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Comparison of Activity Profiles and Physiological Demands Between International Rugby Sevens Matches and Training

Higham, Dean G.1; Pyne, David B.2,3; Anson, Judith M.3; Hopkins, Will G.4; Eddy, Anthony5

The Journal of Strength & Conditioning Research: May 2016 - Volume 30 - Issue 5 - p 1287–1294
doi: 10.1519/JSC.0b013e3182a9536f
Original Research
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Higham, DG, Pyne, DB, Anson, JM, Hopkins, WG, and Eddy, A. Comparison of activity profiles and physiological demands between international rugby sevens matches and training. J Strength Cond Res 30(5): 1287–1294, 2016—The specificity of contemporary training practices of international rugby sevens players is unknown. We quantified the positional group-specific activity profiles and physiological demands of on-field training activities and compared these with match demands. Twenty-two international matches and 63 rugby-specific training drills were monitored in 25 backs and 17 forwards from a national squad of male rugby sevens players over a 21-month period. Drills were classified into 3 categories: low-intensity skill refining (n = 23 drills, 560 observations), moderate- to high-intensity skill refining (n = 28 drills, 600 observations), and game simulation (n = 12 drills, 365 observations). Movement patterns (via Global Positioning System devices) and physiological load (via heart rate monitors) were recorded for all activities, and the differences between training and matches were quantified using magnitude-based inferential statistics. Distance covered in total and at ≥3.5 m·s−1, maximal velocity, and frequency of accelerations and decelerations were lower for forwards during competition compared with those for backs by a small but practically important magnitude. No clear positional group differences were observed for physiological load during matches. Training demands exceeded match demands only for frequency of decelerations of forwards during moderate- to high-intensity skill-refining drills and only by a small amount. Accelerations and distance covered at ≥6 m·s−1 were closer to match values for forwards than for backs during all training activities, but training drills consistently fell below the demands of international competition. Coaches could therefore improve physical and physiological specificity by increasing the movement demands and intensity of training drills.

1Performance Science and Medicine, Buffalo Sabres, Buffalo, New York;

2Physiology, Australian Institute of Sport, Canberra, Australia;

3Research Institute for Sport and Exercise, University of Canberra, Canberra, Australia;

4Sport Performance Research Institute New Zealand, Auckland University of Technology, Auckland, New Zealand; and

5Irish Rugby Football Union, Dublin, Ireland

Address correspondence to Dean G. Higham, dean.higham@outlook.com.

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Introduction

Success in rugby union and the abbreviated rugby sevens format requires a high degree of skill, tactics, and physical ability. The efficacy of practice and training interventions on factors related to rugby performance is well established (1,22,25,29). However, the physical and physiological demands and specificity of individual training drills are largely unknown. Training drills are often designed with a specific learning or adaptation objective, such as strength and conditioning, skill development, tactical team play, or a combination thereof. Match-specific drills simulating game scenarios are designed to prepare players for the physiological, skill, and decision-making demands of competition. The development of all facets of performance, including skill, decision making, fitness, and team structures, warrants dedicated training time. An overemphasis on training these facets in isolation could limit the opportunities for match-specific drills that purportedly replicate physical and tactical competition demands using appropriate work-to-rest ratios. Despite the ostensible advantages of match-specific training, it is unrealistic and potentially undesirable for training to consistently reproduce match loads (10). The positive relationship between on-field training loads and injury rates observed in professional contact team sports highlights the need to minimize the risks to players' health and performance without compromising training adaptations (19).

The capability to define and monitor the demands of training and competition in team sports has improved as a result of measurement techniques such as the Global Positioning System (GPS) technology (17,34). Portable microtechnology devices worn by players now allow for heart rate, physical impacts, distance, and velocity to be quantified without interference to the training and match environment (2). Comparisons of training and competition demands have been examined in several team sports, including field hockey (17), volleyball (15), soccer (21), cricket (34), rugby league (20), and Australian football (10). Research comparing the demands of training and matches in rugby union is limited to a single study of adolescent players (26). The demands of competition and requirements for physical development in international rugby sevens are unique (27,28), yet the effectiveness and specificity of training of rugby sevens players remain unclear. An investigation of contemporary training practices is required to assist in the development of approaches that consider the duration, volume, intensity, and frequency of training relative to the athlete's needs and phase of the season. Understanding the activity profile and demands of various training drills and quantifying the disparity between training and match demands provide a useful scientific framework for coaches to prescribe periodized training programs. Therefore, the purpose of this study was to quantify the positional group-specific (backs and forwards) activity profile and physiological demands of different types of rugby sevens training activities and compare them with the demands of competition.

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Methods

Experimental Approach to the Problem

A prospective, longitudinal, observational study was conducted to characterize the physical and physiological demands of the training activities of a national rugby sevens team. Team members had their movement patterns and heart rate recorded throughout various drills during on-field training sessions. The demands of training activities were then compared with the demands of a sample of international-level matches played by the same players during the data collection period.

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Subjects

Forty-two male rugby sevens players from a national team that competes as a core (top 15) team in the World Rugby Sevens World Series provided written informed consent and volunteered to participate in the study. The players were classified as either forwards (n = 17, age 21.6 ± 2.4 years, height 1.85 ± 0.05 m, body mass 95.8 ± 6.7 kg; mean ± SD at the start of data collection) or backs (n = 25, age 21.0 ± 2.2 years, height 1.81 ± 0.06 m, body mass 86.2 ± 5.6 kg) based on their primary playing position. Results are only reported for players who were free of injury and illness during match and training activities. The study was approved by the University of Canberra Committee for Ethics in Human Research and Australian Institute of Sport Ethics Committee.

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Procedures

Sixty-three on-field training sessions were monitored over a 21-month period. Data were collected on 63 training drills. Drills were classified by the coaches and team physiologist into 1 of 3 types of training activity based on the primary purpose and perceived physical intensity of the drill: low-intensity skill refining (n = 560 observations during 23 drills), moderate- to high-intensity skill refining (n = 600 observations during 28 drills), and game simulation (n = 365 observations during 12 drills). Skill-refining drills aimed to improve the technical aspects of match play, such as tackling and rucking technique, defensive line shape and speed, set-piece play, and passing and catching abilities. Game-simulation drills were designed to practice skills and tactical aspects of play under match-like conditions. The study was delimited to rugby-specific training activities with the ball. Therefore, conditioning drills and warm-up activities were excluded from analyses. Training activities were compared with data from 22 matches collected on the same group of players during 4 international tournaments (Sevens World Series and Federation of Oceania Rugby Unions Oceania Sevens Championship) played during the data collection period (n = 306 observations). Any training or match observation with a duration <1 minute was excluded from the analysis. Matches were split by each half and the half-time interval and any time a player spent off the field were excluded. Each match half, or part thereof, was treated as a single observation. Although differences in the movement patterns between first and second halves, matches within a tournament, and full-match and substitute players are evident and acknowledged (27), match activities and demands were characterized by the mean of all observed competition data.

Activity profiles were assessed during training and matches by fitting players with a portable GPS device sampling at 15 Hz (SPI Pro X, GPSports Systems, Canberra, Australia). The validity and reliability of GPS microtechnology for monitoring sports performance have been reviewed previously (8). Physiological demands were assessed during selected training activities by fitting players with a heart rate transmitter strap (T34, Polar Electro Oy, Kempele, Finland). Heart rate data were recorded to the GPS device at 1 Hz. The GPS device was positioned between the scapulae of each player using a vest worn underneath the training or match attire. The unit was activated, and the satellite lock was established for a minimum of 10 minutes before the commencement of each session. All the players were familiar with the data collection procedure. After each session, recorded data were analyzed using the manufacturer's software (Team AMS release 1 2011 revision 8, GPSports Systems).

Activity profiles were quantified by the frequency of efforts and cumulative distance covered in 5 velocity zones (0–2 m·s−1, 2–3.5 m·s−1, 3.5–5 m·s−1, 5–6 m·s−1, and ≥6 m·s−1) (27). Acceleration and deceleration characteristics were assessed by the frequency with which a player performed an acceleration (≥1 m·s−2) or deceleration (≤1 m·s−2) for a minimum duration of 1 second. The frequency and intensity (reported in gravitational [g] force) of mechanical loading (impacts) on the players were recorded by a 100-Hz triaxial accelerometer housed within the GPS device. Given the questionable validity of accelerometers in quantifying the contact loads on athletes (18), the total number of impacts measured at ≥5g was measured instead of categorizing impact measurements by magnitude as has been reported previously (9). A magnitude of ≥5g encompasses a range from a light impact characterized by a heavy foot strike during a rapid acceleration, deceleration, or change of direction to a severe collision with opposition players (9).

The mean and peak heart rates measured during training drills and matches were recorded. Heart rate data were categorized into 5 zones corresponding to the percentage of each player's maximum heart rate (HRmax) recorded during the Yo-Yo intermittent recovery level 1 test (4), or an incremental running test on a motorized treadmill. Maximum heart rate values were subsequently updated if the testing values were exceeded during training or a match. The cumulative time in 5 heart rate zones was multiplied by a weighting factor (50–59% HRmax = 1, 60–69% HRmax = 2, 70–79% HRmax = 3, 80–89% HRmax = 4, and ≥90% HRmax = 5) to linearly scale the intensity of activity. The adjusted values were then summated to indicate the cardiovascular load in arbitrary units (12). An index describing the efficiency of movement with respect to the relative internal load on the player, termed the performance efficiency index and measured in arbitrary units, was calculated for each training drill and match half as the relative distance covered (meters per minute) per %HRmax (5).

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Statistical Analyses

Most movement and heart rate variables were expressed per minute of activity time to account for the variations in match and training duration. Descriptive statistics (mean ± SD) are reported to characterize movement patterns and physiological load. Variability within players was calculated as the mean of each player's SD, whereas differences between players in activity and physiological load parameters were calculated as the SD of all observations. These SDs were expressed as coefficients of variation (percents of the overall means). Standardized differences in the means of the various training activities and match demands for each positional group were used to assess the magnitudes of effect by dividing the differences by the between-player SD. Magnitudes of standardized differences in means were assessed using the following scale: 0–0.2 trivial, 0.2–0.6 small, 0.6–1.2 moderate, 1.2–2.0 large, 2.0–4.0 very large, and ≥4.0 extremely large (30). To address the issue of quantification of longitudinal changes in performance characteristics, the signal-to-noise ratio of each variable for both positional groups during each activity was calculated as 0.2× between-player SD/within-player SD.

Precision of the estimate of the difference is shown with a confidence interval derived as the appropriate percentiles of 3000 bootstrapped sample values. Bootstrapping was used because a mixed linear model did not converge on a solution in less than a day for each variable. To reduce the likelihood of errors in the inferred magnitudes, 99% was chosen as the level for the confidence intervals. A difference was reported as unclear when the confidence interval of the standardized difference crossed the threshold for both substantially positive (0.2) and negative (−0.2) values. Analyses were performed with the Statistical Analysis System (version 9.2, SAS Institute, Cary, NC).

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Results

Differences Between Positional Groups

Backs recorded higher values than forwards during matches in most movement variables, but there were unclear differences between positional groups in physiological demands represented by heart rate parameters (Table 1). The difference in relative impacts between groups was also unclear. The higher total relative distance covered by backs was because of the small difference in the frequency of entries and relative distance covered in velocity zones ≥3.5 m·s−1. The small difference in the distance covered at a similar relative heart rate resulted in a moderately higher performance efficiency index in backs than in forwards. The within-player coefficient of variation of movement and physiological measures ranged from 2.6% for peak heart rate in forwards during matches to 210% for relative distance covered at ≥6 m·s−1 in forwards during low-intensity skill-refining drills. The coefficient of variation for between-player differences ranged from 3.2% for peak heart rate in forwards during matches to 280% for the relative distance covered at ≥6 m·s−1 during low-intensity skill-refining drills, also in forwards. The signal-to-noise ratio ranged from 0.19 (i.e., the noise was ∼fivefold greater than the signal) in the frequency of entries in the 3.5–5 m·s−1 velocity zone per minute in forwards during moderate- to high-intensity skill-refining drills to 0.43 in relative impacts during matches in backs.

Table 1

Table 1

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Differences Between Training Activities and Matches

Maximal velocity, and relative values of impacts, distance covered, accelerations, and decelerations in training were either unclear or lower (small to extremely large differences) compared with those in matches (Figure 1). The only measure to substantially exceed match values was decelerations in moderate- to high-intensity skill-refining drills in forwards. Moderate- to high-intensity skill-refining drills and game-simulation drills had values closer to match values than low-intensity skill-refining drills in all variables.

Figure 1

Figure 1

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Differences in Velocities

Less relative distance was covered in training drills compared with that covered in matches in all velocity zones (small to very large differences; Figure 2). Less relative distance was covered at all velocities in low-intensity skill-refining drills compared with moderate- to high-intensity skill-refining and game-simulation drills (small to large differences).

Figure 2

Figure 2

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Differences in Physiological Load

The mean and peak heart rates, cardiovascular load, and performance efficiency index did not replicate the demands of international matches for backs and forwards during all training activities (moderate to extremely large differences; Figure 3). Training values were closer to match values for backs than for forwards in all drill types and variables except for performance efficiency during moderate- to high-intensity skill-refining drills.

Figure 3

Figure 3

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Discussion

The ultimate objective of a physical preparation program is to maximize training adaptations to prepare players to achieve optimal competition performance. Training specificity is usually achieved through on-field training approaches that aim to match or exceed the technical, tactical, physical, physiological, and psychological demands of top-level competition. This study is the first to directly compare the activity profiles and physiological demands of backs and forwards during international rugby sevens competition and to assess the positional group-dependent specificity of training activities. Small but practically important differences in movement patterns were observed between backs and forwards during competition. Compared with forwards, backs achieved a higher maximal velocity, performed more accelerations and decelerations, and covered greater distances at ≥3.5 m·s−1 and overall. However, these differences in activity were not accompanied by a corresponding difference in physiological load.

A major finding of this study was the substantial disparity in the activity profiles and internal load of all forms of rugby-specific on-field training activities and international matches. Relative to competition, training was characterized by less distance covered (large to extremely large differences), similar or lower maximal velocities (unclear to very large differences), less impacts (moderate to large differences), and similar or fewer accelerations (unclear to large differences). There were also fewer decelerations in training compared with matches for all training activities except for forwards during moderate- to high-intensity skill-refining drills. Heart rate–based indicators of the physiological load of training activities were lower than those during matches. Marked differences between some training practices and competition should be expected, given that consistently reproducing match demands during training would oversimplify the complex multifaceted factors associated with the development of elite rugby players (11). Even so, the findings of this study provide important information that may be used to implement strategies that emphasize the specificity of movements and conditioning stimuli during training.

Differences in the activity profiles between backs and forwards during matches support the need for position-specific training approaches. Position-specific training is likely to occur to some extent as players typically train in the positions in which they will compete. Positional differences in the total distance covered and the distance traveled at high velocity during competition are consistent with similar observations in 15-player professional rugby union competition (3,7,9,35). Although the specificity of movement pattern parameters varied between positional groups in training, the physiological load of forwards during training was consistently lower relative to matches compared with backs. It is uncertain whether the higher values of movement variables for backs compared with those for forwards during international competition reflect greater demands related to differences in positional roles, higher fitness levels of backs, or a combination of these factors. The unclear differences during matches in the physiological load and distance covered at lower velocity (<3.5 m·s−1) between backs and forwards imply that lower match-specific fitness of forwards may be an explanation for positional variations in activity profiles. Indeed, backs performed marginally better than forwards in the Yo-Yo intermittent recovery level 1 test (2,202 ± 288 vs. 2,093 ± 389 m; mean ± SD), a measure of team sport–specific endurance (4).

Despite there being a lower cardiovascular load, accelerations and distance covered at ≥6 m·s−1 were closer to match values for forwards than for backs during all training activities. The same trend was observed for maximal velocity during all training activities except low-intensity skill-refining drills. The variation in the maximal velocity achieved in low-intensity skill-refining drills may be explained by training drills devoted to set-piece plays with minimal involvement from backline players. Technical drills practicing scrums and line-outs typically involve little to no maximal sprinting.

The acceleration and deceleration of a player's body mass increase the mechanical load and metabolic cost of exercise compared with running the same distance at a constant velocity (31,33). Disregarding the frequent changes in running velocity likely underestimates the true quantity of the high-intensity activity of team-sport athletes (32). Frequency of decelerations of forwards during moderate- to high-intensity skill-refining drills was the only measure to substantially exceed match demands. Similarly, physical impacts, either through contact with the ground or other players, increase the mechanical load on players, concomitantly increasing the time required for recovery from muscle damage and soreness (23,36,37). The lower frequency of impacts of ≥5g in training reflects the combination of reduced high-velocity running volumes that result in a forceful foot strike and limited exposure to “full contact” drills, which increase recovery requirements and potential for injury (6).

The analysis of the training specificity in this study excluded only the periods between training drills for drink breaks, and time allocated for drills to be set up and explained. At least part of the reduced activity and physiological demands of training compared with competition may be explained by the intermittent breaks in activity within a drill for coaching feedback and instruction. We chose to include these breaks within drills in our analyses to reflect the actual physical and physiological demands experienced by players. The other factor that may contribute to the lower physical and physiological loads of training is the use of “closed” drills, whereby technical development is emphasized through the high repetition of skill executions typically without a decision-making component. Closed drills may permit additional recovery time between activity periods while players wait for their turn to perform a task. In contrast, “open” drills simulating match-like conditions are more physically and cognitively demanding (13).

The planning of training programs for international rugby sevens players is influenced by a multitude of factors, including the phase of season and temporal proximity of training to competition; ground firmness and environmental conditions; effects of interstate and international travel; perceived intensity of previous and upcoming competitions; and team and individual considerations, such as fitness and form (10). Despite the importance of these and other considerations, match-specific drills should aim to replicate or exceed match demands to best prepare players for the requirements of competition (10). The game-simulation drills observed in this study failed to reproduce the physical or physiological demands of matches. The low specificity of skill-refining drills may be expected, given their lack of explicit emphasis on conditioning. Unsurprisingly, of the 3 training activities, low-intensity skill-refining drills were the least reflective of match conditions in every variable measured. Subsequent analyses of the standardized differences between training activities with respect to positional groups showed that low-intensity skill-refining drills were substantially lower than moderate- to high-intensity skill-refining and game-simulation drills for all variables (results not shown). In contrast, differences between moderate- to high-intensity skill-refining and game-simulation drills were smaller and more variable. Small standardized differences were observed for some variables, although most comparisons showed unclear to trivial differences (results not shown). Differences in these training activities may be better reflected by quantifying the technical and tactical requirements of training drills rather than the physical and physiological demands alone.

Investigation of the frequency and quality of technical components of match play, such as passes, tackles, kicks, set-piece plays, and decision-making ability, was not within the scope of the current investigation. Future research should investigate the specificity of the technical and tactical components of rugby sevens training and examine the strategies that maximize skill learning. It is possible that there is a compromise between the training time required for optimal physical and technical development in international rugby sevens players. However, given the potential impact of fatigue on the execution of physical and cognitive skills (16,35), training outcomes may be enhanced by the practice of skills under conditions that simulate the high-intensity activity of competition. The optimal balance and timing of instructional skills training and match-specific drills, in either isolation or combination, to maximize the physical and technical development of rugby sevens players also requires further research.

The lower intensity of training may lead to the suboptimal or inappropriate adaptation of the metabolic pathways used during competition. The lower internal load of training, as indicated by heart rate–based measures, is likely to result in a greater emphasis on the aerobic system. International rugby sevens players require well-developed aerobic endurance to tolerate the demands of competition and facilitate rapid recovery within and between matches (28). However, the development of anaerobic systems to support short-duration, high-intensity activity, such as sprinting, should not be neglected. The ability to quickly recover from and repeat performances of high-intensity activity is important in team-sport competitions (24), especially in rugby sevens. The training specificity of repeated bouts of high-intensity exercise is also critical, given the task-dependent nature of physiological adaptations to the performance of this activity. It is unlikely that the consistently lower frequency of, and distance covered during, high-velocity (≥6 m·s−1) running observed in training compared with that in matches offers a sufficient stimulus for optimal adaptation to meet competition demands.

Mean and peak heart rates and cardiovascular load discriminated independently each training activity with the exception of moderate- to high-intensity skill-refining and game-simulation drills (results not shown). However, one could not be confident about quantifying trivial or small changes in the intensity of drills between sessions, owing to the inherent noise of heart rate metrics (evident in the relatively poor signal-to-noise ratios). To longitudinally track an individual player or assess an intervention with a repeated-measures design using realistic sample sizes, several sessions would need to be monitored and averaged to reduce the within-player variability to a value comparable with the smallest important change (a signal-to-noise ratio of ∼1.0). The most reliable measure in this study, the frequency of impacts during matches, would require 6 repeated observations to quantify trivial changes confidently, and other measures would require several times more.

The findings of this study highlight the potential to improve the training efficiency of international rugby sevens players. Training efficiency can be improved through greater physical specificity for a superior return from on-field training time without compromising a player's health or performance. Rugby players are often exposed to high training volumes during the precompetition and in-competition training phases (6). There is an association between training load and incidence of injuries (19) and between training volume and injury severity (6) in professional contact team sports. However, a professional rugby union team's training volume does not significantly correlate with their final competition ranking (6). Further, a reduction of preseason training volume in subelite rugby league players lowered injury rates without any detrimental effect on training adaptations (14). The effect of reducing training volumes on training adaptations, incidence and severity of injuries, and recovery requirements in rugby sevens players is yet to be determined. Nevertheless, the results of our analysis support the assertion that modifying training approaches to improve efficiency may simultaneously reduce the risks associated with high training volumes while maintaining or improving training adaptations.

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Practical Applications

Specificity of training is an important consideration for prescription of physical preparation programs to promote physiological adaptations for the benefit of competition performance. The training activities in this squad over 21 months did not replicate the physical or physiological demands of top-level competition. Although it may be undesirable for technically focused drills to reproduce the physical loads of competition, game-simulation drills should reflect match demands to adequately prepare players for competition. Understanding the demands of competition facilitates the modification of match-specific training drills to improve specificity and adopt position-specific training approaches. The magnitude-based approach used in this study highlights the priorities for improving the specificity of movement patterns and velocities based on a player's position and the type of training drill. For example, although the maximal running velocity achieved by forwards during game-simulation drills was similar to competition, the mean velocity (meters per minute) was substantially lower. Coaches could improve the management of their players' training load and enhance training efficiency by increasing intensity and specificity and reducing training duration. Further, coaches should consider the influence of interruptions in training activity for instruction and feedback on the movement patterns and physiological load imposed on players. Heart rate monitoring provides a useful index of a player's internal response to a training stimulus to ensure that the appropriate adaptations are achieved, whereas GPS devices provide an objective external measure of the work performed by a player. Monitoring the activity profile and physiological load of training activities should ensure that training drills optimally prepare players for the demands of competition.

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Acknowledgments

The authors gratefully acknowledge the cooperation and involvement of the players and the coaching and support staff. This study was funded by the Australian Institute of Sport, Australian Rugby Union, and the Research Institute for Sport and Exercise at the University of Canberra. Higham was with the Australian Institute of Sport, Australian Rugby Union, and University of Canberra at the time of the study. Eddy was with the Australian Rugby Union at the time of the study.

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Keywords:

global positioning system; GPS; rugby union; time-motion analysis; physical preparation; specificity

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