By: Lauren Peterson, MS, CSCS, FMS-level 1

Endurance athletes often engage in persistently high volumes/intensities of training to achieve optimal performance without understanding that physiological adaptation occurs during rest periods following hard physical exertion [1]. Without maintaining a proper balance between training and recovery, complete regeneration cannot occur and performance plateaus and will eventually decline [2]. Other stressors (e.g. emotional, social, malnutrition, infection) can also impact an athlete’s stress load and the recovery time needed [3]. This imbalance of stress and recovery resulting in chronic fatigue is known as Overtraining Syndrome. Overtraining Syndrome is often difficult to detect because physical symptoms often do not manifest until it is too late [1]. While Overtraining most often occurs in elite athletes, youth and recreational adult athletes are also at risk if training load and training response are not closely monitored [4]. From this brief article, you will learn the physiology, how to detect, and how to prevent Overtraining Syndrome.

There are two types of Overtraining Syndrome: sympathetic and parasympathetic [5].  The Sympathetic form is characterized by increased sympathetic response or tone and is more common in anaerobic system dominant sports (i.e. sprinting, power lifting, football). The sympathetic nervous system prepares the body for action (i.e. fight or flight response) by increasing heart rate, increasing glucose release from the liver, etc. Common presentations of Sympathetic Overtraining include: increased heart rate and arterial pressure, decreased appetite and body mass, sleep disturbance and irritability [5]. The Parasympathetic form is more common in aerobic system dominant sports (i.e. endurance sports) and results in domination of parasympathetic tone when the body is at rest and during exercise. The parasympathetic nervous system is responsible for stimulating activities when the body is at rest (i.e. digestion, salivation, urination), and overtraining symptoms include: decreased heart rate and resting arterial pressure, and long periods of sleep and depression [6]. In the literature, endurance athletes tend to present with symptoms of both sympathetic and parasympathetic overtraining [7].

Overtraining can be monitored through the use of blood markers. For instance, decreased sympathetic activity, results in reduced neuro-endocrine control and altered hormone profiles (increased serum cortisol, decreased testosterone) and neurotransmitters (glutamine, dopamine, and serotonin) [8-9]. Additional blood markers can present decreased hemoglobin, iron, ferritin, and elevated C-reactive protein [8]. The process of blood panels can be time consuming and costly; therefore, an easy and practical way to monitor overtraining is by monitoring resting heart rate. Resting heart rate should be taken first thing in the morning, while and athlete is lying in bed. Increased morning heart rate above 10 beats per minute reflects an initial stage of overtraining [9]. Other signs or symptoms that may present prior to increased resting heart rate include: infections, swollen lymph glands, chronic fatigue, sleep disturbance, altered mood states, muscle soreness, joint aches, decreased training tolerance, and decreased coordination [9]. A longer the period of overtraining will require a longer recover time. Proper nutrition, rest, and light exercise that increases volume slowly has shown to be the best treatment [10].

Since you now know the causes and manifestations of Overtraining Syndrome, how can it be prevented? Here are a few suggestions:

  • Implement properly periodized training plans with progressive increase in training load.
  • Training volume should decrease with increased training intensity.
  • Recovery sessions and off days should be included in training plans.
  • Take mental breaks from training and do something else you enjoy.
  • Enjoy time with family and friends.
  • Drink plenty of water.
  • Get plenty of rest.
  • Maintain a proper diet and adequate caloric intake with foods rich in carbohydrates, proteins, and electrolytes.


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