Lower-limb coordination changes following a 6-week training intervention that elicited enhancements to maximum velocity sprint performance.

Alterations to intra- and inter-limb coordination with improved maximal velocity performance remain largely unexplored. This study quantified within-day variability in lower-limb segmental coordination profiles during maximal velocity sprinting and investigated the modifications to coordination strategies in 15 recreationally active males following a 6-week period comprised of a multimodal training programme [intervention group (INT); n=7] or continued participation in sports (control group; n=8). The INT demonstrated a large decrease (effect size=-1.54) in within-day coordination profile variability, suggesting potential skill development. Thigh-thigh coordination modifications for the INT were characterised by an earlier onset of trail thigh reversal in early swing (26 versus 28% stride) and lead thigh reversal in late swing (76 versus 79% stride), rather than increases in overall time spent in anti-phase. Moreover, an increase in backward rotation of thigh relative to shank (effect size, 95% CIs: 0.75, 0.17 to 1.33) and shank relative to foot (0.76, -0.17 to 1.68) during late swing likely facilitated more aggressive acceleration of the limb, contributing to reduced touchdown distance and more favourable lower-limb configuration at initial ground contact. These novel findings provide empirical support for the role of longitudinal coordination modifications in improving maximal velocity performance.

Impact of the COVID-19 pandemic on the self-care and health condition of the older adults. CUIDAMOS+75. A mixed methods study protocol.

Aims: To assess the impact of the COVID-19 pandemic on the health condition of people ≥75 years of age and on their family caregivers in Spain. Design: Multicentric, mixed method concurrent study. Methods: This work, which will be conducted within the primary care setting in 11 administrative regions of Spain, will include three coordinated studies with different methodologies. The first is a population-based cohort study that will use real-life data to analyze the rates and evolution of health needs, care provision, and services utilization before, during, and after the pandemic. The second is a prospective cohort study with 18 months of follow-up that will evaluate the impact of COVID-19 disease on mortality, frailty, functional and cognitive capacity, and quality of life of the participants. Finally, the third will be a qualitative study with a critical social approach to understand and interpret the social, political, and economic dimensions associated with the use of health services during the pandemic. We have followed the SPIRIT Checklist to address trial protocol and related documents. This research is being funded by the Instituto de Salud Carlos III since 2021 and was approved by its ethics committee (June 2022). Discussion: The study findings will reveal the long-term impact of the COVID-19 pandemic on the older adults and their caregivers. This information will serve policymakers to adapt health policies to the needs of this population in situations of maximum stress, such as that produced by the COVID-19 pandemic. Trial Registration: Identifier: NCT05249868 [ClinicalTrials.gov].

CONSTANS alters the circadian clock in Arabidopsis thaliana.

Plants are sessile organisms that have acquired highly plastic developmental strategies to adapt to the environment. Among these processes, the floral transition is essential to ensure reproductive success and is finely regulated by several internal and external genetic networks. The photoperiodic pathway, which controls plant response to day length, is one of the most important pathways controlling flowering. In Arabidopsis photoperiodic flowering, CONSTANS (CO) is the central gene activating the expression of the florigen FLOWERING LOCUS T (FT) in the leaves at the end of a long day. The circadian clock strongly regulates CO expression. However, to date, no evidence has been reported regarding a feedback loop from the photoperiod pathway back to the circadian clock. Using transcriptional networks, we have identified relevant network motifs regulating the interplay between the circadian clock and the photoperiod pathway. Gene expression, chromatin immunoprecipitation experiments, and phenotypic analysis allowed us to elucidate the role of CO over the circadian clock. Plants with altered CO expression showed a different internal clock period, measured by daily leaf rhythmic movements. We showed that CO upregulates the expression of key genes related to the circadian clock, such as CCA1, LHY, PRR5, and GI, at the end of a long day by binding to specific sites on their promoters. Moreover, a high number of PRR5-repressed target genes are upregulated by CO, and this could explain the phase transition promoted by CO. The CO-PRR5 complex interacts with the bZIP transcription factor HY5 and helps to localize the complex in the promoters of clock genes. Taken together, our results indicate that there may be a feedback loop in which CO communicates back to the circadian clock, providing seasonal information to the circadian system.

Are Young Female Basketball Players Adequately Prepared for a Force-Velocity Jumping and Sprinting Assessment?

PURPOSE: The aim of this study was to explore the interday reliability of mechanical variables obtained from the horizontal and vertical force-velocity (FV) profiles in adolescent female basketball players. If found to be reliable, the associations between FV parameters (theoretical maximal force, velocity, and power), squat jump (SJ) height, 30-m sprint, and change of direction (COD) times were evaluated. METHODS: After familiarization, SJ against incremental loads, 30-m sprint, and 505-COD tests were obtained twice in 36 adolescent female basketball players (age = 15.4 [1.2] y). RESULTS: Reliability for vertical FV parameters was unacceptable, whereas 505-COD times and FV horizontal parameters (except for theoretical maximal power) showed a moderate to high reliability. 505-COD time was correlated with FV horizontal parameters (range: r = -.821, -.451), and a large association was observed with both SJ height (r = -.678, -.600) and 30-m sprint time (r = .813, .858). CONCLUSIONS: Due to low levels of strength, our athletes were not adequately prepared to obtain a reliable vertical FV profile. Practitioners can expect acceptable reliability of the horizontal FV profile. Given the association between COD performance and SJ height and 30-m sprint time, we encouraged practitioners with limited equipment at their disposal to use COD and/or 30-m sprint tests.

Family Caregivers' Experiences during the COVID-19 Pandemic: Qualitative Study.

Background: The COVID-19 pandemic imposed lockdown measures that affected caregiving. Understanding caregivers' context provides reveals their adaptive strategies to continue caring in this situation of uncertainty and isolation. Objective: To better understand the caregiving experiences of caregivers looking after dependent individuals living in the community during the pandemic. Design: Qualitative research, phenomenological approach. Setting: Primary healthcare centers in Madrid region (Spain). Participants: 21 family caregivers. Methods: Purposive and theoretical sampling was used to recruit caregivers across nurses from primary healthcare centers. Participants were interviewed using a semi-structured interview guide to explore the caring experience. Interview transcripts were evaluated using thematic analysis. Results: The findings were categorized into two themes: "Caregivers during lockdown-providing care in a time of adversity" and "Caregiving toward normality". The sub-themes identified were the re-structuring of before-care services and the introduction of new care approaches, managing the dependent person's health problems, looking after oneself, and dealing with adversity. To adapt to the new normal, strategies were put in place designed to recover confidence and trust, reincorporate assistance, and reconnect with others. Conclusions: Care intensified during the pandemic. Caregivers took on the task without assistance, focusing on preventing contagion and protecting themselves to be able to continue giving care.

Biceps femoris muscle-tendon strain during an entire overground sprint acceleration: a biomechanical explanation for hamstring injuries in the acceleration phase.

The objectives of this study were to analyse the peak muscle-tendon (MT) strain of the hamstring during an entire acceleration sprint overground and examine their relationship with relative joint angles and segment orientation in the sagittal plane, which are the direct causes of MT strain. Kinematic data were recorded using a 3D inertial motion capture system in 21 male semi-professional soccer players during 40-metre overground sprint. Scaled musculoskeletal models were used to estimate peak MT strain in the hamstring over 16 steps. Biceps femoris long head (BFLH) exhibited the largest peaks in MT strain compared to semitendinosus (ST) and semimembranosus (SM) muscles across all the steps, with its overall strain decreased as the number of steps and maximum speed increased. Hip flexion angle was found to be a strong predictor (p < 0.001) of joint angles, being the orientation of the pelvis in the sagittal plane of the segment with the greatest influence (p < 0.001) on the peak MT strain of BFLH during sprinting. The current study provides a biomechanical explanation for the high proportion of hamstring injuries in the acceleration phase of sprinting.

Physical-Chemical Assessment of Azo Dye Basic Violet I (BVI) Discoloration Using the Corona Plasma in Batch and Flow Systems.

The decolorization of the Basic violet I (BVI) dye when interacted with a corona discharge is studied in the present work, taking in account two systems, batch and flux. The current and voltage were measured during the whole process in which a corona plasma was generated, with an applied power of 51.9 and 167.72 W where the transport gas was air. A batch reactor and a flow reactor were used, where 500 and 5000 mL of samples were treated, respectively. Optical emission spectra (OES) were measured where the oxidizing species ·OH were at wavelengths of 307.597 and 310.148 nm, associated with the A2∑+ - X2Π transition. The absorption spectra for the batch system showed a discoloration of 85.7% in the first 10 min, while in the flow system, the absorption was 93.9% at the same time and 4.5% at the same time by conventional heating. Characteristics of the final sample included an acidic solution with an electrical conductivity of 449.20 ± 55.44 and 313.6 ± 39.58 µS/cm, a dissolved oxygen concentration of 7.74 ± 0.2 and 6.37 ± 0.23 mg/L, an absorbance of 0.04 ± 0.01 and 0.03 ± 0.01 au, with turbidity measuring 1.22 ± 1.59 and 10.34 ± 4.96 NTU, and an energy cost of 1.1 × 10-1 and 6.3 × 10-1 g/kWh in the batch and continuous flow systems, respectively. The interaction of the corona plasma with water promoted the production of reactive species, resulting in the discoloration of the Basic Violet I dye.

A gene regulatory network critical for axillary bud dormancy directly controlled by Arabidopsis BRANCHED1.

The Arabidopsis thaliana transcription factor BRANCHED1 (BRC1) plays a pivotal role in the control of shoot branching as it integrates environmental and endogenous signals that influence axillary bud growth. Despite its remarkable activity as a growth inhibitor, the mechanisms by which BRC1 promotes bud dormancy are largely unknown. We determined the genome-wide BRC1 binding sites in vivo and combined these with transcriptomic data and gene co-expression analyses to identify bona fide BRC1 direct targets. Next, we integrated multi-omics data to infer the BRC1 gene regulatory network (GRN) and used graph theory techniques to find network motifs that control the GRN dynamics. We generated an open online tool to interrogate this network. A group of BRC1 target genes encoding transcription factors (BTFs) orchestrate this intricate transcriptional network enriched in abscisic acid-related components. Promoter::ß-GLUCURONIDASE transgenic lines confirmed that BTFs are expressed in axillary buds. Transient co-expression assays and studies in planta using mutant lines validated the role of BTFs in modulating the GRN and promoting bud dormancy. This knowledge provides access to the developmental mechanisms that regulate shoot branching and helps identify candidate genes to use as tools to adapt plant architecture and crop production to ever-changing environmental conditions.

A New Index to Evaluate Running Coordination Based on Notational Analysis.

The aim of this study was 1) to define a new index to describe running coordination, named % of coordination, and 2) to examine whether it could represent an order parameter in relation to running velocity. Twelve international middle-distance athletes (six males and six females) performed three trials at easy, 5000 m pace and sprint velocities while filmed from a lateral view at 240 Hz. Notational analysis of six lower-limb key events corresponding to touchdown, mid-stance and flight phases was performed with high values of intra- (maximum standard deviation = 7 ms) and inter-operator (maximum systematic bias = 6 ms) reliability. Running velocity manipulations resulted in substantial and progressive increases in stride length, stride frequency (all p's < 0.001) and % of coordination (p < 0.001; η²p = 0.77), while duty factor showed a progressive reduction (p < 0.001, R2c = 0.86). However, % of coordination depended on the stride phase (p < 0.001; η²p = 0.78), with greater time gaps between key events in touchdown and mid-stance than in the flight phase. Results confirmed that % of coordination can illustrate changes in movement organisation, representing an easy tool for evaluating the running technique of competitive athletes.

Percepción de dirigentes deportivos locales y funcionarios municipales sobre políticas públicas deportivas locales de la comuna de Linares / Perception of local sports leaders and municipal officials on local public sports policies in the commune of Linares / Percepção dos líderes esportivos locais e das autoridades municipais sobre as políticas esportivas públicas locais na comuna de Linares

La aplicación de las políticas públicas deportivas locales (PPDL) de la comuna de Linares se han visualizado gracias a la aplicación del Plan de Desarrollo Comunal de Actividad Física y Deportes (PDC AFyD) en el período 2018 - 2022 en la comunidad y las organizaciones deportivas locales (OODD), así como de funcionarios del propio municipio. Para conocer la percepción sobre la aplicación de PPDL se aplica una entrevista semiestructurada y confeccionada para tales efectos, a 28 dirigentes deportivos y 18 funcionarios municipales, de un universo muestral total de 127 posibles. Los individuos indican que, pese a ver cambios favorables en el período desconocen el proceso y, por ende, el mecanismo aplicado para el cambio, lo que despotencia la comprensión de la PPDL y el desarrollo de ésta por medio de las propias OODD y el municipio. La aplicación de las PPDL por medio de sus distintas herramientas e instrumentos requiere que se desarrolle bajo un proceso de consulta, pertinencia y complementación entre municipio, OODD, mundo educativo y vecinos beneficiarios; todo dentro de un marco de comunicación e información concreta y permanente que logre involucrar a todos los actores, brindando con ello una cuota de responsabilidad en su ejecución, control y evaluación.

The application of local public policies on sports (LPSP) of the commune of Linares has been visualized thanks to the application of the Communal Development Plan for Physical Activity and Sports (CDP PA&S) in the period 2018 - 2022 in the community and local sports organizations (LSO), as well as officials of the municipality itself. To know the perception of the implementation of LPSP, a semi-structured interview was applied to 28 sports leaders and 18 municipal officials out of a total sample universe of 127 possible. The individuals indicate that, despite seeing favorable changes in the period, they are unaware of the process and, therefore, the mechanism applied for change, which undermines the understanding of the LPSP and its development through the LSOO and the municipality. The application of the LPSP through its different tools and instruments requires that it be developed under a process of consultation, relevance, and complementarity between the municipality, LSOO, the educational world and beneficiary neighbors; all under a framework of communication and concrete and permanent information that manages to involve all the actors, thus providing a share of responsibility in its execution, control, and evaluation.

A implementação das políticas esportivas públicas locais (PEPL) na comuna de Linares foi visualizada graças à implementação do Plano de Desenvolvimento Comunitário para Atividade Física e Esporte (PDC AFyE) no período 2018 - 2022 na comunidade e organizações esportivas locais (OOEE), bem como funcionários do próprio município. Foi realizada uma entrevista semi-estruturada com 28 líderes esportivos e 18 funcionários municipais de um universo de amostra total de 127. Os indivíduos indicam que, apesar de verem mudanças favoráveis no período, não conhecem o processo e, portanto, o mecanismo aplicado para a mudança, o que prejudica a compreensão do PEPL e seu desenvolvimento através do OOEE e do próprio município. A implementação do PEPL através de suas diferentes ferramentas e instrumentos requer um processo de consulta, relevância e complementaridade entre o município, o OOEE, o mundo educacional e os vizinhos beneficiários; tudo isso dentro de uma estrutura de comunicação e informação concreta e permanente que envolva todos os atores, proporcionando assim uma parcela de responsabilidade em sua implementação, controle e avaliação.

Diagnóstico del proceso de reafirmación profesional, en la carrera de Cultura Física, en Granma

La formación de profesionales, con elevada calidad, es tarea esencial de la Educación Superior, por lo que de manera permanente se demanda de graduados comprometidos con los procesos de desarrollo, donde quedan evidenciados los conocimientos, habilidades y valores en los que se han formado. El diagnóstico tuvo como objetivo caracterizar la situación de la orientación y reafirmación profesional (consolidación de los motivos e intenciones profesionales) en el proceso de estudio de la carrera Licenciatura en Cultura Física, en Granma; a partir de tres dimensiones: pedagógica, psicológica y sociológica. Se aplicaron métodos teóricos y empíricos que mostraron insuficiencias en las acciones planificadas en las estrategias educativas y en el plan de trabajo metodológico de las diferentes disciplinas, un limitado aprovechamiento de las potencialidades del contenido y las actividades extensionistas y bajos niveles de satisfacción por el estudio de la Carrera; lo que se manifestó en la no selección de una esfera de actuación para el futuro desempeño profesional, y en los elevados niveles de deserción de los estudiantes, en los dos primeros años de formación.

A formação de profissionais, com elevada qualidade, é uma tarefa essencial do Ensino Superior, razão pela qual existe uma procura permanente de licenciados comprometidos com processos de desenvolvimento, onde se evidenciam os conhecimentos, competências e valores em que foram formados. O objetivo do diagnóstico foi caracterizar a situação de orientação e reafirmação profissional (consolidação de motivos e intenções profissionais) no processo de estudo do Bacharelado em Cultura Física, no Granma; a partir de três dimensões: pedagógica, psicológica e sociológica. a corrida; o que se manifestou na não seleção de uma esfera de atuação para futura atuação profissional, e nos elevados índices de evasão estudantil, nos dois primeiros anos de formação.

The training of professionals, with high quality, is an essential task of Higher Education, which is why there is a permanent demand for graduates committed to development processes, where the knowledge, skills and values in which they have been trained are evidenced. The objective of the diagnosis was to characterize the situation of professional guidance and reaffirmation (consolidation of professional motives and intentions) in the process of studying the Bachelor's degree in Physical Culture, in Granma; from three dimensions: pedagogical, psychological and sociological. Theoretical and empirical methods were applied that showed insufficiencies in the planned actions in the educational strategies and in the methodological work plan of the different disciplines, a limited use of the potential of the content and extension activities and low levels of satisfaction with the study of the career; which was manifested in the non-selection of a sphere of action for future professional performance, and in the high levels of student dropout, in the first two years of training.

Co-existence of peripheral fatigue of the knee extensors and jump potentiation after an incremental running test to exhaustion in endurance trained male runners.

The aim of the present study was to investigate the effect of an incremental running exercise until exhaustion on twitch responses and jump capacity in endurance trained runners. For this purpose, 8 experienced endurance male runners were required to perform neuromuscular function tests before and after a submaximal running bout (control condition -CTR-) or an incremental running test to volitional exhaustion (experimental conditions -EXP-). The twitch interpolation technique was used to assess voluntary activation and muscle contractile properties before and after each condition (CTR and EXP). Countermovement jump was also used to assess the stretch-shortening cycle function before and after both conditions. In addition, rating of perceived exertion, heart rate, blood lactate and skin temperature were also recorded. Only EXP improved jump performance, however, it was also accompanied by a reduction in maximal voluntary contraction and the peak twitch force of the knee extensors evoked by electrical stimulation at 10 Hz (Db10). It is likely that reductions in maximal voluntary contraction may be related to an excitation-contraction coupling failure (i.e. low-frequency fatigue) as suggest the reduction in the Db10. The current results confirm that acute changes in jump performance may not be appropriate to evaluate acute fatigue in endurance trained runners.

A Load-Velocity Relationship in Sprint?

The aims were to compare predicted maximal velocity from load-velocity relationships established with different resisted and assisted loads by different regression analyses to the measured maximal velocity during sprint running, and to compare maximal velocity measured between a robotic pulley system and laser gun. Sixteen experienced male sprinters performed regular 50 m sprints, a 50 m with 5-kilogram-assisted sprint, and 10, 20, 30, and 30 m resisted sprints with, respectively, 65, 50, 25, and 10% calculated reduction in maximal velocity. Maximal velocity obtained by laser gun during the regular sprint was compared with predicted maximal velocity calculated from four trendlines (linear and polynomial based upon four resisted loads, and linear and polynomial based upon four resisted and one assisted load). Main findings demonstrate that the robotic pulley system and laser measure similar maximal velocities at all loads except at the load of 10% velocity reduction. Theoretical maximal velocity based upon calculated predictions were underestimated by 0.62-0.22 m/s (2.2-0.78 km/h; 6.7-2.3%) compared to measured maximal velocity. It was concluded that different regression analyses underestimated measured maximal velocity in regular sprinting and polynomial regression analysis (with resisted and assisted loads) estimation was closest to measured velocity (2.3%).

Effects of a six-week multimodal training programme on the sprinting ability of adolescent rugby sevens players.

This study evaluated the effects of 6-week multimodal training on the sprinting performance and biomechanics of adolescent rugby players. Twenty-four players were assigned to control group (CG) or intervention group (IG). For 6 weeks, CG maintained their training routine, while IG completed a training programme consisting of unresisted sprints, as well as heavy-resisted sprints, running technique drills and lumbopelvic stability. Before and after, sprint performance, horizontal force-velocity profile (FV-h), sprinting kinematics and spatiotemporal data were obtained. After the training, IG reduced the 0-5 m (p = 0.044), 0-10 m (p = 0.046) and 25-30 m (p = 0.035) split times compared with CG. In FV-h, IG displayed a higher maximal theoretical horizontal force (p = 0.035) and ratio of force (p = 0.048) than CG. Regarding kinematic and spatiotemporal variables, only IG improved step length (p < 0.001), step rate (p = 0.005) and distance between knees (p = 0.048) compared with baseline, but there were no between-group differences. Six weeks of multimodal training improved sprinting acceleration and mechanical variables of force application during sprinting of adolescent rugby players. Although IG improved some biomechanical variables compared with baseline, these changes were similar to those observed in CG.

Longitudinal Effects of Traditional and Rest Redistribution Set Configurations on Explosive-Strength and Strength-Endurance Manifestations.

ABSTRACT: Janicijevic, D, González-Hernández, JM, Jiménez-Reyes, P, Márquez, G, and García-Ramos, A. Longitudinal effects of traditional and rest redistribution set configurations on explosive-strength and strength-endurance manifestations. J Strength Cond Res 37(5): 980-986, 2023-This study aimed to compare the long-term effects of resistance training programs based on traditional and rest redistribution set configurations on explosive-strength and strength-endurance performance of lower-body and upper-body muscles. Thirty physically active men were randomly assigned to a traditional group (TRG: 6 sets of 5 repetitions with 3 minutes of interset rest) or a rest redistribution group (RRG: 30 sets of 1 repetition with 31 seconds of interrepetition rest). The training program lasted 6 weeks (2 sessions·wk -1 ), and in each training session, the squat and bench press exercises were performed with maximal concentric effort against approximately the 75% of the 1 repetition maximum. Before and after training, explosive-strength performance (peak velocity reached at submaximal loads during the countermovement jump and bench press throw) and strength-endurance performance (mean set velocity of 10 repetitions using both traditional and cluster sets in the squat and bench press) were assessed. Significant improvements in all dependent variables were observed after training for both the TRG ( p ≤ 0.004; effect size [ES] = 0.63-3.06) and RRG ( p ≤ 0.001; ES = 0.58-3.23). The magnitude of the changes was comparable for both groups with the only exception of the larger improvements observed in the RRG for the bench press mean set velocity using both traditional (ES = 0.77) and cluster (ES = 0.82) set configurations. Traditional and rest redistribution set configurations are equally effective to improve lower-body explosive strength, lower-body strength endurance, and upper-body explosive strength, whereas rest redistribution set configurations could induce greater adaptations in upper-body strength endurance.

Microdosing Sprint Distribution as an Alternative to Achieve Better Sprint Performance in Field Hockey Players.

Introduction: The implementation of optimal sprint training volume is a relevant component of team sport performance. This study aimed to compare the efficiency and effectiveness of two different configurations of within-season training load distribution on sprint performance over 6 weeks. Methods: Twenty male professional FH players participated in the study. Players were conveniently assigned to two groups: the experimental group (MG; n = 11; applying the microdosing training methodology) and the control group (TG; n = 9; traditional training, with players being selected by the national team). Sprint performance was evaluated through 20 m sprint time (T20) m and horizontal force−velocity profile (HFVP) tests before (Pre) and after (Post) intervention. Both measurements were separated by a period of 6 weeks. The specific sprint training program was performed for each group (for vs. two weekly sessions for MG and TG, respectively) attempting to influence the full spectrum of the F-V relationship. Results: Conditional demands analysis (matches and training sessions) showed no significant differences between the groups during the intervention period (p > 0.05). No significant between-group differences were found at Pre or Post for any sprint-related performance (p > 0.05). Nevertheless, intra-group analysis revealed significant differences in F0, Pmax, RFmean at 10 m and every achieved time for distances ranging from 5 to 25 m for MG (p < 0.05). Such changes in mechanical capabilities and sprint performance were characterized by an increase in stride length and a decrease in stride frequency during the maximal velocity phase (p < 0.05). Conclusion: Implementing strategies such as microdosed training load distribution appears to be an effective and efficient alternative for sprint training in team sports such as hockey.

Effect of different interset rest intervals on mean velocity during the squat and bench press exercises.

This study aimed to compare the effect of three interset rest intervals (1, 3, and 5 minutes) on (I) mean velocity during a resistance training session conducted in a Smith machine with the squat and bench press exercises, and (II) the pre- and post-exercise force-velocity relationship. Fifteen male university students completed three sessions (i.e., Rest 1', Rest 3', and Rest 5') consisting of three sets of five repetitions against the 10RM load during the squat and bench press exercises. The force-velocity relationship (maximal values of force [F0], velocity [v0], and power [Pmax]) was evaluated at the beginning and at the end of each session with the countermovement jump and bench press throw exercises. During training, mean velocity was slower in sets 2 and 3 of the Rest 1' protocol compared to Rest 3' and Rest 5', but no significant differences were present between Rest 3' and Rest 5'. After training, there was a significant decrease in F0 (p = 0.017) and Pmax (p = 0.010), but not in v0 (p = 0.259). These results support the Rest 3' as the most time-efficient protocol, among those analysed, for the maintenance of high mean velocities during training sessions not leading to failure.

Horizontal versus vertical force application: association with the change of direction performance in soccer players.

This study examined which mechanical variables derived from a vertical jump (i.e. concentric peak force [ConcPF] and eccentric peak force [EccPF], flight time [FT]: contraction time [CT], eccentric deceleration rate of force development [EccDecRFD]) and linear sprint (i.e. theoretical maximal force [F0] and velocity [V0], maximal power output [Pmax], the peak ratio of the effective horizontal component [RFpeak], and the index of force application technique [DRF]) determined the change of direction (COD) performance to a greater extent. Sixteen male soccer players (age: 21.8 ± 2.9 years; height: 175.94 ± 6.88 cm; weight: 73.23 ± 9.59 kg) were assessed for a countermovement jump, the horizontal force velocity (FV) profile, and the COD ZigZag test. The horizontal FV profile parameters were significantly associated with COD performance, while jump mechanical variables did not show any significant association (r = 0.08-0.19; p > 0.05). Specifically, F0 (r = -0.56), Pmax (r = -0.68), and RFpeak (r = -0.54) were strongly associated with COD performance. Moreover, a 1 N·kg-1 increase in F0 was associated with -0.11 s to complete the ZigZag test, whereas 1 W·kg-1 and 1% increase in Pmax and RFpeak were associated with -0.05 and -0.03 s, respectively, to complete the COD test. Horizontal force production during sprinting might play a key role in COD performance. Assessing the horizontal FV profile might help coaches to prescribe a specific training programme to maximize sprint acceleration, which might improve COD performance.