Rugby sevens is played by 2 teams of 7 players, on a regular rugby pitch. The game is derived from the original game of rugby union, applying essentially the same laws. The duration of the match is 14 minutes (two 7-minute halves) with a 2-minute half-time interval. In recent years, a large number of time motion analyses have been conducted in soccer (3,8,23,26,33), rugby union (7,9,10), and rugby league (6,19). Few researchers have investigated the physical demands and activity profiles of rugby sevens (11,12,20,27,32), with the majority of these studies oriented to medical and traumatological aspects of the sport. Takahashi et al. (32) showed that the cumulative effects of 2 rugby sevens matches in 1 day negatively affected the athlete's immune system. Moreover, Fuller et al. (11) demonstrated that the risk and severity of injuries in rugby sevens was higher than that during international rugby union matches. Gabbett (12) also examined the incidence of injury in rugby sevens and showed that injury rates were higher than in conventional rugby, with player fatigue contributing to injuries.
Recently, some authors (29–31) have described the physiological and kinematic aspects of rugby sevens. Using global positioning system (GPS) technology, these studies (30,31) have provided general indications on the physical and physiological demands of an entire rugby sevens match (4,17). Higham et al. (16) studied the physiological, anthropometric, and performance characteristics of rugby sevens players. In contrast to 15-a-side players, their results showed small between-athlete variability in characteristics, highlighting the need for relatively uniform physical and performance standards in rugby sevens players (16). A knowledge of the activity profiles and movement demands of rugby sevens allows sport scientists and strength and conditioning staff to plan game-specific training sessions and programs to improve the physical condition of players. This information may also be used to evaluate the physical performance of individual players (1).
Researchers (18,25) have studied the temporal patterns of physical match performance in different team sports. Other studies have investigated the decline in physical performance from the first to the second half to gain an insight into the fatigue that may occur across the course of a match (26). Understanding how physiological and technical-tactical parameters change during a match or in tournaments may provide important an insight into the causes of fatigue and how this fatigue may affect the individual player. These patterns, when consistent, can also be interpreted as useful indicators of the trends of the variables under study. Mohr et al. (24) have described the fatigue that may develop during soccer matches and have provided potential physiological mechanisms responsible for fatigue in soccer. The reduced match performance that occurs as a consequence of fatigue seems to occur at 3 different stages: after short-term intense periods in both halves; in the initial phase of the second half and toward the end of the game (24).
Although the physical demands of soccer have been extensively investigated, no similar studies have been performed in rugby sevens. To date, only Higham et al. (15) have quantified the differences in movement patterns between domestic and international rugby seven tournaments, the effects of fatigue within and between matches during tournaments, and the movement patterns of second half substitute players. The results of the study highlight some significant differences between domestic and International Rugby seven tournaments, with a greater distance covered at high speed and greater accelerations and decelerations performed in international matches. A decrease in speed and the number of changes in speed was found between the first and second halves. Moderate reductions were also observed between the first match (played on day 1) and the last match (played on day 2) of the tournament. Although the study by Higham et al. (15) improved our understanding of rugby sevens, no information was provided on the temporal patterns of fatigue. In addition to fatigue-induced performance reductions from the first to second half, it is likely that fatigue may also occur transiently throughout the course of a match. Therefore, the purpose of this study was to address this gap in the literature by investigating the physical and physiological demands of rugby sevens, with special reference to temporal patterns of fatigue, analyzed minute by minute during international match play. It was hypothesized that transient fatigue, as evidenced by reductions in movement intensities, would occur toward the end of each half in rugby sevens.
Experimental Approach to the Problem
To study the physical demands of rugby sevens match play, we performed kinematic (GPS and Motion Analysis) and physiological (heart rate [HR] and blood lactate [BLa] concentration) measurements during 15 matches of the 2010 (n = 7) and 2011 (n = 8) International “Roma Sevens” competition. Total distance covered, percentage of time spent in 2 distinct (low and high) speed zones, and HR were recorded each minute of match play to gain an understanding of the temporal patterns of fatigue.
Nine rugby sevens players, 4 backs and 5 forwards (age 25.1 ± 3.1 years; body mass 86.0 ± 9.4 kg; height 180.5 ± 3.5 cm; body mass index 27.7 ± 2.6 kg·m−2; V[Combining Dot Above]O2max 52.1 ± 3.4 ml·kg−1·min−1) participated in the study. All the players competed at the professional level in the highest Italian rugby union (“Campionato Italiano di Eccellenza”), with 5 of these players also competing at international level. The players had a minimum rugby training experience of 5 years. The typical weekly training volume was 14–16 hours, which included 4–5 technical training sessions (10–12 hours) and 3 sessions of physical preparation (4–6 hours). Each player was informed about the study, including the risks and benefits and provided written informed consent, in conformity with the Ethical Code of the World Medical Association (Declaration of Helsinki). The Tournament Directors also provided clearance for the use of GPS in matches before the commencement of the study. All experimental procedures were approved by the institutional human ethics committee.
The match activity and physiological data were collected over 2 competitive tournaments. All matches were played on a dry, full-sized rugby pitch (100 × 70 m), covered by natural grass. Matches were played between 11.00 AM and 4.00 PM. The GPS, HR, and motion analysis were synchronized, set with the solar time, so as to know the range for the first half, rest time, and second half. The average temperature and relative humidity for the matches ranged from 24 to 26° C and 67 to 72%, respectively. During the week before the tournaments, each player underwent measurements of standard anthropometry (body mass and height) and the Yo-Yo Intermittent Recovery Test Level 2 was performed to measure the individual maximum HR (HRmax) (21). Heart rate was recorded continuously throughout the Yo-Yo test using Polar Team System HR monitors (Polar Electro OY, Kempele, Finland) sampling at 0.20 Hz.
Global Positioning System Data
A portable GPS device (SPI Elite; GPS Sports Systems Ltd., Canberra, Australia), sampling at 1 Hz, was used. The players were asked to wear an individual GPS unit (mass: 80 g; dimensions: 91 × 45 × 21 mm) encased within a protective harness between the player's shoulder blades in the upper thoracic-spine region. Five minutes before each match, the GPS device was fixed to the torso of the athlete in accordance with the manufacturer instructions. The device was activated and satellite lock established for a minimum of 15 minutes before the commencement of each match. Global positioning system data were analyzed using Microsoft Excel and statistical software.
The GPS files were “cleaned” with Spi Elite software (Team AMS; GPSports, V.1.2) so that only time spent on the field was included in the analysis. Data were log-transformed before analysis to reduce the nonuniformity of error and backtransformed to obtain differences in means and variation as percentages. In accordance with Hartwig et al. (14), the data were divided into 2 speed zones, corresponding to low (0.1 < 14.0 km·h−1) and high intensities (>14.1 km·h−1). The chosen velocity zones represented the range of locomotor activity profiles typical of intermittent team sport and are routinely (14) used during GPS monitoring in rugby-specific match play (13).
The players wore a Cardio belt (Polar Team System, Polar Electro Oy) recording the heart rate (HR) during the 15 matches. Heart rate data were synchronized with GPS data so to exclude rest periods. One-minute averages were calculated for HR data. Taking into consideration that rugby involves strong physical contacts among players during match play, the thorax belt was reinforced and fixed with elastic tape and other bandages around the thorax and shoulders. The recorded data were downloaded and analyzed using Polar Precision Performance v.4.03.043 software. Data involving game interruptions and time spent off the field were excluded from subsequent analysis. The HR was expressed as a percentage of the HRmax measured in the Yo-Yo Intermittent Recovery Test Level 2 (2).
Blood Lactate Concentration
Capillary blood samples were drawn from the ear lobe of 4 players (n = 4), using a sterile lancet (Accu-Check Softclix, Roche—5µ) immediately after the warm-up, at the end of the first half, and at the end of the match. Blood samples were analyzed for BLa concentration. Three BLa analyzers (LactatePro, Arkray, Kyoto, Japan) were used for the analysis of the samples. All blood analysis was made within 2 minutes from the end of each considered period. The validity of the used instrument (Lactate Pro Analyzer) has been verified previously (22).
All the matches were filmed using a single camera (Sony Handycam DCR-SX 30, Tokyo, Japan), placed 12 m above the field and at the end of 1 diagonal, to always have the view of the full field. The exact video recorded times (start and end of each part of the game), playing position (back or forward), and replacements; interruptions of the game were used in postanalysis of kinematic GPS and physiological data (HR and BLa) (28).
Data are presented as mean ± SD. The assumption of normality was assessed using the Shapiro-Wilk test. Parametric and nonparametric statistics were used when appropriate. To identify the differences in the distance covered between first and second halves, a paired t-test was used. To identify differences in physical and physiological variables over time (first and second halves) between forwards and backs a 2-way group × time repeated measures analysis of variance (ANOVA) was also performed. After performing the Mauclhy test of sphericity, the Greenhouse-Geisser [Latin Small Letter Open E] was used when appropriate. Effect sizes (ESs) in ANOVA were computed as partial η2, to assess meaningfulness of practical differences, with η2 < 0.01, 0.01 < η2 < 0.06, 0.06 < η2 < 0.14, and η2 > 0.14 considered trivial, small, moderate, and large, respectively.
In addition to the null hypothesis testing, ES (Cohen's d) were reported for all normally distributed data (5). Absolute ES of 0.20, 0.50, and 0.80 represented small, moderate, and large differences, respectively. The corresponding “p” values were provided for each analysis. Statistical significance was accepted at p ≤ 0.05. Statistical package for Social Sciences (SPSS 15.0) for Windows was used to analyze and process the collected data.
The mean total distance covered throughout the matches, and in the first and second halves was 1,221 ± 118; 643 ± 70; and 578 ± 77 m, respectively. Although a reduction in total distance covered between halves was found (−11.2%), it was not statistically significant (paired t-test: t = 1.823; df = 7; p = 0.111; ES as Cohen d = 0.29). A difference in positional play (backs, n = 4 and forwards, n = 5) was observed between halves for the total distance covered (Factorial ANOVA; p = 0.03). In the first half, the backs covered 677 ± 60 m, whereas the forwards covered 599 ± 60 m. In the second half, the backs covered 615 ± 87 m, whereas the forwards covered 540 ± 51 m.
Table 1 shows the proportion of distances covered and time spent in the 2 different intensity zones. There were no significant differences between halves for the distances covered in these 2 different speed zones. Small to moderate ES (0.41< Cohen d < 0.56) were found for these differences. A meaningful reduction (ES as Cohen d = 1.37) in distance covered per minute for each half of the matches was observed (91.4 ± 13.6 vs. 78.5 ± 18.3 m·min−1, paired t-test: t = 1.438; df = 6; p = 0.200).
Total Distance Covered Per Minute
The distance covered per minute of match play throughout the match is provided in Figure 1. Repeated measure ANOVA showed statistically significant differences among each minute of the game (repeated measure ANOVA with adjustment Greenhouse-Geisser [Latin Small Letter Open E], F (3.06; 60.21) = 3.065; p = 0.016; ES as partial η2 = 0.203; Power = 0.839; α = 0.05) providing a standard profile of the game (Figure 1).
Percentage of Time Spent in Each Speed Zone Per Minute
No significant differences were found among each minute of the game for the percentage of time spent in each speed zone. The relevant statistics are given in Table 1.
Differences in Positional Play
No statistically significant differences were found between playing positions total distance covered per minute: (2-way group × time repeated measures ANOVA: F(1,12) = 2.97; p = 0.11; ES as partial η2 = 0.198; power 0.354 with α = 0.05). Nonetheless, the large ES found suggests some practical implications, worth consideration by the coaches and conditioning staff. Figure 2 highlights the different work rates of each positional role (back and forward) for each minute of the game.
The mean and the peak values of HR, expressed as a percentage of the estimated HRmax, recorded during the matches, are provided in Table 2 and Figure 3. The players spent approximately 86% of the total match time at or >90% of their individual HRmax (Figure 3).
Heart Rate During Each Minute of Match Play
Repeated measures ANOVA confirmed statistically significant differences for mean (F (13,104) = 2.057; p = 0.023; partial η2 = 0.205; power 0.924 with α = 0.05) and peak (F (13,117) = 4.024; p < 0.001; partial η2 = 0.309; power 0.999 with α = 0.05) HRs recorded during the matches, with particular reference to the very first minute of the first and second halves, respectively.
Blood Lactate Concentration
Blood lactate concentration sampled at the end of warm-up, at the end of half time, and at the end of the match were 3.9 ± 0.9, 8.7 ± 1.7, and 11.2 ± 1.4 mmol·L−1, respectively. A significant difference (p = 0.017, Cohen d = −1.5) was found between the values recorded at the end of the first and second halves, respectively. No significant differences were found in postmatch BLa (Mann-Whitney U-Test; p = 0.19, Cohen d = 0.29) between backs (11.6 ± 1.5 mmol·L−1) and forwards (10.4 ± 0.8 mmol·L−1).
To our knowledge, this is the first study to investigate the temporal patterns of physical performance and physiological parameters measured during international level rugby sevens tournament match play. Our data highlight the physical loads observed in rugby sevens and consider the contrasting movement demands of different playing positions (backs and forwards). Significant fatigue, identified as the rate of decay in performance, was observed during match play. A reduction of 11.2% between the first and second halves was observed for total distance covered per minute. Although not statistically significant (p = 0.16), the reduction in performance would certainly be considered practically meaningful, with a large ES when considered as distance covered per minute of match play. The difference found in relation to the playing position (Figure 2), although not statistically significant (p = 0.11), showed a large ES, indicating possible practical implications.
We also conducted a minute-by-minute analysis on the total distance covered by players during the matches. In relation to this parameter, it should be noted that the pace of the game has a significantly different modulation when seen minute by minute, allowing us to identify some “temporal patterns” on the second, seventh, and eleventh minutes of the match. Such typical modulations of the matches were found to be significant and consistent in all the investigated games. These reductions in performance may suggest that rugby sevens players experience transient fatigue during match play.
By reporting the percentages of time spent in each speed zone per minute (Table 1), we found significant differences both in relation to match time, and positional play, as an interaction effect between the minute of play and the positional play. These findings provide evidence of both fatigue occurring transiently throughout rugby 7s matches, and the position-specific nature of this fatigue. The observed differences in low- and high-speed activities provide some interesting observations about international rugby sevens. On a minute-by-minute basis, the 2 speed zones fluctuated considerably (ES as η2 > 0.12; Table 1, Figure 1). These findings may reflect differences in playing tactics or positional play. Alternatively, it is possible that the fluctuations in low-speed activity represent a pacing strategy used on behalf of players to preserve high-speed activity. The trend in mean (88.0 ± 3.7% of HRmax) and peak (92.4 ± 4.0% of HRmax) HR observed during all the investigated matches demonstrates the very intense physiological demands required to compete in international level rugby sevens. It also shows that the mean and peak HR values reached the operating level (∼90% of the HRmax) after the first 2 minutes of play, both in the first and in the second halves.
Our BLa concentration data confirm the glycolytic nature of rugby seven's matches. In particular, we emphasize that the BLa concentrations found in rugby seven's matches are greater than the average BLa concentration found during conventional rugby union match play for backs (5.1 mmol·L−1) and forwards (6.6 mmol·L−1), confirming that rugby sevens presents different and greater physiological demands than those required in conventional rugby union (9). However, it should be noted that if match involvements increased toward the end of the first and second halves, then this could significantly increase BLa concentrations above normal match values.
There are several practical applications from this study that have relevance to the strength and conditioning coach. First, these findings demonstrate the highly intense, glycolytic nature of international rugby sevens match play. Mean HR (88.0% HRmax) during and BLa concentration (11.2 mmol·L−1) after match play demonstrate that strength and conditioning coaches should emphasize the development of anaerobic glycolytic energy pathways and aerobic capacities for this sport. Our minute-by-minute analysis also revealed significant reductions in physical performance, indicative of fatigue, or possibly pacing, throughout various stages of matches. These findings could be used by both applied sport scientists and rugby coaches to inform strategic interchanges throughout match play. For example, with the introduction of “live streaming” of GPS data, movement patterns can be observed in real time, and interchanges made before the onset of fatigue, and reductions in performance. Finally, our results show similarities in the physical demands of rugby sevens backs and forwards. These findings may be a reflection of the greater space afforded to players in Sevens, and the consequent reduction in the number and intensity of collisions compared with the conventional 15-a-side game. These findings suggest that similar strength and conditioning programs can be used for forwards and backs to prepare these players for the physical demands of international rugby sevens match play.
The authors are grateful to the “Gruppo Sportivo Fiamme Oro Roma Italia Sezione Rugby” in particular to Coach Sven Valsecchi, for supporting this research. The results of this study do not constitute endorsement of the product by the authors or the National Strength and Conditioning Association. This study was not supported by any sources of funding. There are no conflicts of interest in this article.
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Keywords:Copyright © 2014 by the National Strength & Conditioning Association.
ecological validity; time-motion analysis; match play demands; team sports