Straight-Line and Change-of-Direction Intermittent Running in Professional Soccer Players

PURPOSE

To investigate the difference between straight-line (STL) and change-of-direction (COD) intermittent-running exercises in soccer players.

METHODS

Seventeen male professional soccer players performed the agility T test and 6 intermittent-running exercises: 10 s at 130% of maximal aerobic speed (MAS) alternated with 10 s of rest (10-10), 15 s at 120% of MAS alternated with 15 s of rest (15-15), and 30 s at 110% of MAS alternated with 30 s of rest (30-30) both in STL and with COD. All exercises were monitored using a global positioning system. Heart rate was measured during exercises, and rating of perceived exertion (RPE) was collected postexercise. The difference (Δ) between covered distance in STL and COD exercises at a similar load was calculated, and relationships between T test and Δ distance were analyzed.

RESULTS

COD intermittent exercises showed a significantly decreased distance covered and an increase in the number of accelerations, peak heart rate, and RPE compared with STL intermittent exercises at a similar load. High relationships were observed between T-test performance and Δ distance in 10-10 (r = .72, P < .01) and 15-15 (r = .77, P < .01), whereas no significant relationships were observed between T-test performance and Δ distance in 30-30 (r = -.37, P = .2).

CONCLUSION

Intermittent COD exercises were associated with higher acceleration, peak heart rate, and RPE than STL during 10-10 and 15-15 exercises. The ability to rapidly change direction is crucial to perform intense sport-specific running in professional soccer players.

Variability of activity profile during medium-sided games in professional soccer

BACKGROUND

In Southern European countries it is very frequent to perform medium-sized games (MSG) as last training drill. We analyzed the individual variability and changes in activity patterns during MSG throughout the preseason.

METHODS

Activity profile during MSGs (10v10+goalkeepers, duration: 10-min, field length: 50 m, width: 90 m, area per player: 204.5 m2) was quantified using a GPS in 14 professional male players (6 defenders, 5 midfielders 5 and attackers).

RESULTS

Inter-individual variability was higher for high-intensity (HIR), very-high speed (VHS), maximum acceleration (Accmax) and maximum deceleration (Decmax) distance (CV=25.2 to 43.3%), compared to total distance (TD), total acceleration (Acctot) and total deceleration (Dectot) distance (CV= 8.3 to 18.3%). Defenders showed higher variability in TD, HIR, VHS, Acctot and Dectot (ES= 1.30 to 11.28) compared to the other field positions, whereas attackers showed higher variability in HIR, VHS Accmax and Decmax (ES=-4.92 to 2.07) than other the field positions. Variability in TD regularly increased (ES= -2.13 to -0.91) towards the end of the preseason, while HIR and VHS variability tended to increase over the 3rd and the 4th preseason week (ES=-0.94 to -3.05). However, the behavior of variability across the preseason period was more unpredictable for Acctot and Dectot, both decreasing in the 3rd week (ES= 0.70 to 1.20), while Decmax increased in the 4th week (ES=-0.91±0.59).

CONCLUSIONS

During MSGs, individual variability of activity differs among field positions, and tends to increase with either speed or acceleration intensity, underlining the need of an individualized approach for training load monitoring.

Validity of the Catapult ClearSky T6 Local Positioning System for Team Sports Specific Drills, in Indoor Conditions

Aim: The aim of the present study was to determine the validity of position, distance traveled and instantaneous speed of team sport players as measured by a commercially available local positioning system (LPS) during indoor use. In addition, the study investigated how the placement of the field of play relative to the anchor nodes and walls of the building affected the validity of the system. Method: The LPS (Catapult ClearSky T6, Catapult Sports, Australia) and the reference system [Qualisys Oqus, Qualisys AB, Sweden, (infra-red camera system)] were installed around the field of play to capture the athletes' motion. Athletes completed five tasks, all designed to imitate team-sports movements. The same protocol was completed in two sessions, one with an assumed optimal geometrical setup of the LPS (optimal condition), and once with a sub-optimal geometrical setup of the LPS (sub-optimal condition). Raw two-dimensional position data were extracted from both the LPS and the reference system for accuracy assessment. Position, distance and speed were compared. Results: The mean difference between the LPS and reference system for all position estimations was 0.21 ± 0.13 m (n = 30,166) in the optimal setup, and 1.79 ± 7.61 m (n = 22,799) in the sub-optimal setup. The average difference in distance was below 2% for all tasks in the optimal condition, while it was below 30% in the sub-optimal condition. Instantaneous speed showed the largest differences between the LPS and reference system of all variables, both in the optimal (≥35%) and sub-optimal condition (≥74%). The differences between the LPS and reference system in instantaneous speed were speed dependent, showing increased differences with increasing speed. Discussion: Measures of position, distance, and average speed from the LPS show low errors, and can be used confidently in time-motion analyses for indoor team sports. The calculation of instantaneous speed from LPS raw data is not valid. To enhance instantaneous speed calculation the application of appropriate filtering techniques to enhance the validity of such data should be investigated. For all measures, the placement of anchor nodes and the field of play relative to the walls of the building influence LPS output to a large degree.

Validity and Reliability of 10-Hz Global Positioning System to Assess In-line Movement and Change of Direction

The objectives of the present study were to examine the validity and reliability of the 10 Hz Johan GPS unit in assessing in-line movement and change of direction. The validity was tested against the criterion measure of 200 m track-and-field (track-and-field athletes, n = 8) and 20 m shuttle run endurance test (female soccer players, n = 20). Intra-unit and inter-unit reliability was tested by intra-class correlation coefficient (ICC) and coefficient of variation (CV), respectively. An analysis of variance examined differences between the GPS measurement and five laps of 200 m at 15 km/h, and t-test examined differences between the GPS measurement and 20 m shuttle run endurance test. The difference between the GPS measurement and 200 m distance ranged from −0.13 ± 3.94 m (95% CI −3.42; 3.17) in the first lap to 2.13 ± 2.64 m (95% CI −0.08; 4.33) in the fifth lap. A good intra-unit reliability was observed in 200 m (ICC = 0.833, 95% CI 0.535; 0.962). Inter-unit CV ranged from 1.31% (fifth lap) to 2.20% (third lap). The difference between the GPS measurement and 20 m shuttle run endurance test ranged from 0.33 ± 4.16 m (95% CI −10.01; 10.68) in 11.5 km/h to 9.00 ± 5.30 m (95% CI 6.44; 11.56) in 8.0 km/h. A moderate intra-unit reliability was shown in the second and third stage of the 20 m shuttle run endurance test (ICC = 0.718, 95% CI 0.222;0.898) and good reliability in the fifth, sixth, seventh and eighth (ICC = 0.831, 95% CI −0.229;0.996). Inter-unit CV ranged from 2.08% (11.5 km/h) to 3.92% (8.5 km/h). Based on these findings, it was concluded that the 10 Hz Johan system offers an affordable valid and reliable tool for coaches and fitness trainers to monitor training and performance.

Differences Between Relative and Absolute Speed and Metabolic Thresholds in Rugby League

Purpose: To compare relative and absolute speed and metabolic thresholds for quantifying match output in elite rugby league. Methods: Twenty-six professional players competing in the National Rugby League were monitored with global positioning systems (GPS) across a rugby-league season. Absolute speed (moderate-intensity running [MIRTh > 3.6 m/s] and high-intensity running [HIRTh > 5.2 m/s]) and metabolic (>20 W/kg) thresholds were compared with individualized ventilatory (first [VT1IFT] and second [VT2IFT]) thresholds estimated from the 30-15 Intermittent Fitness Test (30-15IFT), as well as the metabolic threshold associated with VT2IFT (HPmetVT2), to examine difference in match-play demands. Results: VT2IFT mean values represent 146%, 138%, 167%, and 144% increases in the HIR dose across adjustables, edge forwards, middle forwards, and outside backs, respectively. Distance covered above VT2IFT was almost certainly greater (ES range = 0.79–1.03) than absolute thresholds across all positions. Trivial to small differences were observed between VT1IFT and MIRTh, while small to moderate differences were reported between HPmetVT2 and HPmetTh. Conclusions: These results reveal that the speed at which players begin to run at higher intensities depends on individual capacities and attributes. As such, using absolute HIR speed thresholds underestimates the physical HIR load. Moreover, absolute MIR and high metabolic thresholds may over- or underestimate the work undertaken above these thresholds depending on the respective fitness of the individual. Therefore, using relative thresholds enables better prescription and monitoring of external training loads based on measured individual physical capacities.

Validity and reliability of an accelerometer-based player tracking device

This study aimed to determine the intra- and inter-device accuracy and reliability of wearable athletic tracking devices, under controlled laboratory conditions. A total of nineteen portable accelerometers (Catapult OptimEye S5) were mounted to an aluminum bracket, bolted directly to an Unholtz Dickie 20K electrodynamic shaker table, and subjected to a series of oscillations in each of three orthogonal directions (front-back, side to side, and up-down), at four levels of peak acceleration (0.1g, 0.5g, 1.0g, and 3.0g), each repeated five times resulting in a total of 60 tests per unit, for a total of 1140 records. Data from each accelerometer was recorded at a sampling frequency of 100Hz. Peak accelerations recorded by the devices, Catapult PlayerLoad™, and calculated player load (using Catapult’s Cartesian formula) were used for the analysis. The devices demonstrated excellent intradevice reliability and mixed interdevice reliability. Differences were found between devices for mean peak accelerations and PlayerLoad™ for each direction and level of acceleration. Interdevice effect sizes ranged from a mean of 0.54 (95% CI: 0.34–0.74) (small) to 1.20 (95% CI: 1.08–1.30) (large) and ICCs ranged from 0.77 (95% CI: 0.62–0.89) (very large) to 1.0 (95% CI: 0.99–1.0) (nearly perfect) depending upon the magnitude and direction of the applied motion. When compared to the player load determined using the Cartesian formula, the Catapult reported PlayerLoad™ was consistently lower by approximately 15%. These results emphasize the need for industry wide standards in reporting validity, reliability and the magnitude of measurement errors. It is recommended that device reliability and accuracy are periodically quantified.

Validity and reliability of GPS and LPS for measuring distances covered and sprint mechanical properties in team sports

This study aimed to investigate the validity and reliability of global (GPS) and local (LPS) positioning systems for measuring distances covered and sprint mechanical properties in team sports. Here, we evaluated two recently released 18 Hz GPS and 20 Hz LPS technologies together with one established 10 Hz GPS technology. Six male athletes (age: 27±2 years; VO₂max: 48.8±4.7 ml/min/kg) performed outdoors on 10 trials of a team sport-specific circuit that was equipped with double-light timing gates. The circuit included various walking, jogging, and sprinting sections that were performed either in straight-lines or with changes of direction. During the circuit, athletes wore two devices of each positioning system. From the reported and filtered velocity data, the distances covered and sprint mechanical properties (i.e., the theoretical maximal horizontal velocity, force, and power output) were computed. The sprint mechanical properties were modeled via an inverse dynamic approach applied to the center of mass. The validity was determined by comparing the measured and criterion data via the typical error of estimate (TEE), whereas the reliability was examined by comparing the two devices of each technology (i.e., the between-device reliability) via the coefficient of variation (CV). Outliers due to measurement errors were statistically identified and excluded from validity and reliability analyses. The 18 Hz GPS showed better validity and reliability for determining the distances covered (TEE: 1.6–8.0%; CV: 1.1–5.1%) and sprint mechanical properties (TEE: 4.5–14.3%; CV: 3.1–7.5%) than the 10 Hz GPS (TEE: 3.0–12.9%; CV: 2.5–13.0% and TEE: 4.1–23.1%; CV: 3.3–20.0%). However, the 20 Hz LPS demonstrated superior validity and reliability overall (TEE: 1.0–6.0%; CV: 0.7–5.0% and TEE: 2.1–9.2%; CV: 1.6–7.3%). For the 10 Hz GPS, 18 Hz GPS, and 20 Hz LPS, the relative loss of data sets due to measurement errors was 10.0%, 20.0%, and 15.8%, respectively. This study shows that 18 Hz GPS has enhanced validity and reliability for determining movement patterns in team sports compared to 10 Hz GPS, whereas 20 Hz LPS had superior validity and reliability overall. However, compared to 10 Hz GPS, 18 Hz GPS and 20 Hz LPS technologies had more outliers due to measurement errors, which limits their practical applications at this time.

Effects of Passive and Active Rest on Physiological Responses and Time Motion Characteristics in Different Small Sided Soccer Games

The purpose of this study was to investigate the effects of resting regimes on physiological responses and time motion characteristics between bouts during small sided games (SSGs) in young soccer players. Sixteen players (average age 16.87 ± 0.34 years; body height 176.69 ± 3.21 cm; body mass 62.40 ± 2.59 kg; training experience 3.75 ± 0.44 years) performed four bouts 2-a-side, 3-a-side and 4-a-side games with three minutes active (SSGar: Running at 70% of HRmax) and passive (SSGpr) rest between bouts at two-day intervals. The heart rate (HR) along with total distance covered in different speed zones - walking (W, 0-6.9 km·h-1), low-intensity running (LIR, 7.0-12.9 km·h-1), moderate-intensity running (MIR, 13.0-17.9 km·h-1) and high-intensity running (HIR, >18km·h-1), were monitored during all SSGs, whereas the rating of perceived exertion (RPE, CR-20) and venous blood lactate (La-) were determined at the end of the last bout of each SSG. The results demonstrated that all SSGpr elicited significantly higher physiological responses compared to SSGar in terms of the RPE and La- (p < 0.05). In addition, 2-a-side SSGpr induced significantly lower %HRmax responses and total distance covered than 2-a-side SSGar (p < 0.05). Moreover, the distance covered at HIR was significantly higher in 4-a-side SSGar than 4-side SSGpr. The results of this study indicate that both SSGs with passive and active rest can be used for soccer specific aerobic endurance training. Furthermore, all SSGs with active recovery should be performed in order to increase players and teams’ performance capacity for subsequent bouts.

Weak Relationships between Stint Duration, Physical and Skilled Match Performance in Australian Football

Australian Rules football comprises physical and skilled performance for more than 90 min of play. The cognitive and physiological fatigue experienced by participants during a match may reduce performance. Consequently, the length of time an athlete is on the field before being interchanged (known as a stint), is a key tactic which could maximize the skill and physical output of the Australian Rules athlete. This study developed two methods to quantify the relationship between athlete time on field, skilled and physical output. Professional male athletes (n = 39) from a single elite Australian Rules football club participated, with physical output quantified via player tracking systems across 22 competitive matches. Skilled output was calculated as the sum of involvements performed by each athlete, collected from a commercial statistics company. A random intercept and slope model was built to identify how a team and individuals respond to physical outputs and stint lengths. Stint duration (mins), high intensity running (speeds >14.4 km · hr⁻¹) per minute, meterage per minute and very high intensity running (speeds >25 km·hr⁻¹) per minute had some relationship with skilled involvements. However, none of these relationships were strong, and the direction of influence for each player was varied. Three conditional inference trees were computed to identify the extent to which combinations of physical parameters altered the anticipated skilled output of players. Meterage per minute, player, round number and duration were all related to player involvement. All methods had an average error of 10 to 11 involvements, per player per match. Therefore, other factors aside from physical parameters extracted from wearable technologies may be needed to explain skilled output within Australian Rules football matches.

Officiating Role Influences the Physical Match Activity Profiles of Rugby League Touch Judges and Referees

This study investigated the effect of the officiating role on physical activity profiles of rugby league match officials during match-play. Physical performance indicators were collated from 23 match officials, resulting in 78 observations. Match officials were categorised into two groups: referees and touch judges. Microtechnology facilitated the quantification of total distance (m), relative distance (m⋅min^-1), maximum velocity (m⋅s^-1), the percentage of high intensity running distance (% total > 3.01 m⋅s^-1), walking distance (<1 m⋅s^-1), jogging distance (1.01 – 3 m⋅s^-1), fast jogging distance (3.01 - 5 m⋅s^-1), and sprinting distance (>5 m⋅s-1). Multivariate analysis modelled the main effect of the officiating role with follow up univariate analyses identifying significant differences. A significant effect was noted (V = 750; F(8, 66) = 24.71; p < 0.05) with referees covering a greater total distance (7767 ± 585 vs. 7022 ± 759 m), relative distance (90 ± 6 vs. 82 ± 8 m⋅min^-1), jogging distance (3772 ± 752 vs. 3110 ± 553 m), and fast jogging distance (2565 ± 631 vs. 1816 ± 440 m) compared to touch judges. Touch judges covered greater distances while sprinting (1012 ± 385 vs. 654 ± 241 m). Results provide important guidance in the development of training programs for match officials.

Between-Game Variation of Physical Soccer Performance Measures in Highly Trained Youth Soccer Players

Doncaster, G and Unnithan, V. Between-game variation of physical soccer performance measures in highly trained youth soccer players. J Strength Cond Res 33(7): 1912-1920, 2019-To assess the between-game variation in measures of physical performance during 11 vs. 11 soccer match play, over a short period, in highly trained youth soccer players. A single-cohort, observational, study design was used. Physical match performance data were collected from 17, male, highly trained, youth soccer players (age, 13.3 ± 0.4 years) over 3, 2 × 20 minutes, 11 vs. 11 matches. Using 10-Hz global positioning systems, the variables selected for analyses were total distance (TD), high-speed running (HSR), very high-speed running (VHSR), number of high-speed running efforts (HSReff), and number of very high-speed running efforts (VHSReff). Match data were also separated into cumulative 5-minute epochs, to identify the peak 5-minute epoch and the mean of the cumulative 5-minute epochs for each match. Variability was quantified using the coefficient of variation (CV), standard error of measurement, and intraclass correlation coefficient. Between- and within-player smallest worthwhile changes (SWC) were also calculated for each variable to aid in the interpretation of the data. Analysis of the variance between games reported a low CV for TD (3.8%) but larger CVs for HSR (33.3%), HSReff (35.4%), and VHSR and VHSReff (59.6 and 57.4%, respectively). Analysis of 5-minute epochs (peak and average) found an increase in the CVs beyond that of the values reported for the whole match. Between-player SWC in high-intensity physical performance data ranged from 24.7 to 42.4%, whereas within-player SWC ranged from 1.2 to 79.9%. The between-game variability of high-intensity and very high-intensity activities in youth soccer players, across 3 soccer matches over a short period (2 weeks), is relatively "large" and specific to the individual, thus highlighting the need for caution when interpreting physical performance data between games and players.

When Is a Sprint a Sprint? A Review of the Analysis of Team-Sport Athlete Activity Profile

The external load of a team-sport athlete can be measured by tracking technologies, including global positioning systems (GPS), local positioning systems (LPS), and vision-based systems. These technologies allow for the calculation of displacement, velocity and acceleration during a match or training session. The accurate quantification of these variables is critical so that meaningful changes in team-sport athlete external load can be detected. High-velocity running, including sprinting, may be important for specific team-sport match activities, including evading an opponent or creating a shot on goal. Maximal accelerations are energetically demanding and frequently occur from a low velocity during team-sport matches. Despite extensive research, conjecture exists regarding the thresholds by which to classify the high velocity and acceleration activity of a team-sport athlete. There is currently no consensus on the definition of a sprint or acceleration effort, even within a single sport. The aim of this narrative review was to examine the varying velocity and acceleration thresholds reported in athlete activity profiling. The purposes of this review were therefore to (1) identify the various thresholds used to classify high-velocity or -intensity running plus accelerations; (2) examine the impact of individualized thresholds on reported team-sport activity profile; (3) evaluate the use of thresholds for court-based team-sports and; (4) discuss potential areas for future research. The presentation of velocity thresholds as a single value, with equivocal qualitative descriptors, is confusing when data lies between two thresholds. In Australian football, sprint efforts have been defined as activity >4.00 or >4.17 m·s⁻¹. Acceleration thresholds differ across the literature, with >1.11, 2.78, 3.00, and 4.00 m·s⁻² utilized across a number of sports. It is difficult to compare literature on field-based sports due to inconsistencies in velocity and acceleration thresholds, even within a single sport. Velocity and acceleration thresholds have been determined from physical capacity tests. Limited research exists on the classification of velocity and acceleration data by female team-sport athletes. Alternatively, data mining techniques may be used to report team-sport athlete external load, without the requirement of arbitrary or physiologically defined thresholds.

A Comparison of GPS Workload Demands in Match Play and Small-Sided Games by the Positional Role in Youth Soccer

The external demands of small-sided games (SSGs) according to the positional role are currently unknown. Using a Catapult Minimax X3 5 Hz GPS, with a 100 Hz tri-axial accelerometer, we compared the accumulated tri-axial player workload per min (PLacc·min-1) during friendly youth match play (MP) (11 vs. 11) and SSGs (2 vs. 2, 3 vs. 3, and 4 vs. 4). Significant differences existed between all SSGs and MP for PLacc·min-1 (F = 21.91, p < 0.001, η2 = 0.38), and individual X (F = 27.40, p < 0.001, η2 = 0.43), Y (F = 14.50, p < 0.001, η2 = 0.29) and Z (F = 19.28, p < 0.001, η2 = 0.35) axis loads. Across all conditions, mean PLacc·min-1 was greater for midfielders (p = 0.004, CI: 0.68, 4.56) and forwards (p = 0.037, CI: 0.08, 3.97) than central defenders. In all conditions, greater Y axis values existed for wide defenders (p = 0.024, CI: 0.67, 1.38), midfielders (p = 0.006, CI: 0.18, 1.50) and forwards (p = 0.007, CI: 0.17, 0.15) compared to central defenders. Midfielders reported greater Z axis values compared to central defenders (p = 0.002, CI: 0.40, 2.23). We concluded that SSGs elicited greater external loads than MP, and previous studies may have underestimated the demands of SSGs.

The Work-Rate of Elite Hurling Match-Play

Collins, DK, McRobert, A, Morton, JP, O'Sullivan, D, and Doran, DA. The work-rate of elite hurling match-play. J Strength Cond Res 32(3): 805-811, 2018-This study describes the global work-rate of elite hurling match-play and the influence which positional difference has on work-rate is considered. The movement of ninety-four players was recorded using global positioning system, sampling at 4 Hz in a total of 12 games. Data were classified according to the positional line on the field and period of the match. The total and high-speed distance of match-play was 7,617 ± 1,219 m (95% confidence interval [CI], 7,367-7,866) and 1,134 ± 358 m (95% CI, 1,060-1,206), respectively. The maximum speed attained was 29.8 ± 2.3 km·h with a mean speed of 6.1 ± 1 km·h. The second {271 ± 107 m (p = 0.001; effect size [ES] = 0.25)}, third (278 ± 118 m [p = 0.001; ES = 0.21]), and fourth quarter (255 ± 108 m [p = 0.001; ES = 0.31]) high-speed running distance differed significantly from that of the first quarter (330 ± 120 m). There was a significant difference in total (p = 0.001; ES = 0.01-0.85), high-speed running (p = 0.001; ES = 0.21-0.76), and sprint (p = 0.013; ES = 0.01-0.39) distance across the positions, with midfielders undertaking the highest volume of work, followed by the half-forward and half-back lines and finally the full-forward and full-back lines. A decrease in high-speed running distance seems to occur through out the game and in particular at the latter stages of each half. Distinct positional work profiles are evident. The present finding provide a context on which training which replicates the work-rate of match-play may be formulated, thus helping to improve the physical preparation of elite players.

Gold Standard or Fool's Gold? The Efficacy of Displacement Variables as Indicators of Energy Expenditure in Team Sports

Over recent decades, the use of player tracking technology to monitor physical work output has become established practice in many team sports. Early tracking systems were manual in nature, relying on subjective assessments and arbitrary classifications of movement intensity. Poor spatial and temporal resolution meant that only gross displacement measures could be used to infer energy demands. However, the advent and evolution of automated systems, with higher sampling rates and improved accuracy, have enabled data collection to occur on a mass scale, and served as a catalyst for extensive research into the demands of team sport activity, including comparisons between different groups of athletes, and the effects of various interventions on performance. The inherent assumption with this research is that, based on steady-state models where energy cost is independent of speed, total distance and average speed are indicative of the amount and rate of work done, respectively. This assumption could be justified if the activity was performed at a constant speed in a straight line. However, team sport movement involves continual changes in both speed and direction, both of which increase energy cost. Accordingly, new models have emerged that incorporate both speed and acceleration to determine metabolic power. This provides a more complete measure of energy expenditure in intermittent activity, and is potentially more suitable than displacement variables for research into the demands of team sports.

Rule modification in junior sport: Does it create differences in player movement?

OBJECTIVES

To determine the effects of rule modification on player movement during matchplay in junior Australian football (AF).

DESIGN

Quasi-experimental study design.

METHODS

Time-motion analysis was used to record variables pertaining to player movement including total distance covered, high-speed running (HSR) distance (>14.4km/h) and HSR efforts. GPS data obtained from 145 players (7-12 years) were analysed across four junior AF leagues and three age group combinations (U8/U9, U9/U10 and U11/U12). The four leagues were collapsed into two separate conditions (compliant and non-compliant) based on their adherence to a modified junior sport policy. To control for the influence of age and physical maturity, a secondary analysis was performed on an adequately matched U8 subset of data (n=48).

RESULTS

Significant differences (p<0.05) were found between compliant and non-compliant leagues for age and all player movement variables, with participants in the compliant leagues achieving less player movement. Significant differences were also evident between conditions in the U8 subset in total and relative distance and HSR efforts, with moderate to very large differences (29-60%) observed for all player movement variables.

CONCLUSIONS

Rule modifications limits the extent and intensity of player movement in junior AF compared to standard playing conditions. The unintended effect of reduced physical activity with rule modifications should be compensated for with additional activities wherever possible. League administrators and policy makers should consider the objectives of rule modifications and weigh up both positive and negative outcomes.

Accuracy of a 10 Hz GPS Unit in Measuring Shuttle Velocity Performed at Different Speeds and Distances (5 - 20 M)

The aim of this study was to validate the accuracy of a 10 Hz GPS device (STATSports, Ireland) by comparing the instantaneous values of velocity determined with this device with those determined by kinematic (video) analysis (25 Hz). Ten male soccer players were required to perform shuttle runs (with 180° change of direction) at three velocities (slow: 2.2 m·s^-1; moderate: 3.2 m·s^-1; high: maximal) over four distances: 5, 10, 15 and 20 m. The experiments were video-recorded; the "point by point" values of speed recorded by the GPS device were manually downloaded and analysed in the same way as the "frame by frame" values of horizontal speed as obtained by video analysis. The obtained results indicated that shuttle distance was smaller in GPS than video analysis (p < 0.01). Shuttle velocity (shuttle distance/shuttle time) was thus smaller in GPS than in video analysis (p < 0.001); the percentage difference (bias, %) in shuttle velocity between methods was found to decrease with the distance covered (5 m: 9 ± 6%; 20 m: 3 ± 3%). The instantaneous values of speed were averaged; from these data and from data of shuttle time, the distance covered was recalculated; the error (criterion distance-recalculated distance) was negligible for video data (0.04 ± 0.28 m) whereas GPS data underestimated criterion distance (0.31 ± 0.55 m). In conclusion, the inaccuracy of this GPS unit in determining shuttle speed can be attributed to inaccuracy in determining the shuttle distance.

Positional Match Running Performance in Elite Gaelic Football

Malone, S, Solan, B, Collins, KD, and Doran, DA. Positional match running performance in elite Gaelic football. J Strength Cond Res 30(8): 2292-2298, 2016-There is currently limited information available on match running performance in Gaelic football. The objective of the current study was to report on the match running profile of elite male Gaelic football and assess positional running performance. In this observational study, 50 elite male Gaelic football players wore 4-Hz global positioning systems units (VX Sports) across 30 competitive games with a total of 215 full game data sets collected. Activity was classed according to total distance, high-speed distance (≥17 km·h), sprint distance (≥22 km·h), mean velocity (km·h), peak velocity (km·h), and number of accelerations. The average match distance was 8,160 ± 1,482 m, reflective of a relative distance of 116 ± 21 m·min, with 1,731 ± 659 m covered at high speed, which is reflective of a relative high-speed distance of 25 ± 9 m·min. The observed sprint distance was 445 ± 169 m distributed across 44 sprint actions. The peak velocity was 30.3 ± 1.8 km·h with a mean velocity of 6.5 ± 1.2 km·h. Players completed 184 ± 40 accelerations, which represent 2.6 ± 0.5 accelerations per minute. There were significant differences between positional groups for both total running distance, high-speed running distance, and sprint distance, with midfielders covering more total and high-speed running distance, compared with other positions (p < 0.001). There was a reduction in high-speed and sprint distance between the first and second half (p < 0.001). Reductions in running performance were position dependent with the middle 3 positions experiencing the highest decrement in performance. The current study is the first to communicate a detailed description of match running performance during competitive elite Gaelic football match play.

Application of Global Positioning System and Microsensor Technology in Competitive Rugby League Match-Play: A Systematic Review and Meta-analysis

BACKGROUND

The use of global positioning system (GPS) devices with the inclusion of microsenor technology in rugby league enables measurement of player activity profiles to understand the demands of match-play and optimise on-field performance.

OBJECTIVE

The aim of this review was to systematically review the use of GPS and microsensor technology to quantify player activity profiles in match-play, and conduct a meta-analysis of relevant movement variables in order to present the contemporary and emerging themes within rugby league.

METHODS

A systematic search of electronic databases (MEDLINE, SPORTDiscus, CINAHL, Web of Science, Scopus, ScienceDirect, EMBASE, and Google Scholar) from the earliest record to February 2015 was conducted. Permutations of key words included GPS, microtechnology, activity profiles, match demands (movement or physical demands), and rugby league. A meta-analysis was conducted to provide a pooled mean and confidence intervals on comparable data from at least three studies.

RESULTS

Twenty-seven studies met the eligibility criteria and included 1270 male participants. The studies reported on GPS use in elite competition (n = 16) with limited representation of other competition standards: sub-elite (n = 6), amateur (n = 1) and junior (n = 3). All studies reported on movement variables (distance, relative distance, speed and accelerations), with studies analysing movement at high speed (n = 18, 66.7%), evaluating collision or impact variables (n = 15, 55.6%) and determining the metabolic energy (n = 2, 7.4%) associated with rugby league match-play. Activity profiles of varying positions, positional groups and levels of rugby league competition were described. Meta-analysis indicated that the total distance covered by backs and adjustables were both greater than forward positions, but adjustables covered greater relative distance than forwards and backs. Speed zones were typically categorised into six speed zones ranging from 0 to 36 km·h(-1), or into low- and high-intensity movement. Vast inconsistencies were apparent across studies in categorising movement at high speed, posing difficulties for comparison. Meta-analysis indicated that, although the number of repeated high-intensity effort (RHIE) bouts in elite players were similar to sub-elite (and both greater than juniors), the number of efforts per RHIE were significantly greater in elite than sub-elite players. Differential pacing strategies were adopted according to player selection (whole-match vs. interchange), time period within match-play and match outcome, in order to maintain high-intensity performance or to challenge for a win. Sizeable inconsistencies were also identified in the definitions of reported collisions (classified as mild, moderate and heavy) and impacts (six zone categories provided by manufacturer), making comparisons across studies difficult. Collision profiles were different between competition standard and position where elite players and forwards sustained more moderate- and high-intensity collisions than sub-elite players and backs, respectively. The recent inclusion of GPS-derived metabolic indices to activity profiles has also accentuated the distinctive workloads of positional groups during match-play where adjustables demonstrate the highest energy expenditure and metabolic power.

CONCLUSIONS

This review and the results of the meta-analysis have demonstrated that positional groups have varied kinematic and metabolic demands. During match play, forwards sustain the greatest number of collisions and RHIE bouts, outside backs participate in more high-speed running and cover the greatest distance, and adjustables work at high intensity covering the greatest relative distance with the highest metabolic cost. Therefore, specific training for each positional group should address their match requirements. In addition, sub-elite players exhibit lower intensity of play compared with elite players, as indicated by lower relative distance and less number of efforts per RHIE bout despite similarities in total distance covered and number of RHIE bouts. To prepare them for elite-level play, their training should incorporate higher intensity drills in which greater relative distance and number of efforts per RHIE bout are performed. Furthermore, the lack of consistency in the definition of speed zones, high-intensity movement, collisions and impacts, underscores the difficulties encountered in meaningful comparisons of player activity profiles between studies. Consensus of these definitions would facilitate direct comparisons within rugby league.

On-field Performances of Rugby Union Players--A Review

A review of 16 studies examining on-field performances of rugby union players was conducted. Based on this review, we discuss a number of methodological and measurement concerns, and provide practical implications for practitioners who develop training programs for rugby players. Among the main findings that emerged from our review were (a) rugby is an intermittent sport in nature with many tempo changes, ranging from high-intensity sprints and static exertion to jogging, standing, and walking, and (b) differences in on-field performance among players playing different positions are common, and are especially apparent among forwards, who are involved in more static high-intensity efforts, and backs, who spend more time in high-intensity running. Among the methodological concerns in these studies are the lack of a standardized method of coding movement categories and the lack of data about the opposing team. We suggest that practitioners design training programs, which reflect the specific needs of players playing different positions, and that they use up-to-date technology to accurately assess players' on-field efforts.

Movement Demands and Metabolic Power Comparisons Between Elite and Subelite Australian Footballers

This study examined the differences in movement demands and metabolic power output of elite and subelite Australian football (AF) players and quantified the movement profiles of a subelite AF competition. Movement variables were collected from AF players using Global Positioning System devices over 2 AF League (elite) and North East Australian Football League (NEAFL, subelite) seasons. A total of 500 files were collected from 37 elite and subelite nomadic AF players. NEAFL players covered 13,547 m at an average speed of 124.5 m·min(-1). Elite players performed more high-speed running (5.7-6.3%) and high acceleration and deceleration efforts (1.9-14.7%, p ≤ 0.05). The elite players had a higher mean metabolic power output (3.2%) and time spent at the very high power zone (15.9%, p ≤ 0.05). In contrast, elite players recorded a lower total match duration than the subelite players (4%, p ≤ 0.05). The contrasting amount of high-intensity activities performed by the 2 groups demonstrates the need to alter the training programs of subelite players to ensure they are capable of meeting the demands of elite football. The differences in match duration suggest that reducing subelite players' match time through increasing their rotations would assist the replication of movement profiles of elite players.

Comparison of Non-Invasive Individual Monitoring of the Training and Health of Athletes with Commercially Available Wearable Technologies

Athletes adapt their training daily to optimize performance, as well as avoid fatigue, overtraining and other undesirable effects on their health. To optimize training load, each athlete must take his/her own personal objective and subjective characteristics into consideration and an increasing number of wearable technologies (wearables) provide convenient monitoring of various parameters. Accordingly, it is important to help athletes decide which parameters are of primary interest and which wearables can monitor these parameters most effectively. Here, we discuss the wearable technologies available for non-invasive monitoring of various parameters concerning an athlete's training and health. On the basis of these considerations, we suggest directions for future development. Furthermore, we propose that a combination of several wearables is most effective for accessing all relevant parameters, disturbing the athlete as little as possible, and optimizing performance and promoting health.

Metabolic Power Requirement of Change of Direction Speed in Young Soccer Players: Not All Is What It Seems

Purpose

The aims of this study were to 1) compare the metabolic power demand of straight-line and change of direction (COD) sprints including 45° or 90°-turns, and 2) examine the relation between estimated metabolic demands and muscular activity throughout the 3 phases of COD-sprints.

Methods

Twelve highly-trained soccer players performed one 25-m and three 20-m sprints, either in straight-line or with one 45°- or 90°-COD. Sprints were monitored with 2 synchronized 100-Hz laser guns to assess players’ velocities before, during and after the COD. Acceleration and deceleration were derived from changes in speed over time. Metabolic power was estimated based on di Prampero’s approach (2005). Electromyography amplitude (RMS) of 2 lower limb muscles was measured. The expected energy expenditure during time-adjusted straight-line sprints (matching COD sprints time) was also calculated.

Results

Locomotor-dependant metabolic demand was largely lower with COD (90°, 142.1±13.5 J.kg^-1) compared with time-adjusted (effect size, ES = -3.0; 193.2±18.6 J.kg^-1) and non-adjusted straight-line sprints (ES = -1.7; 168.4±15.3 J.kg^-1). Metabolic power requirement was angle-dependent, moderately lower for 90°-COD vs. 45°-COD sprint (ES = -1.0; 149.5±10.4 J.kg^-1). Conversely, the RMS was slightly- (45°, ES = +0.5; +2.1%, 90% confidence limits (±3.6) for vastus lateralis muscle (VL)) to-largely (90°, ES = +1.6; +6.1 (3.3%) for VL) greater for COD-sprints. Metabolic power/RMS ratio was 2 to 4 times lower during deceleration than acceleration phases.

Conclusion

Present results show that COD-sprints are largely less metabolically demanding than linear sprints. This may be related to the very low metabolic demand associated with the deceleration phase during COD-sprints that may not be compensated by the increased requirement of the reacceleration phase. These results also highlight the dissociation between metabolic and muscle activity demands during COD-sprints, which questions the use of metabolic power as a single measure of running load in soccer.

An Examination of the Relationship Between Movement Demands and Rating of Perceived Exertion in Australian Footballers

This study aimed to determine whether a relationship existed between movement demands, match events, and perceptual match load, as determined by rating of perceived exertion (RPE) in professional Australian footballers. The movement variables were collected between 1 and 22 times using global positioning system units from 21 players during the 2011 and 2012 Australian Football League seasons. A range of movement demands and match events were collected to obtain a complete insight into the physical demands and work rates of these athletes. These data were separated into the high-load (HL, ≥9) and low-load (LL, ≤8) RPE groups. A Mann-Whitney U-test, independent samples t-test, and effect sizes were used to determine whether any differences existed between the 2 groups and the size of the difference. The results revealed that the HL groups covered more distance, spent more time, and produced more efforts at the high deceleration zone (2.4-6.7%). Further, the HL group had more possessions and disposals of the football than the LL group (9.2-29.6%). The findings have highlighted the importance of monitoring accelerations, decelerations, and instantaneous power outputs to obtain a comprehensive insight into the physical demands placed on team sport athletes. Furthermore, the results demonstrate that training sessions should involve a focus on drills that are composed of both skill development and physical stimulus element.

Countermovement jump performance is not affected during an in-season training microcycle in elite youth soccer players

This study examined the change in countermovement jump (CMJ) performance across a microcycle of training in professional soccer players during the in-season period. Nine elite youth soccer players performed a CMJ test before and after 4 consecutive soccer training sessions of an in-season weekly microcycle. Training load was quantified using global positioning systems, heart rate, and rating of perceived exertion. Absolute change (before to after training) in CMJ height across each training session was analyzed using one-way repeated-measures analysis of variance. Magnitude of effects was reported with the effect size (ES) statistic. Correlation analyses assessed the relationships between training load measures and the absolute change in CMJ height. Training load remained similar on all training days apart from a significant decrease in training load (all variables except high-speed distance) on the last training session (p ≤ 0.05). No significant difference was found for CMJ height (p = 0.23) across the training microcycle (ES range, -0.04 to -0.22). No correlations were found between training load variables and absolute change in CMJ height (range: r = -0.21 to 0.22; p > 0.05). This study revealed no significant change in CMJ performance across the in-season microcycle. This finding suggests that soccer players are able to maintain CMJ performance across an in-season training microcycle.

Activity profile of high-level Australian lacrosse players

Despite lacrosse being one of the fastest growing team sports in the world, there is a paucity of information detailing the activity profile of high-level players. Microtechnology systems (global positioning systems and accelerometers) provide the opportunity to obtain detailed information on the activity profile in lacrosse. Therefore, this study aimed to analyze the activity profile of lacrosse match-play using microtechnology. Activity profile variables assessed relative to minutes of playing time included relative distance (meter per minute), distance spent standing (0-0.1 m·min), walking (0.2-1.7 m·min), jogging (1.8-3.2 m·min), running (3.3-5.6 m·min), sprinting (≥5.7 m·min), number of high, moderate, low accelerations and decelerations, and player load (PL per minute), calculated as the square root of the sum of the squared instantaneous rate of change in acceleration in 3 vectors (medio-lateral, anterior-posterior, and vertical). Activity was recorded from 14 lacrosse players over 4 matches during a national tournament. Players were separated into positions of attack, midfield, or defense. Differences (effect size [ES] ± 90% confidence interval) between positions and periods of play were considered likely positive when there was ≥75% likelihood of the difference exceeding an ES threshold of 0.2. Midfielders had likely covered higher (mean ± SD) meters per minute (100 ± 11) compared with attackers (87 ± 14; ES = 0.89 ± 1.04) and defenders (79 ± 14; ES = 1.54 ± 0.94) and more moderate and high accelerations and decelerations. Almost all variables across positions were reduced in quarter 4 compared with quarter 1. Coaches should accommodate for positional differences when preparing lacrosse players for competition.

Effect of different between-match recovery times on the activity profiles and injury rates of national rugby league players

Professional rugby league competition does not coincide with a standardized amount of recovery between matches; matches can be separated by as many as 10 days and as few as 5 days. These variations in recovery time could influence the match activity profiles and injury rates of players. This study investigated the effect of different between-match recovery times on the activity profiles and injury rates of National Rugby League (NRL) players. Forty-three elite male rugby league players participated in this study. Between-match recovery cycles were defined as short (separated by 5 or 6 days), medium (separated by 7 or 8 days), and long (separated by 9 or 10 days) recovery. Movement was recorded using a commercially available microtechnology unit, which provided information on speed, distance, and repeated high-intensity effort activity. Injuries sustained in either training or match play, which resulted in a missed match, were recorded. Significantly greater (p ≤ 0.05) relative total distance was covered after matches involving short recovery than those involving medium (effect size [ES] = 1.13) or long (ES = 1.08) recovery periods. This difference was because of greater low-speed activity. Injury rates for the adjustables positional group were the highest after short between-match recovery cycles, whereas the injury rates of hit-up forwards and outside backs positional groups were the highest after long between-match recovery cycles. These findings suggest that the activity profiles of NRL match play and the injury rates of specific playing positions are influenced by the amount of recovery between matches. The differences in the activity profiles and injury rates between short, medium, and long between-match recovery cycles should be considered when developing recovery strategies for professional rugby league players.

Technologies That Assess the Location of Physical Activity and Sedentary Behavior: A Systematic Review

Background

The location in which physical activity and sedentary behavior are performed can provide valuable behavioral information, both in isolation and synergistically with other areas of physical activity and sedentary behavior research. Global positioning systems (GPS) have been used in physical activity research to identify outdoor location; however, while GPS can receive signals in certain indoor environments, it is not able to provide room- or subroom-level location. On average, adults spend a high proportion of their time indoors. A measure of indoor location would, therefore, provide valuable behavioral information.

Objective

This systematic review sought to identify and critique technology which has been or could be used to assess the location of physical activity and sedentary behavior.

Methods

To identify published research papers, four electronic databases were searched using key terms built around behavior, technology, and location. To be eligible for inclusion, papers were required to be published in English and describe a wearable or portable technology or device capable of measuring location. Searches were performed up to February 4, 2015. This was supplemented by backward and forward reference searching. In an attempt to include novel devices which may not yet have made their way into the published research, searches were also performed using three Internet search engines. Specialized software was used to download search results and thus mitigate the potential pitfalls of changing search algorithms.

Results

A total of 188 research papers met the inclusion criteria. Global positioning systems were the most widely used location technology in the published research, followed by wearable cameras, and radio-frequency identification. Internet search engines identified 81 global positioning systems, 35 real-time locating systems, and 21 wearable cameras. Real-time locating systems determine the indoor location of a wearable tag via the known location of reference nodes. Although the type of reference node and location determination method varies between manufacturers, Wi-Fi appears to be the most popular method.

Conclusions

The addition of location information to existing measures of physical activity and sedentary behavior will provide important behavioral information.

Physiological and Movement Demands of Rugby League Referees: Influence on Penalty Accuracy

Research into the physiological and movement demands of Rugby League (RL) referees is limited, with only 1 study in the European Super League (SL). To date, no studies have considered decision making in RL referees. The purpose of this study was to quantify penalty accuracy scores of RL referees and to determine the relationship between penalty accuracy and total distance covered (TD), high-intensity running (HIR), and heart rate per 10-minute period of match play. Time motion analysis was undertaken on 8 referees over 148 European SL games during the 2012 season using 10-Hz global positioning system analysis and heart rate monitors. The number and timing of penalties awarded was quantified using Opta Stats. Referees awarded the correct decision on 74 ± 5% of occasions. Lowest accuracy was observed in the last 10-minute period of the game (67 ± 13%), with a moderate drop (effect size = 0.86) in accuracy observed between 60-70 minutes and 70-80 minutes. Despite this, there were only small correlations observed between mean heart rate, TD, HIR efforts, and penalty accuracy. Although a moderate correlation was observed between maximum velocity and accuracy. Despite only small correlations observed, it would be rash to assume that physiological and movement demands of refereeing have no influence on decision making. More likely, other confounding variables influence referee decision-making accuracy, requiring further investigation. Findings can be used by referees and coaches to inform training protocols, ensuring training is specific to both cognitive and physical match demands.

Quantifying positional and temporal movement patterns in professional rugby union using global positioning system

This study assessed the positional and temporal movement patterns of professional rugby union players during competition using global positioning system (GPS) units. GPS data were collected from 33 professional rugby players from 13 matches throughout the 2012-2013 season sampling at 10 Hz. Players wore GPS units from which information on distances, velocities, accelerations, exertion index, player load, contacts, sprinting and repeated high-intensity efforts (RHIE) were derived. Data files from players who played over 60 min (n = 112) were separated into five positional groups (tight and loose forwards; half, inside and outside backs) for match analysis. A further comparison of temporal changes in movement patterns was also performed using data files from those who played full games (n = 71). Significant positional differences were found for movement characteristics during performance (P < 0.05). Results demonstrate that inside and outside backs have greatest high-speed running demands; however, RHIE and contact demands are greatest in loose forwards during match play. Temporal analysis of all players displayed significant differences in player load, cruising and striding between halves, with measures of low- and high-intensity movement and acceleration/deceleration significantly declining throughout each half. Our data demonstrate significant positional differences for a number of key movement variables which provide a greater understanding of positional requirements of performance. This in turn may be used to develop progressive position-specific drills that elicit specific adaptations and provide objective measures of preparedness. Knowledge of performance changes may be used when developing drills and should be considered when monitoring and evaluating performance.

Validity and interunit reliability of 10 Hz and 15 Hz GPS units for assessing athlete movement demands

The purpose of this study was to assess the validity and interunit reliability of 10 Hz (Catapult) and 15 Hz (GPSports) Global Positioning System (GPS) units and investigate the differences between these units as measures of team sport athlete movement demands. A team sport simulation circuit was completed by 8 trained male participants. The movement demands examined included: total distance covered (TD), average peak speed, and the distance covered, time spent, and the number of efforts performed low-speed running (0.00-13.99 km · h(-1)), high-speed running (14.00-19.99 km · h(-1)), and very high-speed running (>20.00 km · h(-1)). The degree of difference between the 10 Hz and the 15 Hz GPS units and validity was assessed using a paired samples t-test. Pearson's correlations were also used for validity assessment. Interunit reliability was established using percentage typical error of measurement (%TEM) and intraclass correlations. The findings revealed that 10 Hz GPS units were a valid (p > 0.05) and reliable (%TEM = 1.3%) measure of TD. In contrast, the 15 Hz GPS units exhibited lower validity for TD and average peak speed. Further, as the speed of movement increased the level of error for the 10 Hz and 15 Hz GPS units increased (%TEM = 0.8-19.9). The findings from this study suggest that comparisons should not be undertaken between 10 Hz and 15 Hz GPS units. In general, the 10 Hz GPS units measured movement demands with greater validity and interunit reliability than the 15 Hz units, however, both 10 Hz and 15 Hz units provided the improved measures of movement demands in comparison to 1 Hz and 5 Hz GPS units.