Oliver Gonzalo-Skok

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• PhD
• Associate Professor at Loyola University Andalusia

The current study aimed to assess the effect of including the lateral-step or sidestep exercise with elastic bands on multidirectional speed abilities (linear, change of direction, and curve sprinting) and navicular drop and to know the impact of navicular drop changes on multidirectional sprinting changes in young male football players. Thirty-two...

The study analyzed whether maturation affects young basketball players’ strength training and detraining adaptations. Thirty-five youth male basketballers (U-13 to U-15) performed eight weeks of strength training twice weekly, followed by eight weeks without strength training, maintaining their basketball practices. Changes in performance were asse...

Purpose: The present study analyzed the effects of a maximal-power-endurance (MPE) versus a repeated-power-ability (RPA) training program on different strength, power, and repeated-power measurements in a short- and long-term training period and the relationships between changes in all variables. Methods: Twenty-two young highly trained male bas...

Background: the purpose of this study was to analyze the reliability of a field-based fitness test battery in young trained football players, according to biological age. Methods: 197 young trained football players (12–19 years old) participated in the study. We measured anthropometric measurements (i.e., height, sitting height, length leg, and bod...

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, matu...

Purpose: Different studies indicate that female players in team sports, such as soccer, tend to have a lower change of direction deficit (CODD) than their male counterparts and that players who performed better in linear and curved sprints tended to have a worse CODD, suggesting that maximum speed does not equate to a faster change of direction (CO...

Physical performance is often affected by maturation in young athletes and provides an interesting challenge to optimize performance. The present study analyzed whether maturation affects directional dominance, chronological age, body mass, and biological age predictors, and assessed between chronological or biological age group differences in youn...

Background High-intensity actions have gained increasing significance in contemporary football. Among these actions, the spotlight shines on the enhancement of change of direction (COD) speed. Several training methods have been employed to elevate this skill in football players, with plyometric training (PT) being one of the viable approaches. The...

Background Contracting skeletal muscle produces reactive oxygen species (ROS) originating from both mitochondrial and cytosolic sources. The use of non-specific antioxidants, such as vitamins C and E, during exercise has produced inconsistent results in terms of exercise performance. Consequently, the effects of the mitochondrial-targeted coenzyme...

The present study aimed to determine whether neuromuscular fatigue monitored through countermovement jump height was a reliable and helpful marker for monitoring acute (session) and chronic (between sessions/periods of the season) fatigue throughout an entire basketball season. A longitudinal observational study analyzed the neuromuscular performan...

Aims Flywheel resistance training has become more integrated within resistance training programs in a variety of sports due to the neuromuscular, strength, and task-specific enhancements reported with this training. This paper aimed to present the consensus reached by internationally recognized experts during a meeting on current definitions and gu...

The study aimed to evaluate the progression of the percentage-based change of direction 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 four stages of the season. Forty-seven (U-16, U-18, and U-20) highly-trained female soccer play...

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...

Studies show that although female soccer players often have shorter change of direction (COD) deficits than males, indicating different biomechanical profiles, there is a lack of research on the impact of physical metrics on COD performance in females. The purpose of this work was to analyse whether performance metrics based on speed and jumping co...

Studies show that although female soccer players often have shorter change of direction (COD) deficits than males, indicating different biomechanical profiles, there is lack of research on the impact of physical metrics on COD performance in females. The aim of this study was to analyze whether performance metrics based on speed, and jumping could...

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...

The aims of this study were to determine the feasibility of the injury prevention program (IPP), to examine the reliability of perceptual response to an IPP and to analyze the acute effects of both external and internal demands of in-court training sessions in the IPP. Twelve young basketball players participated in a national team (NT) training ca...

This study aimed to analyze 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 o...

Background Flywheel resistance training has become more integrated within resistance training programs in a variety of sports due to the neuromuscular, strength, and task-specific enhancements reported with this training. Objective This paper aimed to present the consensus reached by internationally recognized experts during a meeting on current d...

Purpose: To compare the effects of unilateral flywheel training (FT), using a rotational conical pulley, including multidirectional movements with either preplanned or random unanticipated/unexpected executions on functional performance in football players. Methods: A total of 32 young male football players were randomly assigned to an FT program i...

This study aimed to test whether agility and change of direction speed (COD) are independent capacities using the same movement pattern (1) in terms of the completion time and (2) the entropy. Seventeen semi-professional female football players participated in the study. The agility task consisted of a Y-shaped (45° COD) task with three possible ex...

Background: Currently, the scientific evidence available on plyometric training in young basketball players is limited. Objectives: The aim of this study was to analyze the effects produced by plyometric training over a period of 8 weeks, with a frequency of two weekly training sessions, combining vertical and horizontal force vectors. Methods: The...

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 tes...

Background: Currently, the scientific evidence available on plyometric training in young basketball players is limited. Objectives: The aim of this study was to analyze the effects produced by plyometric training over a period of 8 weeks, with a frequency of two weekly training sessions, combining vertical and horizontal force vectors. Methods: The...

The main aims of the current study were 1) to determine the main predictors of general and specific repeated-sprint ability (RSA) tests, 2) to analyze the relationships between RSA tests and independent measures of physical performance, 3) to examine whether between-age differences exist, and 4) to assess if maturation affects those mentioned above...

The aims of this study were to: (1) analyze time and movement variability in a football (soccer) agility task performed with or without ball, both in the following situations a) reacting to the movement of two players with a single exit gate (R1), b) reacting to the movement of one player with two possible exit gates (R2) and c) not reacting to a s...

Purpose: Change of direction while dribbling appears to be of interest for on-court performance in basketball. The study aim was to assess the validity and reliability of the V-cut dribbling test (VcutBk) in young basketball players. Methods: Ninety-two young basketball players from 8 to 21 years old (74% male) were classified in relation to pea...

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 analyse the relationships in COD performance (completion time and COD deficit) across tasks. Twenty-four young (U-16...

The first division of Spanish professional football (LaLiga) was suspended for 12 weeks as part of the policies enforced by health authorities during the first wave of COVID-19. During this period, players were confined to home for 8 weeks, followed by a club-based retraining period of 4 weeks. Afterwards, LaLiga’s teams completed 11 matches, with...

This study analyzed the effects of two different training programs on functional performance and inter-limb asymmetries in basketball players. Twenty-four elite youth basketball players were randomly assigned to a training program including variable unilateral horizontal movements (VUH, n = 12) or unilateral lateral movements (VUL, n = 12). Eccentr...

The main aim of this chapter is to review the role of strength training in reducing the risk of sports injuries, which are a major concern in any sport. As strength training has been recognized as one of the best strategies to minimize the risk of injury, we will focus on the current evidence-based information and how we can directly apply this to...

Background: This study compared the effects of performing different unilateral combined training interventions on diverse vertical and horizontal jumping performance parameters, change of direction, concentric and eccentric mean power, and their associated inter-limb asymmetries in young soccer players. Methods: Forty-seven young male soccer pla...

Background Several studies have observed the contribution of chronological age, biological maturation, and anthropometric characteristics to sprinting performance in young soccer players. Nevertheless, there are no studies that have analysed the contribution of these characteristics to running speed qualities in adolescent female soccer players. O...

Background: The present study compared the effects of performing the lateral squat exercise in three different formats from eccentric overload training on concentric/eccentric peak/mean power and inter-limb asymmetries in young soccer players. Methods: Forty-five young male (U-17) soccer players were distributed into three groups. Two groups per...

The association between asymmetries in jump and change of direction (COD)with physical performance in several sports show inconclusive results. The purposes of this study were to: (1) measure inter-limb asymmetries in 3 distinct groups in adolescent female soccer players and, (2) to determine the association between inter-limb asymmetries and physi...

To examine the effects of a strength training program with random recovery times between sets in consideration of several physical parameters, high-intensity actions (HIA), and spatial exploration index during a simulated basketball game. Twenty male basketball players (age: 19.45 ± 4.36 years) were assigned randomly, either to strength training gr...

The aim of this study was to compare the effects of different warm-up conditioning intensities on the physical fitness (i.e., post-activation potentiation -PAP), of professional male field soccer players. Athletes (n = 10; age: 21.6 � 3.2 years) completed a control warm-up and warm-ups aimed to induce PAP, in random and counterbalanced order. After...

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 f...

The aim of this study was to analyse the acute effects of a concentric exercise and two different eccentric overload exercises (EOEs) on blood markers of muscle damage (i.e. creatine kinase [CK], lactate dehydrogenase [LDH], myoglobin [Myo], and malondialdehyde [MDA]) and muscle contractile properties. Ten healthy, young (27 ± 1.5 years, 179 ± 6 cm...

Os objetivos deste estudo foram (i) avaliar a perceção subjetiva de esforço de um programa de prevenção de lesões e, (ii) analisar os efeitos agudos do programa de prevenção de lesões na carga externa e interna durante as sessões de treino de campo. Treze jovens basquetebolistas participaram no estágio na seleção nacional de sub-16, num total de 12...

This study aims (a) to assess and compare the acute mechanical, physiological, and perceptual demands induced by a lower and upper body repeated power ability (RPA) protocols, and (b) to examine how the somatic maturation could predict training response in RPA. Thirteen young male basketball players (chronological age = 15.2 ± 1.1 years; height = 1...

Background: This study aimed to analyze and compare the effects of two different resistance training programs. Methods: Fourteen under-17 youth female basketball players were randomly assigned to repetitions in reserve (RIR, n = 7) or maximum effort (RM, n = 7) resistance training programs. The programs consisted of 3-4 sets of 4 exercises x 7-1...

Background: The aim of this study was to analyse the effects of an inter-repetition variable rotational flywheel training program (Variable) over standard rotational flywheel training (Standard). Methods: Twenty-four youth female team-sports players were randomly assigned to both training groups (Variable, n = 12; Standard, n = 12), which consis...

The aims of this systematic review were to: 1) examine the reliability of the reactive agility tests and, 2) analyse 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 database...

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...

The aim of the study was to investigate the relationships between countermovement jump (CMJ) height and inertial power in squat and sprint variables with change of direction (COD) performance. Fifty young healthy active males participated in the study. To determine these relationships, we carried out a 10-m linear sprint test (T 10 m), vertical jum...

INTRODUCTION: This review aimed: 1) to describe the most common tests used for assessing change of direction (COD) performance; 2) to detail the reliability of current COD tests; 3) to provide an overview of current intervention strategies used to improve COD performance in adolescent female soccer players. EVIDENCE ACQUISITION: A computerized sear...

Actually, there is scarce literature looking for the relationship between inter-limb asymmetries and performance in youth elite team sports. The main purpose of this cross-sectional study was to examine the relationships between inter-limb asymmetries and physical performance in youth elite team-sports players. A secondary objective was to evaluate...

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 XX(X): 000-000, 2020-The purpose of this systematic review was to determine the type...

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 XX(X): 000-000, 2020-The aim of this study was to compare the effects of 8 weeks of isoinertial vs. cable-...

Purpose: The aim of this study was to analyze the relationship between physical preparation, training sessions (TS) and friendly matches’ (FM) demands, and playing status during European Championship (EC). Method: Twelve under-16 (U-16) basketball players performed physical (jumping, agility, aerobic fitness, and lower limb asymmetry index [ASI]) t...

Purpose: To examine the effects of an 8-week combined strength and power training intervention on physical performance and interlimb asymmetries in adolescent female soccer players. Methods: Thirty-seven adolescent female soccer players (age 16.1 [1.1] y) were randomly assigned to a control group (n = 18) or experimental group (n = 19). The expe...

The aim of this study was to assess the effect of an 8-week repeated sprint with change of direction training program on repeated sprint, intermittent endurance and change of direction performance in youth soccer players with different aerobic fitness level. Athletes were randomly assigned into a soccer-only (n=9; age, 14.9±0.4 yr) and soccer plus...

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 conic...

Muniz-Pardos, B, Gomez-Bruton, A, Matute-Llorente, A, Gonzalez-Aguero, A, Gomez-Cabello, A, Gonzalo-Skok, O, Casajus, JA, and Vicente-Rodriguez, G. Swim-specific resistance training: A systematic review. J Strength Cond Res XX(X): 000-000, 2019-The purpose of this systematic review was to determine which type of swim-specific training is most benef...

The aims of the present study were to quantify inter-limb 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 par...

BACKGROUND: The aim of this study was to examine the validity and reliability of the novel inertial measurement unit (named: Gyko Sport) for the measurement of barbell concentric velocity on the bench-press exercise. METHODS: Ten under-16 (U16) basketball players performed 2 repetitions of the bench press exercise with 6 different loads (40, 50, 6...

The aim of this study was to compare the effects of different warm-up conditioning intensities on the physical fitness (i.e., post-activation potentiation -PAP), of professional male field soccer players. Athletes (n = 10; age: 21.6 ± 3.2 years) completed a control warm-up and warm-ups aimed to induce PAP, in random and counterbalanced order. After...

No studies have assessed whether changes in physical performance and inter-limb asymmetries (ILA) can be achieved with the FIFA 11+ prevention programme in adolescent female soccer players. The aim of this study was to assess the effect of the FIFA 11+ programme compared with a standard warm-up on physical performance and ILA in adolescent female s...

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 i...

OBJECTIVE: To examining the relationship between hip adductor strength and groin injury incidence during the competitive season of professional football teams. DESIGN: Prospective Cohort study. SETTING: Controlled laboratory environment. PARTICIPANTS: Seventy-one players volunteered to participate. MAIN OUTCOME MEASURES: In the pre-season, maxi...

Objective: To examining the relationship between hip adductor strength and groin injury incidence during the competitive season of professional football teams. Design: Prospective Cohort study. Setting: Controlled laboratory environment. Participants: Seventy-one players volunteered to participate. Main outcome measures: In the pre-season,...

Change of direction speed (CODS) has been highlighted as a critical component of tennis. Inter-limb asymmetries have been commonly studied in jump tests, but less attention given to the topic during CODS. The aim of this study was to quantify inter-limb asymmetries in jumping and CODS (during traditional and isoinertial tests) and establish their r...

Purpose: This study compared the effects of performing different unilateral strength training interventions on unilateral and bilateral jumping performance and their related asymmetries in young soccer players. Methods: Forty-five male young (U-17) soccer players were randomly assigned to three eccentric overload training programs: The first group...

Purpose: To compare the effects of resisted change-of-direction (COD) movements, using several relative loads, on soccer players' physical performance. Methods: Fifty-four male soccer players were randomly assigned to 1 of the following 3 groups, which differed only in the magnitude of the external load used during the COD training: COD training...

The aim of the present study was to investigate the effects of multiple repeated sprints on unilateral jump performance and inter-limb asymmetries. Eighteen recreationally active males performed three single leg countermovement jumps (SLCMJ) as baseline data. The repeated sprint protocol was 6 x 40 m with 20 seconds of passive rest between each spr...

Purpose: The aim of this study was twofold: to determine the discriminators as variables to select the under-16 (U-16) national team players; and to examine the influence of biological age on physical/technical parameters among young basketball players. Methods: Thirty-four young under-15 (U-15) male basketball players performed several anthropomet...

Purpose: The aim of this study was to assess the reliability, sensitivity and performance changes across the season of jumping, linear sprinting and change of direction ability (CODA) tests in adolescent female football players. Materials and methods: A total of 60 female football players (U-16 and U-18) performed bilateral and unilateral countermo...

The aim of this study was to compare changes in young soccer player’s fitness after traditional bilateral vs. unilateral combined plyometric and strength training. Male athletes were randomly divided in two groups; both received the same training, including strength training for knee extensors and flexors, in addition to horizontal plyometric train...

BACKGROUND: The aim of this study was to evaluate the effects of an in-season strength and conditioning program on physical abilities in under-16 sub-elite basketball players. METHODS: Sixteen young male basketball players were assessed using countermovement jump (CMJ), squat jump (SJ), 10-meters sprint and Pro Agility test, before and after an 8-...

The aim of this study was to compare the activity profile (external loads) during soccer-7 competition versus 6 vs 6 small-sided games (SSGs) in U12 players. Peak velocity (Vmax), total distance completed (DT), total distance relative to match duration, the percentage of DT in acceleration (%DAC) and in deceleration (%DEA), and the percentage of DT...

The aim of the study was to compare the effects of an in-season five weeks of high-intensity training (HIT) with a concurrent HIT eccentric overload training (CT) program on male amateur team-sports players’ fitness performance. Twenty-two athletes were randomly assigned to HIT (n=10) or CT (n=12). Both groups completed a HIT program. The CT group...

Plyometric training composed by unilateral exercises with horizontal jumping direction seems to be an effective way to improve physical performance in athletes. The present study aimed to compare the influence of a combined jumping direction and force application (horizontal-unilateral vs. vertical-bilateral) plyometric training on linear sprinting...

The present study aimed to examine the reliability, usefulness, responsiveness, age-related differences and construct validity of a novel decision-making RSA test (RSA-RANDOM test) in young soccer players. Twenty-five young male soccer players performed the RSA-RANDOM test on 2 occasions separated by 5-7 days to assess test-retest reliability and d...

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 XX(X): 000-000, 2018-The present study analyzed the effects of adding an upper-body repeated power ability (RPA) training to habitual strength training sessions. Twenty youn...

The aim of this study was to compare changes in young soccer player's fitness after traditional bilateral vs. unilateral combined plyometric and strength training. Male athletes were randomly divided in two groups; both received the same training, including strength training for knee extensors and flexors, in addition to horizontal plyometric train...

The aim of the present study was to describe the physiological and technical responses in young female during a basketball 3 vs. 3 small-sided games (SSG) with and without verbal coach encouragement and dribbling. Six young female basketball players (age: 14.3 ± 0.5 years; height: 167.8 ± 0.8 cm; body mass: 56.5 ± 5.7 kg) were recruited to particip...

To compare the effects of high intensity interval training (HIT) with one versus three changes of direction (COD) on youth (age, 17.21.1 y) female basketball players’ performance, 6-wk of regular basketball training (control period) was followed by random allocation of athletes to either HIT with one (HIT-COD1; n=6) or three COD (HIT-COD3; n=6), t...

Background: There is a lack of information about the influence of age on functional movement tests (FMT) and performance tests as well as in their relationships in young basketball players. Purpose: The purpose of the present study was to determine the variations in FMT and jump and/or sprint perfor- mance scores between age groups (U-14 vs. U-16)...

The aim of this study was to analyse the effects of a combined strength-training programme (full-back squat, YoYo(TM) leg curl, plyometrics and sled towing exercises) on performance in elite young soccer players and to examine the effects when this training programme was performed one or two days per week. Thirty-six male soccer players (U-17 to U-...

The aim of the present study was to describe the physiological and technical responses in young female during a basketball 3 vs. 3 small-sided games (SSG) with and without verbal coach encouragement and dribbling. Six young female basketball players (age: 14.3 ± 0.5 years; height: 167.8 ± 0.8 cm; body mass: 56.5 ± 5.7 kg) were recruited to particip...

El objetivo de este trabajo ha sido comparar el efecto de tres calentamientos diferentes (calentamiento aeróbico de baja intensidad, estiramiento estático y estiramiento dinámico) sobre el salto horizontal y la capacidad de repetir esprint con cambios de dirección. Diecisiete practicantes de deportes de equipo de 20.8±1.1 años realizaron 3 tipos de...