Chronological age-based vs. Bio-banded friendly football tournament: Effects on physical performance and spatial exploration behaviour in 7v7 match play.

Biological age-based competitions have been suggested to mitigate maturation bias among youth football players. This study analysed the physical demands and spatial exploration behaviour when playing football matches against biological or chronological age-based opposition. One-hundred and sixteen U-13 and U-14 male regional-level football players were recruited from five Portuguese football academies. Each player completed eight games, four per condition (chronological and biological-based), on the same day. Games were played in 7 vs. 7 formats, with 20-min duration, and conformed to standard officiating and rule procedures. The following variables were considered from GPS-data in each game: distance covered, high-intensity accelerations and decelerations, body impacts, and average and peak speeds. Furthermore, average, and peak heart rates (HRpeak) and spatial exploration index were collected. Players covered significantly less distance (ES = 1.11), performed fewer decelerations (ES = 0.82), achieved lower average speeds (ES = 1.15), had fewer body impacts (ES = 0.94), and recorded lower HRpeak (ES = 0.56) in the biological age-based competition compared to the chronological-age-based. No significant differences were found between the two formats in spatial exploration. Both game formats offer distinct physical demands at the external and internal levels. Finally, practitioners can manipulate the type of opposition to get distinct physical demands to mitigate the effect of maturation bias during development.

Influence of Maturation and Determinants of Repeated-Sprint Ability in Youth Basketball Players.

ABSTRACT: Gonzalo-Skok, O, and Bishop, C. Influence of maturation and determinants of repeated-sprint ability in youth basketball players. J Strength Cond Res 38(2): 325-333, 2024-The main aims of the current study were (a) to determine the main predictors of general and specific repeated-sprint ability (RSA) tests, (b) to analyze the relationships between RSA tests and independent measures of physical performance, (c) to examine whether between-age differences exist, and (d) to assess whether maturation affects those mentioned above in young basketball players. Thirty-five young (U-14 to U-16), highly trained basketball players performed a linear sprint test (5, 10, and 25 m), an incremental running test, and 2 repeated-sprint tests (general [RSG]: 6 × 25 m; specific [RSS]: 6 × 5 + 5 m with a 45° change of direction and 20 seconds of passive recovery in both tests). Anthropometric variables were measured and used to calculate age at peak height velocity (APHV), which was used to determine maturation. The main determinants of RSA tests were aerobic performance and linear sprinting for RSS ( R2 = 0.84) and adding the percentage of body fat for RSG ( R2 = 0.94). Almost perfect relationships ( r = 0.93-0.99) were found between all RSA variables (i.e., the best [RSG b and RSS b ] and mean time [RSG m and RSS m ]). As age increased, performance in RSA was evident, as shown by improved best and mean scores. When APHV was controlled for, no significant differences were apparent in the comparison from U-14 and U-16 in 25 m, RSG b , and RSG m . By contrast, significant differences ( p < 0.05) were still evident with APHV controlled between U-14 and U-16 in 5 m, 10 m, RSS b , and RSS m . In conclusion, maturation positively affects linear sprinting and linear RSA performance, whereas specific (multidirectional) RSA seems to be related to other factors.

Seasonal Variations in Performance and Asymmetry Data for Jump and Change of Direction Abilities in Female Soccer Players.

ABSTRACT: Mainer-Pardos, E, Bishop, C, and Gonzalo-Skok, O. Seasonal variations in performance and asymmetry data for jump and change of direction abilities in female soccer players. J Strength Cond Res XX(X): 000-000, 2024-The study aimed to evaluate the progression of the percentage-based change of direction (COD) deficit (%CODD) over a competitive season, along with its correlation with performance tests and to examine the impact of the magnitude and direction of asymmetry at 4 stages of the season. Forty-seven (U-16, U-18, and U-20), highly trained, female soccer players performed unilateral vertical jumping (countermovement jump [CMJ]) and horizontal jumping (HJ), 10-m sprint, and 180° change of direction (COD180) tests. The %CODD was also calculated. Significant group and time effects (p < 0.05) were observed in CMJ, HJ, 10-m sprint, and COD180 tests, with U-20 players generally outperforming the U-18 and U-16 groups. Nonsignificant differences were reported in the %CODD between any time point or groups throughout the season. Moderate or large significant (r = 0.44-0.64; p < 0.05) relationships were found between %CODD and 10 m. The direction of asymmetry within and between tests at all time points was slight to moderate (k = -0.29 to 0.57). Notwithstanding, 51% of the players showed the best performance in the horizontal jump with the same leg throughout the season, whereas only 36% in %CODD. This study highlights the importance of developing strategies to improve %CODD depending on the player's position demands. Finally, individually monitoring the magnitude and direction of asymmetry can help practitioners monitor the effects of training and competition throughout the season.

Influence of Vertical-Oriented vs. Horizontal-Oriented Combined Strength Training in Young Basketball Players.

ABSTRACT: Sánchez-Sabaté, J, Gutiérrez, H, Marco-Contreras, LA, Younes-Egana, O, Gonzalo-Skok, O, and Piedrafita, E. Influence of vertical-oriented vs. horizontal-oriented combined strength training in young basketball players. J Strength Cond Res 38(7): 1280-1287, 2024-This study aimed to compare the effects of 8-week combined vertical-oriented vs. horizontal-oriented training interventions in basketball athletes. Eighteen highly trained U-16 basketball players participated in this study and were randomly assigned to either a combined vertical-oriented training group (CVG, n = 9) or a combined horizontal-oriented training group (CHG, n = 9). Bilateral and unilateral vertical jump height, unilateral horizontal jump distance, 5-m, 10-m, and 20-m sprint times, change-of-direction sprint times, and a limb symmetry index were among the measured performance variables. Combined strength training was performed twice a week for 8 weeks. CVG was compounded by the squat exercise (3 sets of 6-8 R at 30-45% 1 repetition maximum [1RM]), jump squats (2 sets of 6 R, at 5-12.5% body mass [BM]), and vertical jumps (3-4 sets × 6 R). CHG included the hip thrust exercise (3 sets of 6-8 R at 30-45% 1RM), sled towing sprints (2-3 R, at 5-12.5% BM), and sprints (3-4 R of 20-m). Within-group differences showed significant ( p < 0.05 and statistical power >80%) improvements in unilateral vertical jumping with the right leg after both training interventions. By contrast, only CHG improved 5-m, 10-m, and 20-m sprint times ( p < 0.05 and statistical power >80%). Significant effects were observed for CHG compared with CVG in 5-m, 10-m, and 20-m sprint times ( p < 0.05 and statistical power >80%). This study reinforces the importance of oriented-combined training based on force-vector specificity target, mainly in horizontal-oriented actions.

Injury Risk in Elite Young Male Soccer Players: A Review on the Impact of Growth, Maturation, and Workload.

ABSTRACT: Ribeiro, N, Martinho, DV, Pereira, JR, Rebelo, A, Monasterio, X, Gonzalo-Skok, O, Valente-dos-Santos, J, and Tavares, F. Injury risk in elite young male soccer players: a review on the impact of growth, maturation, and workload. J Strength Cond Res XX(X): 000-000, 2024-The long-term development of young male soccer players involves a prolonged period of significant adjustments, highlighting the importance of studying the complex interaction between dynamic variables, including workload, and inherent elements like growth and maturity. This analysis examines the intricate connections involving the development, maturity, workload, and susceptibility to injuries among adolescent male soccer players. Significantly, these connections become prominent at the peak height velocity (PHV) period, a crucial moment in maturation. Growth rates vary among individuals, and higher rates have been associated with an increased risk of injury in young soccer players, particularly during periods of rapid growth. Identifying possible risk factors and understanding the complex connections between them is crucial to developing specific methods for reducing the risk of injury. Sharing this valuable information with essential stakeholders is crucial for guaranteeing young athletes' comprehensive growth and maturation process. Furthermore, this review emphasizes the immediate need for long-term studies and thorough injury analyses to comprehend better the dynamic interactions that influence injury patterns in young male soccer players. This review will allow practitioners to better understand the main modifiable and nonmodifiable risk factors for injury and provide essential information focusing on practical strategies, facilitating more informed decision making by all stakeholders. The review aims to clarify these complexities and offer crucial insights that can assist in designing and implementing efficient strategies to reduce the risk of injury, specifically for the challenges faced during PHV and within the broader framework of long-term athletic development in young soccer.

Change of direction speed and deficit over single and multiple changes of direction: Influence of biological age in youth basketball players.

The study analysed the difference in change of direction (COD) deficit among young male basketball players of different age groups and biological ages and analysed the relationships in COD performance (time and deficit) across single and multiple CODs depending on their biological age. Fifty-four highly-trained male players (U-13 and U-17) were tested on sprinting (25-m) and COD ability over single and multiple CODs through total times and the percentage-based COD deficit (CODD). Results showed that older age groups performed significantly (ES = 0.43-2.32, p < 0.05) better in linear and COD times, especially those players with post-peak height velocity (PHV) (ES = 0.89-1.90). Controlling for age at PHV, no significant differences were found in any group or inter-limb asymmetries. Moderate relationships were found between CODD in the pool data (r = 0.36 to 0.50). All CODD and time relationships in any test (i.e., 180º COD and V-cut) were considerably lower (r= -0.27 to 0.32) across individual biological groups. The study highlights the impact of maturation on COD performance, whereas CODD seems to be not affected. Interestingly, the CODD is independent, highlighting this measurement's specific nature. Practitioners should use common distances, angles, and the number of CODs linked to biological status to create a COD profile.

Biological maturation, contextual factors, and future career in basketball: A possible interrelationship?

This study aimed to analyse the relationship between the maturational state and contextual factors with future basketball career success in Under-16 (U16) Portuguese youth preparing for the U16 European Basketball Championships. Eighty-five Under-15 (U15) and U16 male basketball players (height: 189.7 ± 6.53 cm; body mass: 81.1 ± 9.96 kg; the age of peak height velocity: 13.3 ± 0.7 y) were selected by the Portuguese national coaching staff to participate in a national team training camp in 2016, 2017, and 2018 years. A binary logistic regression was employed to identify the influence of maturation, born quartile, demographic, geographic and economic characteristics, and sport career (i.e., drop out during first season and chance of playing professionally). Early maturing players were typically classified as inside players. Training experience and predicted adult height, and type of first club were able to predict players who dropped out during their first season at senior level (both p < 0.01). No variables were able to predict who played in a professional league during their first season at senior level. Practitioners should use these data to consider how national level basketball players are identified and developed, but also keep in mind of their specific contextual factors.

Assessing Limb Dominance and Interlimb Asymmetries Over Multiple Angles During Change of Direction Speed Tests in Basketball Players.

ABSTRACT: Gonzalo-Skok, O, Dos' Santos, T, and Bishop, C. Assessing limb dominance and interlimb asymmetries over multiple angles during change of direction speed tests in basketball players. J Strength Cond Res 37(12): 2423-2430, 2023-The aims of this study were to establish whether directional dominance is displayed during change of direction (COD) tasks across various angles, to determine the angle-variation data for the asymmetry magnitude and direction, and to analyze the relationships in COD performance (completion time and COD deficit) across tasks. Twenty-four young (U-16 to U-20), highly trained male basketball players performed a 10-m linear sprint test and four 10-m COD tests (45°, 90°, 135°, and 180°) in left and right directions. Change of direction performance was determined via total times and COD deficit, and asymmetry comparisons were made between faster and slower directions and dominant leg (DL) (i.e., first step leg in lay-up) and nondominant leg (NDL). No significant differences (p > 0.05) were found between DL and NDL for any task excluding 45° COD (p < 0.05, effect size [ES] = 0.44-0.78), but significant differences were established between faster and slower sides for all angles (p < 0.05, ES = 0.70-1.28). Levels of the agreement in directional dominance during COD tasks were generally poor to slight (k = -0.14 to 0.14), excluding a fair agreement between COD45 and COD90 (k = 0.34). Correlations between COD total times and COD deficits between angles were moderate to very large (r = 0.32 to 0.81) and moderate to large (r = -0.30 to 0.55), respectively. Players displayed superior COD performance in a particular direction across various angles. This directional dominance is not necessarily consistent between angles, thus highlighting the angle-dependent nature of COD performance. Consequently, practitioners should investigate multiple angles and directions to create a COD angle profile for their athletes.

Enhancing High-Intensity Actions During a Basketball Game After a Strength Training Program With Random Recovery Times Between Sets.

ABSTRACT: Arede, J, Leite, N, Tous-Fajardo, J, Bishop, C, and Gonzalo-Skok, O. Enhancing high-intensity actions during a basketball game after a strength training program with random recovery times between sets. J Strength Cond Res 36(7): 1989-1997, 2022-To examine the effects of a strength training program with random recovery times between sets in consideration of several physical parameters, high-intensity actions, and spatial exploration index during a simulated basketball game. Twenty male basketball players (age: 19.45 ± 4.36 years) were assigned randomly to either strength training group (n = 10) or control group (n = 10). The strength training included parallel back squat and bench press exercises, twice a week for the duration of 10 weeks, with 2 blocks of 5 sets × 5 repetitions interspersed with variable passive recovery (range = 15-35 seconds) between sets, and constant passive recovery (3 minutes) between blocks with the load that maximized propulsive power output. The pre- and posttest assessments included jumping (bilateral and unilateral), change of direction, straight sprinting, and a 5-on-5 full-court situation. The external training load was assessed using the local positioning system, and the internal load was recorded with the use of individual heart rate monitors. A significant interaction effect (group × time) was observed on countermovement jump, unilateral right hops, high-intensity accelerations and decelerations, and peak accelerations and decelerations in the 5-on-5 full-court situation. Relative improvements observed and recorded in the training group on unilateral right hops, accelerations, and decelerations were correlated. Similar results were observed on 0- to 25-m sprints, high-intensity decelerations, peak accelerations, and decelerations. Strength training paired with random recovery times enhanced physical and game-related aspects in the observed basketball players.

Assessing the Reliability and Validity of Agility Testing in Team Sports: A Systematic Review.

ABSTRACT: Yepes, MM, Feliu, GM, Bishop, C, and Gonzalo-Skok, O. Assessing the reliability and validity of agility testing in team sports: A systematic review. J Strength Cond Res 36(7): 2035-2049, 2022-The aims of this systematic review were to (a) examine the reliability of the reactive agility tests and (b) analyze the discriminatory validity of the agility tests. A literature search was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). We explored PubMed, SPORTDiscus, and Cochrane Plus databases looking for articles about agility in team sports. After filtering for article relevance, only 42 studies met the inclusion criteria; 37 of which assessed the reliability of agility tests and 22 assessing their validity. Reliability showed a high intraclass correlation coefficient (ICC) in almost all studies (range 0.79-0.99) with the exception of 2 studies. In addition, other studies also assessed the reliability of decision time (ICC = 0.95), movement time (ICC = 0.92), and decision accuracy (ICC = 0.74-0.93), all of which exhibited acceptable reliability. Furthermore, these data show high discriminatory validity, with higher performance level players being faster than lower performance level players (mean = 6.4%, range = 2.1-25.3%), with a faster decision time (mean = 23.2%, range = 10.2-48.0%) with the exception of 1 study, and better decision accuracy (mean = 9.3%, range = 2.5-21.0%). Thus, it can be concluded that reactive agility tests show good reliability and discriminatory validity. However, most agility tests occur in simple contexts whereby only 2 possible responses are possible. Therefore, future research should consider creating more specific and complex environments that challenge the cognitive process of high-level athletes.

Effects of 8 Weeks of Isoinertial vs. Cable-Resistance Training on Motor Skills Performance and Interlimb Asymmetries.

ABSTRACT: Madruga-Parera, M, Bishop, C, Fort-Vanmeerhaeghe, A, Beato, M, Gonzalo-Skok, O, and Romero-Rodríguez, D. Effects of 8-weeks of Isoinertial vs. Cable-resistance Training on Motor Skills Performance and Interlimb Asymmetries. J Strength Cond Res 36(5): 1200-1208, 2022-The aim of this study was to compare the effects of 8 weeks of isoinertial vs. cable-resistance training on motor skills performance and interlimb asymmetries in handball players. Thirty-four young male handball players (mean ± SD: age: 15.96 ± 1.39 years; height: 1.74 ± 0.73 m; body mass: 70.5 ± 13.3 kg) participated in a randomized trial. The players performed an isoinertial program using a portable flywheel device or a cable-resistance device. Performance variations and interlimb asymmetries in dominant (D) and nondominant (ND) limb means of the unilateral countermovement jump (UCMJ), the unilateral lateral jump (ULJ), the unilateral broad jump (UBJ), handball throwing (HT), change of direction speed (COD180), the linear sprint (S20), the V-CUT test, and the repeated change of direction (RCOD) were recorded. Significant interactions were shown in RCODD (p = 0.003, ηp = 0.25), HT (p = 0.015, ηp = 0.17) and UCMJASY (p = 0.037, ηp = 0.13). Post-hoc testing revealed higher effect sizes in the isoinertial group (p < 0.05) for the performance improvements in RCODD (-1.35 large vs. -0.22, small) and HT (0.88, moderate vs. 0.00, trivial), in addition to interlimb asymmetry reductions in UCMJASY (-0.70 moderate vs. -0.32, small). Significant main effects of time in COD180, RCOD, UCMJ, and UBJ for both limbs (p < 0.05, from moderate to large effect size), and in ULJND (p < 0.001, large), UCMJASY (p < 0.001, moderate), V-CUT (p = 0.014, small), and HT (p = 0.015, large) were found. The effect sizes revealed greater magnitudes in the isoinertial group. In conclusion, although both resistance training programs improve players' to physical performance and reduce interlimb asymmetries, greater improvements were recorded with the isoinertial resistance training than with the cable-resistance methodology.

Nonspecific Resistance Training and Swimming Performance: Strength or Power? A Systematic Review.

ABSTRACT: Muniz-Pardos, B, Gomez-Bruton, A, Matute-Llorente, A, Gonzalez-Aguero, A, Gomez-Cabello, A, Gonzalo-Skok, O, Casajus, JA, and Vicente-Rodriguez, G. Nonspecific resistance training and swimming performance: Strength or power? A systematic review. J Strength Cond Res 36(4): 1162-1170, 2022-The purpose of this systematic review was to determine the type of nonspecific resistance intervention that is more effective to enhance swimming performance and to determine the nonspecific strength- or power-related variable that better predicts swimming performance. A search was conducted on PubMed, Cochrane Plus, and SportDiscus up to June 2018. Studies were distributed into 4 categories: dry-land strength (DLS), dry-land power (DLP), combination of training methods, and strength and power in start performance. From 1,844 citations, 33 met the inclusion criteria. Cross-sectional DLS studies showed positive associations between swimming performance and DLS development (especially through upper-body isometric assessments), although the efficacy of DLS training interventions remains unclear. Dry-land power training (principally through plyometrics) was a proficient, nonspecific method to enhance swimming block start performance (SBS; the start phase off the block and during the first 5-15 m), and jump assessment was the best predictor of SBS. Some pioneering nonspecific practices such as the acute exposure to high altitude or the maintenance of a high core temperature during the transition phase before competition seem to improve performance, although more research is required to confirm their efficacy. Further high-quality intervention studies are required to clarify the effect of DLP training on sprint swimming performance.

Relationship Between Interlimb Asymmetries and Speed and Change of Direction Speed in Youth Handball Players.

ABSTRACT: Madruga-Parera, M, Bishop, C, Beato, M, Fort-Vanmeerhaeghe, A, Gonzalo-Skok, O, and Romero-Rodríguez, D. Relationship between inter-limb asymmetries and speed and change of direction speed in youth handball players. J Strength Cond Res 35(12): 3482-3490, 2021-The aims of the present study were to quantify interlimb asymmetry from jumping, change of direction speed (CODS), and iso-inertial tests and to establish the association between those asymmetry scores and performance during speed and CODS tests in youth handball athletes. Twenty-six youth handball players (age: 16.2 ± 0.9 years) volunteered to participate in this study and performed single-leg countermovement jumps, single-leg broad jumps, single-leg lateral jumps, CODS tests at 180° (CODS180) and 90° (CODS90), change of direction actions with iso-inertial overload (crossover step [CRO] and lateral shuffle step), and a 20-m sprint test. Excellent intraclass correlation coefficient (ICC) values were found for all tests (ICC = 0.96-1.00) with the exception of the dominant limb during the CODS90 test (ICC = 0.69). Interlimb asymmetry scores ranged from 3.66 to 12.67%. Iso-inertial asymmetry values were higher than those found during jumping tasks (9.8-12.7% vs. 3.66-8.76%). Spearman's r correlations showed significant relationships between CRO asymmetry and CODS90 performance on both limbs (r = 0.48-0.51; p < 0.05) and CODS180 (r = 0.41-0.51; p < 0.05) and a sprint test (r = 0.46; p < 0.05). These results show the test-specific nature of asymmetries in youth handball players, with iso-inertial device and CODS deficit presenting the greatest magnitude of asymmetries. Furthermore, interlimb differences during iso-inertial device (CRO) were associated with reduced CODS and sprint performance. These results suggest that the use of iso-inertial devices for the detection of interlimb asymmetry may be more effective than the total time during traditional CODS tests and that larger imbalances are associated with reduced athletic performance in youth handball players.

Acute Effect of Repeated Sprints on Interlimb Asymmetries During Unilateral Jumping.

ABSTRACT: Bishop, C, McAuley, W, Read, P, Gonzalo-Skok, O, Lake, J, and Turner, A. Acute effect of repeated sprints on interlimb asymmetries during unilateral jumping. J Strength Cond Res 35(8): 2127-2132, 2021-The aim of this study was to investigate the effects of multiple repeated sprints on unilateral jump performance and interlimb asymmetries. Eighteen recreationally active men performed 3 single-leg countermovement jumps (SLCMJ) as baseline data. The repeated sprint protocol was 6 × 40 m with 20 seconds of passive rest between each sprint. This protocol was conducted 4 times, each set separated by 4 minutes of rest. Within that rest period, subjects performed one SLCMJ on each limb after 2 minutes of rest. A 1-way analysis of variance showed significant reductions (p < 0.05; effect size [ES] = -0.52 to -0.99) in jump height on both limbs after each set relative to baseline. Interlimb asymmetries increased at each time point and ranged from 7.62 to 14.67%, with significant increases in asymmetry seen after sets 3 (p = 0.046) and 4 (p = 0.002). Significant increases in sprint time were shown between sprints 1 and 6 in each set (p ≤ 0.01). A fatigue index (%) was also calculated and showed an exponential increase from 5.74% (set 1) to 13.50% (set 4), with significant differences between all sets (p < 0.001) with the exception of sets 3 and 4. Results from this study show that a 6 × 40-m repeated sprint protocol is a sufficient dose for implementing acute fatigue in recreationally active subjects. This was manifested by reductions in jump height at all time points and jump height asymmetries after the third and fourth sets. These findings indicate that jump height from unilateral jump testing may be a useful metric to use during the monitoring process in recreationally trained athletes.

Predicting Loading Intensity Measuring Velocity in Barbell Hip Thrust Exercise.

ABSTRACT: de Hoyo, M, Núñez, FJ, Sañudo, B, Gonzalo-Skok, O, Muñoz-López, A, Romero-Boza, S, Otero-Esquina, C, Sánchez, H, and Nimphius, S. Predicting loading intensity measuring velocity in barbell hip thrust exercise. J Strength Cond Res 35(8): 2075-2081, 2021-The barbell hip thrust is an increasingly used exercise to target the hip extensors. Direct and indirect measurement of 1 repetition maximum (1RM) to determine the relative load of each exercise is time-consuming; therefore, practitioners may be more in favor of monitoring velocity and determining relative load through velocity-based prediction models for an exercise. This study aimed to assess the relationship between mean velocity (MV) and mean propulsive velocity (MPV) at different relative training loads (%1RM) in the barbell hip thrust exercise. One hundred two male sport science students performed an incremental 1RM testing protocol for the barbell hip thrust exercise, and a linear position transducer measured MV and MPV of the barbell. The 1RM was reached at 0.25 ± 0.03 m·s-1, and the regression model generated to estimate a relative load showed an acceptable standard error of estimate (7.01 ± 1.05% 1RM and 7.36 ± 1.05% 1RM for MV and MPV, respectively) with a very large explained variance (R2 = 0.94). These results may have important practical applications for the prescription and monitoring of the accessory exercise of the hip thrust for monitoring training load and predicting 1RM without undertaking a RM test.

Global Positioning System Analysis of Physical Demands in Small and Large-Sided Games with Floaters and Official Matches in the Process of Return to Play in High Level Soccer Players.

The aim of this study was twofold: (i) to analyze the physical demands in the return to play (RTP) process of high-level soccer players in the role of floater in different soccer sided games (SGs) formats (i.e., 4vs4 + 2 and 8vs8 + 1); and (ii) to analyze the differences in physical demands encountered by regular and floater players among the SGs formats and official matches by means of global positioning system technology (GPS APEX pod, North Ireland) was used. Twenty-six highly trained, male soccer players (U16 years) participated in this investigation. Players were classified into two groups: 23 regular and 3 floater players, a total of eight SGs were analyzed, which involved the recording of 80 observations of regular and floater players. Match-play players showed most likely-probable differences in distance covered at high-intensity per minute (D > 14.4/min), at high-speed running per minute (D > 21/min), and peak velocity (Vpeak) in comparison to floaters in the 8vs8 + 1 LSG (large-side-games), and presented most likely differences in accelerations >2/min in comparison to match-play players. Therefore, the use of floaters during the last phase of the RTP (return to play) seems to be a useful strategy for progressive reintroduction into specific training (1) floater in the 4vs4 + 2 SSG; (2) floater in the 8vs8 + 1 LSG; (3) regular player in the 4vs4 + 2 SSG; and (4) regular player in the 8vs8 + 1 LSG before starting full trainings and returning to competition.

A Comparison of Bilateral vs. Unilateral-Biased Strength and Power Training Interventions on Measures of Physical Performance in Elite Youth Soccer Players.

Stern, D, Gonzalo-Skok, O, Loturco, I, Turner, A, and Bishop, C. A comparison of bilateral vs. unilateral-biased strength and power training interventions on measures of physical performance in elite youth soccer players. J Strength Cond Res 34(8): 2105-2111, 2020-The aim of the present study was to compare the effects of bilateral and unilateral-biased strength and power training programs on measures of physical performance in male youth soccer players. Twenty-three elite youth players (age: 17.6 ± 1.2 years) were randomly assigned to either a unilateral (n = 11) or a bilateral (n = 12) group, who completed a strength and power intervention, twice per week for 6 weeks. The unilateral group completed rear foot elevated split squats (RFESS), single-leg countermovement jumps (SLCMJs), single-leg drop jumps (SLDJs), and single-leg broad jumps (SLBJs). The bilateral group intervention performed back squats, CMJs, drop jumps (DJ), and broad jumps (BJ). A 2 × 2 repeated measures analysis of variance showed no between-group differences. However, within-group differences were evident. The bilateral training group showed significant (p < 0.05) improvements in back squat strength (d = 1.27; %Δ = 26.01), RFESS strength (d = 1.64; %Δ = 23.34), BJ (d = 0.76; %Δ = 5.12), 10-m (d = -1.17; %Δ = 4.29), and 30-m (d = -0.88; %Δ = 2.10) performance. The unilateral group showed significant (p < 0.05) improvements in RFESS strength (d = 1.40; %Δ = 33.29), SLCMJ on the left leg (d = 0.76; %Δ = 9.84), SLBJ on the left leg (d = 0.97; %Δ = 6.50), 10 m (d = -1.50; %Δ = 5.20), and 505 on the right leg (d = -0.78; %Δ = 2.80). Standardized mean differences showed that bilateral training favored improvements in back squat strength and unilateral training favored improvements in RFESS strength, SLDJ on the right leg and 505 on the right leg. These results show that although both training interventions demonstrated trivial-to-large improvements in physical performance, the notion of training specificity was evident with unilateral training showing greater improvements in unilateral test measures.

Eccentric-concentric Ratio: A Key Factor for Defining Strength Training in Soccer.

The aims of this study were to analyse the effect of chronic strength training over concentric power (CON), eccentric power (ECC), ECC/CON ratio, and 20 m linear sprint performance in elite young soccer players. Twenty young elite Spanish soccer players were assigned to an experimental group (CPG) which performed a front-step exercise using a conical pulley, 2-3 sets of 6 repetitions each leg, during 9 weeks (CPG, n=10) in addition to its usual strength training, or to a control group (CG, n=10). The improvements in the ECC mean power (36%, ES=1.61), and ECC / CON ratio (17%, ES=1.77) were substantially greater in the CPG than in the CG while the CON mean power (16%, ES=0.83) was substantially greater in the CG than in the CPG. The sprinting time for 10 m (2.8%, ES=0.78) and the 10 m flying time between 10-20 m (1.72%, ES=0.41) were substantially enhanced in CPG and CG respectively. To be efficient when defining a functional strength training and performance increments using an inertial device, the mean power output need to be measured during the CON and ECC phases and an analysis of the ECC / CON ratio should be included.

A Repeated Power Training Enhances Fatigue Resistance While Reducing Intraset Fluctuations.

Oliver, GS, Julio, TF, Moras, G, José Luis, AS, and Alberto, MV. A repeated power training enhances fatigue resistance while reducing intraset fluctuations. J Strength Cond Res 33(10): 2711-2721, 2019-The present study analyzed the effects of adding upper-body repeated power ability (RPA) training to habitual strength training sessions. Twenty young elite male basketball players were randomly allocated into a control group (CON, n = 10) or repeated power group (RPG, n = 10) and evaluated by 1 repetition maximum (1RM), incremental load, and RPA tests in the bench press exercise before and after a 7-week period and a 4-week cessation period. Repeated power group performed 1-3 blocks of 5 sets of 5 repetitions using the load that maximized power output with 30 seconds and 3 minute of passive recovery between sets and blocks, respectively. Between-group analysis showed substantial greater improvements in RPG compared with CON in: best set (APB), last set (APL), mean power over 5 sets (APM), percentage of decrement, fluctuation decrease during APL and RPA index (APLpost/APBpre) during the RPA test (effect size [ES] = 0.64-1.86), and 1RM (ES = 0.48) and average power at 80% of 1RM (ES = 1.11) in the incremental load test. The improvements of APB and APM were almost perfectly correlated. In conclusion, RPA training represents an effective method to mainly improve fatigue resistance together with the novel finding of a better consistency in performance (measured as reduced intraset power fluctuations) at the end of a dynamic repeated effort.

Effects of Repeated Sprints With Changes of Direction on Youth Soccer Player's Performance: Impact of Initial Fitness Level.

Sanchez-Sanchez, J, Ramirez-Campillo, R, Petisco, C, Gonzalo-Skok, O, Rodriguez-Fernandez, A, Miñano, J, and Nakamura, FY. Effects of repeated sprints with changes of direction on youth soccer player's performance: impact of initial fitness level. J Strength Cond Res 33(10): 2753-2759, 2019-The aim of this study was to assess the effect of an 8-week repeated sprint with change of direction (RS-COD) training program on RS, intermittent endurance, and change of direction performance in youth soccer players with different aerobic fitness levels. Athletes were randomly assigned into a soccer-only (n = 9; age, 14.9 ± 0.4 years) and soccer plus RS-COD training programs for players with high (n = 10; age, 14.4 ± 0.5 years) and low (n = 10; age, 14.4 ± 0.5 years) aerobic fitness. Repeated sprint with change of direction was completed 2 days per week, involving 3 sets of ten 18-m sprints with 2 changes of direction of 90°. The soccer-only group achieved greater improvements in intermittent endurance (effect size [ES] = 0.61) and sprint decrement during RS ability test (ES = 0.77) compared with the RS-COD groups (ES = 0.19-0.24; ES = -0.27 to 0.02; respectively). Repeated sprint with change of direction training improved RS (ES = 0.16-0.38) and change of direction (ES = 0.48) performance in high but not in low-fitness players (ES = 0.03-0.13; ES = 0.16; respectively). Moreover, improvements in RS and change of direction were (possibly) greater in high compared with low fitness and soccer-only trained players (possibly to very likely). In conclusion, although RS-COD training may positively affect RS and change of direction performance, its effects may vary according to the initial aerobic fitness of youth soccer players, with trivial effect on intermittent endurance in high-aerobic fitness players and possible beneficial effect on low-aerobic fitness players.