A number of studies have analyzed the movement demands of rugby league matches (2,8,13); however, these have used a small sample size (13,16), broadly grouped positions (2,8,13), or were based in subjective time motion analysis (1,12,14,15). However, more recently global positioning systems (GPS) have emerged as an accurate method to analyze multiple players (4,10). Indeed, GPS has been used to study the movement demands of Australian rules football (3), rugby union (6), and rugby league (2,8,13). Although GPS allows for individual positions to be analyzed, there is no previous research on the movement demands of all 9 playing positions in rugby league. It is this information that requires further examination in order for coaches to gain a greater understanding of the team and individual playing positions to allow greater specificity to training programs.
McLellan et al. (13) and Austin and Kelly (2) studied the movement demands of 2 common positional rugby league groupings of forwards and backs using GPS technology. McLellan et al. (13), studying 5 matches and 22 players, showed that the total distance covered by forwards and backs was 4,982 and 5,573 m, respectively. Austin and Kelly (2) studying 185 professional rugby league players reported that distances covered in games were higher than those reported by McLellan et al. (13), with forwards and backs covering 5,964 and 7,628 m. The distance is substantially higher in Austin and Kelly (2), which may be attributed to the greater number of players and games analyzed.
Gabbett et al. (9), studying 30 professional rugby league players using 5 Hz GPS over training and match play, grouped positions into hit-up forwards (props), wide running forwards (second row and lock), adjustables (hooker, halfback, five-eight, and fullback), and outside backs (center and wing). These playing positions were shown to cover a mean distance of 3,569, 5,561, 6,411, and 6,819 m, respectively, during match play. Of the total distance, 235, 418, 436, and 583 m were shown to be covered in high-intensity running (>18 km·h−1) for hit-up forwards, wide running forwards, adjustables, and outside backs, respectively. Gabbett et al. (9) using the same positional groupings with 37 professional rugby league players and 5 Hz GPS investigated the sprinting demands of the National Rugby League (NRL) competition. The study reported an average frequency of 35 sprints occurred per game, with 39 hit-up forwards, 37 wide running forwards, 31 adjustables, and 35 outside backs.
The broad grouping of positions used in previous studies has limited research quantifying the movement demands of the 9 positions (fullback, wing, center, five-eight, halfback, hooker, lock, back row, and prop) in rugby league. Incorrect prescription of training protocol, based on positional needs, can lead to undertraining or overtraining and increase risk of injury. Because of the paucity of research examining individual playing positions, further analysis is required to gain a greater insight into the movement demands of rugby league match play to develop position appropriate training methodologies. Therefore, the purpose of this study was to quantify the movement demands of all 9 individual playing positions in professional rugby league and the relevance of previously researched playing position categorizations.
Experimental Approach to the Problem
The movement demands of all 9 positions used in a game of rugby league were investigated using GPSports unit (sampling at 5 Hz) during the professional NRL competition. It was hypothesized that meaningful differences would exist among the 9 individual playing positions, which have never been analyzed, for distances covered, high-intensity running, or work rate in professional rugby league. Measuring individual playing positions will enable coaches to replicate the demands of specific positional match play and develop training plans accordingly.
The movement demands of 135 professional rugby league players (n = 15 per individual positional group) from the same NRL club were grouped into 2 positional groups: 1) backs (age: 25 ± 3 years; mass: 106 ± 8 kg; stature: 186 ± 5 cm) consisting of halfback, five-eight, center, wing, and fullback and 2) forwards (age: 24 ± 4 years; mass: 94 ± 4 kg; stature: 185 ± 6 cm) consisting of hooker, lock, back row, and prop from 28 NRL games played in Australia during the 2010 season. The rugby league club and all individual subjects provided written informed consent before data collection. Ethics approval for all experimental procedures was granted by the Ethics Committee of the University of Technology, Sydney.
Players were asked to wear an individual GPS unit (5 Hz SPI Elite; GPSports Systems, Canberra, Australia). The GPS unit was positioned between the scapulae, encased in a vest worn by players. A full descriptive process of the use of GPS units in rugby league has previously been defined by McLellan et al. (13). As per McLellan et al. (13), players had previously worn the units and vest in preseason training, including all outside training sessions involving rugby league match–related skill and conditioning sessions. Furthermore, GPS units had also been worn in preliminary practice games. The Australian Rugby League games analyzed were played in both night and day and in a variety of environmental conditions, during 6 months, predominantly in the winter season. The validity and reliability of 5 Hz GPS units measuring distances and speeds at low-to-high intensity has been demonstrated in previous studies (4,5,11).
The units were turned on 20–30 minutes before the game start, with only match-play data used for analysis. Total time was calculated for “playing time” only, that is, how much time the player was on the playing field only. Time off the field, such as injury, periods on the bench, or reserve, was removed from the data analysis. Time off during match play, such as injury time or video referee, was included in the study because this was a part of the game duration; hence, playing time may exceed the standard 80 minutes of match play. Changes in game movements, distances, and locomotor speeds were analyzed over total playing time. Relative distance was calculated as the distance covered per minute of playing time, referred to as meters per minute.
Distance covered was calculated according to 6 movement categories: standing, walking or jogging (0–12 km·h−1), cruising (12–14 km·h−1), striding (14–18 km·h−1), high-intensity running (18–20 km·h−1), sprinting (20–24 km·h−1), and high-intensity sprinting (>24 km·h−1) (2,13). High-intensity running (> 18 km·h−1) was further analyzed into frequency of occurrences, and minimum, maximum, and average distance covered.
All data were downloaded to a computer using SPI Ezy version 2.1 (GPSports) and analyzed using Team AMS version 2.1 software (GPSports). Once appropriately formatted, data were exported to Microsoft Excel (Microsoft Corporation, Redmond, WA, USA) for the purpose of data management and further analysis.
Data for distance, duration, distance within various speed zones, relative distance, and frequency of high-intensity runs are presented as means ± SD. Analysis of variance (ANOVA) was used to establish differences in the variables among individual playing positions, and residuals were checked for normality. Repeated measures ANOVA was used to assess variance in relative distance covered in first and second half of match play. All statistics were run on SPSS version 18.0 for Windows (SPSS, Inc., Chicago, IL, USA) with an alpha of 0.05 set a priori.
The mean total match time of match play for backs and forwards was 86 ± 6 and 68 ± 15 minutes, respectively. Mean match time for the back positions (fullback, wing, center, five-eight, and halfback) were 85 ± 10, 88 ± 3, 87 ± 3, 85 ± 3, and 84 ± 8 minutes, respectively. Mean match time for the forward positions (hooker, lock, back row, and prop) was 75 ± 13, 63 ± 11, 79 ± 16, and 58 ± 10 minutes, respectively. There was no significant difference (p < 0.05) between playing positions in backs; however, prop forwards were significantly (p < 0.05) lower than back row forwards and hookers.
The mean total distances covered for backs and forwards were 7,802 ± 979 and 5,989 ± 1,551 m, respectively. The mean total distances covered by individual back positions in a game for fullback, wing, center, five-eight, and halfback players were 7,760 ± 1,026, 7,457 ± 800, 7,301 ± 858, 8,402 ± 596, and 8,500 ± 833 m, respectively (Table 1). The mean total distances covered by individual forward positions in a game for hooker, lock, back row, and prop players were 6,988 ± 1,340, 5,481 ± 1,257, 6,936 ± 1,295, and 4,597 ± 713 m, respectively (Table 2). The lock and prop forwards ran significantly less (p < 0.05) distance than other forward positions.
The average number of occurrences in high-intensity running (> 18 km·h−1) was 42 ± 10, 35 ± 11, 34 ± 9, 86 ± 29, and 120 ± 16 for fullback, wing, center, five-eight, and halfback players, respectively. The five-eight and halfback have significantly more (p < 0.05) high-intensity entries than other back positions. The average number of occurrences in high-intensity running (>18 km·h−1) was 74 ± 15, 52 ± 20, 26 ± 9, and 18 ± 6 for hooker, lock, back row, and prop players, respectively. The back row and prop forwards covered significantly less (p < 0.05) distances at high intensity than hooker and lock. The maximum frequency of high-intensity running for backs was 60, 51, 46, 131, and 148 for fullback, wing, center, five-eight, and halfback, respectively. The maximum frequency of high-intensity runs for forwards was 98, 85, 37, and 30 for hooker, lock, back row, and prop forwards, respectively. The average distance traveled greater than 18 km·h−1 for fullback was 17 ± 2 m, wing 18 ± 2 m, center 18 ± 3 m, five-eight 16 ± 3 m, and halfback 17 ± 4 m. The average distance traveled greater than 18 km·h−1 for hooker was 14 ± 3 m, lock 16 ± 2 m, back row 18 ± 3 m, and prop 16 ± 2 m. The range of distances traveled in high intensity for backs was 5–96 m, whereas forward ranged from 5 to 84 m.
Meters Per Minute of Match Play
Backs and forwards completed 89 ± 10 and 89 ± 6 m.min−1, respectively, in match play (Tables 3 and 4). All playing positions, except fullback, had a performance decrement from first to second half match play (expressed in meters per minute) (Figures 1 and 2).
This study is the first to quantify the movement demands of all 9 playing positions in the game of rugby league. Because of the collective grouping of positions by previous studies, there has been a lack of specificity to the match play demands of each position. Given the ability to analyze all positions with the use of presently available technology, the current study has aimed to fill this gap in the literature. Significantly, results from the present study have shown that halfbacks, five-eights, fullbacks, and back row forwards cover greater distances in general and at a higher intensity throughout match play than previously recorded in collective groups. Training implications for coaches, that previously used collective group analysis, would have specific positions either undertraining or overtraining. Given the current study, training should be structured to cater for positional differences to meet the specific match play demands of individual playing positions.
The current study has demonstrated that backs cover 7,802 m on average per game. This is substantially higher than that reported by McLellan et al. (13), who reported that backs covered 5,573 m per game. Results from the current study are similar to Austin and Kelly (2) who found that backs covered 7,628 m per game. Because of the higher distances covered by the five-eight and halfback (8,402 and 8,500 m, respectively) in the current study, the inclusion of these positions may leave them undertrained if grouped distances were used to design training protocols. Forwards covered a mean distance of 5,989 m in the current study, which was similar to that reported by Austin and Kelly (2) who reported 5,964 m per game. This result is again higher than that provided by McLellan et al. (13), who reported an average of 4,982 m per game for forwards. The current study shows how a broad grouping of backs and forwards can underestimate or overestimate the actual values for each position. This is evident in the current study with prop forwards covering 4,597 m, which is much lower than hookers with 6,988 m and back row forwards who covered 6,936 m.
With the use of the groupings explained by Gabbett et al. (9), the current study would have shown hit-up forwards, wide running forwards, adjustables, and outside backs covering a mean distance of 4,597, 6,209, 7,913, and 7,379 m, respectively. The greatest difference is between the adjustable position, covering 6,411 m, described by Gabbett et al. (9) and the adjustable positions in the current study, with fullback, five-eight, and halfback covering 1,349, 1,991, and 2,089 m more in running distance, respectively. Given these large differences in distance covered in this study, it would be advisable to separate these individual positions into their own category. Given the groupings described in the study by Gabbett et al. (9), it is unclear as to what contribution each playing position contributed to the average distance and whether similar results were found for these positions. The style of play of the team and individuals in those positions may also contribute to the differences reported between the studies.
In relative distance, the backs varied by 20 m·min−1 and the forwards by 9 m·min−1 in their respective positional groups. The five-eight and halfback covered the greatest relative distance, whereas the wing and center positions managed the least of all 9 positions. While using the groupings described by Gabbett et al. (9) of hit-up forwards, wide-running forwards, adjustables, and outside backs, the meters per minute of match play in the current study were 85, 90, 96, and 83 m·min−1, whereas the results of Gabbett et al. (9) were 94, 96, 101, and 93 m·min−1, respectively. The current results are slightly lower than those from the study by Gabbett et al. (9); however, the back row forwards (87 m·min−1) may also be better grouped with prop forwards (85 m·min−1) in the current study, rather than locks with 92 m·min−1. The outside backs were also reported to be substantially lower in the meters per minute of match play in the current study. This difference may be the results of the playing styles and structure of the teams analyzed. In line with previous research (2,15), the current study also demonstrated a decrease in meters per minute in the second half of match play when compared with the first half.
The distance covered in high-intensity running for the backs ranged with fullbacks covering the most with 925 m, whereas five-eight was shown to cover the least distance with 477 m. The average distance covered in high-intensity running in this study for the collective grouping of backs was 701 m, compared with that reported by McLellan et al. (13) (440 m), whereas Austin and Kelly (2) showed backs completing 749 m in high-intensity running. This mean value for the backs, when grouped together, underquantifies the distance fullbacks cover in high-intensity running, whereas overquantifying distances covered by the five-eight. Gabbett et al. (9) using a more segregated grouping showed adjustables covered 436 m and outside backs 583 m in high-intensity running. Although these distances are still relatively close for the outside back and adjustable positions, the inclusion of fullback to adjustables does not seem warranted, given the much larger distance covered in high-intensity running.
During the current study, forwards high-intensity running averaged 388 m per game, compared with 432 m reported by Austin and Kelly (2) and 232 m per game reported by McLellan et al. (13). The current study showed that back row forwards covered a much greater distance (545 m) in high-intensity running than that reported by Austin and Kelly (2) and collectively grouping forwards in the current study. Given the results from the study by McLellan et al. (13), all forward positions in the current study, aside from the lock position, would be undertrained to meet the movement demands of rugby league match play and increase the risk of injury occurring (7). Gabbett et al. (9), using a more segregated grouping of forwards, showed that 436 m and 583 m were covered in high-intensity running for hit-up forwards and wide running forwards, respectively. While Gabbett et al. (9) reported hit-up forwards ran further than the current study, back row forwards ran similar distances to wide running forwards. In comparison, the lock position in the current study ran significantly less than the wide running forward in high-intensity running. Differences reported between studies could be the result of the style of play of the different teams and the individuals researched.
The majority of high-intensity running in the current study for all positions were <20 m, which is similar to those reported in the previous studies (1,8,12,15). The average frequency of high-intensity running for all positions in the current study was 54 efforts. When the results were separated into forwards and backs, the frequency of high-intensity efforts was 63 and 43, respectively. These results are substantially higher than those found by Gabbett et al. (9), who reported 35 sprints per game. For all 5 back positions, the greatest variance resulted from the grouping of adjustables, with Gabbett et al. (9) reporting 31 high-intensity running efforts. During the current study, a substantially higher frequency of high-intensity efforts was reported for adjustables, with 80 per game. This difference in values reported between the studies resulted from the much higher frequency of high-intensity efforts by the five-eight and halfback at 86 and 120, respectively. Significantly, the lower frequency achieved by the fullback in the current study, with only 42 high-intensity efforts per game, means grouping these 3 positions as adjustables do not give a true indication of the movement demands of each of these individual positions.
The average number of occurrences in high-intensity running efforts for the forward positions was 74, 52, 26, and 18 for hooker, lock, back row, and prop positions, respectively. By comparison, Gabbett et al. (9) reported that hit-up forwards (prop forwards) achieved 39 high-intensity running efforts per game, which is over twice as high as that found in the current study. Using the grouping of wide running forwards (back row and lock) in the current study, the number of high-intensity running efforts is similar to that reported by Gabbett et al. (9) at 39 and 37, respectively. However, when separated into playing positions during the current study, the lock forward had a much higher frequency of high-intensity efforts than the back row forward. This clearly demonstrates the need to separate data into individual positions to fully understand the movement demands of each position in rugby league.
Limited by the ability of GPS to accurately measure collision events, there is no research via accelerometers within GPS units measuring collision events, such as tackling. Further study needs to be undertaken into load measures calculated from accelerometer data in GPS to establish a greater understanding of the types of impacts and quantifying collision events in rugby league match play. Further limitations exist in the psychological effect on individual player’s response to being monitored through GPS and whether this increases performance because of the pressure of being analyzed. Further research in this area would allow a clearer understanding of player movements and monitoring effects, if any. Understanding the physiological demands of each individual position in field sports is important for coaches to analyze and deliver athletes optimal training programs that elicit appropriate and specific physiological adaptation to not just playing groups but also individual positions. It has also been shown the limitation of previous studies using groups of players to design training programs.
The current study has clearly demonstrated the movement demands of all 9 playing positions in professional rugby league and shown the flaws in combining individual positions into common positional groups. The use of GPS technology has demonstrated plausibility to eliminate the use of grouping of positions in rugby league and for coaches to make specific training protocols for each position. The additional high-intensity running undertaken by fullbacks and back row forwards positions needs to be taken into consideration when planning training protocols for these specific positions. Accommodation in training of the higher work rate (represented by m·min−1) of five-eights and halfbacks should also be considered in training prescription. Given the differences reported in the movement demands of all 9 positions in rugby league, some positions would lack specificity to their positional requirements if using collective grouping for planning of training regimens.
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Keywords:Copyright © 2014 by the National Strength & Conditioning Association.
GPS; high-intensity running; motion analysis; movement demand