The kinetics of rugby union scrummaging

Abstract

Two rugby union forward packs of differing ability levels were examined during scrummaging against an instrumented scrum machine. By systematically moving the front-row of the scrum along the scrum machine, kinetic data on each front-row forward could be obtained under all test conditions. Each forward pack was tested under the following scrummaging combinations: front-row only; front-row plus second-row; full scrum minus side-row, and full scrum. Data obtained from each scrum included the three orthogonal components of force at engagement and the sustained force applied by each front-row player. An estimate of sub-unit contributions was made by subtracting the total forward force on all three front-row players from the total for the complete scrum. Results indicated the primary role of the second-row appeared to be application of forward force. The back-row ('number eight') forward did not substantially contribute any additional forward force, and added only slightly to the lateral and vertical shear force experienced by the front-row. The side-row contributed an additional 20-27% to the forward force, but at the expense of increased vertical forces on all front-row forwards. Results of this investigation are discussed in relation to rule modification, rule interpretation and coaching.

Cervical range of motion, cervical and shoulder strength in senior versus age-grade Rugby Union International front-row forwards

“…Effective scrummaging requires coordinated pushing by the eight players (Trewartha, Preatoni, England, & Stokes, 2014), which produces forces greater than the sum of each forward's individual scrummaging force (Quarrie & Wilson, 2000). Unsurprisingly, scrum engagement forces are positively related to the total body mass of the opposing pack (Du Toit, Olivier, & Buys, 2005;Milburn, 1990). Rugby players' size has increased markedly over the last 25 years (Sedeaud et al, 2012) and therefore, engagement forces have doubled since 1990 (8000 N vs. 16500 N) (Milburn, 1990;Preatoni, Stokes, England, & Trewartha, 2013).…”

BokSmart: Safe and effective techniques in rugby union

“…40 It has been shown that the impulsive impact force on a scrum engagement exceeds the threshold of injury to the spine. 23 This emphasises firstly the importance of specific scrum technique training, which includes correct alignment of the head, neck and trunk, and adequate back, shoulder and neck strength to maintain a safe body position during engagement. 23,36 More than 90% of scrum-related catastrophic cervical spine injuries occurred during either scrum engagement (47%) or a collapsed scrum (46%).…”

“…23 This emphasises firstly the importance of specific scrum technique training, which includes correct alignment of the head, neck and trunk, and adequate back, shoulder and neck strength to maintain a safe body position during engagement. 23,36 More than 90% of scrum-related catastrophic cervical spine injuries occurred during either scrum engagement (47%) or a collapsed scrum (46%). 30 The remainder of injuries were caused by front-row forwards actively extending their necks and driving the opposite front-row upwards; this has been termed 'popping', 25 or more recently 'scrumming up'.…”

“…Research has shown that the magnitude of forward force generated by a pack of forwards once they have engaged is greater when the front row is packed as low as possible, 23 with the head, trunk and legs in alignment, and ensuring a maximal angle at the hip. 13 A practical evaluation of individual scrumming technique has shown that a horizontal spine is a strong predictor of scrumming performance.…”

“…23,24 This indicates poor technique in non-international front-row forwards. Maintenance of a flat straight neutral spine with natural lordosis (spine-in-line) will ensure maximal forward force transfer and no downward force generation.…”