At first the overtraining state can be mild, and if an athlete rests, his body recovers fast. Later it may be more severe, and an athlete will be exhausted. The exhaustion is typical for experienced endurance athletes, who usually react in this way. Overtraining-like states can also be induced by mental, social, economical and environmental stress. These factors together with physical training cause total stress which influences on the body.

Stress can be caused by both positive and negative psychological factors. These may be e.g. holiday, vacation, personal achievement, change in residence, school or job, change in social and recreational habits, financial problems, divorce, trouble at school, trouble with the law, death or birth in the family.

Physiological factors cause stress as well. This kind of factors may be e.g. travel, sleep loss, races, changes in training, environmental changes (altitude, humidity, temperature), illness, injury, menstrual cycle or pregnancy.

Highly motivated athletes have to keep in mind that the balance between training, other stressors and recovery has to be right, i.e., they have to periodisize their training in the right way. If there is an uncompleted recovery time after exercises, fatigue starts to accumulate and after a few days or weeks symptoms of overtraining with a drop in performance will arise. As a result, recovery may take weeks or months.

Symptoms and signs of overtraining vary from athlete to athlete. The symptoms and signs are due to changes in the function of the autonomic nervous system, hormonal status, immunological parameters and other physiological and musculoskeletal changes of the body. Typically, an athlete feels tiredness and fatigue and notices a drop or stagnation in performance despite of continuing training.

Examples of psychological and psychosomatic overtraining signs and symptoms:

• depression, fatigue, irritability, badmood, anxiousness, confusion, excitement, desperation, lack of concentration
• unwillingness to train
• feeling of inability to go on training
• sleeping problems
• bad appetite
• shaking hands
• abnormal sweating
• palpitation
• nausea
• dizziness

Examples of physiological overtraining signs and symptoms:

• increased resting and submaximal heart rate (resting heart rate can also be decreased in overtraining state)
• muscle soreness
• decreased maximal heart rate
• menstrual irregularities
• decreased performance
• loss of strength
• increased illness and injury frequency
• loss of co-ordination

2. Introduction to the overtraining research and
Overtraining test development

Stress as a physiological phenomenon has been investigated since the 1920's. The stress of athletes which is called overtraining however has not been investigated for so long. The term overtraining is familiar from the 1950's when, amongst others, S. Israel investigated overtraining and its various forms. His publication about the two different overtraining forms (sympathetic and parasympathetic overtraining) has been often quoted (Israel 1976). These forms of overtraining point to the important role of the autonomic nervous system in the differentiation of overtraining states. Even despite this, the function of the autonomic nervous system has been barely investigated in conjunction with overtraining, except for hormonal definitions (amongst others M. Lehmann).

The behaviour of the heart rate and the changes arising out of physical training in loading and rest have been considerably studied, but more precise investigations on the autonomic function are lacking. In the 1970's a test battery was developed for investigating the autonomic nervous system which was based on the investigation of cardiovascular reflexes. Since then the investigation of the function of the autonomic nervous system has expanded to cover various illness states (e.g. diabetes, coronary heart diseases, Parkinson's disease).

It is apparent that large changes take place in the function of the autonomic nervous system when athletes go into the overtraining state and the changes in question may be a basic reason for all the overtraining symptoms which appear. Therefore investigation of the autonomic nervous system in the development of athletes' overtraining state is well justified. This conclusion lead to the commencement of studies in 1992 in the Research Institute for Olympic Sports. The aim was to carry out an experimental overtraining investigation in endurance athletes, particularly with respect to changes in the function of the autonomic nervous system. Heart function, blood pressure levels and hormonal changes were studied in various interventions as well as in pharmacological receptor blockade studies.

The athletes have been monitored during an extremely heavy training program and some of the athletes have come into an overstressed state. The changes in the autonomic functions of the overtrained athletes have been seen as changes in heart rate levels and heart beat variations at rest as well as during various interventions (e.g. orthostatic test). The changes were different in different athletes, suggesting a different type of overtraining state form as stated in previous theories. The repeatability and intra- and inter-individual variation of the parameters over the short (a week) and long term (a year) has also been investigated. This data has also been an essential support in creating the Overtraining test.

3 Different types of overtraining states

Two types of overtraining states have been described in the literature: sympathetic and parasympathetic overtraining. Different symptoms and signs, which are mediated by either the sympathetic or parasympathetic part of the autonomic nervous system dominate in these two types.

The signs of sympathetic overtraining are clear and mimic the signs of strong stress reaction. Sympathetic overtraining is typical for young athletes, power athletes and sprinters. In parasympathetic overtraining the signs are often very mild and unnoticeable. Bodily functions change to be slower. Parasympathetic overtraining is typical for athletes who have trained for many years and for endurance athletes. In practice, the overtrained athlete has usually symptoms and signs from both of these overtraining states.

There are also short-term (overreaching) and long-term overtraining states. Both of these can be of the sympathetic or parasympathetic type and they differ by the time in which they have developed and also by recovery time.

Usually the athlete recovers from a heavy exercise load in one or two days during which his/her increased heart rate level returns back to the 'normal' level. Instead, in the overreaching and especially in the overtraining state the heart rate levels start rather to increase than decrease after a short resting period (1 - 2 days) and the athlete does not feel rested.

Finally, muscular overloading can develop after one heavy exercise or during a longer heavy training period. It differs from physiological (systemic) overtraining and can not be measured in the same way. However, if training continues to be heavy in spite of muscular overloading the physiological overtraining starts to develop.

4 Heart rate reactions in overtrained athletes

Recovery from severe overtraining always takes from some weeks to months. Therefore it is important to diagnose overtraining early enough. Measurement of heart rate and heart rate variability (R-R interval measurement) has proved to be the best way to notice the initial state of overtraining.

The sympathetic and parasympathetic parts of the autonomic nervous system and intrinsic heart rate determine the resting heart rate. If sympathetic activity increases, heart rate increases and a short-term heart rate variability decreases. If parasympathetic activity increases, heart rate decreases and the short-term heart rate variability increases. The short-term heart rate variability has been reported to reflect the activity of the sympathetic and parasympathetic nervous system and balance between these two parts. Because the balance between and the activity of these two parts of the autonomic nervous system change with training and overtraining, these markers can be used to indicate training effects (Uusitalo et al. 1996).

Heart rate decreases and heart rate variability increases with the positive training effect. In the overreaching and in sympathetic overtraining state the heart rate increases and heart rate variability decreases. In the parasympathetic overtraining state or in exhaustion both heart rate and heart rate variability decrease.

5. Overtraining test of Polar Precision Performance Software

The Overtraining test is planned to analyse the effects of training in standard conditions. The analysis program is based on the measurement of heart rate and heart rate variability during supine rest and during the active orthostatic test in standard conditions. The test can be conducted only with the Polar Vantage NV Heart Rate Monitor.

The test will tell you early enough if you have trained successfully or if you demonstrate an impending overtraining state. You can focus your training successfully by using the test and following the advice the program gives after analysis. In this way you can maintain the balance between training and recovery.

FOR MORE INFORMATION
Akselrod S., Gordon D., Madwed J.B., Snidman N.C., Shannon D.C., Cohen R.J.. Hemodynamic regulation: investigation by spectral analysis. Am J Phy (Heart Circ Physiol 18)249: H867-H875, 1985.

Israel S. Zur Problematik des Ubertrainings aus internisistischer und leistungs physiologischer Sicht. Med u Sport XVI (1, jan): 1-12, 1976.

Kuipers H., Keizer H.A.: Overtraining in elite athletes. Sport Med 6: 79-92, 1988.

Lehmann M., Knizia K., Gastmann U., Petersen K.G., Khalaf A.N., Bauer S.M., Kerp L., Keul J. Influence of 6- week, 6 days per week, training on pituitary function in recreational athletes. Br J Sports Med 27 (3): 186-192, 1993.

Lehmann M., Baumgartl P., Wiesenack C., Seidel A., Baumann H., Fischer S., Spöri U., Gendrisch G., Kaminski R., Keul J. Training - overtraining: influence of a defined increase in training volume vs training intensity on performance, catecholamines and some metabolic parameters in experienced middle- and long-distance runners. Eur J Appl Physiol 64: 169-177, 1992.

Lehmann M., Scnee W., Scheu R., Stockhausen W., Bachl N. Decreased nocurnal catecholamine excretion: parameter for an overtraining syndrome in athletes? Int J Sports Med 13 (3): 236-242, 1992.

Pagani M., Lombardi F., Guzzetti S. Power spectral analysis of heart rate variabilities as a marker of sympatho-vagal interaction in man and concious dogs. Circ Res, 59, 178-193, 1986.

Uusitalo, A., Väänänen, I., Härkönen, M., Pakarinen, A., Rusko, H.: Overtraining in young male skiers during an intensified training period. Abstract. American College of Sports Medicine Annual Meeting, Seattle, 1993.

Uusitalo, A., Rusko, H.: Autonomic balance vs. heart rate at rest and during deep breathing in female endurance athletes. Abstract. International Conference 'Current Research into Sport Science', St. Petersburg, 1994.

Uusitalo, A., Hanin, Y., Rusko, H.: Effect of exhaustive training on mental state, autonomic regulation and hematological parameters. In Viitasalo J., Kujala, U.: The way to win. Int. Congress on applied research in sports, Helsinki, 1994.

Uusitalo, A., Hanin, Y., Rusko, H.: Effect of exhaustive training period on intrinsic heart rate and autonomic balance. Abstract. XXV FIMS World Congress, Athens, 1994.

Uusitalo, A., Tahvanainen, K., Uusitalo, A, Rusko, H.: Noninvasive evaluation of sympathovagal balance in athletes by time and frequency domain analyses of heart and blood pressure variability. Clinical physiology 16: 575-588, 1996.

Uusitalo, A.L.T., Tahvanainen, K.U.O., Uusitalo, A.J., Rusko, H.K.: Does increase in training intensity vs. volume influence supine and standing heart rate and heart rate variability - A 6-9 weeks' prospective overtraining study. Abstract. Overtraining and Overreaching in Sport - Congress, Memphis, Tennessee, 1996.

Uusitalo, A.L.T., Tahvanainen, K.U.O., Uusitalo, A.J., Rusko, H.K.: Influence of a defined increase in training intensity or trainig volume on maximal oxygen uptake and heart rate variability in endurance athletes. Abstract. XXXIII International Congress of Physiological Sciences. IUPS, St. Petersburg, 1997.