Theoretical Model Describing the Relationship between the Number of Tackles in Which A Player Engages, Tackle Injury Risk and Tackle Performance.

The tackle is a physical contest between opposing players contending for territory and ball possession. During an 80 minute rugby union match, a player will physically engage in the tackle contest, whether as a ball-carrier or tackler, between 10 to 35 times depending on the position of the player (Deutsch et al., 2007; Quarrie and Hopkins, 2008). During a match, tight forwards (position numbers 1-5, who primarily compete in the set phases such scrums and lineouts) engage in the tackle approximately 10-25 times, loose forwards (position numbers 6-8, who mainly competes for possession of the ball at rucks and assist the tight forwards in set pieces) are involved in 25-35 tackles, inside backs (position numbers 9,10,12,13, whose key responsibility is to execute tactics and distribute the ball) competes in 20-25 tackles, and outside backs (position numbers 11,14,15, who are typically quicker and expected to run into open spaces to cross the advantage line and score points) engage in 10-15 tackles (Deutsch et al., 2007; Quarrie and Hopkins, 2008). It follows that a player requires a high level of skill, physical tolerance and resistance to fatigue to repeatedly engage safely and effectively in the tackle. Understanding the physical demands of a tackle is important with many applications. Examples of these applications include the design and development of proper training drills and equipment, planning and management of training and recovery between training sessions and matches. Also, a better understanding of the physical demands contributes to the implementation of strategies designed to reduce the risk of injury and enables replicating the event in the laboratory for research Recently, methods to estimate the magnitude of impact (energy distributed between ball-carrier and tackler upon contact) in real match tackle contests have been developed to further our understanding of the physical demands of the tackle contest (Hendricks et al., 2014). The physical demand of the tackle was determined by calculating the amount of energy distributed between the ball-carrier and tackler upon contact. This excess of energy may cause muscle damage and injury to the mus-culoskeletal system (Takarada, 2003). The estimated magnitudes of impact ranged from 902 joules (J) to 7608 J for front-on tackles, and 595 J to 6209 J for side-on tackles (Hendricks et al. 2014). Repeated exposure to these physical collisions during training and matches, and over a long competitive season may influence the injury risk profile and longevity of a player, and if …