Inclusion and exclusion standards

The inclusion standards had been male soccer gamers aged 15-17 years and people who had been lively gamers on the elite stage. The exclusion standards included youth soccer gamers who refused to take part on this research and gamers who had been injured prior to now month and had been unable to finish the efficiency measures.

Contributors

A complete of 238 elite male soccer gamers aged 15-17 years had been recruited from Chinese language skilled soccer golf equipment and provincial soccer associations. The gamers aged 15 years (n = 87) had been allotted to the U15 group, the gamers aged 16 years (n = 99) had been allotted to the U16 group, and the gamers aged 17 years (n = 52) had been allotted to the U17 group. Contributors within the U15, U16, and U17 teams had at the very least 3, 4, and 5 years of expertise in soccer coaching, respectively. They skilled a median of 4 days per week (80 min per session) and took part in a single official match (90 min). The gamers had been additionally divided into 6 teams in keeping with place: the GK group (n = 20), CD group (n = 41), ED group (n = 48), CM group (n = 44), EM group (n = 65), and FW group (n = 20). All gamers had been acting at a nationwide match stage and took part in all exams with out accidents. A priori energy evaluation was performed to calculate the pattern dimension by way of G*energy 3.1.9.2. For one-way evaluation of variance (ANOVA), a minimal pattern dimension of 156 contributors was essential to detect important variations within the technique of the bodily traits of the three age teams, with the impact dimension calculated on the premise of the earlier evaluate (impact dimension = 0.29; energy = 90%; two-tail α of 0.05) [15].

Anthropometric measurements and bodily efficiency exams had been carried out to gather the info of all of the contributors. The exams had been carried out in 5 cities of China (Weifang, Hangzhou, Wuhan, Beihai, and Beijing) within the midseason interval (September–November) of 2022. All contributors had been requested to take care of an everyday weight loss plan through the testing week, quick for at the very least two hours earlier than the check, and chorus from utilizing depressants (e.g., alcohol) or any identified stimulants (e.g., caffeine) for twenty-four h previous to the check. Previous to the measurement, the athlete had not undergone any coaching and had already defecated and urinated. To cut back measurement errors resulting from elements equivalent to temperature and weight loss plan time, the anthropometric measurements had been carried out between 09:00 and 11:00 within the morning, and the bodily efficiency exams had been carried out between 14:00 and 17:00 within the afternoon. The examiners included 4 PhD college students and 6 sports activities science grasp’s diploma college students who had been uniformly skilled earlier than the experiment. All of the examiners had been acquainted with the check course of and had mastered all of the check strategies. To look at reliability between the examiners, coefficients of variation (CV) had been all examined and confirmed excessive reliability (CV < = 3.47%). Earlier than the check, the measurement tools was unified and standardized, and it was strictly inspected and calibrated.

The research design, protocol, and threat had been well-known to the gamers and their authorized guardians. This research was reviewed and permitted by the Institutional Ethics Board of Tongji Medical Faculty, Huazhong College of Science and Expertise, China (Notification Quantity [2023] IEC (S172)). This research adopted the moral rules of the Helsinki Declaration for human analysis. Written knowledgeable consent varieties had been obtained from all of the contributors and guardians of the minors.

Anthropometric measurements

All of the gamers’ anthropometric traits had been measured. Physique peak (BH) was measured to the closest 0.1 cm utilizing a transportable stadiometer (Seca 217, Hamburg, Germany). Physique mass (BM) was measured with an accuracy of 0.1 kg. Chest girth, calf girth, ankle circumference, and thigh circumference had been measured with an accuracy of 0.1 cm (circumference ruler, Donghuateng Sports activities Equipment Ltd., Beijing, China), as had been the decrease limb size, Achilles tendon size, arm size, and finger distance (Martin ruler, Donghuateng Sports activities Equipment Ltd., Beijing, China). Physique composition (e.g., fats mass, physique fats, and so forth.) was measured with an Inbody 770 (Biospace Co., Ltd., Seoul, Korea) (intraclass correlation coefficients ≥ 0.98) [16]. A 3rd measurement was taken if there was greater than a 5% distinction between the primary two measurements.

Bodily efficiency exams

It was ensured that the variety of contributors in every check group was equal to the variety of examiners, permitting for particular person measurements of contributors through the exams. Gamers participated within the T-test after finishing the Fédération Internationale de Soccer Affiliation (FIFA) 11 + warm-up actions as a gaggle for 3 min. The testing schedule ensured that every one contributors had a 3-minute interval between the T-test and the 30 m dash check, between the 30 m dash check and the CMJ check, and between the SLJ check and the Yo-Yo IR check. The interval between the CMJ check and the SLG check was 5 min. To make sure that the contributors may get better adequately, all of the contributors to have time intervals between every trial of all of the exams. The time intervals had been as follows: (1) 30 s between every trial of the T-test, (2) 3 min between every trial of the 30-metre sprinting check, (3) 1 min between every trial of the CMJ check, and (4) 1 min between every path of the SLJ check. The experimental protocol is proven in Fig. 1.

Sprinting efficiency

As in a earlier research, a 30-m sprinting check was carried out on synthetic turf utilizing a photoelectric cell timing gate system (Smartspeed Professional, Fusion Sport, Brisbane, QLD, Australia) [17]. The gates had been positioned at 5 m, 10 m, 20 m, and 30 m, and the time the contributors handed by way of every gate was recorded. The standing contributors had been concentrating on the sunshine begin sign that will be proven 5 m from the primary timing gate. As quickly as they noticed the sign, they sprinted at most pace whereas carrying soccer footwear. Sturdy verbal encouragement was supplied to every participant through the check. All of the contributors had been requested to dash for 30 m earlier than slowing down. Every participant had two makes an attempt and three minutes for restoration between the 2 exams. Lastly, the shortest sprinting time was chosen.

Leaping efficiency

The CMJ and single leg leap (SLJ) check had been carried out by way of a multifunctional leaping mat system (SmartJump, Fusion Sport, Brisbane, QLD, Australia) to judge the gamers’ leaping capacity. The contributors had been instructed to face on the platform (carrying footwear) in an upright place after which squatted to a self-selected depth previous to leaping vertically as explosively as attainable; the gamers’ palms had been fastened on the hips always through the CMJ check [18]. The contributors had three makes an attempt with 1 min of restoration time between makes an attempt. Within the SLJ check, the contributors stood in an upright place after which squatted to a self-selected depth previous to leaping vertically with one leg; the contributors’ palms hung freely, and so they landed on the identical leg. Three exams had been carried out for every leg, and the restoration time between makes an attempt was 1 min. A five-minute relaxation interval was allowed between the CMJ and SLJ exams for fatigue prevention. Lastly, the perfect end result (peak) was chosen for the info evaluation.

T-test

A T-test was used to judge the gamers’ agility by way of speedy actions carried out on synthetic soccer turf [19]. On this check, contributors began with each toes behind the beginning line A. Every participant sprinted ahead to cone B and touched its base with their proper hand. Dealing with ahead and with out crossing their toes, they shuffled left to cone C and touched its base with their left hand. They then shuffled proper to cone D and touched its base with their proper hand, shuffled again left to cone B and touched its base, and eventually ran backward as quick as attainable to return to line A. (Fig. 2). The modified measurement has been proven to be dependable and has an intraclass correlation coefficient larger than 0.9 [20]. The most effective measurement of the 2 exams was recorded by way of a photoelectric cell timing gate system (Smartspeed Professional, Fusion Sport, Brisbane, QLD, Australia).

Agility T-test. The athlete runs ahead from cone A to cone B, then shuffles to the left (cone C), then shuffles to the proper (cone D), then shuffles again to level B, earlier than working backwards to the beginning/end place (level A)

Yo-Yo intermittent restoration check stage 1 (Yo-Yo IR1)

The contributors repeatedly ran forwards and backwards between the beginning and turning strains within the Yo-Yo IR1 till they grew to become fatigued [21]. The pace was managed by an audio beeps sign whereas working in a twenty-meter shuttle space, and the gamers actively recovered by jogging inside 10 s earlier than every run within the restoration space. The contributors’ working distance through the Yo-Yo IR1 was calculated by the skilled coach once they failed twice to achieve the entrance line in time. Every participant solely had one try for this check.

Statistical analyses

All research information had been analyzed with SPSS 25.0 software program (SPSS Inc., Chicago, IL, USA). The Shapiro‒Wilk check was used to examine the traditional distribution of the info, confirming that every one collected information adopted a standard distribution. One-way ANOVA was used to check for important variations between age and place teams. The least important distinction (LSD) check was subsequently used as a submit hoc check to check two teams. Statistical significance was thought-about at p < 0.05. The impact sizes (ESs) had been additionally calculated with the next standards: 0.04-0.25, small; 0.25-0.64, average; and 0.64-1.0, giant [22].