Coordination of place kicking in Rugby Union

Mathewson, Elizabeth (2020-04)

Thesis (PhD)--Stellenbosch University, 2020.

Thesis

ENGLISH ABSTRACT: Place kicking is a crucial skill in rugby as more than 40 per cent of the points scored in professional rugby matches are achieved by means of place kicks. Research in rugby kicking has mainly focussed on isolated segment position or movement, with limited literature on segments moving relative to each other. The aim of this study was to identify characteristics of place kicking technique from a coordination and coordination variability perspective. Ten male kickers performed five trials from three different distances (40 m, 32 m, and 22 m) in a range that proficient kickers should convert successfully 80 per cent of the time. An optoelectronic motion capture system consisting of ten cameras were used for capturing total body kinematic data. Data collection took place outdoor, on a rugby field. Data reductions included normalisation of kicking phases, extracting discrete kinematic variables, joint angles, joint and segment coordination patterns (hip-knee, knee-ankle, and pelvis-torso), and coordination variability measures. ANOVA comparisons were made on discrete data, while statistical parametric mapping repeated measures ANOVA analysis was used for continuous variables to determine differences groups differences. Coordination patterns were determined by means of vector coding technique. A bivariate method of calculating the area of the ellipse at each time point was used to determine the coordination variability. A hierarchal cluster analysis was performed on sagittal plane angles at kicking events to determine different technique profiles. Parameters such as greater hip extension and external rotation during the backswing (p=0.001, p=0.015) as well as increased pelvic external rotation (p=0.015) in the 40 m kicks compared to the 22 m and 32 m kicks are related to the formation of the tension arc in attempt to increase foot speed by means of the stretch-shortening cycle. The 40 m kicks had increase knee flexion (p<0.001), increasing the pre-stretch in the thigh muscles. Both factors allow greater force to be applied to kicking foot over greater distance during forward swing. During the forward swing a period of in-phase is reported as both the hip and the knee were flexing, creating a whip-like action. During the backswing the pelvis and thorax worked together to create a tension arc, while during the forward swing, the anti-phase with pelvis dominancy was seen. The pelvis was main mover for tension arc release, while the thorax stays more stable. Even though absolute changes in joint angles were seen, no changes were reported for the coordination patterns when kicking at different distances (22 m, 32 m, 40 m). An investigation into coordination variability found no differences between groups, indicating no change in movement strategy when kicking at different intensities. The cluster analysis revealed three clusters of sagittal plane kinematics describing a knee-dominant, hip-dominant as well as a combination technique. Stemming from the above, place kick training can benefit by coaching cues and drills focussing attention on tension arc formation, and the rhythm of movements. These results impart the knowledge that different distances require similar movement coordination strategies.

AFRIKAANSE OPSOMMING: Die stelskop in rugby is ‘n kritiese vaardigheid aangesien meer as 40 persent van die punte aangeteken in ‘n professionele rugbywedstryd te danke aan stelskoppe is. Navorsing in rugby skoppe het meestal geïsoleerde fokus op indivduele segmente, beperkte navoring focks op hoe segmente beweeg relatief tot mekaar. Die doel van die studie was om te eienskappe van stelskoppe te identifiseer vanuit ‘n koördinasie en koördinasie veranderlikheid perspektief. Tien manlike skoppers het elk vyf skoppe vanaf drie verskillende afstande (40 m, 32 m, en 22 m) was vanaf die pale uitgevoer in area waar goeie skoppers 80 persent skopsukses het. Toerusting wat gebruik is vir data-insameling sluit ‘n tien-kamera bewegings analise sisteem in. Data was verwerk deur die normalisering van skop fases, onttrekking van diskrete kinematiese veranderlikes, gewrigshoeke, gewrigskoppelinge (heup-knie, knie-enkel, pelvis-torso), en koördinasie veranderlikheids maatreëls. ANOVA vergelykings is gedoen op die diskrete data, terwyl statistiese parametriese kartering herhaalde metode ANOVA analise uitgevoer is op die kontinue data om beduidende verskille tussen groepe te bepaal. Koppelingshoeke is bepaal deur hoek-hoek plotte en vektorkodering om koördinasie patrone te bepaal. ‘n Tweeverandelike metode is gebruik om die area van die ellips te bereken om die koördinasie variasie te bepaal. ‘n Klusteranaliese was uitgevoer om sagittalevlak skop tegnieke te bepaal. Veranderlikes gekoppel aan spanningsboog formasie, insluitend grooter heup ekstensie en eksterne rotasie gedurende (p=0.001, p=0.015) is verhoog in 40 m skoppe in vergelyking met die 22 m en 32 m skoppe, sowel as meer eksterne rotasie van die pelvis (p=0.015). Die 40 m skoppe het ook verhoogde knie fleksie (p<0.001) getoon in vergelying met die kort afstand skoppe. Beide faktore verhoog krag toegepas oor ‘n groter afstand, op die skopvoet. Koördinasie patrone vir die heup-knie koppeling toon dat die knie die primêre beweger is gedurende die terugswaai. Gedurende die vorentoe swaai kom daar ‘n periode van in-fase voor waartydens die heup en knie albei fleksie ondergaan, wat ‘n sweepslag aksie van die onderste ledemaat tot gelvog het. Gedurende die terugswaai werk die pelvis en toraks saam om ‘n spanningsboog te vorm, terwyl tydens die vorentoe swaai word anti-fase met pelvis dominansie gesien. Die pelvis was dus die primêre beweger vir die vorentoe swaai wat oorseenstem met die vrylating van die spanningsboog, terwyl die toraks meer stabiel bly. Alhoewel absolute verskille gesien is met skoppe vanaf verskillende afstande, bly die koördinasie patrone konstant. ‘n Ondersoek rakende die koördinasie variasie het geen verskille tussen groepe gevind nie wat daarop dui dat daar geen verandering in die bewegings strategie was wanneer geskop word met verskillende intensiteite nie. Dit word vermoed dat die skoppers goed ingeoefende bewegings patrone gehad het vir skoppe vanaf al die afstande. Gebaseer op die bogenoemde resultate, kan navorsingsresultate afrigters help om op spanningsboog, ritmiese koördinasie patrone en die tydsberekening van bewegings te fokus. Die resultate van die studie dui daarop dat geen verandering in bewegings pattrone nodig is nie wanneer daar geskop word met verskillende afstande vanaf die pale.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/107778
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