Wilbur Kraak

Prof. Wilbur Kraak

orcid

Research Focus & Metrics

Academic Career Length

16Years (2011-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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27 March 2015 in Journal of Sports Sciences
Verified
Journal Article
Closed access
SOShaun M. Owen
Shaun M. Owen
Ranel VenterRanel Venter
Ranel Venter
STStephan du Toit
Stephan du Toit
WKWilbur Kraak
Wilbur Kraak
The match-play demands of rugby union have increased over time, and these demands should be quantified so as to provide a basis for optimal player loading during training. The primary aim of this article was to quantify accelerations, decelerations, impacts and aggregated body demands during the first half of match-play in a Super Rugby team. The secondary aim was to determine whether these characteristics are position-specific. Thirty-three players were monitored for 14 matches using global positioning system units with inbuilt microtechnology. Players were grouped according to positional roles and data were analysed for those who completed the entire duration of the first half of a given match. Forwards sustained more (d = 0.44) high-intensity impacts and greater (d = 0.26) aggregated body demands, while backs had more moderate (d = 0.55) and heavy accelerations (d = 0.76), and moderate (d = 0.23) and heavy decelerations (d = 0.54). These differences suggest that conditioning and recovery strategies should reflect the physical demands placed on players in different playing positions. Forwards should be conditioned with a focus on impacts and require longer recovery for the same duration of playing time, whereas conditioning for backs should emphasise rapid accelerations and decelerations.

29 March 2020 in International Journal of Sports Science & Coaching
Verified
Journal Article
Closed access
PDF file
HVHanno van Vuuren
Hanno van Vuuren
KWKaren Welman
Karen Welman
WKWilbur Kraak
Wilbur Kraak
Due to the nature of rugby, concussions are a frequent occurrence and can go undetected by different stakeholders. Knowledge regarding identification of symptoms, management and prevention of re-injury is crucial for the welfare of players. The aim of the study was to determine the concussion knowledge and attitudes among different community club rugby stakeholders. The study gathered quantitative information by utilizing the Rosenbaum Concussion Knowledge and Attitude Survey-Student Version (RoCKAS-ST). Of all the participants (N = 434), medical staff (79 ± 10%) provided the highest Concussion Knowledge Index scores followed by referees (78 ± 8%) and players (67 ± 13%). The stakeholders scored 76% overall for Concussion Attitude Index. Across the scenarios the different participants believed to have safer attitudes compared to that of others within their team. Statistical differences were found between stakeholders when asked if concussion is less important than other injuries, as players, coaches and administrative staff all indicated an unsafe response in contrast to that of referees (p < 0.01). Players indicated an unsafe attitude towards returning to play, while symptomatic as a result of a concussion whereas coaches indicated a safer response (p < 0.01). Only two out of eight legitimate symptoms, headaches and dizziness, were correctly identified by 80% or more of participants, which warrants concern that identification of symptoms could be lacking on this level. Investigating the knowledge and attitudes of concussion at community club rugby level could identify which areas are to be further targeted by the South African Rugby Union.

2 November 2017 in International Journal of Performance Analysis in Sport
Verified
Journal Article
Closed access
HPHeinrich Painczyk
Heinrich Painczyk
SHSharief Hendricks
Sharief Hendricks
WKWilbur Kraak
Wilbur Kraak
The growth and accessibility of performance analysis (PA) is attributed to the growth of modern PA systems and PA companies that provide the services of match coding. The purpose of this study was to determine and compare the utilisation of PA among Western Province Super League club rugby coaches. Fifty-one coaches involved at senior and under 20-level teams participated in this study. The study had a response rate of 88%. The study revealed that only 16% of coaches have access to video footage after every game and 82% of coaches do not have access to and do not use computerised notational systems (CNS). Despite the fact that 80% of coaches value PA extremely, the study concluded that PA is not being used by a large majority of coaches in Western Province Rugby Union clubs. It was further concluded that this is due to the availability of PA resources (video equipment and CNS) due to budget restraints.

1 June 2014 in International Journal of Sports Science & Coaching
Verified
Journal Article
Closed access
WKWilbur Kraak
Wilbur Kraak
KWKaren E. Welman
Karen E. Welman
The contest for possession has resulted in ball release delays. Accordingly the International Rugby Board amended the laws surrounding the ruck area in 2009. The study objective was to determine if a relationship exists between the ruck outcomes and ranking of the 2010 Six Nations Championship teams, establish differences between locations, compare the top to the bottom ranked teams and if the number of players involved influences ruck outcome. Fifteen 2010 Six Nations Championship matches were analysed by a performance analyst. Of the 1479 rucks, 92% retained the ball successfully, with no difference between the ruck success rate and team ranking, regardless if teams were attacking (p=0.74) or defending (p=0.95). Generally four players were involved during rucks. The players involved during unsuccessful and successful retention of the ball differed (p=0.03, d=0.21). Attackers involved mostly two players (50%), whereas defenders had typically one player (68%). Attacking teams were particularly successful, in retaining possession, if they had one more attacker involved than the defenders (p<0.05). Most rucks formed in zone B and fewer rucks were formed by top teams. Training programs should adapt to accommodate law changes.

1 October 2019 in International Journal of Sports Medicine
Verified
Journal Article
Closed access
PDF file
WKWilbur Kraak
Wilbur Kraak
LCLize Coetzee
Lize Coetzee
AKAnika Kruger
Anika Kruger
RSReeco Stewart
Reeco Stewart
HVHanno van Vuuren
Hanno van Vuuren
Concussion is a frequently occurring injury in rugby which is not usually reported to coaches or medical staff. Recognition and treatment of concussion should be a priority; however, education surrounding concussion knowledge and attitudes of the players have been lacking. The aim of this study was to investigate the knowledge and attitudes toward concussion in Western Province Rugby Union (WPRU) Super League senior club rugby players. This study focused on gathering quantitative information from WPRU club rugby players, using the Rosenbaum Concussion Knowledge and Attitudes Survey-Student Version (RoCKAS-ST). The correlation between the Concussion Attitude Index (CAI) and Concussion Knowledge Index (CKI) was (r=0.14). The CKI average for the players was (16.72±2.96). The participants answered 67% (16.72±2.96) of the CKI questions and 62% (46.54±5.75) of the CAI questions correctly. The participants demonstrated sufficient knowledge of concussion, as well as safe attitudes toward concussion. A small number of players lacked knowledge of symptoms and attitudes toward concussion, which may have been influenced by the importance of games. Overall, the participants in this study demonstrated superior knowledge and safe attitudes compared to other studies. The current study found that the players had good knowledge and safe attitudes regarding the severity of concussion.

10 December 2020 in International Journal of Performance Analysis in Sport
Verified
Journal Article
Closed access
MHMichael Horn
Michael Horn
SWSimon de Waal
Simon de Waal
WKWilbur Kraak
Wilbur Kraak
The in match penalty kick may be a decisive event in a match, as well as an opportunity to progress in a knockout competition or ultimately the final standings of a competition. The aims of the current study were to conduct a video-based performance analysis of in-match penalty kicks in the English Premier League (EPL) between the 2009/10 and 2018/19 seasons to identify the relationship between selected situational (match location, match status and match period), technical (penalty taker’s footedness), and performance indicators (shot direction) and in-match penalty kick outcomes and directions. All the in-match penalty kicks (N = 952) that took place in the EPL were analysed using Nacsport video analysis software. In-match penalty kick direction, specifically vertical direction, significantly influenced in-match penalty kick outcomes (p < 0.01). Match period, score line, match location and footedness had no significant effect on in-match penalty kick outcomes or direction of the kick. The study revealed that in-match penalty kicks should be directed towards the top vertical zones of the goal area to optimise the opportunity for success of in-match penalty kicks. Importantly, the risk factor of aiming high and missing is lower than aiming low and being saved, as such; coaches and players should implement systematic penalty kick training programmes aimed at improving penalty kick placements and control into the top areas of the goal.