Roald Bahr

How much is too much? (Part 2) International Olympic Committee consensus statement on load in sport and risk of illness

Athletes participating in elite sports are exposed to high training loads and increasingly saturated competition calendars. Emerging evidence indicates that poor load management is a major risk factor for injury. The International Olympic Committee convened an expert group to review the scientific evidence for the relationship of load (defined broadly to include rapid changes in training and competition load, competition calendar congestion, psychological load and travel) and health outcomes in sport. We summarise the results linking load to risk of injury in athletes, and provide athletes, coaches and support staff with practical guidelines to manage load in sport. This consensus statement includes guidelines for (1) prescription of training and competition load, as well as for (2) monitoring of training, competition and psychological load, athlete well-being and injury. In the process, we identified research priorities.

Why screening tests to predict injury do not work—and probably never will…: a critical review

This paper addresses if and how a periodic health examination to screen for risk factors for injury can be used to mitigate injury risk. The key question asked is whether it is possible to use screening tests to identify who is at risk for a sports injury—in order to address the deficit through a targeted intervention programme. The paper demonstrates that to validate a screening test to predict and prevent sports injuries, at least 3 steps are needed. First, a strong relationship needs to be demonstrated in prospective studies between a marker from a screening test and injury risk (step 1). Second, the test properties need to be examined in relevant populations, using appropriate statistical tools (step 2). Unfortunately, there is currently no example of a screening test for sports injuries with adequate test properties. Given the nature of potential screening tests (where test performance is usually measured on a continuous scale from low to high), substantial overlap is to be expected between players with high and low risk of injury. Therefore, although there are a number of tests demonstrating a statistically significant association with injury risk, and therefore help the understanding of causative factors, such tests are unlikely to be able to predict injury with sufficient accuracy. The final step needed is to document that an intervention programme targeting athletes identified as being at high risk through a screening programme is more beneficial than the same intervention programme given to all athletes (step 3). To date, there is no intervention study providing support for screening for injury risk.

Hamstring and Quadriceps Isokinetic Strength Deficits Are Weak Risk Factors for Hamstring Strain Injuries A 4-Year Cohort Study

Background: A hamstring strain injury (HSI) has become the most common noncontact injury in soccer. Isokinetic muscle strength deficits are considered a risk factor for HSIs. However, underpowered studies with small sample sizes unable to determine small associations have led to inconclusive results regarding the role of isokinetic strength and strength testing in HSIs. Purpose: To examine whether differences in isokinetic strength measures of knee flexion and extension represent risk factors for hamstring injuries in a large cohort of professional soccer players in an adequately powered study design. Study Design: Cohort study; Level of evidence, 2. Methods: A total of 614 professional soccer players from 14 teams underwent isokinetic strength testing during preseason screening. Testing consisted of concentric knee flexion and extension at 60 deg/s and 300 deg/s and eccentric knee extension at 60 deg/s. A clustered multiple logistic regression analysis was used to identify variables associated with the risk of HSIs. Receiver operating characteristic (ROC) curves were calculated to determine sensitivity and specificity. Results: Of the 614 players, 190 suffered an HSI during the 4 seasons. Quadriceps concentric strength at 60 deg/s (odds ratio [OR], 1.41; 95% CI, 1.03-1.92; P = .03) and hamstring eccentric strength at 60 deg/s (OR, 1.37; 95% CI, 1.01-1.85; P = .04) adjusted for bodyweight were independently associated with the risk of injuries. The absolute differences between the injured and uninjured players were 6.9 N·m and 9.1 N·m, with small effect sizes (d < 0.2). The ROC analyses showed an area under the curve of 0.54 and 0.56 for quadriceps concentric strength and hamstring eccentric strength, respectively, indicating a failed combined sensitivity and specificity of the 2 strength variables identified in the logistic regression models. Conclusion: This study identified small absolute strength differences and a wide overlap of the absolute strength measurements at the group level. The small associations between lower hamstring eccentric strength and lower quadriceps concentric strength with HSIs can only be considered as weak risk factors. The identification of these risk factors still does not allow the identification of individual players at risk. The use of isokinetic testing to determine the association between strength differences and HSIs is not supported.

A peek into the future of sports medicine: the digital revolution has entered our pitch

The current wide-scale availability of the internet and connected mobile devices is revolutionising healthcare. Patients and practitioners have unprecedented access to health information; they communicate with each more than ever before. It seems as if new technology is appearing daily and with it comes the promise of greater (cost) efficiency and quality of medical practise.1 The sports medicine community is currently buzzing about ‘eHealth’, which may be defined as the practise of medicine supported by electronic processes and communication. The newest buzzword is ‘mHealth’, referring to eHealth driven by the use of mobile devices, not limited to smartphones. Indeed, we are seeing an increased use of readily available technologies such as SMS messaging, social media platforms, apps and online questionnaires in both clinical and research settings.nnGrindem et al 2 illustrate how online technologies can aid clinical practice. Specifically they monitored return-to-sport after an anterior cruciate ligament (ACL) injury; one of the clinical ‘success’ measures of postinjury rehabilitation. Current methods that register sports activity after ACL injury are usually restricted to knee-demanding sports alone to limit the time-burden for patients and to ensure valid data collection. Participation …

Hamstring Reinjuries Occur at the Same Location and Early After Return to Sport A Descriptive Study of MRI-Confirmed Reinjuries

Background: Despite relatively high reinjury rates after acute hamstring injuries, there is a lack of detailed knowledge about where and when hamstring reinjuries occur, and studies including imaging-confirmed reinjuries are scarce. Purpose: To investigate the location, radiological severity, and timing of reinjuries on magnetic resonance imaging (MRI) compared with the index injury. Study Design: Case series; Level of evidence, 4. Methods: A MRI scan was obtained ≤5 days after an acute hamstring index injury in 180 athletes, and time to return to sport (RTS) was registered. Athletes with an MRI-confirmed reinjury in the same leg ≤365 days after RTS were included. Categorical grading and standardized MRI parameters of the index injury and reinjury were scored by a single radiologist (with excellent intraobserver reliability). To determine the location of the reinjury, axial and coronal views of the index injury and reinjury were directly compared on proton density–weighted fat-suppressed images. Results: In the 19 athletes included with reinjury, 79% of these reinjuries occurred in the same location within the muscle as the index injury. The median time to RTS after the index injury was 19 days (range, 5-37 days; interquartile range [IQR], 15 days). The median time between the index injury and reinjury was 60 days (range, 20-316 days; IQR, 131 days) and the median time between RTS after the index injury and the reinjury was 24 days (range, 4-311 days; IQR, 140 days). More than 50% of reinjuries occurred within 25 days (4 weeks) after RTS from the index injury and 50% occurred within 50 days after the index injury. All reinjuries with more severe radiological grading occurred in the same location as the index injury. Conclusion: The majority of the hamstring reinjuries occurred in the same location as the index injury, early after RTS and with a radiologically greater extent, suggesting incomplete biological and/or functional healing of the index injury. Specific exercise programs focusing on reinjury prevention initiated after RTS from the index injury are highly recommended.

Validation of an inertial measurement unit for the measurement of jump count and height

OBJECTIVESnTo validate the use of an inertial measurement unit (IMU) for the collection of total jump count and assess the validity of an IMU for the measurement of jump height against 3-D motion analysis.nnnDESIGNnCross sectional validation study.nnnSETTINGn3D motion-capture laboratory and field based settings.nnnPARTICIPANTSnThirteen elite adolescent volleyball players.nnnINDEPENDENT VARIABLESnParticipants performed structured drills, played a 4 set volleyball match and performed twelve counter movement jumps.nnnMAIN OUTCOME MEASURESnJump counts from structured drills and match play were validated against visual count from recorded video. Jump height during the counter movement jumps was validated against concurrent 3-D motion-capture data.nnnRESULTSnThe IMU device captured more total jumps (1032) than visual inspection (977) during match play. During structured practice, device jump count sensitivity was strong (96.8%) while specificity was perfect (100%). The IMU underestimated jump height compared to 3D motion-capture with mean differences for maximal and submaximal jumps of 2.5xa0cm (95%CI: 1.3 to 3.8) and 4.1xa0cm (3.1-5.1), respectively.nnnCONCLUSIONnThe IMU offers a valid measuring tool for jump count. Although the IMU underestimates maximal and submaximal jump height, our findings demonstrate its practical utility for field-based measurement of jump load.

Intra- and interrater reliability of three different MRI grading and classification systems after acute hamstring injuries

OBJECTIVEnTo assess and compare the intra- and interrater reliability of three different MRI grading and classification systems after acute hamstring injury.nnnMETHODSnMale athletes (n=40) with clinical diagnosis of acute hamstring injury and MRI ≤5days were selected from a prospective cohort. Two radiologists independently evaluated the MRIs using standardised scoring form including the modified Peetrons grading system, the Chan acute muscle strain injury classification and the British Athletics Muscle Injury Classification. Intra-and interrater reliability was assessed with linear weighted kappa (κ) or unweighted Cohens κ and percentage agreement was calculated.nnnRESULTSnWe observed substantial to almost perfect intra- (κ range 0.65-1.00) and interrater reliability (κ range 0.77-1.00) with percentage agreement 83-100% and 88-100%, respectively, for severity gradings, overall anatomical sites and overall classifications for the three MRI systems. We observed substantial variability (κ range -0.05 to 1.00) for subcategories within the Chan classification and the British Athletics Muscle Injury Classification, however, the prevalence of positive scorings was low for some subcategories.nnnCONCLUSIONSnThe modified Peetrons grading system, overall Chan classification and overall British Athletics Muscle Injury Classification demonstrated substantial to almost perfect intra- and interrater reliability when scored by experienced radiologists. The intra- and interrater reliability for the anatomical subcategories within the classifications remains unclear.

A valid and reliable method to measure jump-specific training and competition load in elite volleyball players

Use of a commercially available wearable device to monitor jump load with elite volleyball players has become common practice. The purpose of this study was to evaluate the validity and reliability of this device, the Vert, to count jumps and measure jump height with professional volleyball players. Jump count accuracy was determined by comparing jumps recorded by the device to jumps observed through systematic video analysis of three practice sessions and two league matches performed by a mens professional volleyball team. Jumps performed by 14 players were each coded for time and jump type and individually matched to device recorded jumps. Jump height validity of the device was examined against reference standards as participants performed countermovement jumps on a force plate and volleyball‐specific jumps with a Vertec. The Vert device accurately counted 99.3% of the 3637 jumps performed during practice and match play. The device showed excellent jump height interdevice reliability for two devices placed in the same pouch during volleyball jumps (r = .99, 95% CI 0.98‐0.99). The device had a minimum detectable change (MDC) of 9.7 cm and overestimated jump height by an average of 5.5 cm (95% CI 4.5‐6.5) across all volleyball jumps. The Vert device demonstrates excellent accuracy counting volleyball‐specific jumps during training and competition. While the device is not recommended to measure maximal jumping ability when precision is needed, it provides an acceptable measure of on‐court jump height that can be used to monitor athlete jump load.

Lunacy revisited – the myth of the full moon: are football injuries related to the lunar cycle?

ABSTRACT Previous literature suggests that human behaviour and physiology are somehow altered by the moon-cycle, with particular emphasis on poorer sleep quality and increased aggressive behaviour during full moon. The latter variables can negatively impact athletes’ recovery and increase the likelihood of injury resulting from collision with another athlete. Therefore, the current study aimed to investigate the association between the lunar cycle and injury risk in professional football players (soccer). We monitored injuries and player exposure in the premier professional league in Qatar during four consecutive seasons (2013–2014 through 2016–2017). Acute (sudden-onset traumatic) injuries (n = 1184; 587 from contact with another player and 597 without player contact) recorded during matches and training were classified according to the lunar cycle characteristics on the date of injury: (i) moon illumination, (ii) lunar distance from earth and (iii) tidal coefficient, acquired from the lunar calendar and tide tables. We used a Poisson regression model to examine the relationship between injury risk and lunar cycle characteristics. We did not detect any association between injury risk and moon illumination, earth-to-moon distance or tidal coefficient, not for all acute injuries, nor for contact and non-contact injuries when examined separately. The findings suggest that the full moon or new moon or the gravitational pull have no effect on football injuries. Thus, organisers need not consult moon or tide tables when planning future event schedules.

Beach Soccer Injuries During the Japanese National Championships.

Background: The frequency and severity of injury in beach soccer are unknown. Purpose: To estimate the incidence rates, characteristics, and risk factors for injuries associated with beach soccer. Study Design: Cohort study; Level of evidence, 3. Methods: The same sports physician examined and recorded injuries incurred during the Japanese National Beach Soccer Championships in 2013 and 2014. Posttournament follow-up was made for all injuries. Match exposure for each player was recorded through video review to examine individual risk factors. Results: A total of 58 injuries were recorded during 54 matches. The overall injury rate was 179.0 (95% CI, 138.4-231.6), and the time-loss injury rate was 28.2 (95% CI, 14.7-54.1) per 1000 player-hours. The foot/toe (34.9%) was the most frequently injured area, followed by the lower leg (22.2%) and thigh (11.1%). There was only 1 ankle injury (1.6%). The most frequent injury type was contusions (60.3%), followed by lacerations/abrasions (14.3%) and sprains/ligament injuries (6.3%). Only 4 injuries resulted in ≥30 days of time-loss (7.4%). After adjusting for age, a previous history of severe injury and longer experience of beach soccer were significantly associated with injury risk. Conclusion: The time-loss injury rate in this study was comparable to the rates reported during the matches of soccer or futsal tournaments. However, a greater incidence of foot/toe injury and lacerations/abrasions as well as a lower incidence of ankle injury distinguished beach soccer from soccer and futsal, possibly related to the specific playing conditions of being barefoot on a sand surface.