Internal and external match loads of university-level soccer players : a comparison between methods
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A need exists to obtain accurate, reliable and valid data to assess the external and internal loads of soccer matches, especially as it relates to South African soccer teams. Consequently, the objectives of this study were firstly to determine the fatigue rates and patterns of a cohort of university-level soccer players during matches when using global positioning system (GPS) to quantify the high-intensity running performances in rolling 5-min periods. Secondly, to determine the influence of Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1) determined training status of a cohort of university-level soccer players on fatigue patterns and rate during match play. Thirdly, to determine the positional-internal match loads of a cohort of university-level soccer players by making use of heart rates and the Yo-Yo IR1-determined threshold values. Lastly, to compare the match analysis results of different methods aimed at determining the external and internal match loads of a cohort of university-level soccer players. Selected groups of university-level soccer players (n = 10–13) were required to complete a 40-m maximum speed test and the Yo-Yo IR1 during a two-week period either before or after each analysed match. The heart rate (HR) values and GPS data of each player were recorded during league soccer matches. For the first and second objectives of the study players were categorised into three activity level categories (low, moderate and high) according to their activity levels of the first half of the match. Furthermore, their high-intensity running (> 3.7m/s) (HIR) was monitored in rolling 5-min periods. The low-activity group showed a small to moderate difference (p <0.05) in high-intensity running (HIR) at 5-min and 15-min after the peak period compared to the average 5-min period. The moderate-activity group showed a moderate difference (p <0.05) in HIR at 5-min after the peak period. The high-activity group showed moderate to large declines in distance covered between the first 15-min of the second half (103.9 m/min) compared to the first 15-min of the first half (122.5 m/min). They also showed small to moderate declines in HIR during the first 10-min of the second half (25.7 m/min) compared to the first half (34.1 m/min). The low-activity group showed a small decline in distance covered during the first 5-min of the second half (76.3 m/min) compared to the first half (87.7 m/min). Conversely the low-activity group 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). The Yo-Yo IR1 was not significantly correlated with any of the variables associated with HIR. For the third objective of the study players’ heart rates that corresponded with the first and second ventilatory thresholds as obtained during a Yo-Yo IR1 were used to classify heart rates into low (LI HR zone), moderate (MI HR zone) and high-intensity zones (HI HR zone). Results showed that attackers spent more time in the LI HR zone (3386 s; 62%; p <0.05) than defenders (2155 s; 40%) and midfielders (2425 s; 42%). 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%). For the fourth objective of the study players’ individualised velocity and heart rate (HR) thresholds were determined from the 40-m maximum speed test and the Yo-Yo IR1. Results showed a large (r = 0.5; p ≤0.01) correlation between the time spent in the LIVZ (5017 ± 368 s) and the LI HR zone (2891 ± 1086 s), with the true correlation value that varied between moderate and large. Similarly, a moderate (r = 0.3; p ≤0.01) to large (r = 0.6; p≤0.01) correlation was found between the relative (11.4 ± 3.7%) and absolute time (669 ± 223 s) spent in the MIVZ and the MI HR zone (41.0 ± 16.8% and 2253 ± 752 s). However, the true correlation value for the absolute time spent in the MI zone fell between the large to very large category, whereas the correlation for the relative time was small to moderate. There were no significant correlations (p ≤0.01) between the HIVZ and the HI HR zone. Although some correlations were found from the Spearman’s rank correlation, when adjusting for 2max O V• and Yo-Yo IR1 performance these correlations became non-significant. From these study results it is clear that the Yo-Yo IR1 and 40-m speed test show promise to be used as valid sports-specific field tests for determining ventilatory thresholds for each player, the heart rates that correspond to these thresholds and the different velocity thresholds. The authors therefore recommend that researchers use these methods in future to determine individualised HR and velocity zones in combination with the GPS analysis results to define both the internal and external match loads of soccer players. Results of these analyses could enable future coaches and sport scientists to develop match-specific conditioning programs that reflect both the internal and external demands of soccer matches.
- Health Sciences