The client is an 18-year-old 6ft tall male, weighing 105kg. He is of mesomorph shape, which is recommended for a forward, according to League (1993). Forwards generally have greater mass, girths, femur breadth than the backs and this is advantageous to them because it means they’re better equipped physiologically to cope with high impact forces experienced in this position for example scrummaging (Cheng et al, 2014). He decided to focus entirely on one sport (rugby) and join a local semi-pro team. He will play as a forward (flanker) who are responsible for catching and kicking the ball as well as getting involved in scrums. A biomechanical application to his technique in these areas as well as others will aid his development; for example, a coach can use his knowledge of mechanics to correct actions of their pupils and improve certain skills (McGinnis, 2013). “If one understands the mechanical principles of a particular activity, … (one can) then integrate the above sources of information with their biomechanical knowledge to help systematically identify and correct performance flaws” (Elliot, 2001). In explanation, understanding biomechanical principles such as the correct kinematics of a movement sequence can be used to improve an individuals’ technique.

 

Dangers of Rugby

According to The French Institute of Sports and Physical Education the average forward in rugby weighs roughly 115kg (INSEP, 2017).  This means during scrums, players have an accumulative weight of 8 players worth of this. King et al (June 2016) published an article highlighting how semi-pro players have higher concussion risk in comparison to amateur or pro rugby players. Data was taken from 25 studies which recorded the number and incidence of concussions in semi-professional rugby matches and training activities. According to the results, semi-pro participants had a threefold greater concussion rate than amateur and 600-fold greater concussion rate than professional players (King, 2016).  Milburn (1993) explained this is because of such large forces coming in at a high speed repeatedly; in addition, more than two-thirds of a tonne is typically shared across the front row (Milburn, 1993) during a scrum. This justifies the recent change in rules regarding scrums. In 2013, the World Rugby Union updated the law for scrums to include crouch, bind and set instructions (laws.worldrugby.org, 2017). This change in rules has been proven to lessen the strain on certain muscles which may mean a decrease in injury according to Preatoni et al (2015). Their research showed that the activity of the erector spinae was significantly lower (over 65%) in the current crouch, bind and set technique than in the previous. Prior and following the change to rules of a rugby scrum, research went into figuring out how to make scrummages safer. Cazzola et al (2014) modified the engagement process and found a way to reduce engagement speed, peak forces, and peak accelerations of landmarks located within the upper spine by 20%. They found that an engagement process involving binding with the opposition prior to the engagement reduces load on players. This can be related to Newton’s 2^nd law: Force = Mass x Acceleration. This is so because as the acceleration factor has been significantly reduced due to the binding process, the only other variable left is mass; this will be explored further later in the blog.

The scrum is a key offensive play in rugby as well as a defensive skill in denying the opposition possession, therefore the client is going to be involved in a lot of scrums. Statistical records from the Six Nations show in 15 matches, scrums took over 3 hours and 40 minutes of playing time. (Six Nations, 2016). Despite this being at a professional level rather than semi-professional, it is still relevant. Warren (2012) discusses the importance of a rugby scrum and evidences that the team who dominates the scrum is usually the team that wins the game. Consecutively, Higham et al (2014) studied performance indicators in relation to scoring/ preventing scoring and ultimately, winning. They found that retaining possession in scrums was a key winning performance indicator along with other factors such as conceding fewer turnovers. This consequently means within the scrum is an opportunity to heavily influence the game.

Scrummaging Technique

As already established, technique during a scrum is pivotal for winning as well as avoiding injury. According to Milburn (1993), the ability of the front-row players to utilise their strength during a scrum can reflect the risk of chronic degeneration of the musculoskeletal system because of repeated exposure to large stresses. Stokes (2015) studied different engagement techniques and how they affected forces in a scrum. This study found that by targeting and modifying the engagement technique used, the load players experience during a scrum can be altered. This is in relation to Bartlett’s (2007) Critical Features. By analysing the key/ critical sections involved in a particular movement e.g. basketball throw or engagement in a rugby scrum, you can then identify what sections need to be altered in order to have a more successful coordination of movement.

Stokes found that by having the front-row “fold in” or point their shoulders at a lower angle during the engagement phase, as well as increasing the time over which the initial contact occurs, the force of the initial impact can be greatly reduced. By adding more downwards force at the point of contact, the peak compression force (horizontal) changed from 16.5kN to 8.6kN. This can be related to Sanders and Wilson’s (1990) biomechanical principles. Concept 5 of this states that forces associated with impact can be reduced by changing motion of objects gradually rather than suddenly. Therefore, stretching out the time over which the impact occurs is something he can apply to improve his technique.

Newton’s second law; Force = object mass x object acceleration (Live Science, 2017) can also be related to scrummaging. Players from both sides try to ram into each other with as much force as possible to push each other back and win possession of the ball. The variable in this situation (assuming players are of similar mass) being the acceleration and therefore players try to engage in the scrum with as much acceleration as possible, potentially causing injuries (Merrick, 1998).  Against an opponent who is of similar mass, the only option to generate more force going by Newton’s second law, is to increase acceleration. Therefore, applying Concept 5 from Sanders and Wilson’s biomechanical principles could help lessen this highly accelerated impact.

Stokes (2015) found a linear relationship between reducing the angle of the engagement sequence of the scrum and impact force. However, a downwards force being applied to the scrum as opposed to horizontal, can cause a misalignment of front row positions and therefore increase the risk of the scrum collapsing (S&E Biomex, 2017). This may be because, the downwards and forwards kinematics of pushing during a scrum means that Alan’s centre of mass is constantly being pushed further away from his base making it easier for gravity to pull him to the ground (S&E Biomex, 2017).

Conclusion

 

Good understanding of the mechanics behind sport e.g. kinematics, momentum, resistance, contributes heavily to the explanation and improvement of technique in sport (Topendsports.com, 2017). Over the course of this blog I have evidenced that injuries to the neck, back or spine as well as winning more rugby matches can be heavily influenced by scrummaging technique. Whilst it’s just one aspect of the game, it’s potentially game changing therefore it’s pivotal the client is able to master this technique. He can do this by bearing in mind the few biomechanical principles likened to scrummaging in this article. To start with, he could utilise the “fold-in” technique hypothesised by Stokes (2015) which would involve him engaging the scrum at a lower angle. The benefit of this technique is that it has been proven to reduce force of impact and therefore lessen the chances of him getting injured. In addition, he needs to be aware of his centre of mass and not allow it to move to far away from his body as it will affect his balance and ability to stay upright, potentially leading to injury or simply losing possession. Winning scrums are key to winning the match (Warren, 2012). If he does these things, he will be at a good enough level for semi-pro Rugby.

 

 

 

 

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Cheng, H.L., O’Connor, H., Kay, S., Cook, R., Parker, H. and Orr, R., 2014. Anthropometric characteristics of Australian junior representative rugby league players. Journal of Science and Medicine in Sport, 17(5), pp.546-551.

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S&E Biomex. (2017). Rugby Scrums… A Question of Force or Farce?. [online] Available at: https://biomechanics101.wordpress.com/2013/04/15/rugby-scrums-a-question-force-or-farce/ [Accessed 16 May 2017].

Cazzola, D., Preatoni, E., Stokes, K.A., England, M.E. and Trewartha, G., 2014. A modified prebind engagement process reduces biomechanical loading on front row players during scrummaging: a cross-sectional study of 11 elite teams. British journal of sports medicine, pp.bjsports-2013.