Relationship between relative age measured through decimal age, physical variables and anthropometry in elite youth soccer players.

INTRODUCTION: Age differences between athletes born in the same year, as well as an over-representation of older players, are known as the Relative Age Effect (RAE). Players born at the beginning of the selection year have a physical and anthropometric advantage over their younger peers. Experts keep looking for new prediction variables for talent identification. OBJECTIVES: The aim of the study is to correlate anthropometric, strength and power variables with the relative age (RA) and the level of the teams in which players played in each age category. METHODS: All players (N = 366) from an elite soccer academy of a Spanish club volunteered to participate in the study (U23-U10). RESULTS: There was a significant correlation between the RA of the players and the level of the team in which they played in each age category but no correlation between trimester of birth and level of the team. We found significant correlations between the players' physical capacities, anthropometry, RA and the level of the team in which they played for the same age category, mainly from U16 to U10. U23 did not show any correlation between RA and physical or anthropometric variables. CONCLUSION: Coaches should be cautious of choosing players based only on anthropometric or physical attributes.

Stable vs. variable eccentric load. Do they induce different training and physical performance outcomes?

Since most movements on the field require athletes to produce forces in variable and unpredictable contexts, the use of training programs based on identical repetitions of an exercise may not be optimal for movement transference. Therefore, the aim of this study was to analyse the effects of unexpected eccentric load variability during resistance training in team sport players. Sixty-three men were randomly allocated to two experimental groups (Variable (VTG) and stable (STG) training group) and control group: (CG) volunteered to participate in this study. Experimental groups trained with the same average load of half-squat exercise twice a week for six weeks using rotary inertial devices (RIDs) with (VTG) and without (STG) an unexpected variability of the load. The squat force was measured for every session with force plates. Counter-movement jump (CMJ), sprint, and change of direction performances were measured pre and post-test. CMJ performance improved for VTG (p = .014; ES = 0.7) and STG (p = .005; ES = 0.79) but not for CG. Exposure to high eccentric forces with RIDs lead athletes to improve physical performance in the trained force vector but, since RIDs induce in high levels of variability per se, increasing the level of variability of the exercise will not add benefits to physical performance and training outcomes.HIGHLIGHTSThe relevance of the study is to analyse if increasing the variability of the load will improve the athlete output to different physical performance tests.The exposure to eccentric overload with RIDs during the squat exercise allows to greater CMJ height improvements than those seen in the literature with RIDs without overloading the eccentric contraction.RIDs induce in high level of variability per se. Therefore, increasing the level of variability of the exercise will not add benefits to physical performance and training outcomes.

The Flywheel Device Shaft Shape Determines Force and Velocity Profiles in The Half Squat Exercise.

Flywheel resistance training devices can be classified by their shaft shape. The objective of this study was to analyze whether using two flywheel resistance training devices shaft shapes can influence force and velocity production, regardless of the inertia used. Thirty-nine (n = 39) healthy active men participated in this study. They were randomized to perform 3 sets of 7 repetitions at maximal concentric voluntary execution, followed by a break in the last third of the eccentric phase in the half squat exercise. A progressive rotational inertial setting of 0.11, 0.22, and 0.33 kg·m2 was used. Force- and velocity-time profiles were captured using two force plates and a synchronized linear encoder. Statistical parametric mapping was used to compare biomechanical output between the flywheel devices. The level of significance was set at p < 0.05. Force application was significantly higher in the horizontal cylinder-shaped device for the three moments of inertia used in the eccentric phase (p < 0.001). In the concentric phase, force application was significantly higher in the horizontal cylinder-shaped device in 0.11 (p < 0.001) and 0.22 kg·m2 (p < 0.001). The resultant speed was higher in the vertical cone-shaped device in the concentric phase and the eccentric phase for the three moments of inertia (p < 0.001). In conclusion, the flywheel shaft type determines the mechanical output of the half squat exercise, regardless of the moment of inertia used. While a horizontal cylinder-shaped device is more suitable to achieve higher forces, especially in the eccentric phase, a vertical cone-shaped device can be used to achieve higher speeds during the execution of the exercise.

Low-Velocity Loss Induces Similar Strength Gains to Moderate-Velocity Loss During Resistance Training.

ABSTRACT: Galiano, C, Pareja-Blanco, F, Hidalgo de Mora, J, and Sáez de Villarreal, E. Low-velocity loss induces similar strength gains to moderate-velocity loss during resistance training. J Strength Cond Res 36(2): 340-345, 2022-This study aimed to analyze the effects of 2 velocity-based resistance training (VBT) programs that used the same relative loading but differed in the velocity loss (VL) throughout the set: 5% (VL5) vs. 20% (VL20). Twenty-eight physically active men (age: 23.0 ± 3.2 years; height: 175.8 ± 4.7 cm; body mass: 73.8 ± 10.8 kg) were randomly assigned to 2 groups: VL5 (n = 15) or VL20 (n = 13). Subjects followed a 7-week (14 sessions) VBT program using the squat exercise while repetition velocity was monitored. The following variables were assessed at pretest and posttest: estimated 1-repetition maximum (1RM); average velocity attained for all absolute loads common to pretest and posttest (AV); average velocity for those loads that were moved faster than 1 m·s-1 (AV > 1); average velocity for those loads that were moved slower than 1 m·s-1 (AV < 1); countermovement jump (CMJ); and 20-m running sprint time (T20). T20 and CMJ height were assessed before each training session to analyze their evolution during the training program. The VL5 group executed only 32.6% of the total repetitions performed by the VL20 group (156.9 ± 25.0 vs. 480.5 ± 162.0 rep). Both groups improved significantly (p < 0.01) in all variables analyzed (1RM, AV, AV > 1, AV < 1, CMJ, and T20) from pretest to posttest, with no significant differences between them. Therefore, a low VL (5%) induced similar gains in strength, jump, and sprint performance to a moderate VL of 20%, despite VL5 performing only 32.6% of the repetitions achieved by the VL20 group.

Variability in the Application of Eccentric Force Using Different Rotary Inertia Devices May Influence the Treatment of Tendinopathy.

High intraset variability has been considered as a potential aid in the treatment of tendinopathy by producing forces in variable and unpredictable contexts that allow the athlete to return to sport pain free. The aim of this study was to compare the intraset variability in force profiles between different rotational inertia devices (RIDs) during concentric and eccentric (ECC) phases of movement and between different moments of inertia. Thirty-nine men performed a half-squat incremental test on 2 different RIDs: a horizontal cylinder and a vertical cone-shaped axis. Intraset variabilities in vertical force and velocity were analyzed using average coefficients of variation. RID squat exercise produced force intraset variability. The ECC phase of the movement showed more intraset variability in force output than the concentric phase. ECC vertical cone-shaped shaft showed a higher intraset variability in force than ECC horizontal cylinder-shaped shaft. This study demonstrated that using an RID to provide resistance in squat training of athletes produced a high intraset variability in the application of force.

Is possible an eccentric overload in a rotary inertia device? Comparison of force profile in a cylinder-shaped and a cone-shaped axis devices.

The aims of this study were to compare the force profile of using a horizontal cylinder-shaped axis or a vertical cone-shaped axis to provide resistance in rotary inertia devices, and to report the evolution of kinetic and kinematic variables in experienced athletes during a half-squat exercise. Twenty-two healthy active men participated in the assessment of time, peak velocity, peak force, time to reach the peak force, average force, impulse, and range of movement, during a half-squat incremental test performed on conical inertial device (CP) and on cylinder inertial device (YY). The analysis showed that YY during CON-ECC phased generates substantial higher peak_force, mean_force, impulse, time, and a lower peak_velocity, than CP. We never obtained eccentric overload for peak_force or mean_force. CP offers less resistance to accelerate-decelerate the movement with respect to YY, we need checking whether eccentric overload it is being produced, and the impulse was the only kinetic variable that was able to discriminate between the inertias and devices.