Pelvic floor dysfunction (PFD) is a nonspecific term encompassing a variety of conditions including urinary incontinence, fecal incontinence, pelvic organ prolapse, pelvic pain, and sexual dysfunction. The prevalence of urinary incontinence among female athletes of different sport modalities has been shown to be 36%, making female athletes almost three times more likely to experience urinary incontinence when compared with nonathletic females (1). Despite the high prevalence of PFD in female athletes, this condition has received limited attention from sports medicine clinicians. The stigma and embarrassment surrounding pelvic concerns leads many female athletes to avoid seeking adequate care for this condition. Female athletes involved in physically demanding training or sports that place an emphasis on “weight,” such as track and field, gymnastics, or dance have been found to have high rates of PFD (1–3), as well as an increased risk for low-energy availability (4–6).
Relative Energy Deficiency in Sport (RED-S) is a syndrome consisting of health and performance impairments resulting from low-energy availability (3). RED-S has both short- and long-term effects on many systems of the body, including the endocrine, central nervous system, musculoskeletal, and reproductive systems (7). Low-energy availability in female athletes may play a role in the development of PFD such as urinary incontinence, fecal incontinence, and pelvic organ prolapse. Indeed, nutritional factors have been identified as a predisposing causal factor of PFD (8,9). The complex nature and impairment of physiological functions by these unique health problems affecting female athletes might suggest an association between the two syndromes.
To date, research evaluating RED-S as an independent risk factor for PFD is scarce. Current findings, nonetheless, demonstrate that those athletes with low-energy availability have increased odds of urinary incontinence than those without energy deficiency. A significant correlation between eating disorders and urinary incontinence was found in a group of 37 female long-distance runners (10). Additionally, a cross-sectional study of 372 elite female athletes and 372 age- and sex-matched nonathletes found that athletes with disordered eating were three times more likely to present with urinary leakage than athletes without disordered eating (11). Urinary incontinence also has been found to be more prevalent in adolescent female athletes (15 to 19 years of age) with low-energy availability compared with those with adequate levels of energy availability (12). A significant prevalence of PFD especially urinary incontinence (37%), anal incontinence (28%), and pelvic girdle pain (18%) was described in a population of 311 adult female triathletes (13). Almost one in four of these triathletes screened positive for at least one component of the female athlete triad (i.e., amenorrhea, osteoporosis, eating disorder). However, the authors found no significant association between the female athlete triad and PFD (13).
In this article, we present RED-S as a potential independent risk factor for PFD and propose a hypothetical pathophysiological model linking low-energy availability to the impairment of the pelvic floor function in female athletes.
The concept of pelvic floor as a whole is composed of several structures and functions (8). Anatomically, the pelvic floor is a complex structure situated in the pelvic cavity. It is composed of the levator ani and ischiococcygeus muscles, urogenital diaphragm, external genitalia, pelvic viscera, sphincters, and pelvic connective and neurological tissue. As part of the musculoskeletal system, the pelvic floor plays a crucial function in continence, parturition, sexuality, stabilization of the sacroiliac articulation, as well as breathing and posture (2). Moreover, the pelvic floor supports the viscera of both the abdominal and the pelvic cavity. Weak levator ani musculature, neurologic compromise, and fascial support detachment can collectively reduce pelvic floor support and consequently result in PFD, such as urinary incontinence or pelvic organ prolapse (9). Hence, PFD results from different combinations of anatomical, physiological, reproductive, and lifestyle factors, including nutrition across the lifespan (8).
The physiology of female athletes with PFD includes a complex interaction of neuromuscular, biomechanical, morphological, hormonal, and nutritional risk factors (2). In the case of female athletes, it has been suggested that the stress and impact of strenuous exercise can weaken and fatigue the pelvic floor (1,2). RED-S has recently been shown to affect many systems of the body, including the neuromuscular system, exhibited as decreased muscle strength, decreased glycogen stores, and decreased endurance performance (3). Consequently, proper activation of the pelvic floor musculature may be affected in female athletes with RED-S. The female continence mechanism is determined by proper structure, function, and communication between the central and peripheral nervous systems, urothelium, detrusor and urethra muscle, and pelvic floor musculature. The urethral sphincter muscle contributes to the maximal closure of the sphincter during high-impact activities that load the bladder, such as jumping, running, or landing. As such, neuromuscular weakness of the urethral support closure mechanism can lead to involuntary urine leakage during physical exertion.
Stress urinary incontinence is the most prevalent PFD found in female athletes (1,2). The lack of energy available for proper skeletal muscle function during training and competition may result in muscle glycogen depletion, leading to pelvic floor neuromuscular fatigue, and poor intramuscular and intermuscular coordination. In elite female athletes, neuromuscular fatigue of the pelvic floor musculature was observed during strenuous training and sport competition (14). When the supporting connections of the pelvic floor are weakened through increases in mechanical loads and intraabdominal pressure, in addition to pelvic floor neuromuscular imbalances and fatigue, the urethral closure mechanism also may be adversely affected.
Vitamin D is a micronutrient essential for musculoskeletal health, strength, and function. Pelvic floor skeletal muscle efficiency, which is crucial for urethral function, may be compromised when vitamin D concentrations are deficient (9,14). Levator ani and external urethral sphincter muscles are both striated skeletal pelvic floor muscles whose cell nuclei contain the vitamin D receptor (15). Therefore, vitamin D insufficient concentrations likely could impact the contractility and function of the levator ani, extrinsic urethral sphincter, and external anal sphincter. However, available research examining the relationship between PFD and vitamin D nutritional status is still limited. One report found that the prevalence of urinary incontinence and pelvic floor disorders was significantly higher in women with vitamin D insufficiency (15). Others reported a similar trend for fecal incontinence, although these findings were not statistically significant (16).
The endocrine sequelae of RED-S, including hypothalamic dysfunction and menstrual irregularities, could be viewed as another predisposing factor for PFD in female athletes. Athletes with low-energy availability may experience alterations in normal sex hormone concentrations and function (17). It is well established that low-energy availability leads to menstrual cycle disruption, reproductive system suppression, and to functional hypothalamic amenorrhea in females (7). One of the effects of the functional disruption of pulsatile hypothalamic gonadotropin-releasing hormone secretion, which occurs in hypothalamic amenorrhea, is a decrease in systemic estrogen levels. In fact, estrogen receptors have been identified in all major supporting structures of the pelvic floor (18). Therefore, the hypoestrogenic state present in female athletes with RED-S, may increase the risk of PFD by influencing the connective tissue properties and the overall neuromuscular functionality of the pelvic floor.
The epidemiological profile of PFD and RED-S supports a relationship between the two clinical entities in female athletes. The underlying pathophysiology, including increased pressure on the pelvic floor structures with strenuous exercise, neuromuscular dysfunction related to muscle energy store depletion, and nervous system impairment, also supports an association (Fig.). PFD may have a negative impact on sports performance, and at the extreme, prematurely terminate a female athletes’ sports career. Sports medicine clinicians need to be aware of PFD and the proposed association with RED-S in female athletes in order to promote timely and effective evaluation and treatment. Future research should continue to explore this relationship.
The authors declare no conflict of interest and do not have any financial disclosures.
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