© Springer Science+Business Media New York 2016
Diana Vaamonde, Stefan S du Plessis and Ashok Agarwal (eds.)Exercise and Human Reproduction10.1007/978-1-4939-3402-7_99. Common Male Reproductive Tract Pathologies Associated with Physical Activity, Exercise, and Sport
(1)
Department of Allied Health Sciences, University of North Carolina, Chapel Hill, NC, USA
(2)
Department of Urology and Reproduction, Insemine Human Reproduction Center, Nilo Peçanha 2825/905, 91330-001 Porto Alegre, Rio Grande do Sul, Brazil
(3)
Department of Obstetrics and Gynecology, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grand do Sul, Brazil
Keywords
Elite sportsMale hypogonadismVaricoceleSemen parametersMale sexual functionIntroduction
The World Health Organization (WHO) defines health as a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity. Physical exercise has been proposed as one of the most beneficial lifestyle interventions to achieve such a state. However, exercise is a powerful stimulus to the body and it can provoke paradoxical effects on human physiology. While it can act as an important beneficial tool preventing lifestyle-related diseases such as obesity, it is also known to induce diverse stress responses in the neuroendocrine system [1]. Elite athletes are increasingly undergoing greater levels of exercise training to improve their performance. The reproductive and endocrine systems are particularly sensitive to the amount of this training stress [2]. This chapter focuses on the existing relationships between exercise training, sports practice, and their influence on the male reproductive system functionality.
Exercise Physiology and the Neuroendocrine System
Testosterone is one of the most potent naturally secreted androgenic-anabolic hormones, and its biological effects include promotion of muscle growth. In muscle, testosterone stimulates protein synthesis (anabolic effect) and inhibits protein degradation (anti-catabolic effect); combined, these effects account for the promotion of an increased muscular cross-sectional area (CSA; hypertrophy + hyperplasia) [3]. Testosterone is also associated with muscle strength, sports competition aggressiveness, and re-synthesis of proteins during recovery [4]. The concentration of testosterone depends on the pulsatile release of luteinizing hormone (LH) by the anterior pituitary. The majority of the circulating testosterone is transported bound to various carrier proteins, but sex hormone-binding globulin (SHBG) is the major one [5]. The concentration of testosterone is a result of the production of the hormone and the metabolic clearance by the liver. The rates of these two processes are affected by a number of changes in the physiological state [2, 5].
Testosterone production is under control of the hypothalamic–pituitary–testicular (HPT) axis. The HPT axis is definitely influenced by exercise and exercise training [2]. However, the magnitude and extent of the effect is highly variable due to the type, intensity, and duration of the exercise performed, as well as the degree of physical fitness of the individuals exercising [1, 2]. Additionally, factors such as psychological stress, sleep disturbances, and/or diet influence the HPT axis and testosterone levels [2]. Regrettably, rarely are all of these factors considered when exercise studies are conducted or reported in the literature [2].
Male Hypogonadism and Sport
The hormonal response to acute exercise is dependent on several factors including the intensity, duration, mode of exercise, and the training level of an athlete [6]. Acute exercise demands a physiological increase in testosterone. Some investigations report that total and free testosterone levels are briefly elevated following a strenuous or prolonged exercise session [7–10]. This implies high volumes of training (e.g., 10–20 h/wk) could increase levels of steroids [11], improve metabolism [12], and protect the athlete from overactivation of the immune system [13]. However, ultimately the repetitive responses of such activity could negatively affect the HPT axis as the training program progresses [14].
Tremblay et al. studied endurance-trained males and verified that with exercise , besides short-term (acute) testosterone elevation, there was an increase in dehydroepiandrosterone sulfate (DHEAS) in a dose–response manner dependent on the intensity of the acute exercise. Furthermore, it appeared that during low-intensity exercises, high exercise volumes were needed to induce a significant increase in cortisol [15]. Interestingly, in nonelite, middle-aged marathon runners, a marathon race resulted in an acute increase in blood cortisol and prolactin levels and a concomitant decline in testosterone level [16].
The HPT axis response to chronic exercise has been investigated in many retrospective studies that found lower testosterone levels in endurance-trained males [2]. In these studies, testosterone levels of athletes were found to be 60–85 % of the levels of controls, not outside the clinical norm, but at the low end of the range [10, 14]. Prospective studies are more inconsistent, since some have found significant reductions in resting testosterone following endurance training regimens, and others found no association at all. Differences in the subjects (i.e., age, mass) and in their training regimens may explain these discrepancies [2] .
Meanwhile, a wide population-based study involving volunteers (not athletes) found no association between total serum testosterone levels nor SHBG levels with aerobic exercise capacity or maximal power output in men [17]. These contrasting findings demonstrate that these relationships are highly complex.
Endurance-trained males also display other hormonal abnormalities such as a lack of elevation in resting LH, despite low testosterone levels and decreased prolactin, a state referred to as the exercise-hypogonadal male condition (EHMC) (i.e., in chronically trained men) [18]. The EHMC is associated with not only hormonal abnormalities, but also detrimental changes in semen characteristics in the spermatogenesis process (see later discussion in the article) [2, 4, 10, 18]. Interestingly, Safarinejad et al. conducted prospective work and induced similar hormonal responses but viewed this as an effect of overtraining the men (i.e, overtraining syndrome) and not the EHMC [19]. Luigi et al. [4], however, states that there are no evidence-based criteria that these athletes would be at risk for osteoporotic fractures, cardiovascular accidents, or sport-related anemia due to their hormonal changes, but antidotal evidence of such events has been reported [2, 19]. Unfortunately, there is no standardized definition in the literature about at which point or with what intensity of training athletes are at risk of developing these hormonal alterations .
Male Sexual Function
Male sexual function is a complex entity because it involves desire, erection , and ejaculation. It has been shown in randomized trials that balanced exercise training in healthy volunteers is beneficial to maximize erectile function and sexual health because it reduces body mass index (BMI) and influences other disorders that affect sexual function such as the metabolic syndrome and cardiovascular diseases [20, 21]. Meanwhile, as previously stated, endurance athletes are at risk for hypogonadism, and consequently, erectile dysfunction (ED) and/or decreased sexual desire occur [22] due to decreased testosterone levels.
Varicocele and Sport
Varicocele may result from abnormally dilated veins in the pampiniform plexus, and it has long been associated with male infertility according to observational studies that report an increased incidence of this pathology in infertile men [23] . Varicocele is also commonly seen in the general population—with a prevalence between 4 and 22 %—but it can reach an incidence of up to 80 % in men with secondary infertility [24]. Effects of varicocele in semen parameters include altered concentration, motility, and morphology. Several studies have focused on how varicocele leads to impaired spermatogenesis , most of them proposing a mechanism of altered blood flow and scrotal temperature [23]. Although debated, there is substantial evidence to support the value of varicocele repair in male infertility in order to improve semen parameters [5].
A trial, evaluating the role of sports medicine in the diagnosis of andrological diseases, found a high incidence of varicocele in athletes—29 % [25]. It has been shown that sports practice does not modify the prevalence of varicocele compared to the general population [26]; however, it seems to progress from subclinical to clinical varicocele [27] . Besides, in these subjects, the effect of varicocele appears to worsen semen parameters . In an elegant study, competitive athletes presenting with varicocele were age-matched with men who engaged only in recreational activities. Although no differences were found in hormonal levels between groups, the percentages of both progressive forward motility and percentage of normal spermatozoa were significantly reduced in athletes with varicocele [28]. Therefore, diagnosis and management of varicocele in men engaging in endurance sports training are imperative to provide safety and preserve fertility.
Prostatitis
Prostatitis (inflammation of the prostate gland) is estimated to affect 2–10 % of men and is the third most common diagnosis in men less than 50 years of age presenting to urologists annually [29]. According to the current medical consensus on establishing an etiology of prostatitis, the condition may be caused by multiple factors, including neuronal, inflammatory, hormonal, and psychological factors [29–31]. One potential method for diagnosing prostatitis involves testing bodily fluids for biomarkers. As prostatic secretions form a substantial proportion (25 %) of the semen , seminal plasma is an excellent fluid to search for such markers of prostatic inflammation [32]. Some studies have investigated the potential of inflammatory proteins and cytokines in the seminal plasma of patients with prostatitis or chronic pelvic pain syndrome, yet none of these biomarkers appears definitive in arriving at a diagnosis [33, 34]. In fact, the most commonly used biomarker for prostate diseases, prostate-specific antigen (PSA), in wide use as a biomarker of prostate cancer, was originally found and isolated from semen [35].
Several lines of evidence indicate that physical exercise can lead to improvements in pain sensitivity and changes in immune, neuroendocrine, and autonomic function [36, 37]; hence, exercise may be an associative or causative factor and may have a role in the etiology of prostatitis [38]. Bicycle riding, for example, combines strenuous physical activity and direct pressure on the perineum and prostate. There are probable mechanisms by which cycling may influence serum PSA levels comprised of systemic factors related to the hormonal effects of strenuous physical activity [39, 40] as well as local factors including mechanical stress of the prostate caused by movement of the pelvic muscles [41], or direct perineal pressure produced by the saddle with a significant massage effect on the prostate [42]. Also, since evidence supports trained athletes may have lower basal concentration of circulating testosterone than untrained men [2, 14, 43, 44], this may result in lower risk of developing prostate diseases in athletes than in untrained subjects [45, 46]. Though studies in this area have not yielded consistent results, it seems that the interaction between physical activities and some prostate disorders may be dependent on the physiological and metabolic factors associated with exercise parameters (intensity, duration, mode of exercise, and level of the athlete) as well as factors inherent to exercise training. Further investigations are required to elucidate the relationship between physical activity and prostate disorders, and the underlying mechanisms responsible for such a relationship.
Sperm Alterations in Athletes
Alterations in motility and concentration of spermatozoa in endurance and resistance athletes were documented in a retrospective study of DeSouza et al. [47]. In a subsequent prospective study, semen volume as well as sperm motility and morphology decreased significantly over a 1-year period of marathon training, but there was no significant alteration observed in sperm count [48]. Some authors argue that exercise volume is the most important variable affecting the semen profile [49], especially for morphological characteristics [50]. Others argue that exercise intensity can be equally deleterious on reproductive function [2, 48] . While the evidence is relatively scant, it is nonetheless clear that endurance athletes may be at risk for semen alterations .
Special Situations
Steroids Abuse
Although highly prevalent in the sporting community, abuse of androgenic-anabolic steroids (AAS) received major public attention only after their use became apparent in the Olympic Games. It was not until 1967 that the International Olympic Committee released the first list of banned substances [51].
Several drugs can be used as anabolic agents such as human chorionic gonadotropin (HCG), LH (i.e., each promoters of testosterone release), as well as exogenous AAS directly, such as nandrolone and tibolone. Common areas of substance abuse include sport performance enhancement (both in strength-based [↑muscle CSA] and endurance-based [↑ recovery capacity] activities) and aging people who are seeking to abate the effects of sarcopenia [4]. AAS can exert strong effects on the human body that may be beneficial for athletic performance. Evidence supports that short-term administration of these drugs by athletes can lead to strength gains of about 5–20 % of their initial strength and increases of 2–5 kg in body mass that may be attributed to increases of the lean body mass [52].
However, AAS abuse can affect a range of organic systems and has been shown to augment mortality rates among users, especially due to cardiovascular disease [53]. Effects on the endocrine and reproductive systems include suppression of spermatogenesis, gynecomastia, and suppression of the HPT axis due to negative feedback when higher doses are used. This can subsequently lead to hypogonadism symptoms, such as ED and decreased libido [54, 55]. Furthermore, even after discontinuation of AAS use, subjects may continue to experience the effects of prolonged hypogonadism until HPT axis recovery [51].
Trauma
Traumatic injuries in sports participants are fairly common. In addition to typical musculoskeletal events, male athletes are at risk of incurring testicular injuries. Traumatic sporting injuries do not infrequently precipitate testicular torsions [56]. Testicular torsion is characterized by acute scrotal pain, and early diagnosis and definitive management are the keys to avoid testicular loss. Nevertheless, young male athletes are usually unaware of testicular pathologies and thus do not typically wear genital protection. Neither do they appreciate the difference in urgency of seeking medical treatment of painless versus painful testicular swelling [57].
Spinal trauma events also impact reproductive function as they are associated with ED and/or retrograde ejaculation. Normal ejaculatory function, a primarily sympathetic phenomenon, consists in a complex and coordinated sequence of striated and smooth muscular contractions, which results in the antegrade emission and expulsion of sperm. Spinal injury is found in participants in many adventure sports as well as a multitude of traditional sporting events [58]. Common spinal injuries that occur include muscle strains, muscle spasms, disc herniations, as well as vertebral body compression and avulsion fractures.
Cycling
Bike riding is one of the most popular sports besides being a common means of transportation. That said, it is a frequent source of significant injuries that can be classified as acute traumatic lesions or chronic overuse injuries, common in recreational riders or competitive racing riders [59]. Since there is an important association between genitourinary tract overuse injuries and cycling, the sport deserves special attention related to sexual dysfunction.
The most common problem is pudendal nerve entrapment (PNE) syndrome, presenting as genitalia numbness, reported by 50–91 % of cyclists [59]. In men attending an infertility clinic, bicycling for more than 5 h a week was associated with lower sperm concentration and motility [60]. Injurious effect of exercise on spermatogenesis can be attributed to increased scrotal temperature and HPT axis alterations, as previously discussed.
Surveys of men in Australia, England, Germany, the Netherlands, and Spain estimate the prevalence of ED to be 11–34 % in men aged 16–80 years old [61–65]. ED is also commonly seen in high-performance and/or endurance sports athletes especially in competitive cyclists [66]. The data from the Massachusetts Male Aging Study (MMAS) showed that bicycling more than 3 h per week was an independent risk factor for males (aged 40–70 years) in the development of moderate to severe ED [67]. In case-control studies, the prevalence of moderate to severe ED in bicyclists was ~ 4.2 % versus age-matched runners (1.1 %) and swimmers (2 %), respectively [68]. Interestingly, research on female bicyclists is very limited but indicates the same impairment as in male bicyclists [66]. The cause of ED resulting from bicycle riding is not fully understood, yet is likely a result of continuous compression and strain on the pudendal nerve as well as insufficiency of penile blood supply because of perineal arterial compression [69, 70]. The extent to which blood flow decreases while cycling in a seated position is significantly affected by seat position, saddle material, size, and geometry [66]. It has been reported that, in male cyclists aged 20–37 years old, cycling in a 90° position resulted in 40 % better penile oxygenation than cycling in a 60° position. More than 50 % better penile oxygenation was demonstrated with a wider saddle than the narrow saddle when compared using the same seat position and padding material. Finally, no significant difference in penile oxygenation was observed when cycling on a flat saddle as compared with riding on a saddle with a hole [66]. Since cyclists are at risk for ED, they should take precautionary measures to minimize the associated risk with bicycle riding: choose a wide, unpadded no-nose saddle that allows proper placement for sitting; choose a horizontal saddle position; ride in a more upright position; change their body position regularly from a seated to a standing position; and use road bicycles instead of mountain bikes.
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