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Overtraining occurs when runners stresses their bodies more than the bodies can handle. There are two types of overtraining: Sympathetic and Parasympathetic. Most runners are familiar with Sympathetic overtraining, because that is the type of overtraining that is discussed in running books. However, Parasympathetic overtraining is more serious and needs to be understood.

Our Nervous System

There are two components to our nervous system: The Sympathetic and the Parasympathetic. Both components are in operation simultaneously, and they balance each other. When we experience stress, our Sympathetic system becomes dominate and causes our heart to beat faster to get more blood flow, our breathing rate to increase to get more oxygen, our sweat glands to function to cool us off, adrenal glands becomes active, etc. After the stress has passed, our Sympathetic system reduces its effect, and our Parasympathetic system becomes dominate and helps us recover. Our heart rate slows, breathing goes down, we stop sweating, etc. Our Sympathetic and Parasympathetic systems have opposite effects on our bodies: one to handle stress and the other to recover from the stress.


Runners overtrain when they have insufficient rest after their training, that is, they don't completely recover from previous stress before they subject their body to new stress. In doing this, they tax the operation of their Sympathetic system, and certain symptoms occur which signal that overtraining is taking place. The following list of sympathetic symptoms is from http://www.grapplearts.com/Overtraining-Article.htm
bulletReduced concentration
bulletInsomnia and/or troubled sleep
bulletDecreased performance
bulletDelayed recovery from training
bullet'Intolerance' to training
bulletElevated morning rested pulse
bulletIncrease in injuries
bulletChronic muscle soreness
bulletWeight loss
bulletFrequent minor infections
bulletAppetite loss
bulletDecreased enthusiasm for training
The basic remedy for sympathetic overtraining is to give our bodies additional rest. The additional rest might need to be complete rest, or it might need to be a reduced activity level and/or cross training.

While this overtraining is going on, the Parasympathetic system is trying to cause the body to recover from the stress, but its effects are overshadowed by the Sympathetic system.

Now, suppose runners ignore the symptoms of overtraining and continue to train at their high level of stress. Eventually, the Sympathetic system becomes exhausted. The Parasympathetic system then becomes dominate and attempts to cause the body to recover. The Sympathetic system isn't able to balance the recovery, and the body recovers too much. This is known as Parasympathetic overtraining. The web site linked above described it this way.

There is also another form of overtraining, 'parasympathetic' overtraining, that is associated with a decreased resting heart rate. This occurs because the athlete has been overtraining for so long that his hormonal and nervous systems become exhausted. This is fairly rare for martial competitors and really only occurs [in] endurance athletes with extreme training volumes.
Web sites I've studied give three symptoms of Parasympathetic overtraining: resting heart rate goes down, quick recovery from stress, such as recovery time between intervals, and no sleep disturbance. Notice that these symptoms are symptoms of recovery.

Am I suffering Parasympathetic overtraining?

If runners experience a drop in their resting heart rate or fast recovery times, they aren't necessarily suffering Parasympathetic overtraining. They may be experiencing the effects of a stronger body. How can they identify, then, the cause of the changes in their bodies?

Parasympathetic overtraining results when the Parasympathetic system becomes dominate due to the Sympathetic system ceasing to function properly. So, lets list the events that likely will have occurred when Parasympathetic overtraining occurs.

  1. Symptoms of Sympathetic overtraining occur. These are the symptoms that are usually discussed in running books. The major ones are listed above.
  2. These symptoms are ignored, or at least not compensated for adequately, and the Sympathetic system becomes exhausted and ceases to be the dominate component of our nervous system.
  3. The Parasympathetic system becomes dominate and puts our body into recovery mode. Because this recovery is not balanced by the Sympathetic system, the recovery goes too far, so to speak, and the resting heart rate decreases, and/or recovery times are decreased.

Each runner, who is experiencing parasympathetic symptoms will have to decide if he/she is suffering from Parasympathetic overload or is experiencing the effects of a stronger body. It seems to me that the key observation is whether #1 and #2 (given above) have occurred.

Tired Heart

An article titled "How Much is Too Much?" from


gives an interesting symptom of overtraining that affects athletes who really train hard.

Most recreational athletes are more used to the notion that an elevated heart rate is the sign of overtraining, specifically during rest, and they’re right in their thinking. Fewer athletes are aware of, or ever experience, a heart that cannot beat fast enough. But professional triathletes are very aware of this phenomenon, especially those who engage in Ironman-style training and racing.

"There are days that I just can't get my HR to the zone I want it to be in," says Ironman and World Champion Karen Smyers. "This is a sign of not being recovered, and I reschedule the hard workout planned for that day. If you recognize it early, you can usually recover in a day or two. If you have pushed through it for a long time, you may need a much longer time to pull yourself out of the slump." Every triathlete who has done the big miles can relate to a time when the heart for some reason won’t beat fast enough under load. What is in question is exactly why this happens and what the physiological mechanism behind it might be.

The article gives the advantage of having a heart rate monitor.
"You won’t know you’re heart-tired without a heart rate monitor," [longtime American pro Mark] Montgomery says. "You feel OK, more or less, it’s just that you’re out there doing an amount of work that should have you up to 150 beats, but your heart is only at 125. Your heart rate monitor is the only way you’ll know it."

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