Differences in strength and speed demands between 4v4 and 8v8 small-sided football games

ABSTRACT

The aims of this study were (i) to characterise the acceleration demands of two different formats of small-sided game (SSG), i.e., 4v4 + goalkeepers (4v4 + GK) and 8v8 + goalkeepers (8v8 + GK); (ii) to analyse the correlation between performance in power-based tests and acceleration-based physical loading during the two different SSG formats and (iii) to analyse the neuromuscular-induced fatigue. Eighteen adult male footballers participated in the study (20.7 ± 1.0 years, 178 ± 5 cm and 71.4 ± 2.1 kg). Baseline measurements were obtained from countermovement jumps, 15 s repeated jumps and 5 and 15 m sprints. A total of 36 min was analysed for each SSG (4v4 + GK: two sets of 3 × 6 min, and 8v8 + GK: 2 × 18 min). Heart rate, blood lactate, perceived exertion and movement pattern (GPS) were analysed. Distances covered by very-high-intensity activities and very-high-speed running were lower in 4v4 + GK than in 8v8 + GK (effect sizes (ES) = ?0.69 ± 0.67 and ?1.04 ± 0.67, respectively; very likely), while accelerations and decelerations were higher in 4v4 + GK than in 8v8 + GK (ES = 1.13–1.52; almost certainly). Blood lactate concentrations were higher (ES = 1.40 ± 0.58; almost certainly) and players perceived themselves to be more tired (ES = 0.80–2.31; almost certainly) after 4v4 + GK than after 8v8 + GK. Sprint ability in 5 and 15 m tests decreased (ES = 0.87 ± 0.58 and 0.89 ± 0.58, respectively; almost certainly) only after 4v4 + GK. This SSG format appeared more demanding in relation to repetitions and fatigue development of muscle power-based actions than 8v8 + GK. It may therefore be logical to use the former type of SSG to target development of power-related football actions.     

Coupling tendencies during exploratory behaviours of competing players in rugby union dyads

This study investigated interpersonal coordination tendencies in 1vs.1 dyads in rugby union, here expressed by participants' movement velocity towards or away from the sideline as they competed to score or prevent a try. We examined whether coupling tendencies of members of each dyad shaped key performance outcomes (try or successful tackle). Data on movement displacement trajectories of eight male rugby union players (aged 11–12 years) were analysed during performance in 47 trials. To assess coordination tendencies during exploratory behaviours in the dyads, analyses of performance time series data were undertaken using variable time graphs, running correlations and cross-correlations. Results revealed distinct coupling patterns characterised by shifts between synchronous coordination and asynchronous coordination tendencies and uncoordinated actions. Observed behaviours were interpreted as attempts of competing participants to create and perceive possibilities for action while seeking to achieve specific performance goals. Findings also revealed that a variety of patterned relations between participants resulted in different performance outcomes.     

Impact of an incremental running test on jumping kinematics in endurance runners: can jumping kinematic explain the post-activation potentiation phenomenon?

This study aimed to determine whether kinematic data during countermovement jump (CMJ) might explain post-activation potentiation (PAP) phenomenon after an exhausting running test. Thirty-three trained endurance runners performed the Léger Test; an incremental test which consists of continuous running between two lines 20 m apart. CMJ performance was determined before (pre-test) and immediately after the protocol (post-test). Sagittal plane, video of CMJs was recorded and kinematic data were obtained throughout 2-Dimensional analysis. In addition to the duration of eccentric and concentric phases of CMJ, hip, knee and ankle angles were measured at four key points during CMJ: the lowest position of the squat, take-off, landing, and at the lowest position after landing. Additionally, heart rate was monitored, and rate of perceived exertion was recorded at post-test. Analysis of variance revealed a significant improvement in CMJ (p = 0.002) at post-test. Cluster analysis grouped according to whether PAP was experienced (responders group: RG, n = 25) or not (non-responders group: NRG, n = 8) relative to CMJ change from rest to post-test. RG significantly improved (p < 0.001) the performance in CMJ, whereas NRG remained unchanged. Kinematic data did not show significant differences between RG and NRG. Thus, the data suggest that jumping kinematic does not provide the necessary information to explain PAP phenomenon after intensive running exercises in endurance athletes.     

Movement velocity as a measure of exercise intensity in three lower limb exercises

The purpose of this study was to investigate the relationship between movement velocity and relative load in three lower limbs exercises commonly used to develop strength: leg press, full squat and half squat. The percentage of one repetition maximum (%1RM) has typically been used as the main parameter to control resistance training; however, more recent research has proposed movement velocity as an alternative. Fifteen participants performed a load progression with a range of loads until they reached their 1RM. Maximum instantaneous velocity (V_max) and mean propulsive velocity (MPV) of the knee extension phase of each exercise were assessed. For all exercises, a strong relationship between V_max and the %1RM was found: leg press (r²_adj = 0.96; 95% CI for slope is [?0.0244, ?0.0258], P < 0.0001), full squat (r²_adj = 0.94; 95% CI for slope is [?0.0144, ?0.0139], P < 0.0001) and half squat (r²_adj = 0.97; 95% CI for slope is [?0.0135, ?0.00143], P < 0.0001); for MPV, leg press (r²_adj = 0.96; 95% CI for slope is [?0.0169, ?0.0175], P < 0.0001, full squat (r²_adj = 0.95; 95% CI for slope is [?0.0136, ?0.0128], P < 0.0001) and half squat (r²_adj = 0.96; 95% CI for slope is [?0.0116, 0.0124], P < 0.0001). The 1RM was attained with a MPV and V_max of 0.21 ± 0.06 m s^?1 and 0.63 ± 0.15 m s^?1, 0.29 ± 0.05 m s^?1 and 0.89 ± 0.17 m s^?1, 0.33 ± 0.05 m s^?1 and 0.95 ± 0.13 m s^?1 for leg press, full squat and half squat, respectively. Results indicate that it is possible to determine an exercise-specific %1RM by measuring movement velocity for that exercise.     

How do firms’ knowledge bases affect intra-industry heterogeneity? : An analysis of the Spanish pharmaceutical industry

This paper aims to contribute to the analysis of within industry inter-firm variety. The paper develops two themes: (i) the analysis of intra-industry heterogeneity, and (ii) the extent to which higher performance is associated with the capacity of firms to expand their knowledge base. The main contribution of the paper is empirical, based on a data source consisting of information on documents published in international scientific journals by Spanish pharmaceutical firms. The empirical results support the argument that the firm's knowledge base is a main driver of persistent heterogeneity within industries. We find systematic variety in terms of how firms articulate their research activities, and positive correlation between firms’ knowledge diversification and performance.     

Towards the reform of science teaching in Spain: the social and personal relevance of junior secondary school science projects for a socially responsible understanding of science

This article describes aspects of more than a decade of research and implementation of cross-curriculum themes as part of the curriculum for secondary school students in Spain. The educational reform described is an attempt to develop a more socially responsible education, using what, for Spain, has been a highly novel breaking down of subject barriers as a way of preparing young adults for life as citizens. It provides other investigators in the field with a commentary on some of the theoretical and practical issues encountered in developing similar projects.     

La comprensión por el niño de la intención del mensaje publicitario

Resumen

El propósito central de este artículo es mostrar cómo un modelo integrado, multidisciplinar, puede dar cuenta de la comprensión del mensaje publicitario por el niño. El modelo parte de la consideración del mensaje como acto-de-habla-global y su representación cognitiva por el receptor, como esquema de acción e interacción. Este doble abordamiento permite trascender el marco de las teorías de la competencia, hasta ahora dominantes, y explicar, en cierto modo, la actuación concreta de los sujetos en la comprensión de los mensajes.     

Circadian Rhythms in Cognitive Processes: Implications for School Learning

Circadian variations have been found in cognitive processes, such as attention, working memory, and executive functions, which may explain oscillations in the performance of many tasks. These cognitive processes improve during the day and decrease during the night and early hours of the morning. Sleep deprivation further decreases these cognitive processes during daytime hours. This review analyses the recent findings on circadian rhythms in cognitive processes, as well as the implications of these rhythms for school learning.