B. Frechede

Tackle Characteristics and Injury in a Cross-Section of Rugby Union Football

BACKGROUND The tackle is the game event in rugby union most associated with injury. This studys main aims were to measure tackle characteristics from video using a qualitative protocol, to assess whether the characteristics differed by level of play, and to measure the associations between tackle characteristics and injury. METHODS A cohort study was undertaken. The cohort comprised male rugby players in the following levels: younger than 15 yr, 18 yr, and 20 yr, grade, and elite (Super 12 and Wallabies). All tackle events and technique characteristics were coded in 77 game halves using a standardized qualitative protocol. Game injuries and missed-game injuries were identified and correlated with tackle events. RESULTS A total of 6618 tackle events, including 81 resulting in a game injury, were observed and coded in the 77 game halves fully analyzed (145 tackle events per hour). An increase in the proportion of active shoulder tackles was observed from younger than 15 yr (13%) to elite (31%). Younger players engaged in more passive tackles and tended to stay on their feet more than experienced players. Younger than 15 yr rugby players had a significantly lower risk of tackle game injury compared with elite players. No specific tackle technique was observed to be associated with a significantly increased risk of game injury. There was a greater risk of game injury associated with two or more tacklers involved in the tackle event, and the greatest risk was associated with simultaneous contact by tacklers, after adjusting for level of play. CONCLUSIONS Tackle characteristics differed between levels of play. The number of tacklers and the sequence of tackler contact with the ball carrier require consideration from an injury prevention perspective.

Numerical reconstruction of real-life concussive football impacts.

PURPOSE To present a protocol of numerical reconstructions of concussive events in football using MADYMO. To refine the knowledge of the dynamics associated with these events. METHODS Twenty-seven cases of concussive head impacts involving unhelmeted Australian football and rugby players were simulated using MADYMO. The cases had been previously analyzed using a video analysis protocol and were fully reconstructed for the purpose of this study. The reliability of these reconstructions had been previously assessed using a sensitivity analysis of the influence of several independent variables on the dynamical outputs. The use of a complete human model enabled consideration for morphometry, initial movements of the players, and an accurate estimate of the effective masses involved in the impacts. RESULTS Mean peak values for concussion were found to be 103 g for the head center of gravity linear acceleration, 8022 rad s(-2) for the head angular acceleration, and 359 for the head impact criterion. An estimate of the average effective energy transferred to the head was 47 J. With the severity grading used in this study, the head impact power was found to be the best predictor of concussion severity. CONCLUSIONS These biomechanical results compare well with other studies. They should contribute to the identification of the energy levels at which concussive impacts occur in football for the purpose of a better evaluation of protective devices in these sports.

An investigation of shoulder forces in active shoulder tackles in rugby union football

In rugby union football the tackle is the most frequently executed skill and one most associated with injury, including shoulder injury to the tackler. Despite the importance of the tackle, little is known about the magnitude of shoulder forces in the tackle and influencing factors. The objectives of the study were to measure the shoulder force in the tackle, as well as the effects of shoulder padding, skill level, side of body, player size, and experimental setting on shoulder force. Experiments were conducted in laboratory and field settings using a repeated measures design. Thirty-five participants were recruited to the laboratory and 98 to the field setting. All were male aged over 18 years with rugby experience. The maximum force applied to the shoulder in an active shoulder tackle was measured with a custom built forceplate incorporated into a 45 kg tackle bag. The overall average maximum shoulder force was 1660 N in the laboratory and 1997 N in the field. This difference was significant. The shoulder force for tackling without shoulder pads was 1684 N compared to 1635 N with shoulder pads. There was no difference between the shoulder forces on the dominant and non-dominant sides. Shoulder force reduced with tackle repetition. No relationship was observed between player skill level and size. A substantial force can be applied to the shoulder and to an opponent in the tackle. This force is within the shoulders injury tolerance range and is unaffected by shoulder pads.

Characteristics of single vehicle rollover fatalities in three Australian states (2000–2007)

An analysis of 2000-2007 single vehicle rollover fatalities in three Australian states was carried out using data from the Australian National Coroners Information System. In this paper, successive selection criteria were applied to the initial dataset to analyse:overall, rollovers accounted for 35% of all occupant fatalities in a single vehicle transport injury event. For these fatalities, the occupant was ejected or stayed contained in equal proportions. However, results showed strong disparities between the more urban and densely populated states of New South Wales and Victoria, compared to the Northern Territory in terms of crash type distribution and containment of the occupant. Differences were also found in rollover initiation, speed at initiation and number of turns. Overall, the strongest association of fatal neck/thoracic spine injuries with head injuries was found for the contained, restrained occupant. This analysis of single vehicle rollover fatalities is consistent with previous findings. It also shows that in Australia, strategies for rollover injury risk mitigation will need to take into account a broad range of characteristics to be effective.

Diving versus roof intrusion: a review of rollover injury causation

Abstract Rollover injuries are the outcome of the inability of a vehicles crashworthiness design, or lack thereof, to protect its occupants during a rollover crash. While countermeasures for injuries due to ejection are well established, there is still much debate ongoing regarding injury mechanisms of occupants contained in a vehicle during a rollover and hence countermeasures required to mitigate such injuries. This paper presents and analyzes the two apparently conflicting views of injury causation for contained occupants in rollovers that have been presented in research literature to date: diving versus roof intrusion. To analyze the validity of each of these theories, the basic physics behind the underlying concepts is investigated. Injury results from the General Motors (GM) rollover Malibu II test series are then used and reanalyzed in light of the findings presented in this paper. Results show that the most injurious events in the Malibu II tests are those where the roof structure was not strengthened. It was also concluded that more work needs to be carried out to establish acceptable injury mechanisms and associated injury criteria for future rollover crash testing protocols.

Injury data from unhelmeted football head impacts evaluated against critical strain tolerance curves

Concussion is a prevalent injury in collision and contact sports, but the biomechanics of concussion has mainly been assessed for helmeted head impacts. Concussion and no-injury cases had previously been reconstructed using rigid body simulations from a larger video database of unhelmeted head impact cases from Australian rules football, rugby union and rugby league. The KTH finite element human head model was used to simulate the 27 concussion and 13 no-injury cases, and the maximum principle strain levels in the corpus callosum were evaluated. The rotational kinematics and strain levels were compared to critical strain tolerance curves and reconstructed pedestrian impacts from the literature. It was found that the 5% critical strain tolerance curve equated to a maximum principal strain level of approximately 0.20 and was associated with concussive impacts involving prolonged loss of consciousness. The results suggest rotational kinematics above 4500 rad/s2 and 33 rad/s for peak resultant angular acceleration and maximum change in resultant angular velocity, respectively, as tentative tolerance levels for concussion involving prolonged loss of consciousness. Cases involving short duration or no loss of consciousness had similar rotational kinematics and strain levels in the corpus callosum, suggesting that these injuries are of similar severity. The findings support the hypothesis that sports concussions share some biomechanical characteristics with diffuse axonal injury.