Inconsistent anticipatory postural adjustments (APAs) in rugby players : a source of injuries ?

Background: We are developing since 2010 with Thales and the Fédération Française de Rugby (FFR) M-Rex, a new kind of rugby scrum simulator. The study questioned whether it could improve safety and protect players from injury by using it as a tool for training/coaching the packs. Aim: To explore the anticipatory postural adjustments (APAs) during the engagement of the ruck, because these predictive neck and back muscles contractions protect the spinal cord at the time of impacts, which is crucial to prevent injuries. Methods: We quantified the kinematics and the EMG activities in high-level front row players during their initial engagement, when scrummaging with M-Rex. All studies were performed with one player interacting with the robot, at first, and then with the three players acting together. Results: For most of the tested high-level players, the APA latencies were highly variable from trial to trial even though the engagement resulted in similar impacts. At time, the onset of the electromyography activity in the neck and back muscles showed latencies inferior to 50 ms or even close to zero prior to the impact, which rendered muscle contractions inefficient as APAs. We were also unable to identify clear muscular synergies underlying the APAs because of their great variability on a trial-to-trial basis. Finally, the APAs were not related to the amplitude of the ensuing impact and were asymmetric in most trials. All these characteristics held true, whether the player was playing alone or with two other frontline players. Conclusion: Our result suggest that APAs should be systematically tested in high-level rugby players as well as in any high-level sport men at risk of neck and back injuries. Because APAs can be efficiently trained, our study paves the way to design individual position-specific injury prevention programme.This study was funded by Fédération Française de Rugb

A cross-sectional study assessing the contributions of body fat mass and fat-free mass to body mass index scores in male youth rugby players

Background. In some sports such as rugby, a large body size is an advantage, and the desire to gain weight can bring young players to become overweight or obese. The aim of this study was to evaluate the prevalence of overweight and obesity and the contribution of body fat mass index (BFMI) and fat-free mass index (FFMI) to body mass index (BMI) changes among young male rugby players (15-a-side rugby). Methods. The criteria of the International Obesity Task Force were used to define overweight and obesity from BMI. The method of skinfold thickness was used to assess percentage of body fat (%BF), BFMI, and FFMI. Excess body fat was defined by using BFMI and %BF above the 75th percentile. Data were grouped according to the age categories of the French Rugby Federation (U11, under 11 years; U13, under 13 years; U15, under 15 years) and to BMI status (NW normal-weight versus OW/OB overweight/obese). Results. Overall, 32.8% of the young players were overweight, and 13.8% were obese. However, 53% of young players classified as obese and overweight by BMI had an excess body fat by using BFMI above the 75th percentile. FFMI increased significantly between U11 and U13 in both groups, without significant change in BMI and BFMI. Both groups had similar significant gains in BMI and FFMI between U13 and U15, while BFMI only increased significantly in OW/OB (+ 18.5%). The strong correlations between BMI and %BF were systematically lower than those between BMI and BFMI. FFMI was strongly or moderately associated with BFMI. Conclusions. Chart analysis of BFMI and FFMI could be used to distinguish changes in body composition across age categories in young male rugby players classified as normal-weight, overweight, and obese by BMI

Collaborative sensorimotor intelligence: the scrum as a model

AimUsing M-Rex, a rugby scrum simulator, we developed tools to describe scrummaging forces and to prevent accident.MethodsWe tested three groups of frontliners at national level. The simulator was passive or responded to the player(s) to simulate the reaction of opposite players. Sensors in the beam measured the force exerted by each of the players. Their movements were recorded with a Codamotion system.ResultsThe force signals exhibited two phases: a transient phase, similar to a damped sinusoid with a dominant frequency around 5 Hz when the players scrummaged alone and with a wider range when playing together; then, a sustained phase could be decomposed in two components: a DC component remained stable whether frontliners played alone or together. In contrast, its variability decreased when the frontliners played together compared with when they played alone. As for the oscillations, the frontliners exhibited a large variability in their ability to synchronise their efforts during the sustained phase. The synchronisation between the hooker and the props was quite efficient, while it was always missing between two props. Finally, we were able to study postural readjustments and their synchronisation among players during the sustained phase.ConclusionThis study shows that by using adequate methods, it is possible to assess the frontline collective intelligence. These findings may pave the way for innovative methods of training to improve players’ collective behaviour

A Comparison of an Alternative Weight-Grading Model Against Chronological Age Group Model for the Grouping of Schoolboy Male Rugby Players

ObjectivesConcerns regarding marked differences in the weights and body composition of young rugby players competing within the same age groups have led to the suggestion of alternative models for grouping young players. The aims of this study were (1) to compare variance in the body size and body composition of schoolboy rugby players (9 to 14 years), across weight- and age-grading models, and (2) to identify morphotypes for the weight model using Hattori’s body composition chart.Materials and MethodsSkinfold thickness measurements were used to assess body fat mass (BF), fat-free mass (FFM), body fat mass index (BFMI), and fat-free mass index (FFMI). Standardized measure of height and weight were taken for all participants. Data were grouped according to the age categories of the French Rugby Federation (U11: Under 11 years, U13: Under 13 years, and U15: Under 15 years), and to the weight categories (W30–44.9; W45–59.9; and W60–79.9) carried out from 25th and 75th weight percentile in each age category. Body mass index status (NW normal-weight versus OW/OB overweight/obese) was considered. Extreme morphotypes are characterized from BFMI and FFMI in the weight-grading model on Hattori’s body composition chart.ResultsThe dispersion of anthropometric characteristics decreased significantly for the weight model, except for height in all groups and BFMI for U13. Among NW, 3, 1.8, and 0% upgraded; 18.2, 68.7, and 45.5% downgraded; among OW, 50, 21.5, and 12.5%; and among OB, 91.3, 83.3, and 74.6% upgraded, respectively, in U11, U13, U15. FFMI/BFMI were correlated in U11 (r = 0.80, p < 0.001), U13 (r = 0.66, p < 0.001), and U15 (r = 0.77, p < 0.001). There was no significant correlation in W45–59.9 and low correlations in W30–44.9 (r = 0.25, p < 0.001) and W60–79.9 (r = 0.29, p < 0.001). Significant grading difference between the centroids (p < 0.05) and the distribution deviates from centroids of BFMI and FFMI (p < 0.0001) were noted between the two models. Thirteen players were located in adipo-slender, twenty-three in adipo-solid, twenty-two in lean-slender, and two located in the lean-solid morphotype in weight model.ConclusionA weight-grading model should be considered to limit mismatches in anthropometric variables. However, variations of body composition also persisted for this model. Hattori’s body composition chart allowed more detailed examination of morphological atypicalities among schoolboy rugby players

Exposure time, running and skill-related performance in international u20 rugby union players during an intensified tournament

Purpose This study investigated exposure time, running and skill-related performance in two international u20 rugby union teams during an intensified tournament: the 2015 Junior World Rugby Championship. Method Both teams played 5 matches in 19 days. Analyses were conducted using global positioning system (GPS) tracking (Viper 2™, Statsports Technologies Ltd) and event coding (Opta Pro®). Results Of the 62 players monitored, 36 (57.1%) participated in 4 matches and 23 (36.5%) in all 5 matches while player availability for selection was 88%. Analyses of team running output (all players completing >60-min play) showed that the total and peak 5-minute high metabolic load distances covered were likely-to-very likely moderately higher in the final match compared to matches 1 and 2 in back and forward players. In individual players with the highest match-play exposure (participation in >75% of total competition playing time and >75-min in each of the final 3 matches), comparisons of performance in matches 4 and 5 versus match 3 (three most important matches) reported moderate-to-large decreases in total and high metabolic load distance in backs while similar magnitude reductions occurred in high-speed distance in forwards. In contrast, skill-related performance was unchanged, albeit with trivial and unclear changes, while there were no alterations in either total or high-speed running distance covered at the end of matches. Conclusions These findings suggest that despite high availability for selection, players were not over-exposed to match-play during an intensified u20 international tournament. They also imply that the teams coped with the running and skill-related demands. Similarly, individual players with the highest exposure to match-play were also able to maintain skill-related performance and end-match running output (despite an overall reduction in the latter). These results support the need for player rotation and monitoring of performance, recovery and intervention strategies during intensified tournaments

Etude électromyographique de muscles striés squelettiques soumis à des compressions mécaniques externes (application à l analyse de l effort du joueur de première ligne en mêlée de rugby)

La mêlée de rugby fortement impliquée dans la survenue de blessures cervicales, constituait une application appropriée dans l étude électromyographique (EMG) de muscles soumis à une compression mécanique. L intérêt de l électromyographie a été tout d abord montré pour étudier l effet de la compression sur la fatigabilité du muscle trapèze supérieur. Un ergomètre a été ensuite développé afin de caractériser les compétences spécifiques du joueur de première ligne en mêlée. Une surprenant activité EMG rythmique, autour de 14Hz, a été observée et caractérisée par une méthode d analyse spectrale cyclique. Une autre étude a par ailleurs montré un phénomène équivalent en situation analytique. Enfin, dans le cadre d un projet de prévention, le développement d un second ergomètre a notamment permis de mettre en évidence l effet du niveau d expertise sur un ensemble de paramètres. L activité EMG rythmique serait en outre due à l implication du système réticulospinal dans le contrôle postural.Rugby scrum, highly implicated in cervical spine injuries, constituted an appropriate application within the electromyographic (EMG) study of muscles being subject to mechanical compression. The relevance of electromyography was first shown for studying the effect of compression on fatigability of upper trapezius muscle. An ergometer was then developed to assess specific front-row player skills during scrimmaging. A surprising rhythmical EMG activity, around 14 Hz, was observed and characterised by a cyclic spectral analysis method. Another study revealed moreover an equivalent activity in an analytical situation. Lastly, within the context of a prevention project, the development of a second ergometer allowed to show particularly the effect of expertise level on a set of parameters. Furthermore, the rhythmical EMG activity would be due to implication of reticulospinal system in postural control.COMPIEGNE-BU (601592101) / SudocSudocFranceF

Chapitre 20. La récupération en rugby

Introduction La récupération en rugby pose le problème plus général de la récupération en sport collectif. Cet aspect, largement étudié, repose sur les bases physiologiques des activités constituées d’efforts intermittents d’intensité variable. En plus de ce type de contraintes, le rugby présente certaines particularités : important volume total de travail isométrique de poussée, nombre élevé d’impacts et de contacts, répétition de chocs, de percussions et d’exercices courts et très intenses ..

Concurrent Training Programming: The Acute Effects of Sprint Interval Exercise on the Subsequent Strength Training

Exercise modality has been proposed to reduce the interferences between aerobic and resistance sessions during concurrent training. The aim of the study was to examine the acute effects of cycling or running sprint interval exercise on subsequent resistance training sessions. Twenty-five competitive male rugby union players were recruited. Players were tested during three conditions: CONTROL (resistance training session only), CYCLE and RUN (corresponding to a concurrent training scheme with cycling or running sprint interval exercise conducted on the morning, followed by a resistance training session). Four hours rest was proposed between the aerobic and resistance training session. Muscle performance (bar velocity during bench press and box squat, counter movement jump height) and subjective ratings (rate of perceived exertion, wellbeing) were assessed during and after aerobic or resistance training sessions. No significant difference was observed for muscle performance (vertical jump height and bar velocity). However, significant higher perceived exertion and low-value scaled subjective wellbeing were observed in RUN (7.7 ± 1.1 and 17.9 ± 4.1, respectively) as compared with the two other conditions (6.7 ± 1.5 and 21.1 ± 3.6 for CONTROL and 7.4 ± 1.1 and 20.1 ± 3.9 for CYCLE). It was concluded that the exercise modality (running or cycling) during the aerobic exercise using a sprint interval exercise did not impact the quality of the resistance session. However, subjective ratings were affected the following days. Cycling exercises might be more adequate when performing a sprint interval training session during concurrent training programs

Concurrent Training in Rugby Sevens: Effects of High-Intensity Interval Exercises

International audiencePurpose:To assess the impact of two high-intensity interval training (HIT) programs (short-interval vs. sprint-interval training) on muscular strength and aerobic performances within a concurrent training program in amateur rugby sevens players.Methods:Thirty six amateur rugby sevens players were randomly assigned to either strength and short interval training (INT), strength and sprint interval training (SIT) or a strength only training group (CON), during an 8-week period. Maximal strength and power tests, aerobic measurements (VO2peak and maximal aerobic velocity) and specific repeated sprint ability test (RSA) were conducted before and immediately after the overall training period.Results:From magnitude-based inference and effect size (ES±90% confidence limit) analyses, the present study revealed substantial gains in maximal strength and jump height performance in all groups. The difference in change of slow-concentric torque production was greater in CON than in SIT (0.65±0.72, moderate). VO2peak and consequently mean performance in the RSA test were improved in SIT group only (0.64±0.29, moderate; -0.54±0.35, moderate).Conclusions:Our study did not emphasize interference on strength development following INT but showed a slight impairment of slow-concentric torque production gains following SIT. As compared with INT, SIT would appear as more effective to develop VO2peak and RSA but could induce lower muscular strength gains especially at slow velocity