Overuse injury and affects in competitive sport: A prospective longitudinal study.

Overuse injuries, which have a high prevalence in sport, are suggested to result in different affective responses in comparison to traumatic injuries. Affects may also reciprocally act as risk factors for overuse injury. The aim of this study was to examine the associations between overuse injury and affects within a longitudinal follow-up design. Competitive athletes (N = 149) of various sports and levels of competition completed the Positive and Negative Affect Schedule (PANAS) and the Oslo Sports Trauma Research Centre Overuse injury questionnaire (OSTRC-O) once a week over 10 consecutive weeks. Bivariate unconditional latent curve model analyses with structured residuals were performed to evaluate the associations within and across weeks between OSTRC-O severity score and affects. Results indicated that OSTRC-O severity score and positive affects (PA) had a statistically significant negative within-week relation (r = -24.51, 95% CI = [-33.9, -15.1], p < 0.001). Higher scores of overuse injury were significantly related to lower levels of PA across weeks (ß = -0.02, 95% CI = [-0.04, -0.001], p = 0.044), while the reciprocal effect of PA on overuse injury was not significant (ß = -0.13, 95% CI = [-0.52, 0.26], p = 0.51). No statistically significant association was observed between OSTRC-O severity score and negative affects, neither within nor across weeks. Our findings suggest that overuse injury may have adverse psychological consequences on the long run through lessened PA and address the need for providing sustainable psychological support focusing upon such PA when working with athletes experiencing overuse injury.

How do sports injury epidemiological outcomes vary depending on athletes' response rates to a weekly online questionnaire? An analysis of 39-week follow-up from 391 athletics (track and field) athletes.

OBJECTIVE: To explore how sports injury epidemiological outcomes (i.e., prevalence, average prevalence, incidence, burden, and time to first injury) vary depending on the response rates to a weekly online self-reported questionnaire for athletes. METHODS: Weekly information on athletics injuries and exposure from 391 athletics (track and field) athletes was prospectively collected over 39 weeks (control group of the PREVATHLE randomized controlled trial) using an online self-reported questionnaire. The data were used to calculate sports injury epidemiological outcomes (i.e., prevalence, average prevalence, incidence, burden, and time to first injury) for sub-groups with different minimum individual athletes' response rates (i.e., from at least 100%, at least 97%, at least 95%, … to at least 0% response rate). We then calculated the relative variation between each sub-group and the sub-group with a 100% response rate as a reference. A substantial variation was considered when the relative variation was greater than one SD or 95% CI of the respective epidemiological outcome calculated in the sub-group with a 100% response rate. RESULTS: Of 15 249 expected weekly questionnaires, 7209 were completed and returned, resulting in an overall response rate of 47.3%. The individual athletes' response rates ranged from 0% (n = 51) to 100% (n = 100). The prevalence, average weekly prevalence, and time to first injury only varied substantially for the sub-groups below a 5%, 10% and 18% minimum individual response rate, respectively. The incidence and injury burden showed substantial variations for all sub-groups with a response rate below 100%. CONCLUSIONS: Epidemiological outcomes varied depending on the minimum individual athletes' response rate, with injury prevalence, average weekly prevalence, and time to first injury varying less than injury incidence and injury burden. This highlights the need to take into account the individual response rate when calculating epidemiological outcomes, and determining the optimal study-specific cut-offs of the minimum individual response rate needed.

Human foot muscle strength and its association with sprint acceleration, cutting and jumping performance, and kinetics in high-level athletes.

The primary objective of this study was to investigate the relationship between metatarsophalangeal joint (MTPj) flexion torque and sprint acceleration, cutting and jumping performance, and kinetics. A secondary aim was to explore this relationship when MTP flexion strength was associated with other foot and lower limb neuromuscular outputs. After an initial MTPj flexion torque assessment using a custom-built dynamometer, 52 high-level athletes performed the following tasks on a force platform system: maximal sprint acceleration, 90-degree cutting, vertical and horizontal jumps, and foot-ankle hops. Their foot posture, foot passive stiffness and foot-ankle reactive strength were assessed using the Foot Posture Index, the Arch Height Index Measurement System and the Foot-Ankle Rebound Jump Test. Ankle plantarflexion and knee extension isometric torque were assessed using an isokinetic dynamometer. During maximal speed sprinting, multiple linear regressions suggested a major contribution of MTPj flexion torque, foot passive stiffness and foot-ankle reactive strength to explain 28% and 35% of the total variance in the effective vertical impulse and contact time. Ankle plantarflexor and quadriceps isometric torques were aggregately contributors of acceleration performance and separate contributors of cutting and jumping performance. In conclusion, MTPj flexion torque was more strongly associated with sprinting performance kinetics especially at high-speed.

Injuries and Illnesses During the 53rd FIS Nordic World Ski Championships 2021 in Oberstdorf: A Prospective Cohort Study.

OBJECTIVE: For the 3 Nordic ski disciplines of cross-country skiing, Nordic combined, and ski jumping, data on injuries and illnesses during major sporting events only exist from the Winter Olympics of 2010 to 2018. So far, an investigation has not been conducted during the Nordic World Ski Championships. DESIGN: Prospective cohort study. SETTING: Fédération Internationale de Ski (FIS) Nordic World Ski Championships 2021 in Oberstdorf, Germany. PARTICIPANTS: Overall, 663 athletes from 65 nations participated in the FIS Nordic World Ski Championships 2021. The study population included 344 athletes from 32 nations. INTERVENTIONS: National medical teams were invited to report daily all newly incurred or exacerbated injuries and illnesses. MAIN OUTCOME MEASURES: All reported injuries and illnesses that occurred during the championships from February 23 until March 7, 2021, were analyzed. Injury and illness rates were calculated with 95% confidence intervals (95% CIs). RESULTS: The 32 reporting nations returned 88.4% of the daily report forms. The incidence of injuries was 4.7 (95% CI, 2.4-6.9) per 100 athletes in the 3 Nordic ski disciplines. The incidence of illness was also 4.7 (95% CI, 2.4-6.9) per 100 athletes with a relative proportion of infection-related illnesses of 31.3%. CONCLUSIONS: Although the incidence of injuries of the Nordic disciplines was comparable with those of the 2010 to 2018 Winter Olympics, the incidence of illnesses was lower than during the previous 3 Winter Olympic Games with a lower rate of infection-related illnesses. This might be caused by the high hygiene measures due to the coronavirus disease 2019 pandemic.

The awareness of injury prevention programmes is insufficient among French- and German-speaking sports medicine communities in Europe.

PURPOSE: Evaluate the current state of sports injury prevention perception, knowledge and practice among sports medicine professionals located in Western Europe and involved in injury prevention. METHODS: Members of two different sports medicine organizations (GOTS and ReFORM) were invited to complete a web-based questionnaire (in German and in French, respectively) addressing perception, knowledge and implementation of sports injury prevention through 22 questions. RESULTS: 766 participants from a dozen of countries completed the survey. Among them, 43% were surgeons, 23% sport physicians and 18% physiotherapists working mainly in France (38%), Germany (23%) and Belgium (10%). The sample rated the importance of injury prevention as "high" or "very high" in a majority of cases (91%), but only 54% reported to be aware of specific injury prevention programmes. The French-speaking world was characterized by lower levels of reported knowledge, unfamiliarity with existing prevention programmes and less weekly time spent on prevention as compared to their German-speaking counterparts. Injury prevention barriers reported by the respondents included mainly insufficient expertise, absence of staff support from sports organizations and lack of time. CONCLUSION: There is a lack of awareness regarding injury prevention concepts among sports medicine professionals of the European French- and German-speaking world. This gap varied according to the professional occupation and working country. Relevant future paths for improvement include specific efforts to build awareness around sports injury prevention. LEVEL OF EVIDENCE: Level IV.

Optimal mechanical force-velocity profile for sprint acceleration performance.

The aim was to determine the respective influences of sprinting maximal power output ( P H max ) and mechanical Force-velocity (F-v) profile (ie, ratio between horizontal force production capacities at low and high velocities) on sprint acceleration performance. A macroscopic biomechanical model using an inverse dynamics approach applied to the athlete's center of mass during running acceleration was developed to express the time to cover a given distance as a mathematical function of P H max and F-v profile. Simulations showed that sprint acceleration performance depends mainly on P H max , but also on the F-v profile, with the existence of an individual optimal F-v profile corresponding, for a given P H max , to the best balance between force production capacities at low and high velocities. This individual optimal profile depends on P H max and sprint distance: the lower the sprint distance, the more the optimal F-v profile is oriented to force capabilities and vice versa. When applying this model to the data of 231 athletes from very different sports, differences between optimal and actual F-v profile were observed and depend more on the variability in the optimal F-v profile between sprint distances than on the interindividual variability in F-v profiles. For a given sprint distance, acceleration performance (<30 m) mainly depends on P H max and slightly on the difference between optimal and actual F-v profile, the weight of each variable changing with sprint distance. Sprint acceleration performance is determined by both maximization of the horizontal power output capabilities and the optimization of the mechanical F-v profile of sprint propulsion.

Hamstring injury patterns in professional male football (soccer): a systematic video analysis of 52 cases.

OBJECTIVE: To closely describe the injury inciting events of acute hamstring injuries in professional male football (soccer) using systematic video analysis. METHODS: Video footage from four seasons (2014-2019) of the two highest divisions in German male football was searched for moderate and severe (ie, time loss of >7 days) acute non-contact and indirect contact match hamstring injuries. Two raters independently categorised inciting events using a standardised procedure to determine specific injury patterns and kinematics. RESULTS: 52 cases of hamstring injuries were included for specific pattern analysis. The pattern analysis revealed 25 sprint-related (48%) and 27 stretch-related hamstring injuries (52%). All sprint-related hamstring injuries occured during linear acceleration or high-speed running. Stretch-related hamstring injuries were connected with closed chain movements like braking or stopping with a lunging or landing action and open chain movements like kicking. The kinematic analysis of stretch-related injuries revealed a change of movement involving knee flexion to knee extension and a knee angle of <45° at the assumed injury frame in all open and closed chain movements. Biceps femoris was the most affected muscle (79%) of all included cases. CONCLUSION: Despite the variety of inciting events, rapid movements with high eccentric demands of the posterior thigh are likely the main hamstring injury mechanism. This study provides important data about how hamstring injuries occur in professional male football and supports the need for demand-specific multicomponent risk reduction programmes.

Determinants of the adoption of injury risk reduction programmes in athletics (track and field): an online survey of 7715 French athletes.

OBJECTIVES: To identify individual characteristics associated with the adoption of injury risk reduction programmes (IRRP) and to investigate the variations in sociocognitive determinants (ie, attitudes, subjective norms, perceived behavioural control and intentions) of IRRP adoption in athletics (track and field) athletes. METHODS: We conducted a cross-sectional study using an online survey sent to athletes licensed with the French Federation of Athletics to investigate their habits and sociocognitive determinants of IRRP adoption. Sociodemographic characteristics, sports practice and history of previous injuries were also recorded. Logistic regression analyses and group comparisons were performed. RESULTS: The final sample was composed of 7715 athletes. From the multivariable analysis, competing at the highest level was positively associated with IRRP adoption (adjusted OR (AOR)=1.66; 99.9% CI 1.39 to 1.99 and AOR=1.48; 99.9% CI 1.22 to 1.80) and presenting a low number of past injuries was negatively associated with IRRP adoption (AOR=0.48; 99.9% CI 0.35 to 0.65 and AOR=0.61; 99.9% CI 0.44 to 0.84), both during their lifetime and the current season, respectively. These results were supported by higher scores of sociocognitive determinants among athletes who reported IRRP adoption compared with other athletes. CONCLUSION: Some characteristics of athletes seem to be associated with IRRP adoption either positively (competing at the highest level) or negatively (presenting a lower number of past injuries), whereas all the sociocognitive determinants tested appear to be linked to IRRP adoption. Since many athlete characteristics are difficult or impossible to change, IRRP promotion may be enhanced by targeting athletes' beliefs and intentions to adopt an IRRP.

French Athletics Stakeholders' Perceptions of Relevance and Expectations on Injury Prevention.

This study aimed to explore how stakeholders in athletics perceive the relevance of injury prevention, determine their communication preferences, and describe their expectations regarding injury prevention. We conducted a cross-sectional study using an exploratory online survey with high-level athletes (i. e. listed by the French ministry of sports), non-high-level athletes (i. e. all competitive level except high-level athletes), coaches, and health professionals licensed with the French Federation of Athletics. The survey was composed of three parts regarding stakeholder's characteristics (4 questions), perceived relevance (2 questions), communication preferences and expectations (3 questions) towards injury prevention. There were 2,864 responders to the survey. Almost all responders found that injury prevention is relevant (97.7% [95% CI 97.0% to 98.2%]), without any significant differences in the distribution between stakeholders' age, experience and sex (p>0.05). About three-quarters of the stakeholders preferred to find injury prevention information on a website (77.4%) without significant differences between stakeholders' categories (p>0.05); other media to find injury prevention information was chosen by less than 50% of responders. Expectations about injury prevention were mainly explanations, advice and tips about injury knowledge, management and prevention, based on expert opinion and/or scientific research. In conclusion, these results confirm that injury prevention is a challenge shared by numerous stakeholders in athletics, within France, and provide some orientation on how and what information to disseminate to these stakeholders.

A novel multifactorial hamstring screening protocol: association with hamstring muscle injuries in professional football (soccer) - a prospective cohort study.

The aim of this pilot study was to analyze the potential association of a novel multifactorial hamstring screening protocol with the occurrence of hamstring muscle injuries (HMI) in professional football. 161 professional male football players participated in this study (age: 24.6 ± 5.36 years; body-height: 180 ± 7.07 cm; body-mass: 77.2 ± 7.70 kg). During the pre- and mid-season, players performed a screening protocol consisting of 11 tests aimed to evaluate their performance in regards to four main musculoskeletal categories: posterior chain strength, sprint mechanical output, lumbopelvic control and range of motion. Univariable cox regression analysis showed no significant association between the isolated test results and new HMI occurrence during the season (n = 17) (p > 0.05). When including injuries that took place between the pre- and mid-season screenings (~90 days), maximal theoretical horizontal force (F0) was significantly associated with higher HMI risk between pre- and mid-season evaluations (n = 14, hazard ratio; 4.02 (CI95% 1.08 to 15.0, p = 0.04). This study identified that 1) no single screening test was sufficient to identify players at risk of HMI within the entire season, while 2) low F0 was associated with increased risk of HMI when occurring closer to the moment of screening. The present results support the potential relevance of additionally including frequent F0 testing for HMI risk reduction management. Replication studies are needed in larger cohorts for more accurate interpretations on "univariable and multivariable levels levels. Finally, future studies should explore whether improving F0 is relevant within a multifactorial HMI risk reduction approach.

Apparent temperature and heat-related illnesses during international athletic championships: A prospective cohort study.

International outdoor athletics championships are typically hosted during the summer season, frequently in hot and humid climatic conditions. Therefore, we analyzed the association between apparent temperature and heat-related illnesses occurrence during international outdoor athletics championships and compared its incidence rates between athletics disciplines. Heat-related illnesses were selected from illness data prospectively collected at seven international outdoor athletics championships between 2009 and 2018 using a standardized methodology. The Universal Thermal Climate Index (UTCI) was calculated as a measure of the apparent temperature based on weather data for each day of the championships. Heat-related illness numbers and (daily) incidence rates were calculated and analyzed in relation to the daily maximum UTCI temperature and between disciplines. During 50 championships days with UTCI temperatures between 15℃ and 37℃, 132 heat-related illnesses were recorded. Average incidence rate of heat-related illnesses was 11.7 (95%CI 9.7 to 13.7) per 1000 registered athletes. The expected daily incidence rate of heat-related illnesses increased significantly with UTCI temperature (0.12 more illnesses per 1000 registered athletes/°C; 95%CI 0.08-0.16) and was found to double from 25 to 35°C UTCI. Race walkers (RR = 45.5, 95%CI 21.6-96.0) and marathon runners (RR = 47.7, 95%CI 23.0-98.8) had higher heat-related illness rates than athletes competing in short-duration disciplines. Higher UTCI temperatures were associated with more heat-related illnesses, with marathon and race walking athletes having higher risk than athletes competing in short-duration disciplines. Heat-related illness prevention strategies should predominantly focus on marathon and race walking events of outdoor athletics championships when high temperatures are forecast.

Training-induced changes in anterior pelvic tilt: potential implications for hamstring strain injuries management.

An association has been reported between dynamic anterior pelvic tilt (APT) and hamstring injuries; however, no research has examined if a training-based preventive intervention could alter APT. Therefore, the aim of the present study was to examine if a specific 6-week multimodal intervention, based on the theoretical influence of neighbouring joints and biomechanical interactions between muscles that are inserted to the pelvis, induced changes in APT, during walking gait, hamstring flexibility and trunk endurance. Thirty-five active healthy males volunteered for this single-blind controlled trial and were split into two groups based on baseline data: a control group (CG, n = 20, continued their normal physical activities), and an intervention group (IG, n = 15, performed the intervention programme for 18 sessions over 6 weeks). A significant (p = 0.001) decrease in the APT kinematics during gait, significant increase in the Active Knee Extension Test (p = 0.001), and a significant increase in trunk endurance performance for flexion (p = 0.001), extension (p = 0.001) and side bridge (p = 0.001) were observed, in IG after the 6-week programme, compared to CG.

Injury frequency and characteristics (location, type, cause and severity) differed significantly among athletics ('track and field') disciplines during 14 international championships (2007-2018): implications for medical service planning.

OBJECTIVE: To analyse differences between athletic disciplines in the frequency and characteristics of injuries during international athletics championships. METHODS: Study design, injury definition and data collection procedures were similar during the 14 international championships (2007-2018). National medical teams and local organising committee physicians reported all newly incurred injuries daily on a standardised injury report form. Results were presented as number of injuries and number of injuries per 1000 registered athletes, separately for male and female athletes, and for each discipline. RESULTS: From a total of 8925 male and 7614 female registered athletes, 928 injuries were reported in male and 597 in female athletes. The discipline accounting for the highest proportion of injuries was sprints, for both men (24%) and women (26%). The number of injuries per 1000 registered athletes varied between disciplines for men and women: highest in combined events for male athletes (235 (95% CI 189 to 281)) and female athletes (212 (95% CI 166 to 257)), and lowest for male throwers (47 (95% CI 35 to 59)) and female throwers (32 (95% CI 21 to 43)) and for female race walkers (42 (95% CI 19 to 66)). Injury characteristics varied significantly between disciplines for location, type, cause and severity in male and female athletes. Thigh muscle injuries were the main diagnoses in the disciplines sprints, hurdles, jumps, combined events and race walking, lower leg muscle injuries in marathon running, lower leg skin injury in middle and long distance running, and trunk muscle and lower leg muscle injuries in throws. CONCLUSIONS: Injury characteristics differed substantially between disciplines during international athletics championships. Strategies for medical service provision (eg, staff, facilities) during athletics championships should be discipline specific and be prepared for targeting the main injuries in each discipline.

Evolution of Functional Recovery using Hop Test Assessment after ACL Reconstruction.

The purpose of this study was to evaluate improvements in functional performance through the use of the Limb Symmetry Index of Single and Triple Hop tests between 12 and 52 weeks after anterior cruciate ligament reconstruction, and to compare these values with usual time-based and performance-based criteria used during the return to sport continuum. Repeated functional assessments using Single and Triple Hop Tests at 12, 16, 22, 26, 39 and 52 postoperative weeks were evaluated. At each session, the median and interquartile range of Limb Symmetry Index of tests were calculated and compared with the usual criteria: return to participation:≥85%, between 12-16 w; return to play:≥90%, between 26-39 w. The results indicate that the median increased over time to 39 postoperative weeks and then stabilized. For Single Hop Test, wide variability was seen at 12 and 16 weeks (interquartile range=20%); this was lower from 22 to 52 weeks (interquartile range=8-6%). At 12 weeks for Single Hop Test, the median was 83.6% and did not meet>85% criteria for return to participation. Hop tests could be interesting functional tests to follow the functional recovery and help decision-making regarding return to participation and return to play.

Features of Chronic Exertional Compartmental Syndrome of the Leg in Elite Nordic Skiers.

This study aimed to assess prevalence and incidence of chronic exertional compartmental syndrome as well as functional outcomes after surgery in elite Nordic skiers. An exhaustive list of 294 elite Nordic skiers from the French national teams between 1994 and 2014 was analyzed through their individual medical files in order to identify cases of chronic exertional compartmental syndrome. Eighteen athletes had confirmed diagnosis and performed a structured interview to identify factors associated with chronic exertional compartmental syndrome and surgery outcomes. The prevalence was 6.1% and the incidence 13 per 1000 skier-years. Biathletes had a higher prevalence than cross-country skiers (OR=0.40, p=0.08). Free-technique skiing and roller-skiing were the main conditions inducing symptoms. All injured athletes had bilateral surgery and 94% of them reported no more or sporadic leg pain after. Almost 90% resumed competition at the same or higher level than prior surgery. Compare to previous studies, the incidence rate of chronic exertional compartmental syndrome is higher in French elite Nordic skiers. The higher prevalence in biathletes and the trigger during free-technique skiing suggest a contribution of this technique to this disease. This study also confirmed that surgery was an efficient therapeutic solution without compromising athletes' career.

Illnesses during 11 international athletics championships between 2009 and 2017: incidence, characteristics and sex-specific and discipline-specific differences.

BACKGROUND: Illnesses impair athletes' participation and performance. The epidemiology of illness in athletics is limited. OBJECTIVE: To describe the occurrence and characteristics of illnesses during international athletics championships (indoor and outdoor), and to analyse differences with regards to athletes' sex and participation in explosive and endurance disciplines. METHODS: During 11 international championships held between 2009 and 2017, physicians from both national medical teams and the local organising committees reported daily on all athlete illnesses using a standardised report form. Illness frequencies, incidence proportions (IPs) and rates (IRs), and relative risks (RR) with 95% CIs were calculated. RESULTS: During the 59 days of the 11 athletics championships, 546 illnesses were recorded in the 12 594 registered athletes equivalent to IP of 43.4 illnesses per 1000 registered athletes (95% CI 39.8 to 46.9) or IR of 1.2 per 1000 registered athlete days (95% CI 1.1 to 1.2). The most frequently reported illnesses were upper respiratory tract infections (18.7%), exercise-induced fatigue/hypotension/collapse (15.4%) and gastroenteritis (13.2%). No myocardial infarction was recorded. A total of 28.8% of illnesses were expected to lead to time loss from sport. The illness IP was similar in male and female athletes, with few differences in illness characteristics. During outdoor championships, the illness IP was higher in endurance than explosive disciplines (RR=1.87; 95% CI 1.58 to 2.23), with a considerably higher IP of exercise-induced illness in endurance disciplines, but a similar upper respiratory tract infection IP in both discipline groups. CONCLUSIONS: Illness prevention strategies during international athletics championships should be focused on the most frequent diagnoses in each discipline group.

Gymnastics injury incidence during the 2008, 2012 and 2016 Olympic Games: analysis of prospectively collected surveillance data from 963 registered gymnasts during Olympic Games.

OBJECTIVE: To determine the incidence and characteristics of injuries in female and male gymnastics disciplines (artistic, rhythmic and trampoline) during three Olympic Games with a view to ultimately improving injury prevention. METHODS: The National Olympic Committee's head physicians and the medical teams of the Local Organising Committee of the Olympic Games reported daily the occurrence (or non-occurrence) of newly sustained injuries in artistic, rhythmic and trampoline gymnastics on a standardised report form during the 2008, 2012 and 2016 Summer Olympic Games. RESULTS: During the three Olympic Games, 81 injuries were reported in a total of 963 registered gymnasts, corresponding to an incidence of 84 injuries (95% CI 67 to 102) per 1000 registered gymnasts, with no difference in injury incidence between female and male gymnasts. Thirty-eight per cent of injuries led to time-loss from sport. The most frequent injury location and injury type were the ankle (22%) and sprain (35%), respectively. The most common diagnosis was ankle sprain (14% of all injuries and 23% of time-loss injuries). The injury incidence was highest in female (107±35) and male artistic gymnastics (83±32), followed by female rhythmic gymnastics (73±30), and lower in male (63±69) and female (43±43) trampoline gymnastics. CONCLUSIONS: Research should focus on preventing injuries in artistic gymnastics and of the condition of ankle sprain. Injury surveillance studies should be continued during major championships and throughout the entire competitive season as the Olympic Games provides only a snapshot (although an important one).

Criteria for return to running after anterior cruciate ligament reconstruction: a scoping review.

OBJECTIVE: To describe the criteria used to guide clinical decision-making regarding when a patient is ready to return to running (RTR) after ACL reconstruction. DESIGN: Scoping review. DATA SOURCES: The MEDLINE (PubMed), EMBASE, Web of Science, PEDro, SPORTDiscus and Cochrane Library electronic databases. We also screened the reference lists of included studies and conducted forward citation tracking. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Reported at least one criterion for permitting adult patients with primary ACL reconstruction to commence running postoperatively. RESULTS: 201 studies fulfilled the inclusion criteria and reported 205 time-based criteria for RTR. The median time from when RTR was permitted was 12 postoperative weeks (IQR=3.3, range 5-39 weeks). Fewer than one in five studies used additional clinical, strength or performance-based criteria for decision-making regarding RTR. Aside from time, the most frequently reported criteria for RTR were: full knee range of motion or >95% of the non-injured knee plus no pain or pain <2 on visual analogue scale; isometric extensor limb symmetry index (LSI)>70% plus extensor and flexor LSI>70%; and hop test LSI>70%. CONCLUSIONS: Fewer than one in five studies reported clinical, strength or performance-based criteria for RTR even though best evidence recommends performance-based criteria combined with time-based criteria to commence running activities following ACL reconstruction.