In the prediction of lower body explosive power (LBEP), very few researchers have investigated th... more In the prediction of lower body explosive power (LBEP), very few researchers have investigated the possibility of making use of anthropometric variables to compile prediction models. Therefore the purpose of this study was to develop a LBEP prediction model from several anthropometric measurements for a cohort of adolescent boys and girls living in the Tlokwe local municipality of the Dr Kenneth Kaunda district in the North West Province, South Africa. This was a cross–sectional experimental design on a purposeively selected cohort of 214 adolescents (15.82±0.68 years) consisting of 88 boys and 126 girls who were part of the Physical Activity and Health Longitudinal Study (PAHLS). Data were obtained by means of skinfold (SF) and LBEP measurements as well as the calculation of maturity age. The results of the forward stepwise regression analysis shows that stature (57%), muscle mass percentage (10%) and maturation age (3%) were the anthropometric variables that served as significant (
Low cardiorespiratory fitness and inactivity are strong health predictors associated with excessi... more Low cardiorespiratory fitness and inactivity are strong health predictors associated with excessive fatness. The objective of this study was to determine the associations between physical activity (PA) and cardiorespiratory fitness and body fatness in South African adolescents. A cross-sectional study was performed with a subsample of 149 school-going adolescents (58 boys and 91 girls) with a mean age of 15.7 ± 0.8 years whom were participating in the Physical Activity and Health Longitudinal Study (PAHLS). Body mass, height, and skinfolds were assessed according to the standards of the International Society for the Advancement of Kinanthropometry (ISAK). Subsequently, body mass index (BMI) and percentage of body fat (%BF) were calculated. Cardiorespiratory fitness was derived from predicted VO2max, and PA assessed by combined heart rate and accelerometry (ActiHeart®, CamNTech). Physical activity was classified according to activity categories. Out of 149 participants, 100 (67.1%) h...
International Journal of Performance Analysis in Sport, 2016
The primary aim of this study was to investigate the relationship between heart rate (HR), heart ... more The primary aim of this study was to investigate the relationship between heart rate (HR), heart rate variability (HRV), heart rate recovery (HRR) and global positioning system (GPS) determined match characteristics of male, elite, African, singles badminton players. Twenty-two players were fitted with a Fix Polar Heart Rate Transmitter Belt and a GPS unit to record HR and court movements every second during each match. Results revealed a strong, non-significant canonical correlation of Rc = 0.99 (p = 0.257) between HR, HRV, HRR and GPS determined match characteristics. The total redundancy values showed that 38.47% of the variance in the nine GPS-related variables could be accounted for by the ten HR-related variables. Likewise 38.88% of the variance in the HRrelated variables could be accounted for by the nine GPS-related variables. Furthermore, distance covered at a low exercise intensity, the amount of low intensity accelerations and player load were highlighted as the highest external match load-related contributors whereas Ln-HFnu power, peak HF (Hz) and Ln-LFnu/Ln-HFnu were identified as the highest internal match load-related contributors. In conclusion, when evaluating badminton internal match loads practitioners should consider and correct for GPS determined external match loads of players to prevent clouded and inaccurate conclusions of autonomic nervous system behaviour from occurring.
South African Journal for Research in Sport Physical Education and Recreation, 2020
Sport coaches and business managers follow similar activities to collect, analyse and communicate... more Sport coaches and business managers follow similar activities to collect, analyse and communicate data related to the opposition, known as competitive intelligence (CI), to gain a competitive advantage through strategic decision making. Little is known about the CI process that coaches follow. This study aimed to develop a CI survey for South African cricket coaches and to determine content and face validity of the items. The CI survey was developed using a mixed-methods approach that integrated at four points during a five-step process. Semi-structured interviews were conducted with high-level cricket coaches and support staff, followed by a constant comparative method of qualitative data analysis with Atlas.TiTM software. Theory and data-driven interview codes and categories were quantitised. A cluster analysis concatenated the codes into five conceptual themes, each with sub-categories. These themes were used to create scales of the survey, whereas the categories were used to cre...
International Journal of Sports Physiology and Performance
Background: The Yo-Yo Intermittent Recovery Test Level 1 (YYIR1) is often utilized to indirectly ... more Background: The Yo-Yo Intermittent Recovery Test Level 1 (YYIR1) is often utilized to indirectly assess the cardiorespiratory fitness of team-sport athletes due to its proposed association with match-play high-speed running performance and predicted maximal oxygen uptake. No previous research has investigated the relationships between YYIR1 performances, actual oxygen uptake recorded during the YYIR1, and true all-out sprint kinetics (eg, maximal sprint speed, maximal force capacity, and maximal power output), which therefore served as the primary objective of this study. Objectives: To assess the true physiological kinetics ( and heart-rate responses) during the YYIR1 and to evaluate the correlations between the physiological kinetics, sprint kinetics, and YYIR1 performance parameters. Methods: A total of 23 amateur male soccer players were recruited for the study (age 22.52 [2.86] y; height 1.75 [0.06] m; body mass 65.61 [8.43] kg). Each participant completed a YYIR1 and 2 all-out...
International Journal of Performance Analysis in Sport, 2016
The aim of this study was to use heart rates and Yo-Yo Intermittent Recovery test level 1 (Yo-Yo ... more The aim of this study was to use heart rates and Yo-Yo Intermittent Recovery test level 1 (Yo-Yo IR1)-derived thresholds to determine the positional internal match loads of semi-professional soccer players. Players completed a Yo-Yo IR1 while wearing a portable gas analyser. Heart rates (HR) that corresponded to the first and second ventilatory thresholds were used to classify internal loads into low- (LI HR zone), moderate- (MI HR zone) and high-intensity zones (HI HR zone). During 12 soccer matches it was found that attackers (n = 17) spent more time in the LI HR zone (3386 s; 62%; P < 0.05) than defenders (2155 s; 40%; n = 36) and midfielders (2425 s; 42%; n = 41). The attackers spent less time in the HI HR zone (260 s; 4%; P < 0.05) than the defenders (964 s; 15%). Midfielders (2444 s; 44%) and defenders (2364 s; 41%) spent more time in the MI HR zone than attackers (1854 s; 44%). This study is the first to show that the Yo-Yo IR1 test can be used to determine individual, physiologically defined intensity zones to determine positional differences in the internal match loads of soccer players.
The Comrades Marathon is South Africa’s – and the world’s – most recognised and largest ultra-mar... more The Comrades Marathon is South Africa’s – and the world’s – most recognised and largest ultra-marathon event, with over 15 000 participants from across the globe competing in the 89-km road running event each year. Historically, the event has been held before the start of austral winter (20 May – 17 June). However, in 2022, organisers of the race moved the event to 28 August, when austral spring commences. We explore the climate, in particular the Universal Thermal Comfort Index (UTCI), of past Comrades events (1980-2019) and compare these data to UTCI data of the new proposed date (28 August) for the same period. The climatology for May, June, July and August was determined to identify periods with the lowest risk for ‘strong’ to ‘very strong’ heat stress. Results show that participants’ risk of exposure to ‘strong’ heat stress and ‘very strong’ heat stress periods will be more likely if the event is held in August as compared to the original event dates. Therefore, it is concluded...
The primary aim of the study was to determine if heart rate variability (HRV), and heart rate rec... more The primary aim of the study was to determine if heart rate variability (HRV), and heart rate recovery (HRR) are related to several subjective indicators of recovery status (muscle soreness, hydration status, sleep quality and quantity as well as precompetition mood states) for different match periods in male, elite, African, singles badminton players. HRV and HRR were measured in twenty-two badminton players before (pre-match), during (in-match), after (post-match) and during rest periods (inmatch rest) of 46 national and international matches. Muscle soreness, hydration status, and sleep quality and quantity were measured on a daily basis whereas mood states were measured just before each match via questionnaires. Prior to each match warm-up, players were fitted with a Fix Polar Heart Rate Transmitter Belt to record heart rate every second during each match and HRR during service breaks and after matches. Kubios HRV software was used for final HRV analyses from the series of R-R-i...
The study's purpose was to establish the inertial sensors-containing device (ISCD)-determined... more The study's purpose was to establish the inertial sensors-containing device (ISCD)-determined match characteristics that predict elite, male badminton players’ performance levels. Twenty-two (22) male single players (aged: 23.39 ± 3.92 years), who represented 10 African countries, participated in the study. Players were categorized as successful and less-successful players according to the results of five championships during two seasons. ISCD units (Catapult MinimaxV4), Polar Heart Rate Transmitter Belts, and digital video cameras were used to collect match data. ISCD-determined variables were corrected for match duration, and independent t-tests, cluster analysis, and a binary forward stepwise logistic regression were used for statistical analyses. A Receiver Operating Characteristic Curve (ROCC) indicated the validity of the group classification model. High-intensity accelerations per second were identified as the only ISCD-determined variable that showed a significant differ...
... In a technical analysis of the hook shot Bob Woolmer, former South African coach, showed that... more ... In a technical analysis of the hook shot Bob Woolmer, former South African coach, showed that a player must step back on his toes so as to maintain balance and power, turn his shoulders, roll the wrists as the bat swings across the body and extend his arms to their fullest to ...
The primary aim of the study was to determine if heart rate variability (HRV), and heart rate rec... more The primary aim of the study was to determine if heart rate variability (HRV), and heart rate recovery (HRR) are related to several subjective indicators of recovery status (muscle soreness, hydration status, sleep quality and quantity as well as pre-competition mood states) for different match periods in male, elite, African, singles badminton players. HRV and HRR were measured in twenty-two badminton players before (pre-match), during (in-match), after (post-match) and during rest periods (in-match rest) of 46 national and international matches. Muscle soreness, hydration status, and sleep quality and quantity were measured on a daily basis whereas mood states were measured just before each match via questionnaires. Prior to each match warm-up, players were fitted with a Fix Polar Heart Rate Transmitter Belt to record heart rate every second during each match and HRR during service breaks and after matches. Kubios HRV software was used for final HRV analyses from the series of R-R...
In the prediction of lower body explosive power (LBEP), very few researchers have investigated th... more In the prediction of lower body explosive power (LBEP), very few researchers have investigated the possibility of making use of anthropometric variables to compile prediction models. Therefore the purpose of this study was to develop a LBEP prediction model from several anthropometric measurements for a cohort of adolescent boys and girls living in the Tlokwe local municipality of the Dr Kenneth Kaunda district in the North West Province, South Africa. This was a cross–sectional experimental design on a purposeively selected cohort of 214 adolescents (15.82±0.68 years) consisting of 88 boys and 126 girls who were part of the Physical Activity and Health Longitudinal Study (PAHLS). Data were obtained by means of skinfold (SF) and LBEP measurements as well as the calculation of maturity age. The results of the forward stepwise regression analysis shows that stature (57%), muscle mass percentage (10%) and maturation age (3%) were the anthropometric variables that served as significant (
Low cardiorespiratory fitness and inactivity are strong health predictors associated with excessi... more Low cardiorespiratory fitness and inactivity are strong health predictors associated with excessive fatness. The objective of this study was to determine the associations between physical activity (PA) and cardiorespiratory fitness and body fatness in South African adolescents. A cross-sectional study was performed with a subsample of 149 school-going adolescents (58 boys and 91 girls) with a mean age of 15.7 ± 0.8 years whom were participating in the Physical Activity and Health Longitudinal Study (PAHLS). Body mass, height, and skinfolds were assessed according to the standards of the International Society for the Advancement of Kinanthropometry (ISAK). Subsequently, body mass index (BMI) and percentage of body fat (%BF) were calculated. Cardiorespiratory fitness was derived from predicted VO2max, and PA assessed by combined heart rate and accelerometry (ActiHeart®, CamNTech). Physical activity was classified according to activity categories. Out of 149 participants, 100 (67.1%) h...
International Journal of Performance Analysis in Sport, 2016
The primary aim of this study was to investigate the relationship between heart rate (HR), heart ... more The primary aim of this study was to investigate the relationship between heart rate (HR), heart rate variability (HRV), heart rate recovery (HRR) and global positioning system (GPS) determined match characteristics of male, elite, African, singles badminton players. Twenty-two players were fitted with a Fix Polar Heart Rate Transmitter Belt and a GPS unit to record HR and court movements every second during each match. Results revealed a strong, non-significant canonical correlation of Rc = 0.99 (p = 0.257) between HR, HRV, HRR and GPS determined match characteristics. The total redundancy values showed that 38.47% of the variance in the nine GPS-related variables could be accounted for by the ten HR-related variables. Likewise 38.88% of the variance in the HRrelated variables could be accounted for by the nine GPS-related variables. Furthermore, distance covered at a low exercise intensity, the amount of low intensity accelerations and player load were highlighted as the highest external match load-related contributors whereas Ln-HFnu power, peak HF (Hz) and Ln-LFnu/Ln-HFnu were identified as the highest internal match load-related contributors. In conclusion, when evaluating badminton internal match loads practitioners should consider and correct for GPS determined external match loads of players to prevent clouded and inaccurate conclusions of autonomic nervous system behaviour from occurring.
South African Journal for Research in Sport Physical Education and Recreation, 2020
Sport coaches and business managers follow similar activities to collect, analyse and communicate... more Sport coaches and business managers follow similar activities to collect, analyse and communicate data related to the opposition, known as competitive intelligence (CI), to gain a competitive advantage through strategic decision making. Little is known about the CI process that coaches follow. This study aimed to develop a CI survey for South African cricket coaches and to determine content and face validity of the items. The CI survey was developed using a mixed-methods approach that integrated at four points during a five-step process. Semi-structured interviews were conducted with high-level cricket coaches and support staff, followed by a constant comparative method of qualitative data analysis with Atlas.TiTM software. Theory and data-driven interview codes and categories were quantitised. A cluster analysis concatenated the codes into five conceptual themes, each with sub-categories. These themes were used to create scales of the survey, whereas the categories were used to cre...
International Journal of Sports Physiology and Performance
Background: The Yo-Yo Intermittent Recovery Test Level 1 (YYIR1) is often utilized to indirectly ... more Background: The Yo-Yo Intermittent Recovery Test Level 1 (YYIR1) is often utilized to indirectly assess the cardiorespiratory fitness of team-sport athletes due to its proposed association with match-play high-speed running performance and predicted maximal oxygen uptake. No previous research has investigated the relationships between YYIR1 performances, actual oxygen uptake recorded during the YYIR1, and true all-out sprint kinetics (eg, maximal sprint speed, maximal force capacity, and maximal power output), which therefore served as the primary objective of this study. Objectives: To assess the true physiological kinetics ( and heart-rate responses) during the YYIR1 and to evaluate the correlations between the physiological kinetics, sprint kinetics, and YYIR1 performance parameters. Methods: A total of 23 amateur male soccer players were recruited for the study (age 22.52 [2.86] y; height 1.75 [0.06] m; body mass 65.61 [8.43] kg). Each participant completed a YYIR1 and 2 all-out...
International Journal of Performance Analysis in Sport, 2016
The aim of this study was to use heart rates and Yo-Yo Intermittent Recovery test level 1 (Yo-Yo ... more The aim of this study was to use heart rates and Yo-Yo Intermittent Recovery test level 1 (Yo-Yo IR1)-derived thresholds to determine the positional internal match loads of semi-professional soccer players. Players completed a Yo-Yo IR1 while wearing a portable gas analyser. Heart rates (HR) that corresponded to the first and second ventilatory thresholds were used to classify internal loads into low- (LI HR zone), moderate- (MI HR zone) and high-intensity zones (HI HR zone). During 12 soccer matches it was found that attackers (n = 17) spent more time in the LI HR zone (3386 s; 62%; P < 0.05) than defenders (2155 s; 40%; n = 36) and midfielders (2425 s; 42%; n = 41). The attackers spent less time in the HI HR zone (260 s; 4%; P < 0.05) than the defenders (964 s; 15%). Midfielders (2444 s; 44%) and defenders (2364 s; 41%) spent more time in the MI HR zone than attackers (1854 s; 44%). This study is the first to show that the Yo-Yo IR1 test can be used to determine individual, physiologically defined intensity zones to determine positional differences in the internal match loads of soccer players.
The Comrades Marathon is South Africa’s – and the world’s – most recognised and largest ultra-mar... more The Comrades Marathon is South Africa’s – and the world’s – most recognised and largest ultra-marathon event, with over 15 000 participants from across the globe competing in the 89-km road running event each year. Historically, the event has been held before the start of austral winter (20 May – 17 June). However, in 2022, organisers of the race moved the event to 28 August, when austral spring commences. We explore the climate, in particular the Universal Thermal Comfort Index (UTCI), of past Comrades events (1980-2019) and compare these data to UTCI data of the new proposed date (28 August) for the same period. The climatology for May, June, July and August was determined to identify periods with the lowest risk for ‘strong’ to ‘very strong’ heat stress. Results show that participants’ risk of exposure to ‘strong’ heat stress and ‘very strong’ heat stress periods will be more likely if the event is held in August as compared to the original event dates. Therefore, it is concluded...
The primary aim of the study was to determine if heart rate variability (HRV), and heart rate rec... more The primary aim of the study was to determine if heart rate variability (HRV), and heart rate recovery (HRR) are related to several subjective indicators of recovery status (muscle soreness, hydration status, sleep quality and quantity as well as precompetition mood states) for different match periods in male, elite, African, singles badminton players. HRV and HRR were measured in twenty-two badminton players before (pre-match), during (in-match), after (post-match) and during rest periods (inmatch rest) of 46 national and international matches. Muscle soreness, hydration status, and sleep quality and quantity were measured on a daily basis whereas mood states were measured just before each match via questionnaires. Prior to each match warm-up, players were fitted with a Fix Polar Heart Rate Transmitter Belt to record heart rate every second during each match and HRR during service breaks and after matches. Kubios HRV software was used for final HRV analyses from the series of R-R-i...
The study's purpose was to establish the inertial sensors-containing device (ISCD)-determined... more The study's purpose was to establish the inertial sensors-containing device (ISCD)-determined match characteristics that predict elite, male badminton players’ performance levels. Twenty-two (22) male single players (aged: 23.39 ± 3.92 years), who represented 10 African countries, participated in the study. Players were categorized as successful and less-successful players according to the results of five championships during two seasons. ISCD units (Catapult MinimaxV4), Polar Heart Rate Transmitter Belts, and digital video cameras were used to collect match data. ISCD-determined variables were corrected for match duration, and independent t-tests, cluster analysis, and a binary forward stepwise logistic regression were used for statistical analyses. A Receiver Operating Characteristic Curve (ROCC) indicated the validity of the group classification model. High-intensity accelerations per second were identified as the only ISCD-determined variable that showed a significant differ...
... In a technical analysis of the hook shot Bob Woolmer, former South African coach, showed that... more ... In a technical analysis of the hook shot Bob Woolmer, former South African coach, showed that a player must step back on his toes so as to maintain balance and power, turn his shoulders, roll the wrists as the bat swings across the body and extend his arms to their fullest to ...
The primary aim of the study was to determine if heart rate variability (HRV), and heart rate rec... more The primary aim of the study was to determine if heart rate variability (HRV), and heart rate recovery (HRR) are related to several subjective indicators of recovery status (muscle soreness, hydration status, sleep quality and quantity as well as pre-competition mood states) for different match periods in male, elite, African, singles badminton players. HRV and HRR were measured in twenty-two badminton players before (pre-match), during (in-match), after (post-match) and during rest periods (in-match rest) of 46 national and international matches. Muscle soreness, hydration status, and sleep quality and quantity were measured on a daily basis whereas mood states were measured just before each match via questionnaires. Prior to each match warm-up, players were fitted with a Fix Polar Heart Rate Transmitter Belt to record heart rate every second during each match and HRR during service breaks and after matches. Kubios HRV software was used for final HRV analyses from the series of R-R...
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