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Autonomic imbalance hypothesis and overtraining syndrome
M Lehmann1, C Foster, H H Dickhuth
1University Hospital Ulm, Department of Sports and Performance Medicine, Germany.
Medicine and Science in Sports and Exercise
|July 15, 1998
Summary
Overtraining syndrome involves autonomic and neuroendocrine imbalances, impacting pituitary-adrenal axis and sympathetic function. This leads to reduced adrenal responsiveness and performance decline in endurance athletes.
Area of Science:
- Endocrinology
- Sports Medicine
- Neuroscience
Background:
- Overtraining syndrome (OTS) is increasingly recognized, with the parasympathetic, Addison type, being dominant.
- Autonomic and neuroendocrine imbalances are hypothesized as key underlying mechanisms in OTS.
Purpose of the Study:
- To investigate the autonomic and neuroendocrine underpinnings of the parasympathetic, Addison type, overtraining syndrome.
- To elucidate the functional alterations in the pituitary-adrenal axis and sympathetic system during OTS.
Main Methods:
- Analysis of adrenal responsiveness to ACTH during heavy endurance training and overreaching.
- Assessment of pituitary ACTH release and cortisol response.
- Evaluation of sympathetic activity, including catecholamine excretion, beta-adrenoreceptor density, and plasma norepinephrine levels.
Main Results:
- Reduced adrenal responsiveness to ACTH, initially compensated by increased pituitary ACTH, but later leading to decreased cortisol response.
- In advanced stages, decreased pituitary ACTH release, reduced sympathetic activity, and impaired target organ sensitivity to catecholamines.
- This pattern is specifically linked to high-volume endurance overtraining with high caloric demands.
Conclusions:
- Functional alterations in the pituitary-adrenal axis and sympathetic system are characteristic of OTS.
- These neuroendocrine and autonomic changes provide a physiological explanation for persistent performance incompetence in affected athletes.