Assessing Cardiorespiratory Fitness of Soccer Players: Is Test Specificity the Issue?-A Review

Aerobic and Anaerobic Fitness according to High-Intensity Interval Training Frequency in Youth Soccer Players in the Last Stage of Rehabilitation

In the last stage of rehabilitation, high-intensity interval training (HIIT) for improving physical fitness is appropriate for return-to-play; however, some youth athletes visit the rehabilitation center less frequently due to conflict with their distance to center, and academic schedule. We tested the effects of short-term low-frequency HIIT in 54 youth male soccer players, after dividing them into a low-frequency group (LFG, n = 27 players) and a high-frequency group (HFG, n = 27 players). Muscle mass and body fat were measured using a body composition test, and VO₂peak and exercise duration were measured using a treadmill. Five sets of anaerobic peak power and fatigue were measured repeatedly using the Wingate test. To evaluate knee joint muscle function, 60°/s, 180°/s, and 240°/s were measured using the isokinetic muscle function equipment. HIIT sessions were conducted twice a week for LFG and five times a week for HFG for 4 weeks. In this study, Wilcoxon signed-rank test and Mann-Whitney U test were mainly used for analysis. Significant improvements in VO₂peak, anaerobic peak power, and knee strength were observed after intervention in both groups (p < 0.05). In the post test, there were significant differences between groups in VO₂peak (LFG, 56.4 vs. HFG, 57.1 mL/kg/min; p = 0.035), exercise duration (LFG, 972.3 vs. HFG, 990.4 s; p = 0.041), Wingate anaerobic peak power 5 sets (LFG, 606.3 vs. HFG, 629.3 Watt; p = 0.039), and muscle function test 240°/s (LFG, 68.5 vs. HFG, 70.2 Jouls; p = 0.010). However, neither group showed significant changes in body composition, such as muscle mass or body fat (p > 0.05). In conclusion, although it is a short-term training, the effect of HIIT was shown in the HFG as well as LFG. Although HFG improved physical fitness, significant improvement was also achieved in LFG. Therefore, in the last stage of rehabilitation, low frequency as well as high frequency HIIT would be an appropriate training method to improve physical fitness for youth soccer players.

A Comparison of Incremental Running Field and Treadmill Tests in Young Soccer Players

The purpose of this study was to compare the incremental running tests performed by young soccer players on a treadmill (Tr) and in the field (FT_cod: 100 m change of direction and FT_cir: 100 m circle). Nineteen players (average age 17.4 ± 1.1 years; body height 172.0 ± 5.7 cm; body mass 68.9 ± 6.7 kg) volunteered to perform incremental Tr , FT_cod and FT_cir running tests. In all three tests, players ran for 3 min at 8, 10, 12 and 14 km∙h^-1 and were given a 1 min rest interval between subsequent stages. Blood lactate concentrations (La^-) were measured at 1 min rest intervals and the heart rate (HR) responses of players were recorded during the tests. After a 5 min recovery period, the second part of the test started; players ran at 15 km∙h^-1 with velocity increments of 1 km∙h^-1 every 1 min until exhaustion. This part was performed to determine maximum HR, maximum La^- and the players’ final velocities. The results showed that players had significantly lower La^- (F = 6.93, p = 0.07, η² = 0.46, 95%CI_(TR-FTcir) = -1.91/-0.34, 95%CI_(TR-FTcod) = -1.59/-0.05) and HR (F = 9.08, p = 0.02, η² = 0.53, 95%CI_(TR-FTcir) = -6.98/-1.68, 95%CI_(TR-FTcod) = -7.19/1.08) responses in the Tr test than in the FT_cir and FT_cod tests at 14 km∙h^-1. It was also found that players completed the Tr test (F = 58.22, p = 0.00, η² = 0.87) at higher final running velocities than the FT_cir (95%CI_(TR-FTcir) = 1.67/2.78) and FT_cod (95%CI_(TR-FTcod) = 1.69/2.85) tests. In conclusion, when coaches or sports scientists plan to train at higher running velocities or according to the final velocity in the test, it is advisable to carry out testing in the circumstances under which training will be carried out (in the field or on a treadmill).

Test-retest reliability of physical fitness tests among young athletes: The FITescola® battery

Monitoring physical fitness in young athletes is essential to improve physical performance, identify talents and develop injury prevention programs. The aim of this investigation was to analyse the reliability of the physical fitness tests from the FITescola^® battery in young athletes with different sports backgrounds and competition levels. Participants comprised of 138 young athletes (boys n = 92) aged 9 and 18 years old. Eight physical fitness tests assessing six components of physical fitness were performed: cardiorespiratory fitness (PACER); upper body muscular fitness (push-up); flexibility (sit and reach); lower-body muscular fitness (horizontal and vertical jump); agility (4 × 10 shuttle run); and speed (sprint at 20 m and 40 m). Each test was performed twice, with a one-week interval (7 days) between duplicate tests. No differences between duplicate tests were found (p > .05), except for the speed at 20 m in boys (p < .001) and speed at 40 m in girls (p = .006). The battery of tests had good or excellent reliability and concordance of the ICC between the two trials (ICC ≥ 0.75) with exception for the 20 m speed run in girls that presented moderate reliability (ICC = 0.57). The Bland-Altman plots showed high reliability for all the fitness tests for both sexes. Hence, The FITescola^® battery may be a novel tool to assess the physical fitness of large groups of young athletes from different sports backgrounds.

Validity and reliability of speed tests used in soccer: A systematic review

Introduction

Speed is an important prerequisite in soccer. Therefore, a large number of tests have been developed aiming to investigate several speed skills relevant to soccer. This systematic review aimed to examine the validity and reliability of speed tests used in adult soccer players.

Methods

A systematic search was performed according to the PRISMA guidelines. Studies were included if they investigated speed tests in adult soccer players and reported validity (construct and criterion) or reliability (intraday and interday) data. The tests were categorized into linear-sprint, repeated-sprint, change-of-direction sprint, agility, and tests incorporating combinations of these skills.

Results

In total, 90 studies covering 167 tests were included. Linear-sprint (n = 67) and change-of-direction sprint (n = 60) were studied most often, followed by combinations of the aforementioned (n = 21) and repeated-sprint tests (n = 15). Agility tests were examined fewest (n = 4). Mainly based on construct validity studies, acceptable validity was reported for the majority of the tests in all categories, except for agility tests, where no validity study was identified. Regarding intraday and interday reliability, ICCs>0.75 and CVs<3.0% were evident for most of the tests in all categories. These results applied for total and average times. In contrast, measures representing fatigue such as percent decrement scores indicated inconsistent validity findings. Regarding reliability, ICCs were 0.11–0.49 and CVs were 16.8–51.0%.

Conclusion

Except for agility tests, several tests for all categories with acceptable levels of validity and high levels of reliability for adult soccer players are available. Caution should be given when interpreting fatigue measures, e.g., percent decrement scores. Given the lack of accepted gold-standard tests for each category, researchers and practitioners may base their test selection on the broad database provided in this systematic review. Future research should pay attention to the criterion validity examining the relationship between test results and match parameters as well as to the development and evaluation of soccer-specific agility tests.