Ben Coetzee

The use of heart rates and graded maximal test values to determine rugby union game intensities.

Abstract Sparks, M and Coetzee, B. The use of heart rates and graded maximal test values to determine rugby union game intensities. J Strength Cond Res 27(2): 507–513, 2013—The aim of this study was to determine the intensities of university rugby union games using heart rates and graded maximal test values. Twenty-one rugby players performed a standard incremental maximal oxygen uptake (V[Combining Dot Above]O2max) test to the point of exhaustion in the weeks between 3 rugby matches. The heart rates that corresponded to the first and second ventilatory thresholds were used to classify the heart rates into low-, moderate-, and high-intensity zones. The heart rates recorded through heart rate telemetry during the matches were then categorized into the different zones. The average heart rates for the different intensity zones as well the percentages of the maximum heart rate (HRmax) were as follows: low, 141–152 b·min−1 (76.2–82.0% HRmax); moderate, 153–169 b·min−1 (82.7–91.4% HRmax); and high, 170–182 b·min−1 (91.9–100% HRmax). The percentages of time players spent in the different intensity zones were as follows: 22.8% for the low-intensity, 33.6% for the moderate-intensity, and 43.6% for the high-intensity zones. The dependant t-test revealed significant differences (p < 0.05) between the low- and high-intensity zones for the second halves, between the low- and moderate- as well as between the low- and high-intensity zones for the matches overall. To conclude, the results of the study showed that the above-mentioned method can be used to determine the intensities of university rugby union games. It also revealed that university rugby games are categorized by significantly more high-intensity activities than was previously reported by other rugby match analyzing–related studies. Thus, sport scientists and conditioning coaches should concentrate more on high-intensity activities for longer periods during training sessions.

Variations in high-intensity running and fatigue during semi-professional soccer matches

The aim of the study was to determine the fatigue rates and pacing strategies of players during matches by quantifying high-intensity running (HIR) in rolling 5-min periods. Ten semi-professional players were monitored with 10Hz global positioning system (GPS) units during 12 official A-league matches. Match data was categorised into total distance covered and HIR (>3.7 m/min) for rolling 5-min intervals. Distance covered in the first half were used to classify players into low- (LAG), moderate- (MAG) and high-activity groups (HAG). The MAG showed a moderate difference in HIR at 5-min after the peak period. The HAG showed moderate to large declines in distance covered between the first 15 min of the second half (103.9 m/min). They also showed small to moderate declines in HIR during the first 10 min of the second half (25.7 m/min). The LAG showed a small to moderate increase in distance covered during the last 10 min of the second half (95.7 m/min) compared to the first half (84.4 m/min). First-half activity profiles had a significant impact on recovery after the most intense 5-min periods. Also, our study showed an end-spurt occurring towards the end of a match supporting the possibility of pacing strategies.

Internal And External Match Loads Of University-Level Soccer Players: A Comparison Between Methods.

Abstract Sparks, M, Coetzee, B, and Gabbett, TJ. Internal and external match loads of university-level soccer players: a comparison between methods. J Strength Cond Res 31(4): 1072–7077, 2017—The aim of this study was to use individualized intensity zones to compare the external (velocity and player load, PL) and internal loads (heart rate, HR) of a cohort of university-level soccer players. Thirteen soccer players completed a 40-m maximum speed test and the Yo-Yo intermittent recovery test 1 (Yo-Yo IR1) to determine individualized velocity and HR thresholds. Heart rate values and global positioning system (GPS) data of each player were recorded during 5 league matches. A large (r = 0.46; p ⩽ 0.01) correlation was found between time spent in the low-intensity (LI) velocity zone (LIVZ) and the LI HR zone. Similarly, there were moderate (r = 0.25; p ⩽ 0.01) to large (r = 0.57; p ⩽ 0.01) correlations between the relative and absolute time spent in the moderate-intensity (MI) velocity zone (MIVZ) and the MI HR zone. No significant correlations (p ⩽ 0.01) existed between the high-intensity (HI) velocity zones (HIVZ) and the HI HR zone. On the other hand, PL showed significant correlations with all velocity and HR (absolute and relative) variables, with the exception of a nonsignificant correlation between the HI HR variables and PL. To conclude, PL showed good correlations with both velocity and HR zones and therefore may have the potential to serve as a good indicator of both external and internal soccer match loads.

Notational singles match analysis of male badminton players who participated in the African Badminton Championships

Abstract Purposes of this study were firstly, to determine the notational singles match analysis results of male badminton players and secondly, to determine relationships between notational singles match analysis determined strokes and foot movements in male badminton players, who participated in the African Badminton Championships. Twenty male singles matches from the team and individual events of the 2014 All Africa Badminton Championships were recorded live via video cameras and analysed using the Dartfish video analysis software package. Average match duration (1470.4 s), real time (432.9 s) and percentage of real time played (29.8%), number of rallies per match (68.4) and shots per rally (6.5) were calculated. Average shots per rally were found to be 6.5 and the work density, .4. Average stroke frequency per match was: drive – 122.1, clear – 118, smash – 56.2, net strokes – 54.3, drop-shot – 24.2 and the round-the-head stroke – 1.2. Foot movements delivered the following average results per match: chasse-step – 174.6, shuffle – 161.7, split-step – 61.6, half-lunge – 52.20, forward-lunge – 46.1 and scissors kick – 38.3. Significant Spearman Rank Correlation Coefficients existed between various foot movements and strokes. The study confirmed the applicability of computerised notational analyses in determining singles badminton match characteristics.

The use of anthropometric measurements and the Influence of demographic factors on the prediction of vo2max in a cohort of adolescents: the Pahl study

Abstract Background: prediction models have not focused on children and adolescents from South Africa and have not included various demographic factors as possible predictors. Aim: The purpose of this study was, therefore, to determine whether a valid prediction function can be developed from several anthropometric measurements and demographic factors of a cohort of adolescents in South Africa. Subjects and methods: A total of 214 adolescent boys (n = 88) and girls (n = 126) (15.82 ± 0.68 years) were selected. Demographic, sport and maturation data were collected by means of questionnaires, whereas anthropometric measurements were taken by accredited anthropometrists and the 20-m Shuttle Run Test (SRT) executed to determine indirect values. A forward stepwise multiple regression analysis was performed to identify the cluster analysis reduced predictors and a cross-validation was performed in order to validate the prediction function. Results: Muscle mass percentage, sport participation level, stature, hip circumference and ectomorphy acted as significant predictors (p < 0.05) of the adolescents’ indirect, 20-m SRT values. Seventy per cent of the variance in the indirect, 20-m SRT values could be explained by this model. Cross-validation also confirmed the model’s validity. Conclusion: Results indicate that the of adolescents from different racial backgrounds, living areas and gender groups can be accurately predicted by making use of a population-specific model.

Heart rate variability and recovery as predictors of elite, African, male badminton players’ performance levels

Abstract The aim of this study was to determine whether pre-match, in-match, resting and post-match heart rate variability (HRV) as well as resting and post-match heart rate recovery (HRR) can serve as significant predictors of male, elite, African, singles badminton players’ performance levels. Twenty-two male badminton players were categorised into successful and less successful player groups according to match results. Heart rates were recorded every second before (pre-match), during (in-match) and directly after (post-match) 46 matches to determine 14 HRV and 2 HRR indices. Binary, forward, stepwise logistic regression analyses’ results showed that log transformed low frequency to high frequency ratio (Ln-LFnu/Ln-HFnu ratio) and peak very low frequency power (VLF power (Hz)), were significantly (p < .05) related to group allocation of successful and less successful badminton players. Overall model fit was good and 75% of players could be classified into their original groups by making use of the HRV-based logistic regression formulas. Furthermore, all models had a large effect in predicting player classification, although only the pre- and in-match models emerged as being useful. In conclusion, short-term frequency domain-related HRV variables are related to badminton match performances and should be considered when measuring HRV in sport and exercise settings.

The competitive intelligence process in sport: data collection properties of high-level cricket coaches

Abstract The aim of this study was to identify the data collection properties of cricket coaches, using the first stage of the 4Cs Competitive Intelligence (CI) process model of Weiss as framework. Semi-structured interviews were performed with high-level cricket coaches in South Africa. Content analysis was performed by developing a codebook through the creation of theory and data-driven codes with ATLAS.TITM computer assisted qualitative data analysis software. Codes were thematised into the what, where, who and how of data collection as well as challenges cricket coaches face. Overall, coaches indicated that they make use of various sources of information on competitors, own team and the environment. Data collection is usually performed by numerous persons within the team set-up and a variety of information formats are utilized. The main findings of the study indicated that easy available sources are not effectively utilized, data collection processes are not performed in a structured manner and coaches need skill development regarding data collection and analysis. Furthermore, the lack of technology as well as the absence of a person who can collect data and a shortage of skills by the person who is responsible for data collection, are the main challenges coaches face.

Relationship between heart rate, heart rate variability, heart rate recovery and global positioning system determined match characteristics of male, elite, African badminton players

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.

Yo-Yo Intermittent Recovery Test thresholds to determine positional internal match loads of semiprofessional soccer players

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.