Masters Degrees (Exercise, Sport and Lifestyle Medicine)

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    Muscle oxygenation and performance adaptations in trained cyclists following a polarized and threshold training intervention
    (Stellenbosch : Stellenbosch University, 2023-12) Fleming, Colin; Terblanche, Elmarie; Stellenbosch University. Faculty of Medical and Health Sciences. Dept. of Exercise, Sport and Lifestyle Medication.
    ENGLISH ABSTRACT: Training intensity, and its distribution within a training program, is a key variable in positively or negatively influencing athletic performance, through varying physiological adaptations stemming from different training intensities. However, experimental research investigating physiological adaptations to various training intensity distributions is scarce. As such, the purpose of this study was to examine the performance and peripheral adaptations to a polarized (POL) and a threshold (THR) training intervention in trained cyclists. Seventeen trained road and mountain bike cyclists, including men (n = 13) and women (n = 4), aged between 19 and 49 years, participated in this study. This study followed a pre-post design, with a random assignment of participants into two experimental groups: a POL or a THR training group. The pre- and post-tests included a ramp incremental test to exhaustion and a 30-s Wingate test, with concurrent cardiorespiratory, muscle oxygenation, power, heart rate, and blood lactate data collection. The intervention consisted of six weeks of polarized (80/0/20% in zone 1/2/3) or threshold (45/55/0% in zone 1/2/3) training. The findings of the present study indicate that both POL and THR training stimulate improvements in power output over a 6-week training period. There were no significant group*time interactions observed for any measured variable (p > 0.05), however, effect sizes were calculated to investigate the magnitude of differences after the training intervention. Both THR and POL displayed improvements in power output at LT2, and PPO, however the effect size was numerically greater after THR than POL training (ES = 0.54, 0.29). It was also found that the effect size of muscle oxygen utilization was greater after POL than THR at LT1, LT2, PPO, and after the 30-s Wingate (ES = 0.72, 0.91, 0.74, 1.76). The magnitude of change in VO₂max was larger for POL than THR (5.9% vs. 1.1% improvement, respectively; ES = 0.40). The THR group showed a greater numerical increase in effect size, compared to POL in anaerobic capacity and explosive power (ES = 0.34, 0.40). A moderate and a small numerical increase was observed in effect size in exercise economy at LT2 and PPO in THR, but not in POL (p > 0.05, ES = 1.11, 0.45). It is suggested that the observed improvement in power output at LT2 and PPO in the POL group may be attributed to peripheral aerobic adaptations, as indicated by an increase in O₂ utilization and VO₂max. Secondly, it is suggested that glycolytic adaptations may contribute to the improvement in power output at LT2 and PPO in the THR group, as reflected by a decrease in VO₂/W, along with increases in anaerobic capacity and explosive power. Over a 6-week period, neither POL nor THR appeared to be superior for improving endurance performance, but they may induce different adaptations.
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    The effect of the 50:22 law trial on the Currie Cup and Varsity Cup rugby tournaments between 2021 and 2022
    (Stellenbosch : Stellenbosch University, 2023-12) Strydom, Wikus; Kraak, Wilbur; Vaz, Luiz; Tucker, Ross; Stellenbosch University. Faculty of Medical and Health Sciences. Dept. of Exercise, Sport and Lifestyle Medication
    ENGLISH ABSTRACT: Tactical kicking is a fundamental aspect of rugby union “rugby”, playing a strategic role in attack and defence, contributing to the success of a team. The 50:22 law was implemented with the aim of compelling defending teams to drop players into the backfield to cover the kick, thereby reducing the number of players in the defensive line and decreasing the line speed during contact situations, lowering the risk of injuries. To the investigators knowledge, the current study was the first to investigate and compare the 50:22 law change to assess the effect of the law change on tactical kicking during match-play. This thesis followed an article format where one research article (Chapter Four) was compiled. The research article aimed to investigate and compare the effect of the 50:22 law changes on rugby union kicking profiles at provincial and university levels between the 2021 and 2022 tournaments. This study employed a descriptive retrospective research design, utilising video-based performance analysis (Nacsport Scout Plus) for data collection. The initial performance indicators and their operational definitions were established using published peer-reviewed studies, and input from an expert panel further validated and enhanced the relevance and comprehensiveness. For reliability of the coded performance indicators, the primary investigator, and an external coder independently re-coded 25% (44 matches) of the matches. The resulting Cohen's Kappa Coefficients demonstrated very good agreement for both intra-coder (r=0.98) and inter-coder (r=0.97) reliability. For this study, a comprehensive analysis was conducted on all the kicks from 177 matches during the 2021 and 2022 Currie Cup (CC) and Varsity Cup (VC) rugby tournaments, resulting in a total of 6,479 kicks being examined across the two seasons. When considering the specific tournaments, the CC yielded a total of 1,497 kicks in the 2021 season, and 1,628 in 2022. On the other hand, the VC produced 1,881 kicks during 2021, and 1,437 in 2022. In 2022, there were 53 successful 50:22 kicks, 30 in the CC and 23 in the VC. That equals to less than one successful 50:22 kick per match. The results indicate that the implemented 50:22 law influence the kicking profile at provincial and university level rugby in South Africa. When combining both tournaments, the results revealed a significant increase in the number of kicks by scrum halves (p < 0.001) and box kicks (p = 0.03) in 2022 compared to 2021. This aligns with the trend that has been seen in modern rugby in previous studies. There was a significant decrease in the number of kicks by flyhalves (p = 0.01), fullbacks (p = 0.01), and kicks that took place from a received kick (p = 0.01). The decrease in the number of kicks by fullbacks and from received kicks are likely due to teams deploying additional backfield players to counter the 50:22 kick, thereby enhancing counter-attacking opportunities upon receiving kicks. The results of the CC revealed an increase in the percentage of kicks by scrum halves (p = 0.01) and inside centres (p < 0.001). This result, together with the decrease in the number of kicks by fly halves (p < 0.001), suggests that teams at the professional level, distribute the responsibility of kicking more amongst the backline players. The study showed an increase in punt kicks (p = 0.01), likely due to a 50:22 kick needing a longer type of kick. The VC results revealed a significant decrease in the number of kicks, likely due to additional space in the defensive line, encouraging teams to run with the ball. A decrease in the number of kicks in the second quarter (p = 0.02) and an increase in the percentage of kicks in the fourth quarter (p = 0.01) was observed. This could possibly be due to teams using the 50:22 kick as an attacking option. When comparing the 2022 season of the CC and VC, the results revealed that scrum halves kick significantly more (p < 0.001) and flyhalves significantly less (p < 0.001) in the CC compared to VC. The VC used the punt kick significantly more (p < 0.001) compared to the CC, whereas the CC used contestable kicks (p < 0.001) significantly more. The findings deepen our understanding of how the 50:22 law influences how teams’ utilise kicking strategies during the match. This study provides valuable insights to coaches, performance analysts, and players in their preparation and utilisation of this law in their kicking strategy.
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    An exploratory study into select technical key performance Indicators and estimated transfer fees in the 2nd division of the German Bundesliga
    (Stellenbosch : Stellenbosch University, 2023-03) Horn, Carsten; Jacobs, Shaundre; Lamberts, Robert; Meyer, Tim; Stellenbosch University. Faculty of Medical and Health Sciences. Dept. of Exercise, Sport and Lifestyle Medication.
    ENGLISH ABSTRACT: In light of the escalating transfer fees in professional football, an inflated market and clubs having to adjust their budgets due to the ongoing restrictions resulting from the COVID-19 pandemic, accurate financial management of sporting organisations is required. This especially applies to football clubs playing outside Europe’s big five leagues, as well as those in the lower divisions of professional football. The overall aim of this MSc project was to shed light on a second division league which has previously received less attention than first divisions. More specifically, the current study assessed how a player’s performance in the season immediately before his transfer influenced his transfer fee. This was done through the lens of the Moneyball approach, which states that specific characteristics and/or skills are being undervalued by the labour market. As transfer fees can rise to millions of euros paired with clubs being under financial pressure, quantitative rather than intuitive decision-making is required. This study assessed the relationship between select technical key performance indicators (KPIs) and their relationship to estimated transfer fees in the 2nd division of the German Bundesliga, using publicly available data. The selected KPIs for defenders, midfielders and strikers were tackles and interceptions, tackles and assists, and goals and assists, respectively. A statistician was consulted for a sample size calculation and revealed a minimum of 12 participants per position (defender, midfielder, striker) were required. Statistical analysis was performed with the use of GraphPad Prism (Version 9.3.1, GraphPad Software, LLC, USA). Prior to statistical analyses, normality tests were conducted using the Kolmogorov-Smirnoff and Shapiro-Wilk tests. A Kruskal Wallis test was employed to assess the differences between the various player positions. Where significant differences were found, a Dunn’s post hoc test was performed. Associations between variables were tested for by means of Spearman correlations. All data are presented as median, and significance was set at p < 0.05. Analyses revealed that interceptions have no association with the transfer fees of defenders (rs=0.06, p=0.76). Tackles were found to be negatively associated with the transfer fees of defenders (rs=-0.41, p=0.03), while no association was found between tackles and the transfer fees of midfielders (rs= 0.17, p=0.24). Midfielders’ transfer fees displayed a positive association with assists (rs=0.44, p=0.00), while no association was found between the transfer fees of strikers and assists (rs=0.15, p=0.34). In addition, strikers’ transfer fees also did not display any association with goals (rs=0.22, p=0.16). As interceptions were found to be negatively associated with the transfer fees of defenders, it is possible that interceptions are being undervalued. However, as more successful teams tend to dominate ball possession, it is likely that players from less successful teams have more opportunity to intercept a ball, and, as less success reduces transfer fees, this would explain this association. Tackles, on the other hand, may display a negative association with transfer fees of defenders as tackles may be a sign of an error prone and/or tactically inapt player, as tackles may be used to recover from tactical and/or technical errors. Assists’ positive association with the transfer fees of midfielders is explained by the increased chances of success with an increased number of assists. Consequently, one would also expect such an association for strikers. However, previous studies have found that the transfer fees of strikers in higher divisions are associated with a publicity premium. Consequently, it is hypothesised, that due to the reduced media attention in the lower leagues, this publicity premium only exists to a much smaller degree and thereby reduces the extend to which assists influence strikers’ transfer fees. The same reasoning applies to how goals influence a strikers transfer fees, as goals also did not show an association with the transfer fees of strikers. As the current study did not control for players moving up or down a division, results need to be interpreted with caution. The findings support previous research with tackles displaying a negative association with the transfer fees of defenders and assists displaying a positive association with the transfer fees of midfielders. However, as opposed to most other leagues, goals are not the determining factor for the transfer fees of strikers transferring to or within the 2nd division of the Bundesliga. This implies that other characteristics and/or KPIs may be at play that impact the transfer fees of strikers significantly more than the selected ones, and future research is tasked with identifying these.
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    The change in postural control in highly trained trail runners following a short, competitive, off-road time trial
    (Stellenbosch : Stellenbosch University, 2023-03 ) Price, Nicholas; De Waal, Simon; Arnold, Sarah; Stellenbosch University. Faculty of Medical and Health Sciences. Dept. of Exercise, Sport and Lifestyle Medication.
    ENGLISH ABSTRACT: Research on acute effects of trail running (TR) induced fatigue and postural control (PC) in highly trained trail runners is scarce. Therefore, the aim of this study was to measure the change in select postural control variables following a short, real-world, trail run time trail (26km; +900m) in a sample of highly trained trail runners. Thirteen (N=13) male, highly trained trail runners (age: 30.00  5.58 years old; weekly running: 65.00  6.45 kilometres) participated in this study. Participants completed five postural control system (PCS) tests before and after a short, real-world, TR time trial (26km +900m ascent). Balance tests included a Modified Clinical Test of Sensory Interaction of Balance (MCTSIB), Single Leg Modified Clinical Test of Sensory Interaction of Balance (SLMCTSIB) and a Star Excursion Balance Test (SEBT). Postural sway and sway frequencies were measured via a Gyko Inertial Measurement Unit (Microgate, Italy) during four different stance conditions; firm surface with eyes open (FO), firm surface with eyes closed (FC), compliant surface with eyes open (CO), and compliant surface with eyes closed (CC). Jump tests included a Countermovement Jump Test (CMJ) and Single-Leg Countermovement Jump test (SLCMJ). Jump height and flight time were measured using OptoJump (Microgate, Italy) and two Logitech web cameras (30 fps). Tests for normality were performed using the Shapiro-Wilk test. A combination of paired samples t-tests and Wilcoxon signed-rank tests were used to identify differences in mean scoresbefore and after the time trial (significance flagged as p<0.05). Statistically significant increases (p<0.05) in mediolateral sway were observed in stance conditions FO, FC and CC while anteroposterior sway showed significant increases (p<0.05) for stance conditions FO, and CO during the MCTSIB. A statistically significant increase (p<0.05) in mediolateral sway was observed in the SLMCTSIB for the FO stance condition. A significant decrease in reach length was observed during the SEBT in the anterior movement only (p<0.05) and only on the right foot. No statistically significant changes (p>0.05) were observed for maximal and mean jump height and time for CMJ. However, statistically significant decrements (p<0.05) were found for all variables during the SLCMJ test. This study's key finding was that significant changes in select PC variables were observed following a short TR time trial. In conclusion, it appears general TR-induced fatigue negatively impacts PC regulation following a 26km (+900m) trail run time trial. However, a combination of training status, task experience and compensatory strategies appear to limit the magnitude that general neuromuscular fatigue can have on PC regulation. A greater contribution from cognitive resources such as increased awareness and attentional demand could improve sensory detection capabilities needed to identify optimal balance demands via proprioceptive sensory sources. Future studies should measure trail runners of varying training statuses to better understand this phenomenon.
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    Comparison of kinematic, and gait-spatio-temporal factors in ultra-trail runners with zero-drop versus regular-drop shoes
    (2023-03 ) Henning, Robert; De Waal, Simon Jake; Lamberts, Robert P.; Venter, Ranel; Stellenbosch University. Faculty of Medical Health Sciences. Dept. of Exercise, Sport and Lifestyle Medication.
    ENGLISH ABSTRACT: Few studies have explored zero-drop (ZD) shoes, with no studies investigating these shoes in trail- and ultra-trail running. The aim of this study was to investigate the difference in relative oxygen uptake related and gait-spatiotemporal variables in a homogenous group of ultra-trail runners wearing ZD shoes versus those wearing regular-drop (RD) shoes. Twenty-nine recreational ultra-trail runners participated in this study: 15 habitually RD runners (age 36 ± 8.9 years; mass 70.48 ± 11.85 kg; height 174.14 ± 7.85 cm), and 14 habitually ZD runners (age 32 ± 9.31 years; mass 75.53 ± 32.99 kg; height 174.5 ± 8.23 cm). Participants ran a VO2 max protocol to determine maximal fitness, as well as to determine treadmill speed at VO2 max (vVO2 max). Thereafter, participants ran a protocol at 70% and 85% of their vVO2 max to determine relative oxygen uptake, gait spatio-temporal variables, ankle kinematics at ground contact and foot strike pattern. All physiological measures were determined by breath-by-breath analysis (COSMED, Rome, Italy), and gait-spatiotemporal measurements were done via the Optogait system (Microgate, Bolzano, Italy) and video interpretation (Kinovea, Belgium). ZD runners displayed a significantly greater VO2 max and VO2 at anaerobic threshold (AT) (p < 0.05). There was no significant difference between ZD and RD runners for all the gait-spatiotemporal variables at both 70% and 85% vVO2 max. However, a large effect size for ankle angle was observed for both 70% (d=1.24) and 85% (d=1.11) speeds, indicating that ZD runners (86.54 ± 3.12o) were more dorsiflexed than RD runners (85.81 ± 4.15o) at ground contact. Furthermore, RD runners increased stride length significantly between 70% (202.46 ± 35.14 cm) and 85% (213.36 ± 41.83cm) vVO2 max, while ZD increased cadence significantly (96.83 ± 12.59 to 106.65 ± 20.88 steps.min). The first null hypothesis was rejected, as the VO2 max in the ZD group was significantly higher than the RD group. The second null hypothesis was accepted, as there were no significant differences between the ZD and RD groups for physiological fitness variables at both 70% and 85% vVO2 max. The third null hypothesis was partially rejected, as no significant difference in any of the gait-spatiotemporal variables between ZD and RD ultra-trail runners were observed, barring the distribution in foot strike pattern at 70% vVO2 max, where the ZD (n = 9) runners displayed a significantly higher distribution of MF/FF striking pattern compared to the RD (n = 1) runners. No studies have shown differences in physiological fitness and gait-spatiotemporal variables between ZD and RD ultra-trail runners. These results help runners understand how shoe drop-height affects relative oxygen uptake related variables to make informed choices in shoe selection, namely that runners wearing ZD shoes tend to strike the ground with a MF/FF pattern, as well as to expand the current body of literature regarding trail running. Further studies could investigate the effects of ZD shoes on physiological and gait-spatiotemporal variables in a much larger sample, which should provide a more accurate description of these effects.