Overtraining Syndrome as a Risk Factor for Bone Stress Injuries among Paralympic Athletes

ackground and Objectives:In this review, we have explored the relationship between over- training syndrome (OTS) and bone stress injuries among paralympic athletes. OTS is a complex condition that arises from an imbalance between training volume, nutrition, and recovery time, leading to significant negative effects on paralympic athlete’s performance and overall well-being. On the other hand, bone stress injuries occur when abnormal and repetitive loading is applied to normal bone, resulting in microdamage accumulation and potential. The prevalence of overtraining syndrome and bone stress injuries among athletes highlights the need for a better understanding of their relationship and implications for prevention and management strategies.Methods:A litera- ture review from the PubMed, Web of Science, and Google Scholar databases including the MeSH keywords “overtraining syndrome”, “bone”, and

is applied to normal bone, resulting in microdamage accumulation and potential. The prevalence of overtraining syndrome and bone stress injuries among athletes highlights the need for a better understanding of their relationship and implications for prevention and management strategies.Methods:A litera- ture review from the PubMed, Web of Science, and Google Scholar databases including the MeSH keywords “overtraining syndrome”, “bone”, and “paralympic athletes”.Results:Studies have consis- tently shown that athletes engaged in endurance sports are particularly susceptible to overtraining syndrome. The multifactorial nature of this condition involves not only physical factors, but also psychological and environmental determinants. In addition, the diagnosis and management of OTS and bone stress injuries present challenges in clinical practice.Conclusions:Currently, there are no definitive biochemical markers for overtraining syndrome. The diagnosis is based on a combination of subjective measures such as questionnaires, symptoms checklists, and objective biomarkers, in- cluding hormone levels, inflammatory markers, and imaging studies. However, these diagnostic approaches have limitations regarding their specificity and sensitivity. Keywords:overtraining syndrome; risk factor; bone stress injuries; paralympic athletes 1. Introduction Overtraining syndrome (OTS) and associated bone stress injuries are significant con- cerns among athletes, with a subsequent profound impact on their performance and overall health. OTS refers to a state of chronic fatigue and decreased performance resulting from an imbalance between training load, nutrition, and recovery time [1]. On the other hand, bone stress injuries are a common type of overuse injury characterized by the accumulation of microdamage in bone tissue due to repetitive loading [2]. The prevalence of OTS and bone stress injuries among athletes is a growing concern in the field of sports medicine. Currently, varying rates of overtraining syndrome have been reported, even up to 30% among young athletes. Additionally, around 10–20% of all sports medicine injuries were stress fractures. These conditions can have significant Medicina2024,60, 52.

Medicina2024,60, 52 2 of 11 consequences for athletes, leading to decreased performance, prolonged recovery periods, and even long-term health implications [1,2]. OTS can also affect paralympic athletes just as it can impact athletes in other sports. Paralympic athletes face unique challenges due to their disabilities, but the principles of overtraining and risk factors remain largely the same. Paralympic athletes often participate in intensive training programs to enhance their physical performance and excel in their respective sports. However, when the training load exceeds the body’s ability to recover, OTS can occur. Diagnosing OTS can be challenging as it involves a combination of subjective and objective measures. There is no specific medical test that can definitively diagnose OTS. Instead, healthcare professionals rely on a comprehensive evaluation of an athlete’s symptoms, training history, and performance changes. Detailed understanding of the relationship between OTS and bone stress injuries is crucial for the development of effective prevention and management strategies. The interplay between training load, energy availability, hormonal imbalances, genetic fac- tors, neuromuscular control, biomechanics, inflammatory markers, and psychosocial fac- tors has been explored as they are potential contributors to the development of both conditions [3–6]. In this review article, our aim was to contribute to the body of knowl- edge surrounding OTS as a risk factor for bone stress injuries among paralympic athletes by encompassing risk factors, mechanism of action explanations, diagnostic possibili- ties, and prevention strategies. Due to the nature and classification of paralympic ath- letes there are high possibilities of overtraining in disability compensation compared to non-paralympic athletes. 2. Methods A literature review from the PubMed, Web of Science, and Google Scholar databases including the MeSH (Medical Subject Headings) keywords “overtraining syndrome”, “bone”, and “paralympic athletes” has been made. Out of 37 found papers, we included 28 papers in the English language with full-text availability covering the last 20 years (from 2003 to 2023). 3. Risk Factors and their Mechanism of Action Age has been identified as an intrinsic factor that may influence an athlete’s risk of developing OTS. Younger athletes are often more susceptible due to their higher training intensities and

found papers, we included 28 papers in the English language with full-text availability covering the last 20 years (from 2003 to 2023). 3. Risk Factors and their Mechanism of Action Age has been identified as an intrinsic factor that may influence an athlete’s risk of developing OTS. Younger athletes are often more susceptible due to their higher training intensities and inadequate recovery periods [1]. However, the role of age as a risk factor for OTS remains controversial. While some studies suggested that younger athletes are at higher risk [7], others did not report a significant association between age and the incidence of OTS [8]. Gender is another important intrinsic factor that appears to influence the prevalence of OTS among athletes. Females have been found to be at a higher risk compared to males [1]. Hormonal fluctuations throughout the menstrual cycle may contribute to this increased vulnerability among women. For example, estrogen levels during certain phases of the menstrual cycle have been associated with decreased exercise performance and increased fatigue [9]. Armento et al. investigated gender differences in physiological responses to training load among endurance runners and found that female athletes exhibited different patterns of hormonal responses compared to males during periods of high training load. This highlights the importance of considering gender-specific factors when studying overtraining syndrome and bone stress injuries [4]. A medical history of previous injury has also been suggested as a potential risk factor for developing OTS. Athletes with previous injuries may have altered movement patterns or imbalances that can contribute to overuse and overtraining [1]. However, there is limited research that specifically examines the relationship between previous injury history and OTS incidence. Extrinsic factors related to training volume/intensity, recovery periods, and nutri- tion are crucial contributors to the risk of developing OTS in an athlete. A high training

Medicina2024,60, 52 3 of 11 volume/intensity without adequate recovery periods is a common cause of OTS [1]. Nu- merous studies have emphasized the importance of periodization in training programs by incorporating appropriate rest periods [10,11]. OTS is a complex condition influenced by various intrinsic and extrinsic factors that can increase an athlete’s susceptibility to its development. 3.1. Inflammatory Cytokines In recent years, there has been an emerging interest in investigating the role of inflam- matory markers in the pathogenesis of OTS and bone stress injuries among athletes [3,5]. Inflammation plays a crucial role in tissue repair processes, but excessive or prolonged inflammation may contribute to tissue damage, highlighting the potential role of inflam- matory cytokines, such as interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and C-reactive protein (CRP), in OTS. Studies have proposed that elevated levels of these mark- ers may contribute to the development of fatigue, muscle damage, and impaired immune function commonly observed in athletes with OTS. Schwellnus et al. discussed the possible involvement of inflammation in bone stress injuries among athletes. They suggested that pro-inflammatory cytokines and chemokines released during repetitive loading can lead to an imbalance between bone resorption and formation processes, ultimately increasing the risk of stress fractures [3]. Furthermore, it was thoroughly described how IL-6 and other pro-inflammatory cytokines stimulate osteoblasts to express receptor activator of nuclear factor kappa-B ligand (RANKL), which then binds to receptor activator of nuclear factor kappa-B (RANK) in osteoclasts, leading to the stimulation of bone resorption [12]. Although these studies provided information on the potential role of inflammation in both OTS and bone stress injuries, further research is needed to elucidate the underlying mechanisms and establish causality. 3.2. Genetic Factors Genetic factors have also been implicated as potential contributors to individual susceptibility to OTS and bone stress injuries. Tenforde et al. discussed the importance of neuromuscular control in preventing excessive loading on bones and highlighted the potential benefits of targeted strength training programs to improve neuromuscular func- tion [5]. Furthermore, investigating potential genetic factors that influence susceptibility to OTS could provide valuable information on individual variations in response to training

individual susceptibility to OTS and bone stress injuries. Tenforde et al. discussed the importance of neuromuscular control in preventing excessive loading on bones and highlighted the potential benefits of targeted strength training programs to improve neuromuscular func- tion [5]. Furthermore, investigating potential genetic factors that influence susceptibility to OTS could provide valuable information on individual variations in response to training loads. Understanding genetic predispositions may help identify athletes at higher risk for developing OTS or bone stress injuries. Several genetic variations have been investigated for their potential association with overtraining-related outcomes such as fatigue resistance, muscle damage markers, and in- flammatory responses. For example, polymorphisms in genes related to collagen synthesis, such as COL5A1 and COL1A1, have been studied in the context of OTS and bone stress injuries. However, the specific genetic factors that contribute to the risk of OTS are still not well understood, and more research is required to elucidate their role [13,14]. 3.3. Nutritional Deficiencies and Energy Availability Nutritional deficiencies or imbalances can significantly impact an athlete’s susceptibil- ity to both OTS and bone stress injuries. Inadequate energy intake, particularly low energy availability (LEA), has emerged as a significant risk factor for the development of both con- ditions [15]. LEA occurs when an athlete’s energy intake does not meet the energy demands of training and normal physiological functions, leading to negative consequences on vari- ous body systems including hormonal regulation, immune function, metabolic processes, and bone health [15,16]. Studies have shown that athletes with LEA are at increased risk for developing both OTS and bone stress injuries [4,5]. Cupka and Sedliak reviewed the impact of low energy availability on the performance and testosterone levels of male endurance athletes. This metabolic disturbance can contribute to the onset of OTS symptoms [17]. Energy availability refers to the amount of dietary energy intake available for physiological

Medicina2024,60, 52 4 of 11 functions after accounting for energy expended during exercise. It is influenced by factors such as caloric intake, exercise expenditure, thermoregulation, growth, repair processes, and reproductive function [15]. The balance between energy intake and expenditure is crucial to maintaining optimal health and performance among athletes. This imbalance can have significant consequences for various physiological systems in the body. In the context of athletics, low energy availability often arises from intentional or unintentional restrictions in food intake due to concerns about body weight or composition [16]. The influence of energy availability, a key component in the development of OTS, has also been explored in relation to bone stress injuries. Low energy availability can lead to a condition known as relative energy deficiency in sport (RED-S), characterized by hormonal imbalances, impaired bone health, and increased risk of injury [5]. Mountjoy et al. proposed that RED-S encompasses a range of adverse health outcomes resulting from inade- quate energy availability, including suppression of metabolic rates, menstrual disturbances in women, decreased testosterone levels in men, impaired bone health, cardiovascular dysfunction, immunological impairments, psychological disturbances, gastrointestinal problems, hematological abnormalities, and impaired growth and development in ado- lescents [15]. Several studies have examined the association between RED-S/LEA and an increased risk of bone stress injuries among athletes. A narrative review by Hamstra- Wright et al. highlighted the importance of a holistic approach to monitoring training load in relation to bone stress injuries. The authors emphasized the need for a personalized assessment that considers individual risk factors and cumulative risks associated with the training load capacity [18]. The relationship between low energy availability and bone health has been extensively studied. LEA can disrupt hormonal balance, leading to menstrual irregularities in female athletes and decreased testosterone levels in male athletes [16]. These hormonal changes can have detrimental effects on bone health, resulting in decreased bone mineral density and increased susceptibility to fractures [15]. In a study by Tenforde et al., female college distance runners with LEA were found to have significantly lower bone mineral density in the lumbar spine compared to their counterparts with normal

testosterone levels in male athletes [16]. These hormonal changes can have detrimental effects on bone health, resulting in decreased bone mineral density and increased susceptibility to fractures [15]. In a study by Tenforde et al., female college distance runners with LEA were found to have significantly lower bone mineral density in the lumbar spine compared to their counterparts with normal EA. Furthermore, LEA can affect bone remodeling processes by affecting both osteoblasts and osteoclast activity [5]. Armento et al. discussed how LEA may lead to decreased osteoblast function through alterations in insulin-like growth factor-1 (IGF-1), estrogen levels, leptin signaling pathways, and mechanical loading responses. Furthermore, reduced estrogen concentrations resulting from LEA can enhance osteoclast activity, leading to excessive bone resorption [4]. Carbohydrate intake predicts quick hormonal responses to stress and improves ex- plosion responses during exercise when above 5.0 g/kg/day, higher carbohydrate intake stimulates chronic growth hormone release (despite its acute suppressive effects); to- gether, carbohydrate and protein intake predicted the late prolactin response (30 min after hypoglycemia), muscle recovery speed was directly predicted by overall calorie intake, regardless of the proportion of macronutrients, protein intake prevents body and visceral fat accumulation and increases basal metabolism rate when above 1.6 g/kg/day, sleep patterns are the major determinants of mood states, and excessive concurrent physical and cognitive effort decreases fat oxidation, increases muscle catabolism, and impairs libido [19]. 3.4. Psychological and Psychosocial Factors Although the role of physical factors in OTS has been extensively studied, there is growing recognition of the importance of psychological factors in its development among athletes. Psychosocial factors have also gained attention as potential contributors to both OTS and bone stress injuries among athletes. Psychological stressors associated with high-performance sports may impact an athlete’s risk of these conditions through various mechanisms, including altered immune function, disrupted sleep patterns, or maladaptive coping strategies [6]. OTS is a complex condition that arises from an imbalance between training load, nutrition, and recovery time. It is characterized by a decrease in training

conditions through various mechanisms, including altered immune function, disrupted sleep patterns, or maladaptive coping strategies [6]. OTS is a complex condition that arises from an imbalance between training load, nutrition, and recovery time. It is characterized by a decrease in training

Medicina2024,60, 52 5 of 11 performance and persistent fatigue, which can have detrimental effects on an athlete’s physical and mental well-being. This section aims to dive into the physiological changes associated with OTS by incorporating additional research studies [1]. Psychological stressors have been identified as crucial contributors to the onset and progression of OTS. These stressors can arise from multiple sources such as training de- mands, competition pressure, personal life stressors, and perfectionistic tendencies. The review highlights how these stressors can lead to increased levels of anxiety and depres- sion symptoms among athletes with OTS. However, it is important to note that not all athletes who experience high levels of psychological distress develop OTS. This suggests that individual differences play a role in determining susceptibility to OTS [1]. To gain a deeper understanding of the relationship between psychological factors and OTS, recent research has proposed approaching OTS as a complex system phenomenon. This perspective acknowledges the intricate interactions between various biological systems involved in OTS development. Authors have suggested employing techniques like tran- somics analyses and machine learning for comprehensive evaluation of individuals with suspected or diagnosed OTS. They have also highlighted that future research should focus on the analysis of brain neural networks in relation to the prevention and management of OTS. Neuroimaging studies could provide information on how prolonged exposure to psychological stress affects brain structure and function among athletes with, or at risk of developing, OTS. Furthermore, investigating hypothalamic–pituitary–adrenal responses to stress may elucidate hormonal imbalances associated with excessive training loads and inadequate recovery periods in athletes prone to developing OTS. Although psychological interventions have shown promise in managing various mental health conditions among athletes, their effectiveness specifically in preventing or managing OTS remains an area that needs further exploration. Valovich McLeod et al. suggest that cognitive behavior therapy (CBT) and stress management techniques could be valuable approaches to address psychological distress associated with OTS [20]. As pointed out by Maccagnano at al., for shoulder arthroplasty it is very important to perform a psychological analysis of each patient in order to choose the appropriate treatment [21]. This

needs further exploration. Valovich McLeod et al. suggest that cognitive behavior therapy (CBT) and stress management techniques could be valuable approaches to address psychological distress associated with OTS [20]. As pointed out by Maccagnano at al., for shoulder arthroplasty it is very important to perform a psychological analysis of each patient in order to choose the appropriate treatment [21]. This rule can also be applied to injured paralympic athletes. Psychological factors play a significant role in the development of overtraining syn- drome among athletes. Psychological stressors arising from training demands, competition pressure, and stressors of personal life can contribute to increased levels of anxiety and depression symptoms among individuals with OTS. Recent research suggests approach- ing OTS as a complex system phenomenon that involves interactions between multiple biological systems. 3.5. Hormonal Status, Oxidative Stress, and Immune System Hormonal imbalances play an important role in the pathophysiology of OTS. Cade- giani and Kater conducted a study investigating the predictive value of basal hormones in male athletes with OTS. Their findings revealed lower levels of testosterone and higher levels of estradiol in athletes with OTS compared to healthy individuals. These hormonal alterations may contribute to the fatigue and decreased performance observed in OTS [22]. Immune system dysfunction has been identified as a contributing factor to both OTS and bone stress injuries. Schwellnus et al. discussed the relationship between the training load in sports and the risk of illness and overtraining. They highlighted that excessive training load can lead to immunosuppression, making athletes more susceptible to infections and other immune-related disorders. This compromised immune function may further exacerbate fatigue symptoms and impair the ability of an athlete to recover [3]. Collectively, exploring the physiology and mechanisms underlying overtraining syn- drome is crucial to unraveling its complexities. Hormonal imbalances such as altered testosterone–estradiol ratios have been observed in individuals with OTS. Oxidative stress resulting from the production of reactive oxygen species in exercise can contribute to fa- tigue symptoms seen in athletes with OTS. Inflammation and immune system dysfunction

unraveling its complexities. Hormonal imbalances such as altered testosterone–estradiol ratios have been observed in individuals with OTS. Oxidative stress resulting from the production of reactive oxygen species in exercise can contribute to fa- tigue symptoms seen in athletes with OTS. Inflammation and immune system dysfunction

The article reviews overtraining syndrome as a risk factor for bone stress injuries in paralympic athletes.