TRAINING LOAD PRIOR TO INJURY IN PROFESSIONAL RUGBY LEAGUE PLAYERS: ANALYSING INJURY RISK WITH MACHINE LEARNING

This study explores the application of Global Positioning System tracking data from field training sessions and supervised machine learning algorithms for predicting injury risk of players across a single National Rugby League season. Previous work across a range of sporting codes has demonstrated associations between training loads and increased incidence of injury in professional athletes. Most of the work conducted has applied a reductionist approach, identifying training load characteristics as risk factors using generalised models to show population trends. This study demonstrates promising results by applying processing techniques and machine learning algorithms to analyse the injury risk associated with complex training load patterns. The accuracy of the algorithms are investigated along with the importance of training load predictors and data window sizes

Exercise tolerance during flat over-ground intermittent running: modelling the expenditure and reconstitution kinetics of work done above critical power

Purpose We compared a new locomotor-specific model to track the expenditure and reconstitution of work done above critical power (W´) and balance of W´ (W´BAL) by modelling flat over-ground power during exhaustive intermittent running. Method Nine male participants completed a ramp test, 3-min all-out test and the 30–15 intermittent fitness test (30–15 IFT), and performed a severe-intensity constant work-rate trial (SCWR) at the maximum oxygen uptake velocity (vV̇O2max). Four intermittent trials followed: 60-s at vV̇O2max + 50% Δ1 (Δ1 = vV̇O2max − critical velocity [VCrit]) interspersed by 30-s in light (SL; 40% vV̇O2max), moderate (SM; 90% gas-exchange threshold velocity [VGET]), heavy (SH; VGET + 50% Δ2 [Δ2 = VCrit − VGET]), or severe (SS; vV̇O2max − 50% Δ1) domains. Data from Global Positioning Systems were derived to model over-ground power. The difference between critical and recovery power (DCP), time constant for reconstitution of W´ (τW′), time to limit of tolerance (TLIM), and W´BAL from the integral (W´BALint), differential (W´BALdiff), and locomotor-specific (OG-W´BAL) methods were compared.Results The relationship between τW′ and DCP was exponential (r2 = 0.52). The τW′ for SL, SM, and SH trials were 119 ± 32-s, 190 ± 45-s, and 336 ± 77-s, respectively. Actual TLIM in the 30–15 IFT (968 ± 117-s) compared closely to TLIM predicted by OG-W´BAL (929 ± 94-s, P > 0.100) and 0.100) and W´BALdiff (938 ± 84-s, P > 0.100) but not to 0.100) but not to W´BALint (848 ± 91-s, P = 0.001). Conclusion The OG-W´BAL accurately tracked W´ kinetics during intermittent running to exhaustion on flat surfaces

Importance, reliability and usefulness of acceleration measures in team sports

Abstract: Delaney, JA, Cummins, CJ, Thornton, HR, and Duthie, GM. Importance, reliability and usefulness of acceleration measures in team sports. J Strength Cond Res 32(12): 3494-3502, 2018-The ability to accelerate, decelerate, and change direction efficiently is imperative to successful team sports performance. Traditional intensity-based thresholds for acceleration and deceleration may be inappropriate for time-series data and have been shown to exhibit poor reliability, suggesting other techniques may be preferable. This study assessed movement data from one professional rugby league team throughout 2 full seasons and 1 preseason period. Using both 5 and 10 Hz global positioning systems (GPS) units, a range of acceleration-based variables were evaluated for their interunit reliability, ability to discriminate between positions, and associations with perceived muscle soreness. The reliability of 5 Hz global positioning systems for measuring acceleration and deceleration ranged from good to poor (CV = 3.7-27.1%), with the exception of high-intensity deceleration efforts (CV = 11.1-11.8%), the 10 Hz units exhibited moderate-to-good interunit reliability (CV = 1.2-6.9%). Reliability of average metrics (average acceleration/deceleration, average acceleration, and average deceleration) ranged from good to moderate (CV = 1.2-6.5%). Substantial differences were detected between positions using time spent accelerating and decelerating for all magnitudes, but these differences were less clear when considering the count or distance above acceleration/deceleration thresholds. All average metrics detected substantial differences between positions. All measures were similarly related to perceived muscle soreness, with the exception of high-intensity acceleration and deceleration counts. This study has proposed that averaging the acceleration/deceleration demands over an activity may be a more appropriate method compared with threshold-based methods, because a greater reliability between units, while not sacrificing sensitivity to within-subject and between-subject changes

Isolated & combined wearable technology underestimate the total energy expenditure of professional young rugby league players ; a doubly labelled water validation study

Accurately determining total energy expenditure enables the precise manipulation of energy balance within professional collision-based sports. Therefore, this study investigated the ability of isolated or combined wearable technology to determine the total energy expenditure of professional young rugby league players across a typical pre-season and in-season period. Total energy expenditure was measured via doubly labelled water, the criterion method, across a fourteen-day pre-season (n=6) and seven-day in-season (n=7) period. Practical measures of total energy expenditure included SenseWear Pro3 Armbands in isolation and combined with metabolic power derived from microtechnology units. SenseWear Pro3 Armbands significantly under-reported pre-season (5.00 (2.52) MJ.day-1; p = 0.002) and in-season (2.86 (1.15) MJ.day-1; p < 0.001) total energy expenditure, demonstrating a large and extremely large standardised mean bias, and a very large and large typical error, respectively. Combining metabolic power with SenseWear Pro3 Armbands almost certainly improved pre-season (0.95 (0.15) MJ.day-1; ES = 0.32 ±0.04; p < 0.001) and in-season (1.01 (0.15) MJ.day-1; ES = 0.88 ±1.05; p < 0.001) assessment. However, SenseWear Pro3 Armbands combined with metabolic power continued to significantly under-report pre-season (4.04 (2.38) MJ.day-1; p = 0.004) and in-season (2.18 (0.96) MJ.day-1; p = 0.002) expenditure, demonstrating a large and very large standardised mean bias, and a very large and large typical error, respectively. These findings demonstrate the limitations of utilising isolated or combined wearable technology to accurately determine the total energy expenditure of professional collision-based sport athletes across different stages of the season

Correction to: Quantifying the Collision Dose in Rugby League: A Systematic Review, Meta-analysis, and Critical Analysis

An amendment to this paper has been published and can be accessed via the original article

Sports-related injuries in New Zealand: National Insurance (Accident Compensation Corporation) claims for five sporting codes from 2012 to 2016

**Objectives** To provide epidemiological data and related costs for sport-related injuries of five sporting codes (cricket, netball, rugby league, rugby union and football) in New Zealand for moderate-to-serious and serious injury claims. **Methods** A retrospective analytical review using detailed descriptive epidemiological data obtained from the Accident Compensation Corporation (ACC) for 2012–2016. **Results** Over the 5 years of study data, rugby union recorded the most moderate-to-serious injury entitlement claims (25 226) and costs (New Zealand dollars (NZD$)267 359 440 (£139 084 749)) resulting in the highest mean cost (NZD$10 484 (£5454)) per moderate-to-serious injury entitlement claim. Rugby union recorded more serious injury entitlement claims (n=454) than cricket (t(4)=−66.6; P<0.0001); netball (t(4)=−45.1; P<0.0001); rugby league (t(4)=−61.4; P<0.0001) and football (t(4)=66.6; P<0.0001) for 2012–2016. There was a twofold increase in the number of female moderate-to-serious injury entitlement claims for football (RR 2.6 (95%CI 2.2 to 2.9); P<0.0001) compared with cricket, and a threefold increase when compared with rugby union (risk ratio (RR) 3.1 (95%CI 2.9 to 3.3); P<0.0001). Moderate-to-serious concussion claims increased between 2012 and 2016 for netball (RR 3.7 (95%CI 1.9 to 7.1); P<0.0001), rugby union (RR 2.0 (95% CI 1.6 to 2.4); P<0.0001) and football (RR 2.3 (95%CI 1.6 to 3.2); P<0.0001). Nearly a quarter of moderate-to-serious entitlement claims (23%) and costs (24%) were to participants aged 35 years or older. **Conclusions** Rugby union and rugby league have the highest total number and costs associated with injury. Accurate sport exposure data are needed to enable injury risk calculations

The propensity of non-concussive and concussive head contacts during elite-level women's rugby league matches : A prospective analysis of over 14,000 tackle events

Objectives Identify the frequency, propensity, and factors related to tackle events which result in contact with the head in elite-level women's rugby league. Design Prospective video analysis study. Methods Video footage from 59 Women's Super League matches were analysed (n = 14,378 tackle events). All tackle events were coded as no head contact or head contact. Other independent variables included: area contacting head, impacted player, concussion outcome, penalty outcome, round of competition, time in match and team standard. Results There were 83.0 ± 20.0 (propensity 304.0/1000 tackle events) head contacts per match. The propensity of head contact was significantly greater for the tackler than ball-carrier (178.5 vs. 125.7/1000 tackle events; incident rate ratio 1.42, 95 % confidence interval 1.34 to 1.50). Head contacts occurring from an arm, shoulder, and head occurred significantly more than any other contact type. The propensity of concussions was 2.7/1000 head contacts. There was no significant influence of team standard or time in match on the propensity of head contacts. Conclusions The observed head contacts can inform interventions, primarily focusing on the tackler not contacting the ball-carrier's head. The tackler's head should also be appropriately positioned to avoid contact with the ball-carrier's knee (highest propensity for concussion). The findings are consistent with other research in men's rugby. Law modifications and/or enforcement (reducing the number of un-penalised head contacts), concurrent with coaching interventions (optimising head placement or reducing the head being contacted) may help minimise head contact risk factors for women's rugby league

Modelling the relationships between volume, intensity and injury-risk in professional rugby league players

Objective This study aimed to: (a) identify the association between external-workloads and injury-risk in the subsequent week; and (b) understand the effectiveness of workload variables in establishing injury-risk. Design Retrospective cohort study. Methods Workload and injury data (soft-tissue) were collected from forty-eight professional male rugby league players. Load variables included duration (min), total distance (m), relative distance (m min−1), high speed distance ([m]&gt;20 km h−1), very-high speed distance ([m]&gt;25 km h−1), acceleration and deceleration efforts (count) and PlayerLoad (Arbitrary Unit: AU). Cumulative two-, three- and four-weekly loads; Acute:Chronic Workload Ratio (ACWR); Mean-Standard Deviation Workload Ratio (MSWR) and strain values were calculated and divided into three equally-sized bins (low, moderate and high). Generalised Estimating Equations analysed relationships between workload variables and injury probability in the subsequent week. Results Injury-risk increased alongside increases in the ACWR for duration, total distance and PlayerLoad. Conversely, injury-risk decreased (Area Under Curve: 0.569–0.585) with increases in the four-weekly duration, total distance, accelerations, decelerations and PlayerLoad. For relative distance, high four-weekly workloads (high: &gt;60 m min−1) demonstrated a positive association with injury-risk, whilst high two-weekly loads (high: &gt;82 m min−1) were negatively associated. Conclusions A range of external workload metrics and summary statistics demonstrate either positive or negative associations with injury-risk status. Such findings provide the framework for the development of decision-support systems in which external workload metrics (e.g. total or high speed distance) can be uniquely and routinely monitored across a range of summary statistics (i.e. cumulative weekly loads and ACWR) in order to optimise player performance and welfare

Forest-Stream Linkages: Effects of Terrestrial Invertebrate Input and Light on Diet and Growth of Brown Trout (Salmo trutta) in a Boreal Forest Stream

Subsidies of energy and material from the riparian zone have large impacts on recipient stream habitats. Human-induced changes, such as deforestation, may profoundly affect these pathways. However, the strength of individual factors on stream ecosystems is poorly understood since the factors involved often interact in complex ways. We isolated two of these factors, manipulating the flux of terrestrial input and the intensity of light in a 2×2 factorial design, where we followed the growth and diet of two size-classes of brown trout (Salmo trutta) and the development of periphyton, grazer macroinvertebrates, terrestrial invertebrate inputs, and drift in twelve 20 m long enclosed stream reaches in a five-month-long experiment in a boreal coniferous forest stream. We found that light intensity, which was artificially increased 2.5 times above ambient levels, had an effect on grazer density, but no detectable effect on chlorophyll a biomass. We also found a seasonal effect on the amount of drift and that the reduction of terrestrial prey input, accomplished by covering enclosures with transparent plastic, had a negative impact on the amount of terrestrial invertebrates in the drift. Further, trout growth was strongly seasonal and followed the same pattern as drift biomass, and the reduction of terrestrial prey input had a negative effect on trout growth. Diet analysis was consistent with growth differences, showing that trout in open enclosures consumed relatively more terrestrial prey in summer than trout living in covered enclosures. We also predicted ontogenetic differences in the diet and growth of old and young trout, where we expected old fish to be more affected by the terrestrial prey reduction, but we found little evidence of ontogenetic differences. Overall, our results showed that reduced terrestrial prey inputs, as would be expected from forest harvesting, shaped differences in the growth and diet of the top predator, brown trout

The Application Of Global Positioning Systems (GPS) and Microtechnology Sensors within Elite Rugby League

The application of microtechnology devices (Global Positioning Systems (GPS) and integrated triaxial accelerometers) has become common practice in team sports due to the ability to provide objective information on the physiological requirements of match-play and training. The aims of this thesis were to review the literature examining the application of GPS technology in team sports; and utilise novel applications of GPS and integrated accelerometer technology in rugby league to quantify pre-season training loads, match collision forces and the energetic demands of match-play; as well as to examine positional group differences. GPS was used to measure training demands, video and accelerometer data were utilised to quantify collision forces, and energetic demands were estimated via a time-motion model from accelerometer data. The systematic review highlighted inconsistencies in movement demand classifications and the difficulties encountered in quantifying collisions/impacts. The four studies identified marked differences in positional specific demands throughout training and match-play. Pre-season training differences in various external load parameters were observed in drills where players trained within specific positions, whereas minimal differences were evident between positional groups within conditioning, generic skill and speed/agility drills. Outside backs as full-match players expended the most energy per match from increased running demands, but experienced the lowest collision demands, the majority of which arose from attacking play. Adjustables, also full-match players (apart from hookers who interchange), experienced elevated energy expenditure from increased anaerobic demands, however sustained reduced collision demands. As interchange players, hit-up and wide-running forwards expended the least energy (due to decreased running demands), but endured increased collision demands. Indeed, hit-up forwards performed five times more tackles per minute than outside backs and twice as many hit-ups per minute as adjustables. However, despite differences in total energy expenditure, the anaerobic work performed by the outside backs and wide-running forwards at high speed equates to a similar load on the metabolic system as the accelerated running patterns of adjustables and hit-up forwards. The differential positional demands identified indicate that position-specific conditioning drills are required to replicate the energetic and collision demands of match-play