Effect of Data-Processing Methods on Acceleration Summary Metrics of GNSS Devices in Elite Australian Football.

This study aimed to measure the differences in commonly used summary acceleration metrics during elite Australian football games under three different data processing protocols (raw, custom-processed, manufacturer-processed). Estimates of distance, speed and acceleration were collected with a 10-Hz GNSS tracking technology device from fourteen matches of 38 elite Australian football players from one team. Raw and manufacturer-processed data were exported from respective proprietary software and two common summary acceleration metrics (number of efforts and distance within medium/high-intensity zone) were calculated for the three processing methods. To estimate the effect of the three different data processing methods on the summary metrics, linear mixed models were used. The main findings demonstrated that there were substantial differences between the three processing methods; the manufacturer-processed acceleration data had the lowest reported distance (up to 184 times lower) and efforts (up to 89 times lower), followed by the custom-processed distance (up to 3.3 times lower) and efforts (up to 4.3 times lower), where raw data had the highest reported distance and efforts. The results indicated that different processing methods changed the metric output and in turn alters the quantification of the demands of a sport (volume, intensity and frequency of the metrics). Coaches, practitioners and researchers need to understand that various processing methods alter the summary metrics of acceleration data. By being informed about how these metrics are affected by processing methods, they can better interpret the data available and effectively tailor their training programs to match the demands of competition.

Changing the criteria applied to acceleration and deceleration efforts changes the types of player actions detected.

This study identified and profiled the types of player actions of Australian football players executed during high acceleration and/or deceleration efforts and identified how the duration exceeding the acceleration or deceleration threshold influenced the identified executed player actions. The commencing speed of the acceleration and deceleration efforts were also assessed. Acceleration and deceleration efforts of 22 Australian football players monitored with a 10-Hz GNSS device across two matches were analysed. Synchronised video footage of the matches was used to identify the player actions executed during acceleration and deceleration efforts. Linear mixed models were conducted to examine the relationship between commencing speed, player action, and duration exceeding the effort threshold. 'Linear movement' and 'jump' were the most frequently executed player actions for high accelerations and 'stop' and 'being tackled' for high decelerations. Significant differences were observed in commencing speed between player actions for the high deceleration efforts. Furthermore, it was found that a higher commencing speed was associated with an increased duration exceeding the deceleration threshold. These findings will help practitioners and researchers with selecting minimum-duration criteria for acceleration and deceleration efforts and provide an understanding of the types of player actions executed during these efforts.

Techniques to derive and clean acceleration and deceleration data of athlete tracking technologies in team sports: A scoping review.

The application of acceleration and deceleration data as a measure of an athlete's physical performance is common practice in team sports. Acceleration and deceleration are monitored with athlete tracking technologies during training and games to quantify training load, prevent injury and enhance performance. However, inconsistencies exist throughout the literature in the reported methodological procedures used to quantify acceleration and deceleration. The object of this review was to systematically map and provide a summary of the methodological procedures being used on acceleration and deceleration data obtained from athlete tracking technologies in team sports and describe the applications of the data. Systematic searches of multiple databases were undertaken. To be included, studies must have investigated full body acceleration and/or deceleration data of athlete tracking technologies. The search identified 276 eligible studies. Most studies (60%) did not provide information on how the data was derived and what sequence of steps were taken to clean the data. Acceleration and deceleration data were commonly applied to quantify and describe movement demands using effort metrics. This scoping review identified research gaps in the methodological procedures and deriving and cleaning techniques that warrant future research focussing on their effect on acceleration and deceleration data.

Interchangeability of player movement variables from different athlete tracking systems in professional soccer.

This study assessed the interchangeability between 10-Hz multi-GNSS GPS devices (Vector®) and two optical tracking systems (TRACAB® and Second Spectrum®). The agreement between data from the optical tracking systems when processed with manufacturer and GPS-filtered software was also assessed. Thirty players competing in the English Premier League were monitored using three different tracking systems across five matches. To determine the interchangeability between systems, player movement variables including, total distance, high-speed running distance (19.8-25.2 km·h-1), sprinting distance (>25.2 km·h-1), efforts >19.8 km·h-1 and maximal speed were compared. Equations were formed using linear regression and linear mixed-effects models to allow interchangeability of player movement variables between systems. Over half of the variance of most interchangeability equations were explained and associated with very strong positive correlations (r > 0.72). Small to huge differences were found between systems for most player movement variables. Data of optical tracking systems had decreased values in speed variables >19.8 km·h-1 when processed through GPS software. This study provides equations for practitioners to interchange player movement variables between TRACAB, Second Spectrum and Vector GPS systems with reduced error. This will enable practitioners to combine and share data captured with different tracking systems to analyse and improve their training.

External load differences between elite youth and professional football players: ready for take-off?

This study examines differences in weekly load between the first (FT) and the under 19 team (U19) within a professional football setting. Data were collected in 11 FT and 9 U19 players (2016-2017 season). FT data was divided into weeks with (FT-M1) or without (FT-M0) a mid-week match. Indicators were total distance (TD) and TD at 12-15, 15-20, 20-25 and >25 km‧h-1 and were analysed as external load (m), intensity (m‧min-1) and load monotony (a.u.). TD-based load was higher for U19 compared to FT-M0 (very likely moderate) and FT-M1 (likely large). Differences at higher velocities were substantially less (trivial to possibly small), with TD >25 km‧h-1 being lower than FT-M0 (very likely moderate) and FT-M1 (likely small). All intensity indicators were lower for U19 (likely small to almost certainly large). Load monotony was higher compared to FT-M1 (possibly small to almost certainly very large). Compared to FT-M0, monotony was higher for TD (possibly very large) and TD >25 km‧h­1 (possibly moderate) but lower for TD 12-15 (possibly small) and 15-20 km‧h­1 (likely moderate). So, despite higher weekly external loads at low velocity for elite youth players, external intensity and load variation increases when these players may transition to professional football.

A survey of talent identification and development processes in the youth academies of professional soccer clubs from around the world.

Talent identification (TID) and development (TDE) are large fields in professional soccer and in science. However,  TID and TDE processes in youth academies have not been assessed in detail. As such, our aim was to survey professional clubs from around the world about their youth academy TID and TDE processes, with 29 clubs responding to the survey. TID and TDE processes changed as a function of player age. TID processes involved finding the best players locally and regionally, but for older players the search widened to nationally and internationally for the needs of the first team. Clubs used a multidisciplinary approach to TID, but more so with older players. Median number of academy players was 80, 100, and 66 players at 8-11 years, 12-16 years, and 17-21 years, respectively. Annual player turnover in the most recent season (selections/de-selections) was 29% across all age groups, with competition from other clubs cited as a limitation to TID. TDE processes involved weekly matches and 3-5 training sessions per week led by experienced, well-qualified coaches, with most clubs providing players with academic education, residency and transportation services. Our findings extend previous research assessing professional soccer youth academy TID and TDE processes by quantifying worldwide practices.

Harmful association of sprinting with muscle injury occurrence in professional soccer match-play: A two-season, league wide exploratory investigation from the Qatar Stars League.

OBJECTIVES: To investigate the impact of physical efforts performed in the period preceding activity as a potential risk factor of muscle injury during match-play within a sample of professional soccer players. DESIGN: Observational cohort study. METHODS: Match load (running [>14.4-19.8km/h], high-speed running [>19.8-25.2km/h], sprinting [>25.2km/h], leading and explosive sprint type) averaged in 1-min and 5-min periods prior to an event or non event for 29 professional outfield soccer players. Conditional logistic and Poisson regression models estimated the relationship between load and injury for a 2 within-subject standard deviation in match load or 1-action increment in the number of sprinting activities, respectively. Associations were deemed beneficial or harmful based on non-overlap of the 95% confidence intervals against thresholds of 0.90 and 1.11, respectively. RESULTS: An increment in sprinting distance [+2-SDs=11m] covered over a 1-min period (odds ratio [OR]: 1.22, 95%CI, 1.12 to 1.33) increased the odds of muscle injury. CONCLUSIONS: Our study provides novel exploratory evidence that the volume of sprinting during competitive soccer match-play has a harmful association with muscle injury occurrence.

Goal Orientation and the Presence of Competitors Influence Cycling Performance.

Introduction: The aim of this study was to investigate time-trial (TT) performance in the presence of one competitor and in a group with competitors of various abilities. Methods: In a randomized order, 24 participants performed a 5-km cycling TT individually (IND), with one similarly matched participant (1v1), and in a group of four participants (GRP). For the GRP session, two pairs of matched participants from the 1v1 session were used. Pairs were selected so that TT duration was considered either inferior (INF) or superior (SUP) compared to the other pair of participants. Results: Overall, TT duration (P = 0.86, ηp2 < 0.01) was not different between conditions, while heart rate (HR) was significantly greater in GRP compared to IND (P < 0.01, ηp2 = 0.16). For INF, a large effect size for both mean power (P = 0.07, ηp2 = 0.15) and HR (P = 0.05, ηp2 = 0.16), indicates greatest effort in GRP. Pacing behavior was affected by competition but similar in 1v1 and GRP for SUP, while large effect sizes indicate an increased power output in the initial 750-m for INF in GRP. Additionally, for INF, there was a significant correlation with ego orientation for an increase in TT duration between the GRP session and both the IND (r = 0.43, P = 0.04) and 1v1 (r = 0.54, P = 0.01) sessions. Conclusion: For INF participants, intensity was increased when competing in GRP. Yet, the presence of the SUP competitors resulted in lesser performance improvements for ego oriented INF participants. These findings demonstrate that consideration should be given to the ability of competitors in a group setting to provide adequate motivation.

The Occurrence of Repeated High Acceleration Ability (RHAA) in Elite Youth Football.

The aim of the present study was to investigate the occurrence of Repeated High-Acceleration Ability (RHAA) bouts in elite youth football games using 10-Hz GPS devices and two relative thresholds derived from players' actual maximal acceleration. Thirty-six outfield soccer players (age 14.9±0.6 years) participated in the study. Players wore 10-Hz GPS units during 41 official games. High accelerations were defined as efforts commencing above a threshold corresponding to 70% (T70%) or 80% (T80%) of the average 5-m acceleration obtained during a 40-m sprint test; RHAA bouts were defined as ≥3 efforts with ≤45 s recovery between efforts. Results were analysed via generalised linear mixed model and magnitude-based inferential statistics. On average, 8.0±4.6 and 5.1±3.5 bouts were detected in an entire game using T70% and T80%, respectively. When all positions were analysed together, there was a very-likely small difference in the number of RHAA bouts between first and second half for T70% and T80%, respectively. RHAA bouts occur frequently in elite youth football, with small differences between halves and between playing positions within the first or second half in most variables assessed.

Effect of Match Factors on the Running Performance of Elite Female Soccer Players.

Trewin, J, Meylan, C, Varley, MC, Cronin, J, and Ling, D. Effect of match factors on the running performance of elite female soccer players. J Strength Cond Res 32(7): 2002-2009, 2018-The purpose of this study was to examine the effects of match factors on the match running of elite female soccer players. Players from the same women's national team (n = 45) were monitored during 47 international fixtures (files = 606) across 4 years (2012-2015) using 10-Hz global positioning system devices. A mixed model was used to analyze the effects of altitude, temperature, match outcome, opposition ranking, and congested schedules. At altitude (>500 m), a small increase in the number of accelerations (effect size [ES] = 0.40) and a small decrease in total distance (ES = -0.54) were observed, whereas at higher temperatures, there were decreases in all metrics (ES = -0.83 to -0.16). Playing a lower ranked team in a draw resulted in a moderate increase in high-speed running (ES = 0.89), with small to moderate decreases in total distance and low-speed running noted in a loss or a win. Winning against higher ranked opponents indicated moderately higher total distance and low-speed running (ES = 0.75), compared with a draw. Although the number of accelerations were higher in a draw against lower ranked opponents, compared with a win and a loss (ES = 0.95 and 0.89, respectively). Practitioners should consider the effect of match factors on match running in elite female soccer.

The match-to-match variation of match-running in elite female soccer.

OBJECTIVES: The purpose of this study was to examine the match-to-match variation of match-running in elite female soccer players utilising GPS, using full-match and rolling period analyses. DESIGN: Longitudinal study. METHODS: Elite female soccer players (n=45) from the same national team were observed during 55 international fixtures across 5 years (2012-2016). Data was analysed using a custom built MS Excel spreadsheet as full-matches and using a rolling 5-min analysis period, for all players who played 90-min matches (files=172). Variation was examined using co-efficient of variation and 90% confidence limits, calculated following log transformation. RESULTS: Total distance per minute exhibited the smallest variation when both the full-match and peak 5-min running periods were examined (CV=6.8-7.2%). Sprint-efforts were the most variable during a full-match (CV=53%), whilst high-speed running per minute exhibited the greatest variation in the post-peak 5-min period (CV=143%). Peak running periods were observed as slightly more variable than full-match analyses, with the post-peak period very-highly variable. Variability of accelerations (CV=17%) and Player Load (CV=14%) was lower than that of high-speed actions. Positional differences were also present, with centre backs exhibiting the greatest variation in high-speed movements (CV=41-65%). CONCLUSIONS: Practitioners and researchers should account for within player variability when examining match performances. Identification of peak running periods should be used to assist worst case scenarios. Whilst micro-sensor technology should be further examined as to its viable use within match-analyses.

The influence of successive matches on match-running performance during an under-23 international soccer tournament: The necessity of individual analysis.

This study investigated the effects of successive matches on match-running in elite under-23 soccer players during an international tournament. Match-running data was collected using a semi-automated multi-camera tracking system during an international under-23 tournament from all participating outfield players. Players who played 100% of all group stage matches were included (3 matches separated by 72 h, n = 44). Differences in match-running performance between matches were identified using a generalised linear mixed model. There were no clear effects for total, walking, jogging, running, high-speed running and sprinting distance between matches 1 and 3 (effect size (ES); -0.32 to 0.05). Positional analysis found that sprint distance was largely maintained from matches 1 to 3 across all positions. Attackers had a moderate decrease in total, jogging and running distance between matches 1 and 3 (ES; -0.72 to -0.66). Classifying players as increasers or decreasers in match-running revealed that match-running changes are susceptible to individual differences. Sprint performance appears to be maintained over successive matches regardless of playing position. However, reductions in other match-running categories vary between positions. Changes in match-running over successive matches affect individuals differently; thus, players should be monitored on an individual basis.

Familiarization Protocol Influences Reproducibility of 20-km Cycling Time-Trial Performance in Novice Participants.

Introduction: Exercise performance is reproducible in experienced athletes; however, less trained participants exhibit greater variability in performance and pacing. To reduce variability, it is common practice to complete a familiarization prior to experimental testing. However, there are no clear guidelines for familiarizing novice participants to a cycling time-trial (TT), and research findings from novice populations may still be influenced by learning effects. Accordingly, the aims of this study were to establish the variability between TTs after administering differing familiarization protocols (duration or type) and to establish the number of familiarization trials required to limit variability over multiple trials. Methods: Thirty recreationally active participants, with no prior experience of a TT, performed a 20-km cycling TT on five separate occasions, after completing either a full (FF, 20-km TT, n = 10), a half (HF, 10-km TT, n = 10) or an equipment familiarization (EF, 5-min cycling, n = 10). Results: Variability of TT duration across five TTs was the lowest after completing FF (P = 0.69, η p2 = 0.05) compared to HF (P = 0.08, η p2 = 0.26) and EF (P = 0.07, η p2 = 0.21). In the FF group after TT2, the effect size for changes in TT duration was small (d < 0.49). There were large differences between later TTs in HF (d = 1.02, TT3-TT4) and EF (d = 1.12, TT4-TT5). The variability in mean power output profiles between trials was lowest within FF, with a similar pacing profile reproduced between TT3-TT5. Discussion: Familiarization of the exercise protocol influenced reproducibility of pacing and performance over multiple, maximal TTs, with best results obtained after a full experience of the exercise compared to HF and EF. The difference of TT1 to later TTs indicates that one familiarization is not adequate in reducing the variability of performance for novice participants. After the FF and an additional TT, performance changes between TTs were small, however, a reproducible pacing profile was not developed until after the FF and two additional TTs. These findings indicate that a minimum of three full familiarizations are necessary for novice participants to limit systematic error before experimental testing.

Monitoring Athlete Training Loads: Consensus Statement.

Monitoring the load placed on athletes in both training and competition has become a very hot topic in sport science. Both scientists and coaches routinely monitor training loads using multidisciplinary approaches, and the pursuit of the best methodologies to capture and interpret data has produced an exponential increase in empirical and applied research. Indeed, the field has developed with such speed in recent years that it has given rise to industries aimed at developing new and novel paradigms to allow us to precisely quantify the internal and external loads placed on athletes and to help protect them from injury and ill health. In February 2016, a conference on "Monitoring Athlete Training Loads-The Hows and the Whys" was convened in Doha, Qatar, which brought together experts from around the world to share their applied research and contemporary practices in this rapidly growing field and also to investigate where it may branch to in the future. This consensus statement brings together the key findings and recommendations from this conference in a shared conceptual framework for use by coaches, sport-science and -medicine staff, and other related professionals who have an interest in monitoring athlete training loads and serves to provide an outline on what athlete-load monitoring is and how it is being applied in research and practice, why load monitoring is important and what the underlying rationale and prospective goals of monitoring are, and where athlete-load monitoring is heading in the future.

No Influence of Transcutaneous Electrical Nerve Stimulation on Exercise-Induced Pain and 5-Km Cycling Time-Trial Performance.

Introduction: Afferent information from exercising muscle contributes to the sensation of exercise-induced muscle pain. Transcutaneous electrical nerve stimulation (TENS) delivers low-voltage electrical currents to the skin, inhibiting nociceptive afferent information. The use of TENS in reducing perceptions of exercise-induced pain has not yet been fully explored. This study aimed to investigate the effect of TENS on exercise-induced muscle pain, pacing strategy, and performance during a 5-km cycling time trial (TT). Methods: On three separate occasions, in a single-blind, randomized, and cross-over design, 13 recreationally active participants underwent a 30-min TENS protocol, before performing a 5-km cycling TT. TENS was applied to the quadriceps prior to exercise under the following conditions; control (CONT), placebo with sham TENS application (PLAC), and an experimental condition with TENS application (TENS). Quadriceps fatigue was assessed with magnetic femoral nerve stimulation assessing changes in potentiated quadriceps twitch force at baseline, pre and post exercise. Subjective scores of exertion, affect and pain were taken every 1-km. Results: During TTs, application of TENS did not influence pain perceptions (P = 0.68, [Formula: see text] = 0.03). There was no significant change in mean power (P = 0.16, [Formula: see text] = 0.16) or TT duration (P = 0.17, [Formula: see text] = 0.14), although effect sizes were large for these two variables. Changes in power output were not significant but showed moderate effect sizes at 500-m ([Formula: see text] = 0.10) and 750-m ([Formula: see text] = 0.10). Muscle recruitment as inferred by electromyography data was not significant, but showed large effect sizes at 250-m ([Formula: see text] = 0.16), 500-m ([Formula: see text] = 0.15), and 750-m ([Formula: see text] = 0.14). This indicates a possible effect for TENS influencing performance up to 1-km. Discussion: These findings do not support the use of TENS to improve 5-km TT performance.

Variations in Hypoxia Impairs Muscle Oxygenation and Performance during Simulated Team-Sport Running.

Purpose: To quantify the effect of acute hypoxia on muscle oxygenation and power during simulated team-sport running. Methods: Seven individuals performed repeated and single sprint efforts, embedded in a simulated team-sport running protocol, on a non-motorized treadmill in normoxia (sea-level), and acute normobaric hypoxia (simulated altitudes of 2,000 and 3,000 m). Mean and peak power was quantified during all sprints and repeated sprints. Mean total work, heart rate, blood oxygen saturation, and quadriceps muscle deoxyhaemoglobin concentration (assessed via near-infrared spectroscopy) were measured over the entire protocol. A linear mixed model was used to estimate performance and physiological effects across each half of the protocol. Changes were expressed in standardized units for assessment of magnitude. Uncertainty in the changes was expressed as a 90% confidence interval and interpreted via non-clinical magnitude-based inference. Results: Mean total work was reduced at 2,000 m (-10%, 90% confidence limits ±6%) and 3,000 m (-15%, ±5%) compared with sea-level. Mean heart rate was reduced at 3,000 m compared with 2,000 m (-3, ±3 min-1) and sea-level (-3, ±3 min-1). Blood oxygen saturation was lower at 2,000 m (-8, ±3%) and 3,000 m (-15, ±2%) compared with sea-level. Sprint mean power across the entire protocol was reduced at 3,000 m compared with 2,000 m (-12%, ±3%) and sea-level (-14%, ±4%). In the second half of the protocol, sprint mean power was reduced at 3,000 m compared to 2,000 m (-6%, ±4%). Sprint mean peak power across the entire protocol was lowered at 2,000 m (-10%, ±6%) and 3,000 m (-16%, ±6%) compared with sea-level. During repeated sprints, mean peak power was lower at 2,000 m (-8%, ±7%) and 3,000 m (-8%, ±7%) compared with sea-level. In the second half of the protocol, repeated sprint mean power was reduced at 3,000 m compared to 2,000 m (-7%, ±5%) and sea-level (-9%, ±5%). Quadriceps muscle deoxyhaemoglobin concentration was lowered at 3,000 m compared to 2,000 m (-10, ±12%) and sea-level (-11, ±12%). Conclusions: Simulated team-sport running is impaired at 3,000 m compared to 2,000 m and sea-level, likely due to a higher muscle deoxygenation.

Methodological Considerations When Quantifying High-Intensity Efforts in Team Sport Using Global Positioning System Technology.

PURPOSE: Sprints and accelerations are popular performance indicators in applied sport. The methods used to define these efforts using athlete-tracking technology could affect the number of efforts reported. This study aimed to determine the influence of different techniques and settings for detecting high-intensity efforts using global positioning system (GPS) data. METHODS: Velocity and acceleration data from a professional soccer match were recorded via 10-Hz GPS. Velocity data were filtered using either a median or an exponential filter. Acceleration data were derived from velocity data over a 0.2-s time interval (with and without an exponential filter applied) and a 0.3-second time interval. High-speed-running (≥4.17 m/s2), sprint (≥7.00 m/s2), and acceleration (≥2.78 m/s2) efforts were then identified using minimum-effort durations (0.1-0.9 s) to assess differences in the total number of efforts reported. RESULTS: Different velocity-filtering methods resulted in small to moderate differences (effect size [ES] 0.28-1.09) in the number of high-speed-running and sprint efforts detected when minimum duration was <0.5 s and small to very large differences (ES -5.69 to 0.26) in the number of accelerations when minimum duration was <0.7 s. There was an exponential decline in the number of all efforts as minimum duration increased, regardless of filtering method, with the largest declines in acceleration efforts. CONCLUSIONS: Filtering techniques and minimum durations substantially affect the number of high-speed-running, sprint, and acceleration efforts detected with GPS. Changes to how high-intensity efforts are defined affect reported data. Therefore, consistency in data processing is advised.

Wearable Training-Monitoring Technology: Applications, Challenges, and Opportunities.

The need to quantify aspects of training to improve training prescription has been the holy grail of sport scientists and coaches for many years. Recently, there has been an increase in scientific interest, possibly due to technological advancements and better equipment to quantify training activities. Over the last few years there has been an increase in the number of studies assessing training load in various athletic cohorts with a bias toward subjective reports and/or quantifications of external load. There is an evident lack of extensive longitudinal studies employing objective internal-load measurements, possibly due to the cost-effectiveness and invasiveness of measures necessary to quantify objective internal loads. Advances in technology might help in developing better wearable tools able to ease the difficulties and costs associated with conducting longitudinal observational studies in athletic cohorts and possibly provide better information on the biological implications of specific external-load patterns. Considering the recent technological developments for monitoring training load and the extensive use of various tools for research and applied work, the aim of this work was to review applications, challenges, and opportunities of various wearable technologies.

Unpacking the Black Box: Applications and Considerations for Using GPS Devices in Sport.

Athlete-tracking devices that include global positioning system (GPS) and microelectrical mechanical system (MEMS) components are now commonplace in sport research and practice. These devices provide large amounts of data that are used to inform decision making on athlete training and performance. However, the data obtained from these devices are often provided without clear explanation of how these metrics are obtained. At present, there is no clear consensus regarding how these data should be handled and reported in a sport context. Therefore, the aim of this review was to examine the factors that affect the data produced by these athlete-tracking devices and to provide guidelines for collecting, processing, and reporting of data. Many factors including device sampling rate, positioning and fitting of devices, satellite signal, and data-filtering methods can affect the measures obtained from GPS and MEMS devices. Therefore researchers are encouraged to report device brand/model, sampling frequency, number of satellites, horizontal dilution of precision, and software/firmware versions in any published research. In addition, details of inclusion/exclusion criteria for data obtained from these devices are also recommended. Considerations for the application of speed zones to evaluate the magnitude and distribution of different locomotor activities recorded by GPS are also presented, alongside recommendations for both industry practice and future research directions. Through a standard approach to data collection and procedure reporting, researchers and practitioners will be able to make more confident comparisons from their data, which will improve the understanding and impact these devices can have on athlete performance.

Activity Profile of International Rugby Sevens: Effect of Score Line, Opponent, and Substitutes.

PURPOSE: To investigate the influence of score line, level of opposition, and timing of substitutes on the activity profile of rugby sevens players and describe peak periods of activity. METHODS: Velocity and distance data were measured via 10-Hz GPS from 17 international-level male rugby sevens players on 2-20 occasions over 4 tournaments (24 matches). Movement data were reported as total distance (TD), high-speed-running distance (HSR, 4.17-10.0 m/s), and the occurrence of maximal accelerations (Accel, ≥2.78 m/s2). A rolling 1-min sample period was used. RESULTS: Regardless of score line or opponent ranking there was a moderate to large reduction in average and peak TD and HSR between match halves. A close halftime score line was associated with a greater HSR distance in the 1st minute of the 1st and 2nd halves compared with when winning. When playing against higher- compared with lower-ranked opposition, players covered moderately greater TD in the 1st minute of the 1st half (difference = 26%; 90% confidence limits = 6, 49). Compared with players who played a full match, substitutes who came on late in the 2nd half had a higher average HSR and Accel by a small magnitude (31%; 5, 65 vs 34%; 6, 69) and a higher average TD by a moderate magnitude (16%; 5, 28). CONCLUSIONS: Match score line, opposition, and substitute timing can influence the activity profile of rugby sevens players. Players are likely to perform more running against higher opponents and when the score line is close. This information may influence team selection.