Several researchers have suggested that reproductive hormones in exercise-hypogo-nadal men are suppressed because they are "overtraining," or are developing the "overtraining syndrome." This terminology can be confusing to non exercise physiology researchers; hence, some explanation is warranted. The terms "overtraining syndrome" and "overtraining" frequently are used interchangeably. The term "overtraining" refers to the process of heavier-than-usual exercise training, whereas the term "overtraining syndrome" refers to the product of too much of the overtraining process (2,4,7-9,97-101). The overtraining syndrome is a pathological condition in which an athlete experiences consistent and persistent exercise performance incompetence that does not reverse itself after a few days of rest and recovery. Furthermore, there is no underlying medical reason or explanation for the declining performance. This exercise performance impairment can manifest itself within athletic competition as well as during exercise training. Concurrent with the declining physical performance is a host of other psychophysiolog-ical consequences that are adverse and negative. Some of the most general and commonly reported consequences and symptoms are listed in Table 3.
Consequences and Symptoms of the Overtraining Syndrome (see refs. 2,4,102).
I Physical performance
Severe constant fatigue
Persistent muscle soreness
Overuse musculoskeletal injuries
Disturbed sleep patterns
Overall mood disturbances—shifts
Immune system deficits
Mental concentration difficulties
A Submaximal—maximal heart rate responses to exercise
I Maximal oxygen uptake
A Submaximal—maximal lactate response to exercise ^ = Decrease
A = Change decrease and/or increase.
One commonly reported endocrine change in overtrained athletes is suppressed or extremely low circulating testosterone levels (2,4,7,9,99-101). Furthermore, in some cases, suppressed LH, FSH, and inhibin levels have been reported (24,97,100-102). Although these changes are nearly identical to those reported for exercise-hypogo-nadal men, it does not represent the same phenomena. The hormone changes that are found in overtraining athletes are only temporary. When the exercise-training load of these overtraining athletes is reduced, or increased periods of rest are incorporated into the training program, their hormonal profiles return to normal (102). Incorporation of more rest into the training of exercise-hypogonadal men has no substantial effect on their resting hormone levels. Neither do exercise-hypogonadal men display overtraining syndrome symptoms (see Table 3). Furthermore, most researchers studying the exercise-hypogonadal issue have been careful to ensure that their subjects under investigation are not going through periods of intensive training, and, that when they are evaluated, they are well rested.
Thus, the hormonal changes found in exercise-hypogonadal men are a more stable accommodation in the hypothalamic-pituitary-testicular axis, whereas those in overtraining athletes are transient and are associated with a declining physical performance.
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