Sports Medicine

Sports Medicine

RETRACTED ARTICLE: Determining the Sites of Neural Adaptations to Resistance Training: A Systematic Review and Meta-Analysis

01-11-2019 – U Siddique,S Rahman,AK Frazer,G Howatson,DJ Kidgell

Journal Article, Review

Correction to: Applied Physiology of Rugby League

01-11-2019 – T Gabbett,T King,D Jenkins

Published Erratum

The original article ‘Science of Rugby League Football: A Review’

How the 2018 US Physical Activity Guidelines are a Call to Promote and Better Understand Acute Physical Activity for Cognitive Function Gains

01-11-2019 – YK Chang,KI Erickson,E Stamatakis,TM Hung

Letter

Effectiveness of Education Interventions Designed to Improve Nutrition Knowledge in Athletes: A Systematic Review

01-11-2019 – R Tam,KL Beck,MM Manore,J Gifford,VM Flood,H O’Connor

Journal Article, Review

Abstract Background A range of nutrition education strategies are used to assist athletes to improve nutrition knowledge. Evaluation of nutrition education interventions guides the delivery of efficacious nutrition education for athletes. Aim Our aim was to systematically review sport/general nutrition education interventions delivered to athletes, and to evaluate their effectiveness. Methods A search was conducted using terms related to nutrition knowledge, athletes, education, and intervention. Included studies had to be conducted in athletes (all calibres), use a scored nutrition knowledge assessment tool, and measure knowledge before and after a nutrition education intervention. Peer-reviewed and unpublished theses were included. Results Thirty-two manuscripts (randomised controlled trial, n = 13; single-arm pre/post design, n = 19) met the inclusion criteria. Participants (n = 2180; mean age 17.4 ± 1.7 years) were mostly female (66.1%), university-level (56.3%) athletes based in the US (75%). Comparison of different education methods was limited since the majority of interventions (n = 28/36, 77.8%) used face-to-face education. Most intervention conditions (n = 19) had a total contact time of < 300 min (5 h). The majority of interventions (n = 30, 85.7%) reported significant knowledge improvement, with a mean increase of 16.1 ± 0.7% (mean effect size 1.72; range 0.4–17.1). Only 15.6% of studies used well-validated knowledge assessment tools (more than three types of validity or reliability testing). Conclusions Most interventions reported a significant improvement in nutrition knowledge. Unfortunately, the wide range of knowledge assessment tools with limited validation, and the predominant use of face-to-face interventions, prohibits identification of the most effective modality and dose for nutrition education in athletes.

The Effect of Low-Volume High-Intensity Interval Training on Body Composition and Cardiorespiratory Fitness: A Systematic Review and Meta-Analysis

01-11-2019 – RN Sultana,A Sabag,SE Keating,NA Johnson

Journal Article, Review

Abstract Background Evidence for the efficacy of low-volume high-intensity interval training (HIIT) for the modulation of body composition is unclear. Objectives We examined the effect of low-volume HIIT versus a non-exercising control and moderate-intensity continuous training (MICT) on body composition and cardiorespiratory fitness in normal weight, overweight and obese adults. We evaluated the impact of low-volume HIIT (HIIT interventions where the total amount of exercise performed during training was ≤ 500 metabolic equivalent minutes per week MET-min/week) compared to a non-exercising control and MICT. Methods A database search was conducted in PubMed (MEDLINE), EMBASE, CINAHL, Web of Science, SPORTDiscus and Scopus from the earliest record to June 2019 for studies (randomised controlled trials and non-randomised controlled trials) with exercise training interventions with a minimum 4-week duration. Meta-analyses were conducted for between-group (low-volume HIIT vs. non-exercising control and low-volume HIIT vs. MICT) comparisons for change in total body fat mass (kg), body fat percentage (%), lean body mass (kg) and cardiorespiratory fitness. Results From 11,485 relevant records, 47 studies were included. No difference was found between low-volume HIIT and a non-exercising control on total body fat mass (kg) (effect size ES: − 0.129, 95% confidence interval CI − 0.468 to 0.210; p = 0.455), body fat (%) (ES: − 0.063, 95% CI − 0.383 to 0.257; p = 0.700) and lean body mass (kg) (ES: 0.050, 95% CI − 0.250 to 0.351; p = 0.744), or between low-volume HIIT and MICT on total body fat mass (kg) (ES: − 0.021, 95% CI − 0.272 to 0.231; p = 0.872), body fat (%) (ES: 0.005, 95% CI − 0.294 to 0.304; p = 0.974) and lean body mass (kg) (ES: 0.030, 95% CI − 0.167 to 0.266; p = 0.768). However, low-volume HIIT significantly improved cardiorespiratory fitness compared with a non-exercising control (p < 0.001) and MICT (p = 0.017). Conclusion These data suggest that low-volume HIIT is inefficient for the modulation of total body fat mass or total body fat percentage in comparison with a non-exercise control and MICT. A novel finding of our meta-analysis was that there appears to be no significant effect of low-volume HIIT on lean body mass when compared with a non-exercising control, and while most studies tended to favour improvement in lean body mass with low-volume HIIT versus MICT, this was not significant. However, despite its lower training volume, low-volume HIIT induces greater improvements in cardiorespiratory fitness than a non-exercising control and MICT in normal weight, overweight and obese adults. Low-volume HIIT, therefore, appears to be a time-efficient treatment for increasing fitness, but not for the improvement of body composition.

Is Fatigue a Risk Factor for Anterior Cruciate Ligament Rupture?

01-11-2019 – MN Bourne,KE Webster,TE Hewett

Journal Article

Abstract Neuromuscular fatigue is a commonly accepted risk factor for anterior cruciate ligament (ACL) injury. It has been proposed that fatigue leads to transient reductions in muscle strength, and deleterious changes in lower limb kinematics and kinetics, during potentially hazardous tasks such as cutting or landing. The purpose of this clinical commentary is to (1) highlight the complexity of fatigue; (2) discuss the theoretical basis by which it is thought to contribute to ACL injury; and (3) critically discuss the evidence underpinning this hypothesis. Despite a significant amount of research, none of the published fatigue protocols appear to have any consistent effect on any lower limb kinematic or kinetic variables known to increase ACL injury risk. On the contrary, fatigued athletes appear to land with greater peak knee and hip flexion angles, and lower landing forces than unfatigued athletes—all of which are considered favourable movement strategies for reducing ACL loading. These data support recent analyses demonstrating no relationship between player workload in training and competition and the occurrence of ACL injury in sport.

Comparing the Effectiveness of Bloodxa0Flow Restriction and Traditional Heavy Load Resistance Training in the Post-Surgery Rehabilitation of Anterior Cruciate Ligament Reconstruction Patients: A UK National Health Service Randomised Controlled Trial

01-11-2019 – L Hughes,B Rosenblatt,F Haddad,C Gissane,D McCarthy,T Clarke,G Ferris,J Dawes,B Paton,SD Patterson

Journal Article

Abstract Background We implemented a blood flow restriction resistance training (BFR-RT) intervention during an 8-week rehabilitation programme in anterior cruciate ligament reconstruction (ACLR) patients within a National Health Service setting. Objective To compare the effectiveness of BFR-RT and standard-care traditional heavy-load resistance training (HL-RT) at improving skeletal muscle hypertrophy and strength, physical function, pain and effusion in ACLR patients following surgery. Methods 28 patients scheduled for unilateral ACLR surgery with hamstring autograft were recruited for this parallel-group, two-arm, single-assessor blinded, randomised clinical trial following appropriate power analysis. Following surgery, a criteria-driven approach to rehabilitation was utilised and participants were block randomised to either HL-RT at 70% repetition maximum (1RM) (n = 14) or BFR-RT (n = 14) at 30% 1RM. Participants completed 8 weeks of biweekly unilateral leg press training on both limbs, totalling 16 sessions, alongside standard hospital rehabilitation. Resistance exercise protocols were designed consistent with standard recommended protocols for each type of exercise. Scaled maximal isotonic strength (10RM), muscle morphology of the vastus lateralis of the injured limb, self-reported function, Y-balance test performance and knee joint pain, effusion and range of motion (ROM) were assessed at pre-surgery, post-surgery, mid-training and post-training. Knee joint laxity and scaled maximal isokinetic knee extension and flexion strength at 60°/s, 150°/s and 300°/s were measured at pre-surgery and post-training. Results Four participants were lost, with 24 participants completing the study (12 per group). There were no adverse events or differences between groups for any baseline anthropometric variable or pre- to post-surgery change in any outcome measure. Scaled 10RM strength significantly increased in the injured limb (104 ± 30% and 106 ± 43%) and non-injured limb (33 ± 13% and 39 ± 17%) with BFR-RT and HL-RT, respectively, with no group differences. Significant increases in knee extension and flexion peak torque were observed at all speeds in the non-injured limb with no group differences. Significantly greater attenuation of knee extensor peak torque loss at 150°/s and 300°/s and knee flexor torque loss at all speeds was observed with BFR-RT. No group differences in knee extensor peak torque loss were found at 60°/s. Significant and comparable increases in muscle thickness (5.8 ± 0.2% and 6.7 ± 0.3%) and pennation angle (4.1 ± 0.3% and 3.4 ± 0.1%) were observed with BFR-RT and HL-RT, respectively, with no group differences. No significant changes in fascicle length were observed. Significantly greater and clinically important increases in several measures of self-reported function (50–218 ± 48% vs. 35–152 ± 56%), Y-balance performance (18–59 ± 22% vs. 18–33 ± 19%), ROM (78 ± 22% vs. 48 ± 13%) and reductions in knee joint pain (67 ± 15% vs. 39 ± 12%) and effusion (6 ± 2% vs. 2 ± 2%) were observed with BFR-RT compared to HL-RT, respectively. Conclusion BFR-RT can improve skeletal muscle hypertrophy and strength to a similar extent to HL-RT with a greater reduction in knee joint pain and effusion, leading to greater overall improvements in physical function. Therefore, BFR-RT may be more appropriate for early rehabilitation in ACLR patient populations within the National Health Service.

Contemporary Periodization of Altitude Training for Elite Endurance Athletes: A Narrative Review

01-11-2019 – I Mujika,AP Sharma,T Stellingwerff

Journal Article, Review

Abstract Since the 1960s there has been an escalation in the purposeful utilization of altitude to enhance endurance athletic performance. This has been mirrored by a parallel intensification in research pursuits to elucidate hypoxia-induced adaptive mechanisms and substantiate optimal altitude protocols (e.g., hypoxic dose, duration, timing, and confounding factors such as training load periodization, health status, individual response, and nutritional considerations). The majority of the research and the field-based rationale for altitude has focused on hematological outcomes, where hypoxia causes an increased erythropoietic response resulting in augmented hemoglobin mass. Hypoxia-induced non-hematological adaptations, such as mitochondrial gene expression and enhanced muscle buffering capacity may also impact athletic performance, but research in elite endurance athletes is limited. However, despite significant scientific progress in our understanding of hypobaric hypoxia (natural altitude) and normobaric hypoxia (simulated altitude), elite endurance athletes and coaches still tend to be trailblazers at the coal face of cutting-edge altitude application to optimize individual performance, and they already implement novel altitude training interventions and progressive periodization and monitoring approaches. Published and field-based data strongly suggest that altitude training in elite endurance athletes should follow a long- and short-term periodized approach, integrating exercise training and recovery manipulation, performance peaking, adaptation monitoring, nutritional approaches, and the use of normobaric hypoxia in conjunction with terrestrial altitude. Future research should focus on the long-term effects of accumulated altitude training through repeated exposures, the interactions between altitude and other components of a periodized approach to elite athletic preparation, and the time course of non-hematological hypoxic adaptation and de-adaptation, and the potential differences in exercise-induced altitude adaptations between different modes of exercise.

Quality of Life and Life Satisfaction in Former Athletes: A Systematic Review and Meta-Analysis

01-11-2019 – S Filbay,T Pandya,B Thomas,C McKay,J Adams,N Arden

Journal Article, Review

Abstract Background Sport participation has many physical and psychosocial benefits, but there is also an inherent risk of injury, subsequent osteoarthritis and psychological challenges that can negatively impact quality of life (QOL). Considering the multifaceted impacts of sport participation on QOL across the lifespan, there is a need to consolidate and present the evidence on QOL in former sport participants. Objective To evaluate QOL and life satisfaction in former sport participants, and determine what factors are associated with QOL and life satisfaction in this population. Methods Eight electronic databases were systematically searched in July 2018 to retrieve all articles that evaluated QOL or life satisfaction in former sport participants. Two authors independently screened titles/abstracts and full texts, extracted data, and appraised methodological quality using a modified Downs and Black Checklist. Random-effects meta-analysis estimated pooled mean and 95% confidence intervals (Cis) for Mental Component Scores (MCS) and Physical Component Scores (PCS) derived from the SF-12, SF-36, VR-12 and VR-36 measures. MCS and PCS were pooled for all former sport participants, as well as professional- and collegiate-athlete subgroups. Data that were inappropriate for meta-analysis (i.e. EQ-5D, PROMIS and life-satisfaction outcomes) were collated and reported descriptively. Results Seventeen articles evaluated QOL or life satisfaction in a total of 6692 former athletes eight studies (n = 4255) former professional athletes; six studies (n = 1946) former collegiate athletes; two studies (n = 491) included both with a mean age ranging from 21 to 66 years. Most studies were cross-sectional (15 of 17 articles) and 12 studies had a moderate risk of bias (n = 1 high-risk, n = 4 low-risk). Unpublished data were provided for five studies. Meta-analysis of seven studies resulted in a pooled PCS mean (95% CI) of 50.0 (46.6–53.3) former professional athletes from two studies: 46.7 (42.1–51.2), former collegiate athletes from five studies: 51.2 (48.4–53.9) and a pooled MCS of 51.4 (50.5–52.2) former professional athletes: 52.7 (51.3–54.2), former collegiate athletes: 50.9 (50.0–51.8). Factors associated with worse QOL or life satisfaction in former athletes included involuntary retirement from sport (three studies), collision/high-contact sport compared with low/no-contact sport (three studies), three or more concussions compared with no/fewer concussions (two studies), increased body mass index (BMI) (worse PCS, three studies), and osteoarthritis or musculoskeletal issues (worse PCS and MCS, three studies; worse PCS but not MCS, two studies). Conclusions Former athletes had similar PCS and better MCS, compared to general-population norms. Former athletes with impaired PCS reported better MCS than population norms, highlighting the need to use an instrument that differentiates between physical and mental components of QOL in former sport participants. Factors associated with worse QOL that may explain between-study variation include involuntary retirement, collision/high contact sports, concussion, BMI and osteoarthritis. PROSPERO CRD42018104319.

Resistance Training and Skeletal Muscle Protein Metabolism in Eumenorrheic Females: Implications for Researchers and Practitioners

01-11-2019 – OE Knowles,B Aisbett,LC Main,EJ Drinkwater,L Orellana,S Lamon

Journal Article, Review

Abstract Resistance training is essential for health and performance and confers many benefits such as increasing skeletal muscle mass, increasing strength and power output, and improving metabolic health. Resistance training is a major component of the physical activity guidelines, yet research in female populations is limited. Recent increases in the promotion of, and the participation by, females in sport and exercise, highlight the need for an increase in understanding of evidence-based best practice exercise prescription for females. The aim of this review is to provide an overview of the current research regarding resistance training performance and skeletal muscle adaptation in females, with a focus on the hormonal variables that may influence resistance training outcomes. Findings suggest that the menstrual cycle phase may impact strength, but not skeletal muscle protein metabolism. In comparison, oral contraception use in females may reduce skeletal muscle protein synthesis, but not strength outcomes, when compared to non-users. Future research should investigate the role of resistance training in the maintenance of skeletal muscle protein metabolism during pregnancy, menopause and in athletes experiencing relative energy deficiency in sport. The review concludes with recommendations for researchers to assist them in the inclusion of female participants in resistance training research specifically, with commentary on the most appropriate methods of controlling for, or understanding the implications of, hormonal fluctuations. For practitioners, the current evidence suggests possible resistance training practices that could optimise performance outcomes in females, although further research is warranted.

The Effectiveness of Sedentary Behaviour Reduction Workplace Interventions on Cardiometabolic Risk Markers: A Systematic Review

01-11-2019 – ML Brierley,AM Chater,LR Smith,DP Bailey

Journal Article, Review

Abstract Background Sedentary behaviour is a risk factor for type 2 diabetes and cardiovascular disease. Objectives The aims of this work were to systematically review the effects of workplace sedentary behaviour reduction interventions on cardiometabolic risk markers (primary aim) and identify the active behaviour change techniques (BCTs) by which these interventions work (secondary aim). Methods A systematic search of 11 databases for articles published up to 12 April 2019 yielded a total of 4255 unique titles, with 29 articles being identified for inclusion. Interventions were rated as very promising, quite promising or non-promising based on their effects on cardiometabolic risk markers compared with baseline and/or a comparison arm. Interventions were coded for BCTs used. To assess the relative effectiveness of BCTs, a promise ratio was calculated as the frequency of a BCT appearing in all promising interventions divided by its frequency of appearance in all non-promising interventions. Results A narrative synthesis included 29 published studies of varying study design and comprised of 30 interventions. Risk of bias was high for blinding and allocation concealment, moderate for random sequence generation, and low for outcome assessment. Nine interventions were very promising, 11 were quite promising, 10 were non-promising, and 10 active control groups did not experience cardiometabolic changes. Significant sedentary behaviour reductions were present in all but five studies where cardiometabolic risk markers improved. The BCTs of social comparison, problem solving, demonstration of the behaviour, goal setting (behaviour), behaviour substitution, and habit reversal, demonstrated moderate to high promise ratios. Conclusions Workplace interventions show promise for improving cardiometabolic risk markers. The BCTs with the greatest promise of cardiometabolic risk marker improvements included social comparison, those related to individual habits, and behaviour goals. Registration This systematic review was prospectively registered in PROSPERO (CRD42017072427).

Bio-Banding in Youth Sports: Background, Concept, and Application

01-11-2019 – RM Malina,SP Cumming,AD Rogol,MJ Coelho-E-Silva,AJ Figueiredo,JM Konarski,SM Kozieł

Journal Article, Review

Abstract Inter-individual differences in size, maturity status, function, and behavior among youth of the same chronological age (CA) have long been a concern in grouping for sport. Bio-banding is a recent attempt to accommodate maturity-associated variation among youth in sport. The historical basis of the concept of maturity-matching and its relevance to youth sport, and bio-banding as currently applied are reviewed. Maturity matching in sport has often been noted but has not been systematically applied. Bio-banding is a recent iteration of maturity matching for grouping youth athletes into ‘bands’ or groups based on characteristic(s) other than CA. The percentage of predicted young adult height at the time of observation is the estimate of maturity status of choice. Several applications of bio-banding in youth soccer have indicated positive responses from players and coaches. Bio-banding reduces, but does not eliminate, maturity-associated variation. The potential utility of bio-banding for appropriate training loads, injury prevention, and fitness assessment merits closer attention, specifically during the interval of pubertal growth. The currently used height prediction equation requires further evaluation.

Correction to: Injury Risk in New Zealand Rugby Union: A Nationwide Study of Injury Insurance Claims from 2005 to 2017

09-10-2019 – K Quarrie,S Gianotti,I Murphy

Published Erratum

Page 11, column 2, section 4.2 Injury Epidemiology, paragraph 4:

Return-to-Play Practices Following Hamstring Injury: A Worldwide Survey of 131 Premier League Football Teams

08-10-2019 – G Dunlop,CL Ardern,TE Andersen,C Lewin,G Dupont,B Ashworth,G O’Driscoll,A Rolls,S Brown,A McCall

Journal Article

Abstract Purpose Return-to-play (RTP) is an on-going challenge in professional football. Return-to-play related research is increasing. However, it is unknown to what extent the recommendations presented within research are being implemented by professional football teams, and where there are gaps between research and practice. The purposes of this study were (1) to determine if premier-league football teams worldwide follow a RTP continuum, (2) to identify RTP criteria used and (3) to understand how RTP decision-making occurs in applied practice. Methods We sent a structured online survey to practitioners responsible for the RTP programme in 310 professional teams from 34 premier-leagues worldwide. The survey comprised four sections, based on hamstring muscle injury: (1) criteria used throughout RTP phases, (2) the frequency with which progression criteria were achieved, (3) RTP decision-making process and (4) challenges to decision-making. Results One-hundred and thirty-one teams responded with a completed survey (42%). One-hundred and twenty-four teams (95%) used a continuum to guide RTP, assessing a combination of clinical, functional and psychological criteria to inform decisions to progress. One-hundred and five (80%) teams reported using a shared decision-making approach considering the input of multiple stakeholders. Team hierarchy, match- and player-related factors were common challenges perceived to influence decision-making. Conclusions General research recommendations for RTP and the beliefs and practices of practitioners appear to match with, the majority of teams assessing functional, clinical and psychological criteria throughout a RTP continuum to inform decision-making which is also shared among key stakeholders. However, specific criteria, metrics and thresholds used, and the specific involvement, dynamics and interactions of staff during decision-making are not clear.

Correction to: Relationships Between Dry-land Resistance Training and Swim Start Performance and Effects of Such Training on the Swim Start: A Systematic Review

03-10-2019 – S Thng,S Pearson,JWL Keogh

Published Erratum

No sources of funding were used in the preparation of this article.

Correction to: DNA Damage Following Acute Aerobic Exercise: A Systematic Review and Meta-analysis

01-10-2019 – DV Tryfidou,C McClean,MG Nikolaidis,GW Davison

Published Erratum

Page 17, Fig. 2

Correction to: Motor Competence Levels and Developmental Delay in Early Childhood: A Multicenter Cross-Sectional Study Conducted in the USA

01-10-2019 – A Brian,A Pennell,S Taunton,A Starrett,C Howard-Shaughnessy,JD Goodway,D Wadsworth,M Rudisill,D Stodden

Published Erratum

Page 1, Abstract, Results, sentence 1: The following sentence, which previously read:

Comment on: “Incidence, Severity, Aetiology and Prevention of Sports Injuries: A Review of Concepts”

01-10-2019 – A Chandran,AK Nedimyer,JK Register-Mihalik,L DiPietro,ZY Kerr

Letter

Resistance Priming to Enhance Neuromuscular Performance in Sport: Evidence, Potential Mechanisms and Directions for Future Research

01-10-2019 – PW Harrison,LP James,MR McGuigan,DG Jenkins,VG Kelly

Journal Article, Review

Abstract Recent scientific evidence supports the use of a low-volume strength–power ‘resistance priming’ session prior to sporting competition in an effort to enhance neuromuscular performance. Though research evidence relating to this strategy is presently limited, it has been shown to be effective in improving various measures of neuromuscular performance within 48 h. Post-activation potentiation strategies have previously been shown to enhance strength–power performance within 20 min of completing maximal or near-maximal resistance exercise. Comparably, a delayed potentiation effect has been demonstrated following ‘resistance priming’ at various times between 1 and 48 h in upper- and lower-body performance measures. This may have significant implications for a range of athletes when preparing for competition. Various exercise protocols have been shown to improve upper- and lower-body neuromuscular performance measures in this period. In particular, high-intensity resistance exercise through high loading (≥ 85% 1 repetition maximum) or ballistic exercise at lower loads appears to be an effective stimulus for this strategy. Although current research has identified the benefits of resistance priming to some physical qualities, many questions remain over the application of this type of session, as well as the effects that it may have on a range of specific sporting activities. The aims of this brief review are to assess the current literature examining the acute effects (1–48 h) of resistance exercise on neuromuscular performance and discuss potential mechanisms of action as well as provide directions for future research.

Test–Retest Reliability of the Yo-Yo Test: A Systematic Review

01-10-2019 – J Grgic,L Oppici,P Mikulic,J Bangsbo,P Krustrup,Z Pedisic

Journal Article, Review

Abstract Background The Yo-Yo test is widely used both in the practical and research contexts; however, its true test–retest reliability remains unclear. Objective The present systematic review aims to identify studies that have examined the test–retest reliability of the Yo-Yo test and summarize their results. Methods A search of ten databases was performed to find studies that have investigated test–retest reliability of any variant of the Yo-Yo test. The COSMIN checklist was employed to assess the methodological quality of the included studies. Results Nineteen studies of excellent or moderate methodological quality were included. When considering all variants of the Yo-Yo test, the included studies reported intra-class correlation coefficients for test–retest reliability ranging from 0.78 to 0.98 where 62% of all intra-class correlation coefficients were higher than 0.90, while 97% of intra-class correlation coefficients were higher than 0.80. The coefficients of variation ranged from 3.7 to 19.0%. Regardless of the variant of the test, the participants’ familiarization with the test, and previous sport experience, the intra-class correlation coefficients generally seem high (≥ 0.90) and coefficients of variation low (< 10%). Conclusions The results of this review indicate that the Yo-Yo test (in all its variants) generally has good-to-excellent test–retest reliability. The evidence concerning reliability arises from 19 included studies that were of moderate or high methodological quality. Considering that most of the included studies examined the Yo-Yo intermittent recovery level 1 test while including Association Football players, more reliability studies examining Yo-Yo intermittent recovery level 2 test and Yo-Yo intermittent endurance level 1 and level 2 tests, and in the context of sports other than Association Football as well as in non-athletic populations, are required. Finally, future studies should explicitly state the type of intra-class correlation coefficient used for the reliability data analysis to allow for better between-study comparisons.