Browsing by Author "Kraak, Wilbur Julio"

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    The effect of a rhythmic movement intervention on selected bio-motor skills of academy players in the Western Cape, South Africa
    (SAGE, 2020) Solomons, Jocelyn; Kraak, Wilbur Julio; Kidd, Martin; Africa, Eileen Katherine
    Rhythmic movement, also referred to as “dance”, involves the execution of different motor skills as well as the integration and sequencing of actions between limbs, timing and spatial precision. The aim of this study was therefore to investigate and compare the effect of a 16-week rhythmic movement intervention on flexibility, dynamic balance, agility, power and local muscular endurance of academy rugby players in the Western Cape, according to positional group. Players (N=54) (age 18.66 ± 0.81 years; height 1.76 ± 0.69 cm; weight 76.77 ± 10.69 kg), were randomly divided into a treatment-control [TCA] (n=28) and a control-treatment [CTB] (n=26) group. In this crossover experimental design, the interaction effect of the treatment order and the treatment time between the TCA and CTB group, was determined. Results indicated a statistically significant improvement (p<0.05) in agility2 (p=0.06), power2 (p=0.05), local muscular endurance1 (p=0.01) & 3 (p=0.01) and dynamic balance (p<0.01). Likewise, forwards and backs also showed statistically significant improvements (p<0.05) per positional groups. Therefore, a rhythmic movement intervention has the potential to improve rugby-specific bio-motor skills and furthermore, improve positional specific skills should it be designed with positional groups in mind. Future studies should investigate, not only the effect of rhythmic movement on improving specific rugby bio-motor skills, but the potential of its application as an alternative training method during off-season (or detraining phases) or as a recovery method.
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    The effect of law changes on the match profile of international and national rugby union between 2007 and 2013
    (Stellenbosch : Stellenbosch University, 2015-12) Kraak, Wilbur Julio; Venter, Ranel; Coetzee, Frederik; Stellenbosch University. Faculty of Education. Dept. of Sport Science.
    ENGLISH ABSTRACT: Rugby union has changed continually since the inception of professionalism in 1995. For example, to increase the appeal, continuity and safety of the game several law changes were introduced after the 2007 Rugby World Cup. The primary aim of this study was to determine the impact of these law changes on selected performance indicators on the match profile of international rugby union between 2007 and 2013 and national rugby union between 2008 and 2013. To this end, three specific objectives were set. The first was to compare the scoring profile of international rugby between 2007 and 2013. The second was to compare the changes in the general match profile of international rugby and the third was to compare the scoring and general match profile of Super Rugby between 2008 and 2013. The study followed a mixed-method study design for data collection. A total of 248 international and 646 national matches were recorded by the Fika Coding Centre and analyzed by the researcher using the Fairplay video analysis software package. Semi-structured interviews were conducted with 30 international- and national-level coaches, referees, specialist coaches and players.The year 2007 was used as baseline for international matches and 2008 for national matches in order to compare and track the changes over the different years. Results indicate that law changes over the years have indeed had an influence on the profile of international and national rugby. The scoring profile of international rugby revealed a significant increase in the number of penalty kicks (p<0.01). With regard to the origin of tries, there was a decrease in the number of tries from structured play (47 to 43%) and an increase from turnover possession (27 to 43%). The duration of the international matches increased owing to the increase in the number of stoppages, mainly as a result of greater use being made of the Television Match Official (TMO), substitutions and on-field concussion tests. There was a small practical significant increase in total match time (d=0.34), and a moderate increase in ball-in-play time (d=0.87). Results of the study show that the profile of international rugby has changed to a more continuous game dynamic with a moderate practical significant increase in the number of passes (d=0.73), large ball carries (d=1.22) and tackle breaks (d=2.03), and a very large increase in line breaks (d=3.00), which has led to a moderate increase in the number of tackles (d=0.65). The number of rucks (d=0.86), mauls (d=0.90) and scrums (d=1.03), scrum resets (d=0.74) and line-outs (d=0.61) showed a moderate practical significant decrease. Both penalty kicks (d=0.98) and free kicks (d=1.22) decreased significantly. The scoring profile of national rugby indicated fewer tries (p<0.01), conversion kicks (p<0.01) and significantly more penalty kicks (p<0.01). The duration of national matches decreased due to fewer stoppages, mainly thanks to the improved skill level of the players. There was a small practical significant decrease in total match time (d=0.41). The ball-in-play time (d=0.91) showed a moderate practical significant decrease. Results of the study show that the profile of national rugby has changed to a game with more contact situations, with a small practical significant increase in the number of passes (d=0.43), a large practical significant increase in the number of ball carries (d=1.34), tackle breaks (d=1.59) and line breaks (d=2.40), and has led to a moderate practical significant increase in the number of tackles (d=0.63). A large practical significant decrease in the number of rucks (d=1.73) and scrum resets (d=1.36) was found. A moderate practical significant increase in penalty kicks (d=2.04) and a moderate practical significant decrease in free kicks (d=4.53) between 2008 and 2013 were observed. By analyzing the scoring and match profile of international and national rugby, coaches and trainers could be better informed in order to develop training programmes that are specific to the technical, tactical and physical demands of modern rugby. Based on the findings of this study, coaches and trainers should develop individual and team performance profiles to better understand the demands experienced by the players and teams. This type of information could assist with implementing more specific periodization models, strategic planning, drill design, recovery strategies and planning of training loads.
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    Legal and illegal ruck cleanouts in South African non-professional youth rugby
    (SAGE, 2019) Kruger, Stephanie; Moore, Lee; Viljoen, Wayne; Lambert, Mike; Readhead, Clint; Kraak, Wilbur Julio
    The ruck area is responsible for the second-highest number of rugby union injuries, therefor it is necessary to investigate and understand the ruck better for improved player safety. The study aimed to investigate and compare incidents of legal and illegal ruck cleanouts in non-professional youth rugby. Using Nacpsort Scout Plus software, 118 South African Rugby Union under 18 Youth Week tournament matches were coded between 2015 and 2019. In total, 35 545 ruck cleanouts were coded, of which 32 641 (91.8%) were legal and 2 904 (8.2%) were illegal. Of the 2 904 illegal cleanouts, 2 676 (92.2%) were deemed ‘not dangerous’ and 228 (7.8%) were considered ‘dangerous’. The ‘dangerous’ ruck cleanouts represented 0.6% of the total ruck cleanouts. Of the most common illegal ruck cleanouts, “not supporting own body weight” were mostly ‘not dangerous’ (2 498; 99.4%, p=0.01); and all “neck rolls” were considered ‘dangerous’ (147; 100.0%, p=0.02). The findings of the study suggest player behaviour can still be improved, with regular participation in regular safe and effective technique training drills. The risk of injury during the ruck can further be influenced positively by coaches, through regular coaching and training of safe and effective ruck techniques.
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    Positional in-match running demands of university rugby players in South Africa
    (Frontiers Media, 2020) Donkin, Cameron; Venter, Ranel; Coetzee, Derik; Kraak, Wilbur Julio
    The implementation of the Varsity Cup rugby competition among South African universities has sparked interest in university rugby cultures around the country. The Varsity Cup has established itself as one of the most important rugby competitions for full-time students. The development of specific conditioning programs for rugby players requires a thorough understanding of the game and the unique demands of playing positions. Therefore, the study aimed to investigate the in-match running demands of South African university rugby players by using GPS during match play for primary and secondary positional groups. Rugby players (n = 40) from two universities were assessed during match play (n = 17) over a competitive season by using GPS. Players were grouped into two primary positional groups, forwards (n = 22) and backs (n = 18), and five secondary positional groups, tight forwards (n = 14), loose forwards (n = 8), half backs (n = 5), inside backs (n = 6), and outside backs (n = 7). The GPS analysis provided the following match-play movements: total distance, high-speed meters, maximum velocity, match intensity, the number of accelerations and decelerations, and velocity zone. Halfbacks recorded the highest total distance (6620.9 ± 784.4 m; p = 0.02) and match intensity (77.7 ± 11.6 m/min; p = 0.01). Outside backs recorded the highest maximum velocity (8.385 ± 1.242 m/s; p = 0.00). Loose forwards registered the highest number of accelerations (385.5 ± 122.1) and decelerations (378.7 ± 108.1). Backs and their specific subgroups play at and within high velocity thresholds, significantly higher (p = 0.01) than that of the forwards. Forwards tend to be involved in a higher amount of accelerations and decelerations during match play, suggesting that forward play is at close quarters to the opposition. During university rugby matches, the backs covered greater distances and speeds than the forwards, whereas the forwards achieved more accelerations and decelerations than backs. Results from the study can assist Varsity Cup strength and conditioning coaches to prepare players for the position-specific demands of the competition.
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    Sanctioning of illegal and dangerous ruck cleanouts during the 2018 super rugby competition
    (Frontiers Media, 2019) Kraak, Wilbur Julio; Bam, Jenna; Kruger, Stephanie; Henderson, Stephanie; Josias, Ugan; Stokes, Keith
    Rugby is a high contact sport that results in many injuries. The majority of injuries at senior elite levels result from contact phases during match-play. It is estimated that 10% of all match injuries are associated with the ruck in professional and community rugby. Surveillance of legal and illegal ruck cleanouts and the sanctions imposed by the on-field referees will help identify whether referees are actually enforcing the law according to the laws of the game, which will consequently contribute to the creation and implementation of further injury prevention strategies. Players should play the game in accordance with the laws of the game and be mindful of their own safety and that of others. Coaches and trainers of the game have the responsibility to ensure that players are prepared in a manner that comply with the World Rugby (WR) laws of the game and safe practices. Laws and law amendments are fundamental to the development of sport and introduced for a variety of reasons. The aim of this study was to investigate the rate of sanctioning of illegal and dangerous ruck cleanouts during the 2018 Super Rugby competition by using Nacsport Basic+ video software; 120 round robin matches from the 2018 Super Rugby competition were coded and analyzed. The analysis of the intra reliability showed an almost perfect (>0.95) agreement between all the performance indicators. In total, 22,281 ruck cleanouts were coded of which 9% (n = 2111) were illegal ruck cleanouts and 93% were not sanctioned by the referees; 57% (1087 out of 1953) of the illegal ruck cleanouts not sanctioned by the referees were deemed dangerous. The majority of dangerous illegal ruck cleanouts not sanctioned by the referees were “shoulder charge” (88%, n = 280), “neck roll” (86%, n = 100), and “contact above the shoulder” (81%, n = 201). To aid injury prevention efforts in rugby, future research studies should investigate why on-field referees are not sanctioning all illegal and dangerous ruck cleanouts according to WR Laws of the Game.