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Why Should Athletes Brake Fast? Influence of Eccentric Velocity on Concentric Performance During Countermovement Jumps at Different Loads

2026-03-31T01:08:23Z

Título : Why Should Athletes Brake Fast? Influence of Eccentric Velocity on Concentric Performance During Countermovement Jumps at Different Loads Autor : Hernández-Davó, José L.; Sabido-Solana, Rafael; Omar-García, Manuel; Boullosa, Daniel Resumen : Purpose: The aim of the present study was to analyze the effect of different eccentric tempos on eccentric kinetics and kinematics and the subsequent concentric performance when performing countermovement jumps against different loads. Methods: After 1-repetition-maximum assessment and 2 familiarization sessions, 13 well-trained participants performed, in randomized order, 12 sets (4 tempos × 3 loads) of 4 repetitions of the loaded countermovement-jump exercise. The eccentric tempos analyzed were 5 and 2 seconds, as fast as possible, and accelerated (ie, without pause between repetitions), while the loads used were 30%, 50%, and 70% of 1-repetition maximum. Several kinetic and kinematic variables during both phases were recorded by linking a linear position transducer to the barbell. Results: The eccentric work was greater in the accelerated condition despite no changes in the eccentric depth. The peak and mean propulsive velocities were greater in the as-fast-as-possible and accelerated conditions. Correlation analysis showed that, compared with the 5-second condition, the increased concentric performance in the accelerated condition was related to the difference in eccentric work performed in the last 100 milliseconds of the eccentric phase (r > .770). Conclusions: Contrary to current practices, the current study highlights the need for performing the eccentric phase of loaded countermovement jumps, a common exercise performed by athletes for both training and evaluation purposes, as fast as possible. This allows not only a greater eccentric work but also improved concentric performance.

Variations induced by the use of unstable surface do not facilitate motor adaptation to a throwing skill

2026-03-31T01:08:25Z

Título : Variations induced by the use of unstable surface do not facilitate motor adaptation to a throwing skill Autor : Moreno, Francisco J.; Barbado, David; Caballero, Carla; Urbán, Tomás; Sabido-Solana, Rafael Resumen : Induced variability by the use of unstable surfaces has been proposed to enhance proprioceptive control to deal with perturbations in the support base better. However, there is a lack of evidence about its benefits facilitating motor adaptions in upper body skills. In this experiment, practice on an unstable surface was applied to analyze the adaptations in an upper limb precision throwing skill. After a pretest, twenty-one participants were randomly allocated into two groups: one group practiced the throwing task on a stable surface and the other group practiced the same task on an unstable support base. Differences in throwing performance between pre- and post-practice were analyzed in accuracy, hand movement kinematics and variability of the throw in both surface conditions. Fuzzy entropy of the horizontal force was calculated to assess the complexity dynamics of postural sway. Participants improved their performance on the stable and the unstable surface. Induced variability using an unstable surface reduced participants' variability and the complexity of postural sway, but it did not facilitate a superior adaptation of the throwing task. The results suggest that the variations induced by unstable surfaces would fall far from the family of specific motor solutions and would not facilitate additional motor performance of the throwing task.

The Use of Incremental, Decremental or a Random Order of Loads does not Affect Peak velocity Values during Bench Press Throw Load-Velocity Relationships

2026-03-31T01:08:24Z

Título : The Use of Incremental, Decremental or a Random Order of Loads does not Affect Peak velocity Values during Bench Press Throw Load-Velocity Relationships Autor : Sabido-Solana, Rafael; Asencio, Pablo; García-Valverde, Adrián; García-Aguilar, Fernando; Moreno-Lila, Rodrigo; Hernández-Davó, José Luis Resumen : The aim of this study was to assess the influence of the load order used (i. e. incremental, decremental or random loads order) during the bench press throw load-velocity profile on peak velocity achieved against four different loads (20–40–60–80 % of one repetition maximum [1RM]). Both intraclass cor-relation coefficient (ICC) and coefficient of variation (CV) were calculated to assess the reliability of the measures. A repeated measures ANOVA was used to assess differences between pro-tocols. A linear regression analysis was performed to assess the load-velocity relationships among the different protocols. Peak velocity showed good to high ICC values independently of the load used (ICC = 0.83–0.92). CV scores showed good reliability (ranging between 2.2 and 6.2 %). No significant differences in peak velocity attained at each load were found between the three testing protocols (p > 0.05). In addition, peak velocity at each load was very large to almost perfect, correlated between protocols (r = 0.790–0.920). The linear regression model showed a significant relationship between testing protocols (p < 0.001; R2 = 0.94). In conclusion, due to some ICC scores below 0.9 and R2 below 0.95, the indistinct use of different load-order protocols to assess load-velocity relationships in the bench press throw exercise is not recommended.

Standardized vs relative intensity in CrossFit

2026-03-28T02:09:27Z

Título : Standardized vs relative intensity in CrossFit Autor : Oliver-López, Alejandro; García-Valverde, Adrián; Sabido-Solana, Rafael Resumen : CrossFit is characterized by being a standardized training program that improves physical performance through the provision of several stimuli regardless of the participant’s strength level. This study aimed to compare the acute response in total repetitions as a measurement of performance, jump ability, physiological demand (heart rate and blood lactate), and perceived effort considering the participants’ strength level with individualized intensity in CrossFit. Thirty-five participants were assessed and asked to participate on two separate days in a standardized and relative ‘As Many Repetitions As Possible’ (AMRAP) CrossFit circuit. Both AMRAPs comprised strength, gymnastic and aerobic exercises, although only strength was individualized according to the participant’s level. Before the statistical analysis, participants were allocated to higher- or lower-strength groups following the one-repetition maximum-bodyweight ratio in the push press exercise. Results support the existence of a strong relationship between strength level and total repetitions in both AMRAPs. In addition, differences in total repetitions and rate of perceived exertion between strength groups are discarded when AMRAP intensity is individualized while physiological demand and jump ability are maintained. Thus, the higher-strength participants may benefit from similar responses with a lower number of repetitions. Therefore, CrossFit trainers should be encouraged to prescribe strength tasks based on the percentage of 1RM for every training.

Relationship between initial motor variability and learning and adaptive ability. A systematic review

2026-03-28T02:09:28Z

Título : Relationship between initial motor variability and learning and adaptive ability. A systematic review Autor : López-Fernández, Miguel; Sabido-Solana, Rafael; Caballero, Carla; Moreno, Francisco J. Resumen : Motor variability is an intrinsic feature of human beings that has been associated with the ability for learning and adaptation to specific tasks. The purpose of this review is to examine whether there is a possible direct relationship between individuals’ initial variability in their ability for learning and adaptation in motor tasks. Eighteen articles examined the relationship between initial motor variability and the ability for learning or adaptation. Twelve found a direct relationship. In reward-based tasks, greater initial variability was associated with greater learning and adaption improvement when assessed using linear measures of dispersion, however, this association was not observed with temporal structure variability. While in error-based task associations were reported with both greater amount variability and more complexity temporal structure. Nevertheless, bias in initial performance related to the amount of variability was found, so the temporal structure of initial variability seems to be a better indicator of improvement in this type of task. Further research is needed for further research to better understand the potential relationship between initial motor variability and the ability for learning or adaptation in motor tasks.

Motor variability during resistance training: Acceleration signal as intensity indicator

2026-03-28T02:09:29Z

Título : Motor variability during resistance training: Acceleration signal as intensity indicator Autor : López-Fernández, Miguel; García-Aguilar, Fernando; Asencio, Pablo; Caballero, Carla; Moreno, Francisco J.; Sabido-Solana, Rafael Resumen : Analysis of variability in physiological time series has been shown to be an indicator of the state of the organism. Although there is evidence of the usefulness of analysis of the amount and/or structure of variability (complexity) in cycling actions, there is limited knowledge about its application in resistance exercise. The aim of this study is to find out whether variability in acceleration signals can be an indicator of intensity level in a squat task. For this purpose, an experimental design was developed in which the following participated seventy- two participants (age = 25.7 ± 4.4 years; height = 169.2 ± 9.8 cm; body mass = 67.7 ± 11.2 kg; ratio 1RM/body mass = 1.4 ± 0.3). They performed four repetitions of back squat at loads of 10%, 30%, 50%, 70%, and 90% of 1RM. Acceleration during the exercise was recorded using an inertial measurement unit (IMU) and a force platform. The variability of the movement was then analyzed using Standard Deviation (SD), Detrended Fluctuation Analysis (DFA), Fuzzy Entropy (FuzzyEn), and Sample Entropy (SampEn). For the IMU and for the force platform, significant effects were observed in all variables (p < 0.001). In pairwise comparisons, IMU showed a significant increase in motor complexity with increasing intensity, among most intensities, in DFA, FuzzyEn and SampEn. Differences in force platform were more limited, and only DFA detected differences between most intensities. The results suggest that measures of signal and acceleration variability may be a useful indicator of the relative intensity at which a squat exercise is performed.

How does fatigue affect handstand balance? a non‑linear approach to study fatigue influence in handstand performance

2026-03-28T02:09:25Z

Título : How does fatigue affect handstand balance? a non‑linear approach to study fatigue influence in handstand performance Autor : Sabido-Solana, Rafael; García-Aguilar, Fernando; Caballero, Carla; Moreno, Francisco J. Resumen : Background The handstand is an essential skill in acrobatic sports. This skill requires the athlete to maintain an inverted upright stance with only the hands supported, which requires a great effort of muscular coordination and motor control. Several factors influence the ability to control the posture, including fatigue, which is a bit studied constraint of handstand performance. Research question With the aim to find out whether variability in movement control can be an indicator of fatigue, the present study was carried out. Method Fourteen male acrobatic gymnasts were required to perform handstands. The time series for analyzing variability were capturing using Force Platforms, which is a traditional laboratory instrument, and Inertial Measurement Units (IMU), which is a more recent and less widely used, but more accessible tool. For this purpose, an analysis of the amount of variability was carried out, using the standard deviation. And analysis of the structure of variability (or complexity), using Detrended Fluctuation Analysis (DFA) and Fuzzy Entropy (FuEn). Results Our results reveal that fatigue causes significant increases in the amount of variability in the medio-lateral axis on the force platform, and in the IMU located in the area of the L5 vertebra. These changes are accompanied by increased auto-correlation in the medio-lateral axis of the force platform, and more unpredictable behavior in the L5 IMU. Key points • Amount of variability can discriminate between non-fatigued and fatigued states in force platform. • Structure of variability can discriminate between non-fatigued and fatigued states in force platform. • Movements are most affected in the medio-lateral axis. • Forces produced to maintain balance exhibit smoother adjustments in fatigue state. • Acceleration in the L5 tends to be less predictable in fatigue state.

Effects of variable intensity and constant intensity flywheel resistance training programs on specific soccer players’ performance

2026-03-28T02:09:23Z

Título : Effects of variable intensity and constant intensity flywheel resistance training programs on specific soccer players’ performance Autor : Asencio, Pablo; Moreno, Francisco J.; Hernández-Davó, José Luis; Sabido-Solana, Rafael Resumen : Resistance training programs play a crucial role in optimizing soccer performance. The aim of this study is to compare performance outcomes in sport-specific tasks after implementing two different flywheel resistance training (FRT) programs: variable intensity (VI) and constant intensity (CI). Seventeen (n = 17) amateur footballers were divided into VI and CI groups with the same training volume. For the VI group, a decrease in inertial load was implemented every four sessions, whereas the CI group maintained a constant load during the entire program. After different familiarization sessions and testing (sprint, change of direction, jump, one-repetition maximum and flywheel strength variables), ten sessions of FRT were performed over 5 weeks. Both groups showed similar improvements in the one-repetition maximum (p < 0.01) but the CI group had significant improvements in the 10-m sprint (p = 0.04; ES = 0.72), emphasizing the potential benefits of medium inertial loads to maximize power and specificity in sport tasks. However, no significant differences were observed in the countermovement jump, change of direction and 30-m sprint, possibly attributed to neuromuscular fatigue from a high-volume training schedule and friendly matches. The study highlights the importance of considering training load distribution in FRT programs. The findings emphasize the need for complementary training to maximize the jump and change of direction abilities and caution against high-volume training and friendly match scenarios. In conclusion, FRT programs, whether varying in intensity or not, can yield medium-term performance improvements for soccer players.

Effects of four consecutive one-repetition maximum testing days on neuromuscular performance, muscle soreness and perceived recovery

2026-03-28T02:09:20Z

Título : Effects of four consecutive one-repetition maximum testing days on neuromuscular performance, muscle soreness and perceived recovery Autor : García-Valverde, Adrián; Asencio, Pablo; Hernández-Davó, José Luis; Sabido-Solana, Rafael Resumen : Purpose: The aim of this study was to evaluate the reliability of the one-repetition maximum (1RM) test and to assess the potential negative effects of this test on subsequent neuromuscular performance and perceived recovery. Method: A cross-sectional study in which subjects attended four consecutive days to perform an incremental 1RM test in the bench press. During each testing session, 1RM value, movement velocity against a submaximal (50% 1RM) load, perceived recovery, muscle soreness (DOMS), and rating of perceived exertion (RPE) were recorded. The analysis was performed by sorting the subjects into two groups (stronger: ≥ 1.2 1RM/bodyweight; and weaker: < 1.2 1RM/ bodyweight). Results: The reliability of 1RM values was good to excellent (ICC3,1 = 0.83-0.99), while SEm values were low (< 6%). The results showed no significant changes either in 1RM values or in movement velocity against 50% 1RM load over the days. The reported RPE values were high (6.5 to 8) but remained unchanged across sessions. Perceived recovery was only affected in the stronger group from the third day, despite the reported values being between “moderately” and “well recovered.” DOMS were significantly higher during the third and fourth testing days in both groups but remained low in values (< 3.3 in a 0 to 10 scale). Conclusions: Consecutive days of 1RM testing did not significantly affect neuromuscular performance, and only slight effects were found on perceived muscle soreness and perceived recovery.; Propósito: El objetivo de este estudio fue evaluar la confiabilidad de la prueba de una repetición máxima (1RM) y evaluar los posibles efectos negativos de esta prueba sobre el rendimiento neuromuscular posterior y la recuperación percibida. Método: Estudio transversal en el que los sujetos asistieron durante cuatro días consecutivos para realizar una prueba incremental de 1RM en press de banca. Durante cada sesión de test, se registró el valor de 1RM, la velocidad de movimiento contra una carga submáxima (50% de 1RM), la recuperación percibida, el dolor muscular (DOMS) y la calificación del esfuerzo percibido (RPE). El análisis se realizó clasificando a los sujetos en dos grupos (más fuertes: ≥ 1,2 1RM/peso corporal; y más débiles: < 1,2 1RM/peso corporal). Resultados: La confiabilidad de los valores de 1RM fue de buena a excelente (ICC3,1= 0,83-0,99), mientras que los valores de SEm fueron bajos (< 6%). Los resultados no mostraron cambios significativos en los valores de 1RM ni en la velocidad de movimiento frente a una carga de 50% de 1RM a lo largo de los días. Los valores de RPE informados fueron altos (6,5 a 8) pero se mantuvieron sin cambios entre las sesiones. La recuperación percibida sólo se vio afectada en el grupo más fuerte a partir del tercer día, a pesar de que los valores informados estaban entre "moderadamente" y "bien recuperados". Los DOMS fueron significativamente más altos durante el tercer y cuarto día de test en ambos grupos, pero se mantuvieron bajos en valores (<3,3 en una escala de 0 a 10). Conclusiones: El test de 1RM en días consecutivos no afectó significativamente el rendimiento neuromuscular, y sólo se encontraron efectos leves sobre el dolor mus-cular percibido y la recuperación percibida.

Differences in kinetic characteristics during countermovement jump of football players with cerebral palsy according to impairment profiles

2026-03-27T02:06:49Z

Título : Differences in kinetic characteristics during countermovement jump of football players with cerebral palsy according to impairment profiles Autor : Henríquez, Matías; Sabido-Solana, Rafael; Barbado, David; Roldan, Alba; López-Elvira, José L.; Yanci, Javier; Reina, Raúl Resumen : Objectives: The purpose of this study was 1) to determine and compare kinetic parameters during the realization of a countermovement jump (CMJ) between footballers with cerebral palsy (CP) and non-impaired footballers, and 2) to analyze the differences in this action between different players’ impairment profiles and a group of non-impaired footballers. Methods: This study involved 154 participants comprising 121male footballers with CP from 11 national teams and 33 male non-impaired football players recruited as the control group (CG). The footballers with CP were described according to the different impairment profiles (bilateral spasticity = 10; athetosis or ataxia = 16; unilateral spasticity = 77; minimum impairment = 18). All participants performed three CMJs on a force platform to record kinetic parameters during the test. Results: The group of para-footballers presented significantly lower values than the CG in the jump height (p < 0.01, d = −1.28), peak power (p < 0.01, d = −0.84), and the net concentric impulse (p < 0.01, d = −0.86). Concerning the pairwise comparisons between CP profiles and the CG, significant differences were found for the bilateral spasticity, athetosis or ataxia, and unilateral spasticity subgroups compared to the non-impaired players for jump height (p < 0.01; d = −1.31 to −2.61), power output (p < 0.05; d = −0.77 to −1.66), and concentric impulse of the CMJ (p < 0.01; d = −0.86 to −1.97). When comparing the minimum impairment subgroup with the CG, only significant differences were found for jump height (p = 0.036; d = −0.82). Footballers with minimum impairment presented higher jumping height (p = 0.002; d = −1.32) and concentric impulse (p = 0.029; d = −1.08) compared to those with bilateral spasticity. Also, the unilateral spasticity subgroup reports a higher jump height performance than the bilateral group (p = 0.012; d = −1.12). Conclusion: These results suggest that the variables related to power production during the concentric phase of the jump are crucial for the performance differences between groups with and without impairment. This study provides a more comprehensive understanding of kinetic variables that would differentiate CP and non-impaired footballers. However, more studies are necessary to clarify which parameters better differentiate among different profiles of CP. The findings could help to prescribe effective physical training programs and support the classifier’s decision-making for class allocation in this para-sport.