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Dudley C, Johnston R, Jones B, Till K, Westbrook H, Weakley J. Methods of Monitoring Internal and External Loads and Their Relationships with Physical Qualities, Injury, or Illness in Adolescent Athletes: A Systematic Review and Best-Evidence Synthesis. Sports Med 2023; 53:1559-1593. [PMID: 37071283 PMCID: PMC10356657 DOI: 10.1007/s40279-023-01844-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/19/2023] [Indexed: 04/19/2023]
Abstract
BACKGROUND With the increasing professionalisation of youth sports, training load monitoring is increasingly common in adolescent athletes. However, the research examining the relationship between training load and changes in physical qualities, injury, or illness in adolescent athletes is yet to be synthesised in a systematic review. OBJECTIVE The aim of this review was to systematically examine the research assessing internal and external methods of monitoring training load and physical qualities, injury, or illness in adolescent athletes. METHODS Systematic searches of SPORTDiscus, Web of Science, CINAHL and SCOPUS were undertaken from the earliest possible records to March 2022. Search terms included synonyms relevant to adolescents, athletes, physical qualities, injury, or illness. To be eligible for inclusion, articles were required to (1) be original research articles; (2) be published in a peer-reviewed journal; (3) include participants aged between 10 and 19 years and participating in competitive sport; (4) report a statistical relationship between a measure of internal and/or external load and physical qualities, injury or illness. Articles were screened and assessed for methodological quality. A best-evidence synthesis was conducted to identify trends in the relationships reported. RESULTS The electronic search yielded 4125 articles. Following screening and a review of references, 59 articles were included. The most commonly reported load monitoring tools were session ratings of perceived exertion (n = 29) and training duration (n = 22). Results of the best-evidence synthesis identified moderate evidence of positive relationships between resistance training volume load and improvement in strength, and between throw count and injury. However, evidence for other relationships between training load and change in physical qualities, injury, or illness were limited or inconsistent. CONCLUSIONS Practitioners should consider monitoring resistance training volume load for strength training. Additionally, where appropriate, monitoring throw counts may be useful in identifying injury risk. However, given the lack of clear relationships between singular measures of training load with physical qualities, injury, or illness, researchers should consider multivariate methods of analysing training load, as well as factors that may mediate the load-response relationship, such as maturation.
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Affiliation(s)
- Charles Dudley
- School of Behavioural and Health Sciences, Australian Catholic University, Banyo Campus, Brisbane, Australia.
- St Joseph's Nudgee College, Boondall, Brisbane, Australia.
| | - Rich Johnston
- School of Behavioural and Health Sciences, Australian Catholic University, Banyo Campus, Brisbane, Australia
- Carnegie Applied Rugby Research (CARR) Centre, Carnegie School of Sport, Leeds Beckett University, Leeds, UK
| | - Ben Jones
- Carnegie Applied Rugby Research (CARR) Centre, Carnegie School of Sport, Leeds Beckett University, Leeds, UK
- Health through Physical Activity, Lifestyle and Sport Research Centre (HPALS), Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
- Premiership Rugby, London, UK
- Leeds Rhinos Rugby League Club, Leeds, UK
- England Performance Unit, The Rugby Football League, Leeds, UK
| | - Kevin Till
- Carnegie Applied Rugby Research (CARR) Centre, Carnegie School of Sport, Leeds Beckett University, Leeds, UK
- Leeds Rhinos Rugby League Club, Leeds, UK
| | | | - Jonathon Weakley
- School of Behavioural and Health Sciences, Australian Catholic University, Banyo Campus, Brisbane, Australia
- Carnegie Applied Rugby Research (CARR) Centre, Carnegie School of Sport, Leeds Beckett University, Leeds, UK
- Sports Performance, Recovery, Injury and New Technologies (SPRINT) Research Centre, Australian Catholic University, Brisbane, Australia
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Baker C, Hunt J, Piasecki J, Hough J. Lymphocyte and dendritic cell response to a period of intensified training in young healthy humans and rodents: A systematic review and meta-analysis. Front Physiol 2022; 13:998925. [PMID: 36439269 PMCID: PMC9691956 DOI: 10.3389/fphys.2022.998925] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Accepted: 10/14/2022] [Indexed: 01/25/2023] Open
Abstract
Background: Intensified training coupled with sufficient recovery is required to improve athletic performance. A stress-recovery imbalance can lead to negative states of overtraining. Hormonal alterations associated with intensified training, such as blunted cortisol, may impair the immune response. Cortisol promotes the maturation and migration of dendritic cells which subsequently stimulate the T cell response. However, there are currently no clear reliable biomarkers to highlight the overtraining syndrome. This systematic review and meta-analysis examined the effect of intensified training on immune cells. Outcomes from this could provide insight into whether these markers may be used as an indicator of negative states of overtraining. Methods: SPORTDiscus, PUBMED, Academic Search Complete, Scopus and Web of Science were searched until June 2022. Included articles reported on immune biomarkers relating to lymphocytes, dendritic cells, and cytokines before and after a period of intensified training, in humans and rodents, at rest and in response to exercise. Results: 164 full texts were screened for eligibility. Across 57 eligible studies, 16 immune biomarkers were assessed. 7 were assessed at rest and in response to a bout of exercise, and 9 assessed at rest only. Included lymphocyte markers were CD3+, CD4+ and CD8+ T cell count, NK cell count, NK Cytolytic activity, lymphocyte proliferation and CD4/CD8 ratio. Dendritic cell markers examined were CD80, CD86, and MHC II expression. Cytokines included IL-1β, IL-2, IL-10, TNF-α and IFN-γ. A period of intensified training significantly decreased resting total lymphocyte (d= -0.57, 95% CI -0.30) and CD8+ T cell counts (d= -0.37, 95% CI -0.04), and unstimulated plasma IL-1β levels (d= -0.63, 95% CI -0.17). Resting dendritic cell CD86 expression significantly increased (d = 2.18, 95% CI 4.07). All other biomarkers remained unchanged. Conclusion: Although some biomarkers alter after a period of intensified training, definitive immune biomarkers are limited. Specifically, due to low study numbers, further investigation into the dendritic cell response in human models is required.
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Affiliation(s)
- Carla Baker
- SHAPE Research Centre, Department of Sport Science, Nottingham Trent University, Nottingham, United Kingdom,*Correspondence: Carla Baker,
| | - John Hunt
- Medical Technologies Innovation Facility, Nottingham Trent University, Nottingham, United Kingdom
| | - Jessica Piasecki
- SHAPE Research Centre, Department of Sport Science, Nottingham Trent University, Nottingham, United Kingdom
| | - John Hough
- SHAPE Research Centre, Department of Sport Science, Nottingham Trent University, Nottingham, United Kingdom
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Silva SEF, Bernaciková M, Svobodová L, Janíková M, Junior HS, Paludo AC. DESCRIPTION OF A SCHOOL SPORTS TRAINING PROGRAM FOR NOVICE GYMNASTS: THE LOAD DISTRIBUTION AND WELLBEING RESPONSES. SCIENCE OF GYMNASTICS JOURNAL 2022. [DOI: 10.52165/sgj.14.3.323-333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The description of the training program structure and the measurement of dose-response for novice gymnasts at the scholarly level is still not elucidated in the literature. The study aimed to describe a rhythmic gymnastics training program for novices and to examine their perceptions of training load and wellbeing. Eight Brazilian gymnasts (10.6±0.5 years old), from a specific school, participated in a training program that lasted 26 weeks, and was separated into general preparation (1), specific preparation (2), intensification (3), tapering (4), competitive (5), and transitioning (6) phases. In each session, wellbeing and the internal training load (ITL) were measured by a Likert scale. The comparison of wellbeing and ITL during the program was performed by repeated-measure tests, with a significance of p< 0.05. A significant difference in ITL amongst the phases was found (x2= 110, p<0.001), with Phases 3, 4, and 5 presenting higher values compared to 2 and 6. Phase 6 had lower ITL compared to 2. Higher values of wellbeing were described during the program, however, Phase 6 presented a significantly higher score compared to Phases 2 and 5 (x2= 12.0, p=0.018). In conclusion, the rhythmic gymnastics training program developed for novice scholar participants seems to be adequate in terms of structure and training load distribution. In addition to the gymnasts reporting higher overall wellbeing during the program, attention should be paid to the competitive week, to avoid a decrease in wellbeing and possible negative effects on the gymnasts’ performance.
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Alkemade P, Gerrett N, Daanen HAM, Eijsvogels TMH, Janssen TWJ, Keaney LC. Heat acclimation does not negatively affect salivary immunoglobulin-A and self-reported illness symptoms and wellness in recreational athletes. Temperature (Austin) 2022; 9:331-343. [PMID: 36339091 PMCID: PMC9629114 DOI: 10.1080/23328940.2022.2088029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Heat acclimation (HA) protocols repeatedly expose individuals to heat stress. As HA is typically performed close to the pinnacle event, it is essential that the protocol does not compromise immune status, health, or wellbeing. The purpose of this study was to examine the effect of HA on resting salivary immunoglobulin-A (s-IgA) and salivary cortisol (s-cortisol), self-reported upper-respiratory tract symptoms, and self-reported wellness parameters. Seventeen participants (peak oxygen uptake 53.2 ± 9.0 mL·kg−1·min−1) completed a 10-day controlled-hyperthermia HA protocol, and a heat stress test both before (HST1) and after (HST2) HA (33°C, 65% relative humidity). Resting saliva samples were collected at HST1, day 3 and 7 of the HA protocol, HST2, and at 5 ± 1 days post-HA. Upper-respiratory tract symptom data were collected weekly from one week prior to HA until three weeks post HA, and wellness ratings were reported daily throughout HA. HA successfully induced physiological adaptations, with a lower end-exercise rectal temperature and heart rate and higher whole-body sweat rate at HST2 compared to HST1. In contrast, resting saliva flow rate, s-IgA concentration, s-cortisol concentration, and s-cortisol secretion rate remained unchanged (n = 11–14, P = 0.10–0.48). Resting s-IgA secretion rate increased by 39% from HST1 to HST2 (n = 14, P = 0.03). No changes were observed in self-reported upper respiratory tract symptoms and wellness ratings. In conclusion, controlled-hyperthermia HA did not negatively affect resting s-IgA and s-cortisol, self-reported upper-respiratory tract symptoms, and self-reported wellness parameters in recreational athletes.
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Affiliation(s)
- Puck Alkemade
- Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands
| | - Nicola Gerrett
- Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands
- Gentherm, Northville, MI, USA
| | - Hein A. M. Daanen
- Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands
| | - Thijs M. H. Eijsvogels
- Radboud Institute for Health Sciences, Department of Physiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Thomas W. J. Janssen
- Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands
| | - Lauren C. Keaney
- Sports Performance Research Institute New Zealand, Auckland University of Technology, Auckland, New Zealand
- Defence Technology Agency, New Zealand Defence Force, Auckland, New Zealand
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Batista EDS, Ribeiro BLL, Leite Galvão-Coelho N, Almeida RND, Teixeira RV, Silveira JCD, Ferreira ABDM, Mortatti AL. Effects of Training Loads on Stress Tolerance and Mucosal Immunity in High-Intensity Functional Fitness Athletes. RESEARCH QUARTERLY FOR EXERCISE AND SPORT 2022:1-10. [PMID: 35416755 DOI: 10.1080/02701367.2021.2011828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Accepted: 11/21/2021] [Indexed: 06/14/2023]
Abstract
Purpose: This study aimed to analyze the effects of training load on stress tolerance (ST) and secretory immunoglobulin A (SIgA) in male and female high-intensity functional fitness (HIFF) athletes during two different 10 and consecutive weekly training volume loads [higher (week 1) and lower volume (week 2)]. Methods: 14 athletes [7 males: 29.3 (±5.8) years; 86.3 (±8.2) kg and 176.8 (±3.8) cm and 7 females: 32.7 (±4.4) years; 60.0 (±6.7) kg and 162.5 (±5.9) cm] participated. The ST, assessed by Daily Analysis of Life Demand in Athletes questionnaire (DALDA) and Saliva sampling were performed in four time-points (pre (T1) and post (T2) week 1; pre (T3) and post (T4) week 2). Results: Female athletes showed a decrease in ST (symptoms of stress) from 15 T1 to T3 [F(3,36) = 7.184, p˂ 0.001, ηp2 = 0.374], without difference in male athletes (p > .05). There is a significant difference of SIgA concentration [F(3.36) = 3.551; p = .024; ηp2 = 0.228], with a significant decrease in female athletes group in T2 compared to T1 (p = .013) and T4 (p = .023). In addition, the different training volume loads did not impact mucosal immunity in male athletes (p > .05). Conclusion: The current findings suggest that higher HIFF volume results in decreased ST and SIgA concentration in female 20 athletes and a subsequent decrease in training volume loads contributed to restoring these variables.
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Teoh L, Chatfield MD, Acworth JP, McCallum GB, Chang AB. How Does the Canadian Acute Respiratory Illness and Flu Scale Relate to Other Scales in Pediatric Asthma Exacerbations? J Asthma 2021; 59:1590-1596. [PMID: 34156320 DOI: 10.1080/02770903.2021.1946823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Objectives: In children with asthma exacerbations, we evaluated the relationship between Canadian Acute Respiratory Illness and Flu Scale (CARIFS) scores and (a) Asthma Diary Scale (ADS) scores for 14 days; (b) Pediatric Asthma Caregiver's Quality of Life (QoL) Questionnaire (PACQLQ) scores on days 1, 7 and 14; (c) viral detection. We hypothesized that in children with acute asthma, CARIFS scores correlate with ADS and PACQLQ scores over time and that viruses have little impact on CARIFS scores.Methods: In children aged 2-16 years who presented with acute asthma to the Emergency Departments of 2 hospitals, we documented the clinical history, examination, asthma severity at baseline and on presentation. Eighteen respiratory pathogens were determined by PCR on nasopharyngeal aspirate (NPA) collected on recruitment. The parent(s) recorded their child's daily CARIFS and ADS and weekly PACQLQ for 14 days. We used Spearman's correlation to relate the scores of 108 children.Results: CARIFS scores correlated well with ADS scores throughout 14 days (rs ranged 0.30-0.67). CARIFS and PACQLQ scores correlated -0.28, -0.14 and -0.44 on days 1, 7 and 14 respectively. There was no significant difference in CARIFS scores between children whose NPAs were PCR virus-positive or -negative over 14 days.Conclusions: CARIFS and ADS scores correlated well as a disease severity measure during the recovery period in children with acute asthma and this was not influenced by the virus state. The ADS may be used as an alternative in selected situations. The CARIFS reflects different aspects to acute asthma severity and QoL.
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Affiliation(s)
- Laurel Teoh
- Child Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, Northern Territory, Australia.,Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia
| | - Mark D Chatfield
- Child Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, Northern Territory, Australia.,Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia
| | - Jason P Acworth
- Emergency Medicine Department, Queensland Children's Hospital, Brisbane, Queensland, Australia
| | - Gabrielle B McCallum
- Child Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, Northern Territory, Australia
| | - Anne B Chang
- Child Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, Northern Territory, Australia.,Department of Respiratory and Sleep Medicine, Queensland Children's Hospital and Australian Centre for Health Services Innovation, Queensland University of Technology, Brisbane, Queensland, Australia
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Debien PB, Miloski B, Werneck FZ, Timoteo TF, Ferezin C, Filho MGB, Gabbett TJ. Training Load and Recovery During a Pre-Olympic Season in Professional Rhythmic Gymnasts. J Athl Train 2020; 55:977-983. [PMID: 32731261 PMCID: PMC7534931 DOI: 10.4085/1062-6050-402.19] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
CONTEXT Rhythmic gymnastics requires a high level of complexity and perfection of technical gestures, associated with well-developed physical and artistic capacities. The training-load and recovery profiles of rhythmic gymnasts across a season are unknown. OBJECTIVE To analyze the training load and recovery of professional rhythmic gymnasts during 1 season. DESIGN Cohort study. SETTING Brazilian National Training Center of Rhythmic Gymnastics and competition facilities. PATIENTS OR OTHER PARTICIPANTS Eight gymnasts from the Brazilian national senior rhythmic gymnastics group. MAIN OUTCOME MEASURE(S) Session rating of perceived exertion (session-RPE) and total quality recovery (TQR) scores were collected daily for 43 weeks. We obtained the session-RPE after each session and TQR score before the first session of the day. Performances during 5 competitions were also recorded. The season was divided into 8 periods. Total weekly internal training load (wITL), training intensity, frequency, duration, recovery, and acute : chronic workload ratio were calculated for analysis. RESULTS The season mean wITL was 10 381 ± 4894 arbitrary units, mean session-RPE score was 5.0 ± 1.6, and mean TQR score was 12.8 ± 1.3. The gymnasts trained an average of 8.7 ± 2.9 sessions per week, with a mean duration of 219 ± 36 minutes. Each competitive period showed increased wITL compared with the previous period. Training-load variables (wITL and session-RPE) and recovery were inversely correlated. Gymnasts were poorly recovered (TQR < 13) during 50.9% of the season (n = 167 times), especially during competitive weeks. Spikes in load (acute : chronic workload ratio ≥ 1.5) occurred across 18.1% of the season (n = 55 times). CONCLUSIONS The training-load variables and recovery changed throughout a professional rhythmic gymnastics group season, mainly during competitive periods. The correct distribution of training load is critical to ensure that gymnasts are entering competitions in a recovered state.
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Affiliation(s)
- Paula Barreiros Debien
- Faculty of Physical Education and Sports, Federal University of Juiz de Fora, Minas Gerais, Brazil
| | - Bernardo Miloski
- Federal Institute of Southeast of Minas Gerais, Barbacena, Brazil
| | | | - Thiago Ferreira Timoteo
- Faculty of Physical Education and Sports, Federal University of Juiz de Fora, Minas Gerais, Brazil
| | - Camila Ferezin
- Brazilian Gymnastics Federation, Aracaju, Sergipe, Brazil
| | | | - Tim J. Gabbett
- University of Southern Queensland, Institute for Resilient Regions, Ipswich, Australia
- Gabbett Performance Solutions, Brisbane, Australia
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Upper respiratory tract symptoms and salivary immunoglobulin A of elite female gymnasts: a full year longitudinal field study. Biol Sport 2020; 37:285-293. [PMID: 32879551 PMCID: PMC7433336 DOI: 10.5114/biolsport.2020.95639] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 03/28/2020] [Accepted: 05/17/2020] [Indexed: 01/01/2023] Open
Abstract
The aim of this study was to determine the frequency of upper respiratory tract symptoms (URS) in elite female gymnasts during a training season. In addition, we aimed to observe the extent to which salivary immunoglobulin A (sIgA) is associated with URS in these athletes, including potential effects of the season and timing of sample collection. Over one year, 18 elite female gymnasts completed URS and fatigue questionnaires weekly and provided 1 mL of saliva after a minimum 36 h of rest (morning or afternoon) to measure relative sIgA concentration (= mean absolute sIgA value of the week divided by the mean absolute sIgA value of the weeks without URS). Mean weekly URS and mean relative sIgA values per gymnast correlated negatively (r = -0.606, P = 0.022). Most URS were noted in the most fatigued gymnasts (7.4 ± 10.1 vs. 2.5 ± 5.6 (P < 0.001) for ‘normal’ and 2.1 ± 3.7 (P = 0.001) for ‘better than normal’ rested). In spring, relative sIgA was higher compared to autumn (112 ± 55 vs. 89 ± 41%, P < 0.001) and winter (92 ± 35%, P = 0.001), while during summer, relative sIgA appeared higher compared to autumn (110 ± 55 vs. 89 ± 41%, P = 0.016). The interaction effect with timing of sample collection showed higher relative sIgA values in morning samples in spring and summer compared to afternoon samples, with the inverse observed in autumn and winter (F = 3.565, P = 0.014). During a gymnastics season, lower relative sIgA values were linked to higher susceptibility to URS in elite gymnasts. However, relative sIgA values were influenced by season and timing of sample collection and thus should be considered when interpreting sIgA data.
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Vitamin D₃ Supplementation Reduces the Symptoms of Upper Respiratory Tract Infection during Winter Training in Vitamin D-Insufficient Taekwondo Athletes: A Randomized Controlled Trial. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2018; 15:ijerph15092003. [PMID: 30223447 PMCID: PMC6164435 DOI: 10.3390/ijerph15092003] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 09/08/2018] [Accepted: 09/10/2018] [Indexed: 12/13/2022]
Abstract
Vitamin D insufficiency may be associated with increased risk of upper respiratory tract infection (URTI) in athletes. This study examined the effects of vitamin D3 supplementation on salivary immune functions and symptoms of URTI in vitamin D-insufficient taekwondo athletes. Twenty-five male taekwondo athletes, aged 19–22 years with vitamin D insufficiency [serum 25-hydroxyvitamin-D concentrations (25(OH)D, 31.3 ± 1.39 nmol/L)], participated in this study. They were randomized to receive 5000 IU/day of vitamin D3 (n = 13) or placebo capsule (n = 12) during 4 weeks of winter training. Blood samples were collected two times (pre- and post-tests) for analyzing serum 25(OH)D concentration while salivary samples were obtained three times (pre-, mid-, and post-tests) for secretory immunoglobulin A (SIgA) and lactoferrin analyses. The symptoms of URTI were reported daily during the intervention. Serum 25(OH)D concentration significantly increased by 255.6% in the vitamin D group, whereas in the placebo group it did not change (p < 0.001). While the significant increase in SIgA was observed in both groups (p < 0.001), elevated salivary lactoferrin level in response to winter training was found only in the placebo group (p = 0.011). The change in serum 25(OH)D concentration was negatively associated with total URTI symptoms (r = −0.435, p = 0.015). Vitamin D3 supplementation may be effective in reducing the symptoms of URTI during winter training in vitamin D-insufficient taekwondo athletes.
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