VO2 Max and maximal heart rate resulting from overtraining. Also found was increases in blood lactate concentration at a given workload. In other words, toughen up as much as you want, the body does have a limit.
There are two types of overtraining according to research done in the 1950’s by Dr. S. Israel. Athletes typically experience either an Addisonoid or a Basedovoid syndrome. Both are the result of an unbalanced autonomic nervous system. Addisonoid type of overtraining is when the parasympathetic system and vagal tone or dominant. Basedovoid overtraining is when the sympathetic system dominates and the athlete is in a hyperadrenergic state. Basedovoid overtraining encompasses the more classic symptoms you have probably all experienced: sleep disturbance, lack of appetite, high resting heart rate, depression, and irritability. As a distance runner you would experience this during the intense workout part of the season, and it is generally encountered in power sports. Addisonoid overtraining is harder to diagnosis because you do not show the classic symptoms, but the end result, a.k.a. your performance will be hindered. Addisonian overtraining is typically a result of high volume monotonous training, as seen in base training. Bringing it back to hormones; these types are both related to adrenocortical subactivity or thyroid hyperfunction. I have experienced both of these over the years and I can say the Addisonoid overtraining is far more frustrating. Everything felt fine, even the easy running days were ok, but once I had to “hammer” it felt like I had a restrictor plate on my engine. Frustrated, I would run my workouts ever more intense. As a result, I was so fried I had to shut down an entire track season and rest completely for 8 weeks. Overtraining “rest” is different then a injury because even cross training can have a negative impact.