Part I: Relationship among Training Load Management, Salivary Immunoglobulin A, and Upper Respiratory Tract Infection in Team Sport: A Systematic Review

The Role of Biomarkers in Monitoring Chronic Fatigue Among Male Professional Team Athletes: A Systematic Review

This systematic review synthesizes evidence on biomarker responses to physiological loads in professional male team sport athletes, providing insights into induced fatigue states. Structured searches across major databases yielded 28 studies examining various biomarkers in elite team sport players. Studies evaluated muscle damage markers, anabolic/catabolic hormones reflecting metabolic strain, inflammatory markers indicating immune activity and tissue damage, immunological markers tied to infection risk, and oxidative stress markers showing redox imbalances from excessive physiological load. Responses were examined in official matches and training across competitive seasons. The evidence shows that professional team sports induce significant alterations in all studied biomarkers, reflecting measurable physiological strain, muscle damage, oxidative stress, inflammation, and immunosuppression during intensive exercise. These effects tend to be larger and more prolonged after official matches compared to training. Reported recovery time courses range from 24-h to several days post-exercise. Monitoring biomarkers enables quantifying cumulative fatigue and physiological adaptations to training/competition loads, helping to optimize performance while mitigating injury and overtraining. Key biomarkers include creatine kinase, testosterone, cortisol, testosterone/cortisol ratio, salivary immunoglobulin-A, and markers of inflammation and oxidative stress. Further research should extend biomarker monitoring to cover psychological stress and affective states alongside physiological metrics for deeper insight into athlete wellness and readiness.

Vertebral Subluxation and Systems Biology: An Integrative Review Exploring the Salutogenic Influence of Chiropractic Care on the Neuroendocrine-Immune System

In this paper we synthesize an expansive body of literature examining the multifaceted influence of chiropractic care on processes within and modulators of the neuroendocrine-immune (NEI) system, for the purpose of generating an inductive hypothesis regarding the potential impacts of chiropractic care on integrated physiology. Taking a broad, interdisciplinary, and integrative view of two decades of research-documented outcomes of chiropractic care, inclusive of reports ranging from systematic and meta-analysis and randomized and observational trials to case and cohort studies, this review encapsulates a rigorous analysis of research and suggests the appropriateness of a more integrative perspective on the impact of chiropractic care on systemic physiology. A novel perspective on the salutogenic, health-promoting effects of chiropractic adjustment is presented, focused on the improvement of physical indicators of well-being and adaptability such as blood pressure, heart rate variability, and sleep, potential benefits that may be facilitated through multiple neurologically mediated pathways. Our findings support the biological plausibility of complex benefits from chiropractic intervention that is not limited to simple neuromusculoskeletal outcomes and open new avenues for future research, specifically the exploration and mapping of the precise neural pathways and networks influenced by chiropractic adjustment.

Immunosurveillance associated with upper respiratory symptoms in elite swimmers: The 8-month period leading into Commonwealth Games

OBJECTIVES

To monitor individual mucosal immunity and identify potential risk factors of upper respiratory symptoms in elite swimmers over a competitive season.

DESIGN

Eight-month longitudinal study, observing mucosal immunity, Epstein-Barr virus status, training loads and illness symptoms of elite international swimmers, leading into the Commonwealth Games 2018.

METHODS

Participants were fourteen elite swimmers (age ± standard deviation = 19.9 ± 0.8 years, height = 178.9 ± 6.3 cm, and mass = 75.0 ± 7.7 kg). Self-reported upper respiratory symptoms, training load and saliva samples were collected weekly. Venous blood samples were taken at study commencement to determine Epstein-Barr virus status.

RESULTS

Throughout the study, 70 episodes of upper respiratory symptoms were recorded resulting in 34 days of missed training. Incidence (p = 0.001), severity (p = 0.022), and duration of upper respiratory symptoms (p = 0.001) were significantly higher during high training loads, compared to low. Eight swimmers (61 %) had evidence of past infection with Epstein-Barr virus, but this had no relationship with incidence, severity, or duration of upper respiratory symptoms (p > 0.05). Relative individual salivary immunoglobulin A concentration was 12 % lower when upper respiratory symptoms were present but was not statistically significant (p = 0.101).

CONCLUSIONS

This study highlights the importance of individual athlete monitoring, to identify swimmers at increased illness risk. Identification of possible risk factors for upper respiratory symptoms, such as increased training load, may allow for modifications in training or other illness preventative strategies for elite swimmers.

Does elite European match-play affect salivary immunoglobulin-A and cortisol in soccer players? The influence of playing status and match outcome

Introduction: The aims of this study were to: a) investigate salivary immunoglobulin A (s-IgA) and cortisol (s-Cort) responses to nine competitive fixtures in starting and non- starting soccer players; and b) compare s-IgA and s-Cort responses of starters and non-starters considering match outcome. Methods: Saliva from 19 male outfield players from an elite soccer team (mean ± SD, age 26 ± 4 years; weight 80.5 ± 8.1 kg; height 1.83 ± 0.07 m; body-fat 10.8% ± 0.7%) was collected. Saliva samples were taken on the day before each match (MD-1), 60-min before kick-off (MDpre), 30-min post-match (MDpost), and 72-h post-match (MD+3). There were five wins, one draw and three losses. Results: The mean s-IgA value was found to be significantly lower at MD+3 compared to MDpre and MDpost. s-Cort was significantly higher at MDpost compared to MD-1 and MDpre. When compared to MDpre, a statistically significant decrease in s-Cort was observed at MD+3 compared to MDpost. Starters displayed higher s-Cort values across the nine matches. There was a significant group-by-time interaction for s-Cort. There was a significant increase in s-Cort levels at MDpost compared to MD-1 and from MDpre to MDpost in starting players. At MDpost, starters had significantly higher s-Cort values. s-IgA values of starting and non- starting players following successful and unsuccessful matches did not reveal a significant difference. However, similar analysis of s-Cort in successful matches showed a significant difference between starters and non-starters. s-IgA values at MD-1, MDpre, MDpost and MD+3 in starters and non-starters following successful and unsuccessful matches revealed significant differences at MDpre and MDpost in starters, respectively. Furthermore, s-Cort values at MD-1, MDpre, MDpost and MD+3 in starters and non-starters in successful and unsuccessful matches revealed significant differences at MD+3 in starting players. Discussion: The present study suggests that in elite level soccer players, both starting status and match outcome influence s-IgA and s-Cort responses, particularly starters. Specifically, s-IgA was lower for starters before and after the match following successful outcomes. Moreover, higher s-Cort values were found before the match while lower values occurred after the match for starters in successful matches.

Biomarkers of post-match recovery in semi-professional and professional football (soccer)

High-level football (soccer) players face intense physical demands that result in acute and residual fatigue, impairing their physical performance in subsequent matches. Further, top-class players are frequently exposed to match-congested periods where sufficient recovery times are not achievable. To evaluate training and recovery strategies, the monitoring of players' recovery profiles is crucial. Along with performance and neuro-mechanical impairments, match-induced fatigue causes metabolic disturbances denoted by changes in chemical analytes that can be quantified in different body fluids such as blood, saliva, and urine, thus acting as biomarkers. The monitoring of these molecules might supplement performance, neuromuscular and cognitive measurements to guide coaches and trainers during the recovery period. The present narrative review aims to comprehensively review the scientific literature on biomarkers of post-match recovery in semi-professional and professional football players as well as provide an outlook on the role that metabolomic studies might play in this field of research. Overall, no single gold-standard biomarker of match-induced fatigue exists, and a range of metabolites are available to assess different aspects of post-match recovery. The use of biomarker panels might be suitable to simultaneously monitoring these broad physiological processes, yet further research on fluctuations of different analytes throughout post-match recovery is warranted. Although important efforts have been made to address the high interindividual heterogeneity of available markers, limitations inherent to these markers might compromise the information they provide to guide recovery protocols. Further research on metabolomics might benefit from evaluating the long-term recovery period from a high-level football match to shed light upon new biomarkers of post-match recovery.

Relationship between Training Load Management and Immunoglobulin A to Avoid Immunosuppression after Soccer Training and Competition: A Theoretical Framework Based on COVID-19 for Athletes' Healthcare

Immunoglobulin A (IgA), which is the main effector against upper respiratory tract viruses such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been related to training load management. The aim of this systematic review was to establish the relationship between training load and salivary IgA based on current evidence in order to avoid immunosuppression after exercise and players´ vulnerability to virus contagion. A systematic review of relevant articles was carried out using two electronic databases (PubMed and Web of Science) until 19 May 2021. From a total of 127 studies initially found, 23 were included in the qualitative synthesis. These studies were clustered depending on stress level. The salivary IgA was analysed considering soccer-specific treadmill exercise and repeated sprint drills (n = 5), matches (n = 7), and during certain periods during the season or pre-season (n = 11). Repeated sprint ability tests and treadmill exercises are suitable exercises for the first steps on return to play periods yet still maintain social distance. A rest or moderate training sessions (technical/tactical) are suggested after official matches to ensure 16-18 h to recover IgA levels, while periods with multiple matches per week with limited recovery time should be avoided. Weekly training load should assume a small increment (<10%) to ensure IgA immune responses, especially, during the post coronavirus disease 2019 (COVID-19) season.