The aim of this study is to examine how physical performance has changed after 15 weeks (109 days) long-term absence of organized training in youth soccer players imposed by the stay at home orders. A total of sixty-eight young male soccer players from different age categories (U15, U16, U17 and U19) voluntarily participated in the prospective cohort study. Body fat percentage (BF%), counter-movement jump (CMJ), 30 m sprint, change-of-direction (COD) and yo-yo intermittent recovery test level-1 (YYIRTL-1) were evaluated twice (before and after the detraining period). Subsequently, 2 × 2 repeated measures ANOVA was used to investigate group and time differences in repeated measurements. A significance level of p < 0.05 was implemented. CV and SWC values were calculated to test the reliability of the tests performed at different times. Statistical analysis was performed using the IBM SPSS statistics software (v.25, IBM, New York, NY, USA). Significant increments in BF%, 30 m sprint, and COD (left and right), and also significant decrements in CMJ and YYIRTL-1, were found after the detraining period. A long-term detraining period due to the stay at home orders has a detrimental effect on body composition, neuromuscular performances, and aerobic capacity in youth soccer players.

The purpose of this study was two-fold: (i) analyze the variations of locomotor profile, sprinting, change-of-direction (COD) and jumping performances between different youth age-groups; and (ii) test the interaction effect of athletic performance with playing positions. A cross-sectional study design was followed. A total of 124 youth soccer players from five age-groups were analyzed once in a time. Players were classified based on their typical playing position. The following measures were obtained: (i) body composition (fat mass); (ii) jump height (measured in the countermovement jump; CMJ); (iii) sprinting time at 5-, 10-, 15-, 20-, 25- and 30-m; (iv) maximal sprint speed (measured in the best split time; MSS); (v) COD asymmetry index percentage); (vi) final velocity at 30-15 Intermittent Fitness Test (V_IFT); and (vii) anaerobic speed reserve (ASR = MSS − V_IFT). A two-way ANOVA was used for establishing the interactions between age-groups and playing positions. Significant differences were found between age-groups in CMJ (p < 0.001), 5-m (p < 0.001), 10-m (p < 0.001), 15-m (p < 0.001), 20-m (p < 0.001), 25-m (p < 0.001), 30-m (p < 0.001), V_IFT (p < 0.001), ASR (p = 0.003), MSS (p < 0.001), COD (p < 0.001). Regarding variations between playing positions no significant differences were found. In conclusion, it was found that the main factor influencing changes in physical fitness was the age group while playing positions had no influence on the variations in the assessed parameters. In particular, as older the age group, as better was in jumping, sprinting, COD, and locomotor profile.

This study aimed to determine the relationships of locomotor profile (combination of a player’s maximal oxygen uptake and running economy)—measured by the final velocity attained at 30-15 Intermittent Fitness Test (V_IFT) and the anaerobic speed reserve (ASR)—with the body composition, countermovement jump (CMJ), sprinting performances, and change-of-direction (COD) ability of youth soccer players. A cross-sectional study design was implemented. A total of 124 youth soccer players from different age groups (15, 16, 17, 18, and 19 years old) were voluntarily recruited. ASR was determined based on the difference between maximal sprint speed (MSS) and V_IFT. Players were tested for the following measures: (i) body composition (body mass and body fat percentage); (ii) CMJ (height of jump); (iii) sprinting time measured at 5, 10, 15, 20, 25, and 30 m; (iv) MSS measured in the best split time (5 m) over the 30 m test; (v) COD ability (time, asymmetry index); and (vi) final velocity at 30-15 IFT (V_IFT). A Pearson product-moment correlation test was used to examine the relationships. Height and body mass exhibited large correlations with V_IFT (r = 0.835 and r = 0.699, respectively) and small correlations with ASR (r = 0.177 and r = 0.256, respectively). The CMJ was largely correlated with V_IFT (r = 0.631 to r = 0.650) while presenting small correlations with ASR (r = 0.227 to r = 0.232). Both V_IFT and ASR had moderate (r = 0.3 to r = 0.5) correlations with sprinting time at different distances and very large correlations with MSS (r = 0.797 to r = 0.866). The COD time was largely correlated with V_IFT (r = 0.765 and r = 0.775) while exhibiting small-to-moderate correlations with ASR (r = −0.279 and r = −0.301). In conclusion, it was found that locomotor performance at 30-15 V_IFT presents high levels of correlation with anthropometry and physical fitness; ASR also presents correlations with these variables, but they are smaller. This suggest that ASR is an independent variable that should be considered for inclusion in information for characterizing players’ capacities.

In contemporary research literature, inconsistencies regarding the validity and reliability of different brands of global positioning systems (GPSs) have been reported regarding the positioning of GPS units on athletes. For this reason, the present work investigates the validity and reliability of the measurements of GPS units placed at different locations. Thirty-two amateur soccer players (age: 21.18 ± 3.16 years; height: 175 ± 8.03 cm; body mass: 74.21 ± 4.85 kg) voluntarily participated in the current study. Participants were asked to complete a team sport simulation cycle (TSSC). During the tests, two GPS units were placed between the shoulder blades and on the chest of each athlete. Data from Polar Team Pro GPS units at both locations on the body, previously measured test area distance, and a radar gun (the gold standard) were compared to determine validity. The reliability of GPS units in measuring maximum speed is moderate (CV = 9.77–9.08, ICC = 0.23). The reliability of GPS units in measuring total distance is good (CV = 4.43–9.39, ICC = 0.15). The reliability of GPS units in measuring distance covered is poor (CV = 17.51–35.37). The measurements of total distance covered, and maximum speed recorded by the chest and back GPS units are not valid (Max speed = GPS chest-radar gun; R² = 0.075, GPS back-radar gun; R² = 0.106, total distance = GPS chest-1200 m; R² = 0.003, GPS back-1200 m; R² = 0.097). Consequently, it can be said that 10-Hz Polar GPS sensors have good reliability for measuring total distance when placed on the chest and moderate reliability for measuring peak speed when placed on the chest and back; however, they have poor reliability at both positions for evaluating distances at different running speeds.

The aim of this study is to determine the reliability and validity of the IVMES H-Bord eccentric hamstring strength measurement device. Thirty-eight healthy male athletes (age: 20.9 ± 2.11 years, height: 1.79 ± 0.03 m, body weight: 76.6 kg, body mass index: 22.6 ± 0.69 kg/m ² ) participated in this study. Each test protocol was applied in eccentric mode and isometric mode respectively. Between-session test-retest reliability of the IVMES H-Bord was analyzed for the intraclass correlation coefficient (ICC) with 95% coefficient intervals (CI). Validity of the IVMES H-Bord was examined for eccentric mode (NHT _ecc ), and isometric mode (NHT _iso ) using Pearson’s correlation coefficient with 95% CI and limits of agreement. Bland-Altman plots were also created to provide a representation of the agreement between two test devices. Strong correlations, good ICC values and acceptable typical errors of the estimate were observed between the NHT and isokinetic strength testing (IST) during both limbs with no proportional bias for validity analysis. In conclusion, the “IVMES H-Bord” is a reliable and valid measurement device for eccentric hamstring muscle strength and it provides important advantages for medical staff, fitness coaches and practitioners because it is portable, low cost, and field-based assessment.

The aim of this study is to compare the movement characteristics and heart rate (HR) response of hearing-impaired futsal players based on their playing positions during a simulated game. The study involved twelve players from the Turkish Deaf Men's Futsal National Team, and PlayerLoad (PL) metrics such as total PL (PLTOTAL), PL per minute (PL·min⁻¹), peak PL (PLPEAK), low to very high PL bands (PLLOW-PLVHIGH), and external load variables such as acceleration (ACC), deceleration (DEC), explosive efforts (EXPEFF), and right/left change of direction (COD-R, COD-L), were analyzed using inertial movement analysis (IMA). Additionally, the internal load metrics, including minimum, average, and maximum HR (HRMIN, HRAVE, HRMAX), percentage of HRMAX (%HRMAX) and percentage of time spent in different HR zones (HRZONE1 to HRZONE4) were continuously monitored. IMA variables and HR metrics, based on playing position, were analysed with the Kruskal-Wallis H test. Group comparisons were conducted using the Mann-Whitney U test, and Bonferroni correction was applied. As a result, PL variables change with notable distinctions between defenders and wingers. Additionally, the PLVHIGH stands out as the only significant difference when comparing wingers and pivots. Wingers generally exhibit different external load, including ACC and COD-L, compared to defenders. Additionally, differences were observed in COD-L between pivots and defenders, as well as in COD-R between pivots and wingers. In conclusion, external and internal load metrics during the simulated game vary depending on the players’ positions in hearing-impaired futsal players, highlighting the importance for coaches to consider this diversity in their athlete monitoring approaches.