Improving the Diagnosis of Nonfunctional Overreaching and Overtraining Syndrome

Excessive exercise elicits poly (ADP-ribose) Polymerase-1 activation and global protein PARylation driving muscle dysfunction and performance impairment

Excessive exercise combined with inadequate recovery time may trigger fatigue, performance impairment, and ultimately the overtraining syndrome. The intramyocellular mechanisms involved in the overtraining syndrome remain only partially known. Here, we combined multi-omics analyses from isogenic BXD mouse strains with a mouse model of overtraining and excessive exercise protocol in mice and humans to evaluate the molecular mechanism involved in the performance impairment induced by excessive exercise. We identified that BXD mouse strains with elevated levels of Parp1 gene expression in the skeletal muscle displayed features like overtraining syndrome and abnormal muscle genetic signature. High PARP1 protein content and aberrant PARylation of proteins were detected in the skeletal muscle of overtrained, but not in trained mice. Overtraining syndrome reduced mitochondrial function promoted by exercise training, induced muscle hyperalgesia, reduced muscle fiber size and promoted a similar gene signature of myopathy and atrophy models. Short periods of excessive exercise also increased PARylation in the skeletal muscle of mice and healthy subjects. The pharmacological inhibition of PARP1, using Olaparib, and genetic Parp1 ablation, preserved muscle fiber morphology and protected against physical performance impairment and other symptoms of the overtraining syndrome in mice. In conclusion, PARP1 excessive activation is related to muscle abnormalities led by long or short periods of excessive exercise, and here we suggest that PARP1 is a potential target in the treatment and prevention of overtraining syndrome.

The return from underperformance to sustainable world-class level: A case study of a male cross-country skier

Purpose: To determine the main factors associated with unexpected underperformance and prospectively describe the holistic process of returning to sustainable world-class level in a male cross-country skier. Methods: Longitudinal training data was retrospectively analyzed across nine seasons (2012-2013 to 2020-2021), and categorized into training forms (endurance, strength, and speed), intensities [low- (LIT), moderate- (MIT), and high-intensity training (HIT)], and modes (specific and non-specific). Performance data was obtained from the International Ski and Snowboard Federation. Following two seasons of unexpected underperformance (2019-2020 and 2020-2021), the participant was prospectively followed in the process of returning to sustainable world-class level (2021-2022). Day-to-day training data and physiological tests were analyzed, and interviews with the participant and the head coach conducted. Results: Longitudinal training data from 2012-2013 to 2018-2019 demonstrated a non-linear 30% increase in total training volume (from 772 to 1,002 h), mainly caused by increased volume of ski-specific endurance training without changes in intensity distribution. Coincidingly, the participant gradually reached a world-class performance level. After two seasons of unexpected underperformance with relatively similar training volumes and intensity distributions as in the preceding seasons, the possible contributing factors were identified: lack of training periodization, limited monitoring and intensity control, particularly in connection with a "extreme" regime of training with low carbohydrate availability and days including two MIT sessions, as well as lack of systematic technique training and follow-up by coaches on a daily basis. Consequently, the return to world-class level included the introduction of a clear micro-cycle periodization, more systematic physiological monitoring and testing, more accurate intensity control, increased carbohydrate intake during and between sessions, as well as increased emphasize on technique training and an assistant coach present during day-to-day training. Conclusion: These longitudinal data describe the main factors leading to unexpected underperformance, in addition to providing unique insights into the corresponding process of returning to sustainable world-class level in a male cross-country skier. The holistic approach described in this case study may serve as a theoretical framework for future studies and practical work with underperforming endurance athletes.

Diagnosing Overtraining Syndrome: A Scoping Review

CONTEXT

Overtraining syndrome (OTS) is a condition characterized by a long-term performance decrement, which occurs after a persisting imbalance between training-related and nontraining-related load and recovery. Because of the lack of a gold standard diagnostic test, OTS remains a diagnosis of exclusion.

OBJECTIVE

To systematically review and map biomarkers and tools reported in the literature as potentially diagnostic for OTS.

DATA SOURCES

PubMed, Web of Science, and SPORTDiscus were searched from database inception to February 4, 2021, and results screened for eligibility. Backward and forward citation tracking on eligible records were used to complement results of database searching.

STUDY SELECTION

Studies including athletes with a likely OTS diagnosis, as defined by the European College of Sport Science and the American College of Sports Medicine, and reporting at least 1 biomarker or tool potentially diagnostic for OTS were deemed eligible.

STUDY DESIGN

Scoping review following the guidelines of the Joanna Briggs Institute and PRISMA Extension for Scoping Reviews (PRISMA-ScR).

LEVEL OF EVIDENCE

Level 4.

DATA EXTRACTION

Athletes' population, criteria used to diagnose OTS, potentially diagnostic biomarkers and tools, as well as miscellaneous study characteristics were extracted.

RESULTS

The search yielded 5561 results, of which 39 met the eligibility criteria. Three diagnostic scores, namely the EROS-CLINICAL, EROS-SIMPLIFIED, and EROS-COMPLETE scores (EROS = Endocrine and Metabolic Responses on Overtraining Syndrome study), were identified. Additionally, basal hormone, neurotransmitter and other metabolite levels, hormonal responses to stimuli, psychological questionnaires, exercise tests, heart rate variability, electroencephalography, immunological and redox parameters, muscle structure, and body composition were reported as potentially diagnostic for OTS.

CONCLUSION

Specific hormones, neurotransmitters, and metabolites, as well as psychological, electrocardiographic, electroencephalographic, and immunological patterns were identified as potentially diagnostic for OTS, reflecting its multisystemic nature. As exemplified by the EROS scores, combinations of these variables may be required to diagnose OTS. These scores must now be validated in larger samples and within female athletes.

The Athlete's Paradox: Adaptable Depression

We proposed that an athlete's depressive symptoms may be different from the general population in etiology if considered from the context of a depressive disorder. By shifting focus from a limited notion of symptoms onto a comprehensive model of depression, the full scope of the phenomenon becomes clearer. This paper investigated the relationship between neurotransmitters and allostatic load to explain the incidence of depression among elite athletes. This literature review extensively analyzed exercise-induced neurohormonal imbalance resulting in depressive states among athletes. The research revealed that 5-HTTLPR polymorphism, brain-derived neurotrophic factor (BDNF), extensive psychological demands, social stigma, and overtraining syndrome (OTS) may all contribute to a unique version of depression. The research revealed that the biological standards of athletes differ from those of non-athletes, to the point that the new model may be useful, thereby introducing the new term "Adaptable Depression (AD)" to the literature. This framework suggests a new direction for future research to precisely measure the neurotransmitter-related brain changes that result in "Adaptable Depression" in athletes and to establish a better understanding of the depressive tipping point.

The Role of Workload Management in Injury Prevention, Athletic, and Academic Performance in the Student-Athlete

ABSTRACT

Workload plays important roles in sports-related injury and athletic performance by influencing exposure to external injury risk factors and potential events, promoting changes in fitness level, which involves positive adaptations to training that may lead to improved performance, and/or stimulating fatigue which leads to negative effects in the body that may increase the risk of injury and negatively affect performance. In addition to the physical stress and significant time required for practice and training, student athletes also face subjective stressors. The total workload affects injury risk, but acute changes or spikes in external and/or internal loads seem to affect injury risk the most. These also may lead to poor recovery practices that may affect physical and academic performance. It is important for the medical team, coaches, parents, and the student athlete to understand the vulnerability of this population to increased amounts of workload and its positive and negative effects.

Overtraining Syndrome as a Complex Systems Phenomenon

The phenomenon of reduced athletic performance following sustained, intense training (Overtraining Syndrome, and OTS) was first recognized more than 90 years ago. Although hundreds of scientific publications have focused on OTS, a definitive diagnosis, reliable biomarkers, and effective treatments remain unknown. The present review considers existing models of OTS, acknowledges the individualized and sport-specific nature of signs/symptoms, describes potential interacting predisposing factors, and proposes that OTS will be most effectively characterized and evaluated via the underlying complex biological systems. Complex systems in nature are not aptly characterized or successfully analyzed using the classic scientific method (i.e., simplifying complex problems into single variables in a search for cause-and-effect) because they result from myriad (often non-linear) concomitant interactions of multiple determinants. Thus, this review 1) proposes that OTS be viewed from the perspectives of complex systems and network physiology, 2) advocates for and recommends that techniques such as trans-omic analyses and machine learning be widely employed, and 3) proposes evidence-based areas for future OTS investigations, including concomitant multi-domain analyses incorporating brain neural networks, dysfunction of hypothalamic-pituitary-adrenal responses to training stress, the intestinal microbiota, immune factors, and low energy availability. Such an inclusive and modern approach will measurably help in prevention and management of OTS.

Overtraining Syndrome (OTS) and Relative Energy Deficiency in Sport (RED-S): Shared Pathways, Symptoms and Complexities

The symptom similarities between training-overload (with or without an Overtraining Syndrome (OTS) diagnosis) and Relative Energy Deficiency in Sport (RED-S) are significant, with both initiating from a hypothalamic-pituitary origin, that can be influenced by low carbohydrate (CHO) and energy availability (EA). In this narrative review we wish to showcase that many of the negative outcomes of training-overload (with, or without an OTS diagnosis) may be primarily due to misdiagnosed under-fueling, or RED-S, via low EA and/or low CHO availability. Accordingly, we undertook an analysis of training-overload/OTS type studies that have also collected and analyzed for energy intake (EI), CHO, exercise energy expenditure (EEE) and/or EA. Eighteen of the 21 studies (86%) that met our criteria showed indications of an EA decrease or difference between two cohorts within a given study (n = 14 studies) or CHO availability decrease (n = 4 studies) during the training-overload/OTS period, resulting in both training-overload/OTS and RED-S symptom outcomes compared to control conditions. Furthermore, we demonstrate significantly similar symptom overlaps across much of the OTS (n = 57 studies) and RED-S/Female Athlete Triad (n = 88 studies) literature. It is important to note that the prevention of under-recovery is multi-factorial, but many aspects are based around EA and CHO availability. Herein we have demonstrated that OTS and RED-S have many shared pathways, symptoms, and diagnostic complexities. Substantial attention is required to increase the knowledge and awareness of RED-S, and to enhance the diagnostic accuracy of both OTS and RED-S, to allow clinicians to more accurately exclude LEA/RED-S from OTS diagnoses.

Analysis of human neutrophil phenotypes as biomarker to monitor exercise-induced immune changes

The amplitude of the innate immune response reflects the degree of physiological stress imposed by exercise load. An optimal balance of exercise intensity and duration is essential for a balanced immune system and reduces the risk of dysfunction of the immune system. Therefore, it is hypothesized that neutrophils, as key players in the innate immune system, can be used as biomarker in detecting overtraining. The aim was to monitor the state of the innate immune system by phenotyping neutrophils during consecutive bouts of prolonged exercise. Study subjects were recruited from a cohort of walkers participating in a walking event on 3 consecutive days. Participants with immune deficiencies were excluded. Questionnaires to determine the physiological status of the participants were completed. Analysis of neutrophil receptor expression was done by a point-of-care fully automated flow cytometer. A total of 45 participants were recruited, of whom 39 participants were included for data analysis. Study participants had a median age of 64 (58-70) years. The absolute numbers CD16^dim /CD62L^bright and CD16^bright /CD62L^dim neutrophils were increased after the first 2 days of exercise followed by an adaptation/normalization after the third day. Participants with activated neutrophils (high CD11b expression) had an impaired physical feeling indicated by the participant on a lower visual analog scale compared to participants who did not have activated neutrophils (P = 0.017, P = 0.022). Consecutive days of prolonged exercise results in an initial systemic innate immune response, followed by normalization/adaptation. Increased neutrophil activation was associated with impaired physical feeling measured by a validated VAS score indicated by the participant. Fully automated point-of-care flow cytometry analysis of neutrophil phenotypes in a field laboratory might be a useful tool to monitor relevant differences in the systemic innate immune response in response to exercise.

Effects of military training on plasma amino acid concentrations and their associations with overreaching

IMPACT STATEMENT

The diagnosis of overtraining syndrome and overreaching poses a great challenge. Military training aims at improving the physical performance of the conscripts, but an excessive training load could also lead to overreaching. This study of Finnish conscripts provides new insights into the pathophysiology of overreaching and overtraining through amino acids concentrations. In addition to confirming the possible use of plasma glutamine/glutamate concentration to indicate and predict overreaching, we made a novel finding, i.e. low alanine and arginine concentrations might have a role in performance decrement and fatigue related to overreaching. Moreover, this study is the first to show the possible association between amino acids with putative neuronal properties and overreaching. Thus, the present findings might help to detect and prevent overreaching and offer a reliable diagnostic approach. In order to avoid overreaching, military training should be planned more periodically and individually, especially during the first four weeks of military service.