The terminology to refer to these endurance-trained men with low resting testosterone had not been universally standardized, but in 2005 researchers from our laboratory group proposed the use of the phrase the “exercise-hypogonadal male” as a name to refer to this condition. Hence, more research is needed, especially prospective studies as most information is based upon cross-sectional research designs. The prevalence of the problems seems low (~15 to 25% of men doing chronic endurance training), but as noted the research studies examining this condition and its consequences are few in the literature. Such hormonal changes may result in diminished bone mineral content and spermatogenesis, as well as male infertility problems.
The majority of these men display clinically “normal” levels of testosterone, but the levels are at the very low end of normal, and in some cases reach a sub-clinical status (i.e., “testosterone deficiency”). Research studies on men show the existence of a select group who, through their exposure to chronic endurance exercise training, have developed alterations in their reproductive hormonal profile - principally, low resting testosterone levels. Unfortunately, the number of findings on this latter topic is still relatively sparse as compared to the number of women-based studies, but initial insights revealed that similarities exist for the effect of exercise on aspects of the reproductive system within the genders. Researchers, however, have recently begun to address the question of how exercise training affects the reproductive endocrine system in men too. The majority of the research on this topic has concentrated upon women athletes that is, specifically the study of “athletic amenorrhea” and the “Female Athlete Triad”. Over the last several decades, an increasing number of research studies have pointed to how chronic exposure to endurance exercise training results in the development of endocrine dysfunction, which may subsequently compromise normal reproductive processes. This is particularly true for the components of the endocrine system associated with the control and regulation of reproductive function. One of the body’s physiological systems that is extremely sensitive to the stress of exercise training is the endocrine system. Some of the common unwanted consequences of high volume training include development of the “Overtraining Syndrome” condition, which can completely compromise the ability of an athlete to perform, or lead to musculo-skeletal trauma and injury ( i.e., “pulled muscles”). Yet exercise training to this extent can also place an incredible amount of stress and strain on the athlete’s body and result in unwanted physiological responses and health problems. Such physiological changes result in an increased human performance capacity. For example, there is an enhancement of the maximal cardiac stroke volume, maximal cardiac output, maximal arterial-venous oxygen differential, increased erythrocyte number, decreased levels of stored adiposity and increased skeletal muscle mitochondrial density. Chronic exercise training to this extent results in positive physiological adaptations that are highly advantageous to the human body. For instance, it is not uncommon for a marathon or ultra-distance runner to perform 150 to 200 kilometers of intensive running per week as part of their regular training. Sportsmen and women who participate in endurance events perform a tremendous amount of exercise training.
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