Tests to measure core stability in laboratory and field settings: reliability and correlation analyses

Although core stability (CS) has been assessed through many different tests, the relationships among them are currently unknown. The main objective was to analyse the relationship between five representative tests used to assess CS in: i) laboratory settings: Sudden Loading Test (SLT) and Stable and Unstable Sitting Test (SUST); ii) field settings: Biering-Sorensen Test (BST), Three-Plane Core Strength Test (TPCT) and Double-leg Lowering Test (DLLT). The reliability of these tests was also examined. Thirty-three recreationally active males performed the tests twice. The relationship between all variables was examined using Pearson-correlation coefficient in those variables with a good reliability. Only stiffness and angular displacement in the SLT, dynamic unstable tasks in the SUST and the holding-time in the BST showed good reliability (ICC: 0.63-0.91; typical error: 9.8%-21.0%). Few and low correlations were observed between the SLT, SUST and BST. Despite finding several significant correlations among the dynamic unstable tasks of the SUST (r≥0.807; p<0.01), no correlations were found between the loading directions of the SLT. The absence of correlations between these tests suggests that CS measurements are not generalisable, as they probably assess different dimensions of CS, or in the case of the BST, a different capacity (i.e. trunk extensor endurance)

Acute and Time-Course Effects of Traditional and Dynamic Warm-Up Routines in Young Elite Junior Tennis Players

Despite the large number of studies that have examined the acute effects of different warm up modalities (WU) on physical performance, none of them have documented the time course of potential performance recovery in tennis players. The aim of this study was twofold: (a) to analyze and compare the acute effects of two different WU modalities (traditional WU [TWU] and dynamic WU [DWU]) on physical performance (i.e., CMJ, sprint, serve speed and accuracy) in elite junior players, as well as (b) to monitor the time course of any WU-induced changes after 30 and 60 min of simulated match-play. Twelve junior elite players completed both WUs modalities (TWU and DWU) in a counterbalanced order on separate days. In each experimental session, counter movement jump (CMJ), 20-m sprint, tennis serve speed and accuracy tests were performed before (immediately after TWU or DWU) during (30 min) and after 60 min of a simulated match play. Measures were compared via four factorial (WU intervention and time) repeated measures ANOVAs. There were main effects of WU (TWU and DWU) throughout the time for all the variables analysed. The results indicate that DWU routine led to significantly faster 20 m sprint times and higher CMJs as well as faster and more accurate tennis serves at both post warm-up and 30 min match-play testing moments in comparison with the scores reported by the TWU routine (p 75-99%). No significant intergroup differences were found at 60-min match-play testing moment in any variable (except for the 20 m sprint). Therefore, the findings of this study recommend for optimal performance in these elite tennis players, DWU routines should be performed prior to formal training and competition rather than TWU routines.SIThe authors have no support or funding to report

Reliability of the Star Excursion Balance Test and Two New Similar Protocols to Measure Trunk Postural Control

Background: Although the Star Excursion Balance test (SEBT) has shown a good intrasession reliability, the intersession reliability of this test has not been deeply studied. Furthermore, there is an evident high influence of the lower limbs in the performance of the SEBT, so even if it has been used to measure core stability, it is possibly not the most suitable measurement. Objective: (1) To assess the absolute and relative between-session reliability of the SEBT and 2 novel variations of this test to assess trunk postural control while sitting, ie, the Star Excursion Sitting Test (SEST) and the Star Excursion Timing Test (SETT); and (2) to analyze the relationships between these 3 test scores. Design: Correlational and reliability testeretest study. Setting: Controlled laboratory environment. Participants: Twenty-seven physically active men (age: 24.54 3.05 years). Method: Relative and absolute reliability of the SEBT, SEST, and SETT were calculated through the intraclass correlation coefficient (ICC) and standard error of measurement (SEM), respectively. A Pearson correlation analysis was carried out between the variables of the 3 tests. Main Outcome Measures: Maximum normalized reach distances were assessed for different SEBT and SEST directions. In addition, composite indexes were calculated for SEBT, SEST, and SETT. Results: The SEBT (dominant leg: ICC ¼ 0.87 [0.73-0.94], SEM ¼ 2.12 [1.66-2.93]; nondominant leg: ICC ¼ 0.74 [0.50-0.87], SEM ¼ 3.23 [2.54-4.45]), SEST (ICC ¼ 0.85 [0.68-0.92], SEM ¼ 1.27 [1.03-1.80]), and SETT (ICC ¼ 0.61 [0.30-0.80], SEM ¼ 2.31 [1.82-3.17]) composite indexes showed moderate-to-high 1-month reliability. A learning effect was detected for some SEBT and SEST directions and for SEST and SETT composite indexes. No significant correlations were found between SEBT and its 2 variations (r .366; P > .05). A significant correlation was found between the SEST and SETT composite indexes (r ¼ .520; P > .01). Conclusions: SEBT, SEST, and SETT are reliable field protocols to measure postural control. However, whereas the SEBT assesses postural control in single-leg stance, SEST and SETT provide trunk postural control measures with lower influence of the lowerlimbs

Isokinetic trunk flexion–extension protocol to assess trunk muscle strength and endurance: Reliability, learning effect, and sex differences

PurposeThe purpose of this study was to examine the reliability and the learning effect of an isokinetic trunk flexion–extension protocol designed to simultaneously assess trunk muscle strength and endurance. In addition, the effect of the participants' sex on the reliability data was examined.MethodsFifty-seven healthy and physically active young men (n = 28) and women (n = 29) performed the isokinetic protocol 5 times, separated by a week between each of the first 4 sessions and by a month between the last 2 sessions. The protocol consisted of performing 4 trials of 15 maximum flexion–extension concentric exertions at 120°/s (range of trunk motion = 50°). The absolute and relative peak torque and total work were calculated to assess trunk flexion and extension strength. In addition, endurance ratio, modified endurance ratio, fatigue final ratio, recovery ratio, and modified recovery ratio variables were used for the assessment of trunk muscle endurance in both directions.ResultsRegarding the absolute reliability, no relevant changes were found between paired-comparison sessions for most strength and endurance variables, except for total work and relative total work variables in the flexion movement in both sexes. In addition, the typical error of the isokinetic variables was lower than 10% in both males and females, and minimum detectable changes ranged from 7%–20%, with a tendency to be higher in females and in endurance variables. The strength variables showed high intraclass correlation coefficients (ICC; >0.74); however, for the endurance variables only the endurance ratio and the modified endurance ratio obtained moderate to high ICC values (0.57 < ICC < 0.82). In addition, the analysis of the variance reported no significant differences between consecutive pairs of sessions for most variables in both sexes.ConclusionOverall, these findings provide clinicians, trainers, and researchers with a 10-min single-session protocol to perform a reliable muscle strength and endurance evaluation of trunk flexor and extensor muscles, all within the same protocol

Observational Screening Guidelines and Smartphone Accelerometer Thresholds to Establish the Intensity of Some of the Most Popular Core Stability Exercises

The lack of training load control, mainly exercise intensity, is one of the main limitations of core stability (CS) programs, which makes the training individualization and the analysis of the dose-response relationship difficult. The objectives of this study were to assess the inter-and intra-rater agreement when using new observational screening guidelines to decide if a core stability exercise represents an adequate training intensity level for a given participant. Besides, the relationship between experts' ratings based on these criteria and pelvic accelerations recorded with a smartphone accelerometer was also analyzed. Ten healthy physically active participants with a smartphone accelerometer placed on their pelvis were video-taped while performing a progression of seven variations of the front bridge, back bridge, side bridge and bird-dog exercises. Two expert and four non-expert raters watched the videos and used the observational screening guidelines to decide for each exercise variation if it represented an adequate training intensity level or not. In order to analyze the inter-and intra-rater agreement, several Kappa (κ) statistics were used. Receiver operating characteristic (ROC) curves to explore if the accelerometry allowed to establish pelvic acceleration thresholds representing the minimum level of exercise intensity for CS training. Cut-off acceleration values were calculated balancing sensitivity (Se) and 1-specifity (1-Sp) indexes (i.e., Youden index) or minimizing 1-Sp. The intra-and inter-rater analysis showed a substantial-high level of agreement with a prevalence-adjusted bias-adjusted Kappa > 0.69. The ROC curves showed that the acceleration thresholds for the bridging exercises were very similar, with global cut-off values of 0.35 m/s2 (Se = 82%; 1-Sp = 15%) when using the Youden Index and of 0.50 m/s2 when minimizing 1-Sp (Se = 31%), whilst the bird-dog exercise showed lower cut-off values (Youden Index: 0.21 m/s2, Se = 90%, 1-Sp = 16%; minimizing 1-Sp: 0.32 m/s2, Se = 40%). Overall, this study provides observational screening guidelines and smartphone accelerometer thresholds to facilitate the decision-making process when setting the intensity of some of the most popular core stability exercises in young physically active individual

Confidentiality and Integrity with Untrusted Hosts: Technical Report

Several security-typed languages have recently been proposed to enforce security properties such as confidentiality or integrity by type checking. We propose a new security-typed language, SPL@, that addresses two important limitations of previous approaches. First, existing languages assume that the underlying execution platform is trusted; this assumption does not scale to distributed computation in which a variety of differently trusted hosts are available to execute programs. Our new approach, secure program partitioning, translates programs written assuming complete trust in a single executing host into programs that execute using a collection of variously trusted hosts to perform computation. As the trust configuration of a distributed system evolves, this translation can be performed as necessary for security. Second, many common program transformations do not work in existing security-typed languages; although they produce equivalent programs, these programs are rejected because of apparent information flows. SPL@ uses a novel mechanism based on ordered linear continuations to permit a richer class of program transformations, including secure program partitioning. This report is the technical companion to [ZM00]. It contains expanded discussion and extensive proofs of both the soundness and noninterference theorems mentioned in Section 3.3 of that work

Progressions of core stabilization exercises based on postural control challenge assessment

Purpose The intensity progression of core stabilization exercises (CSEs) is usually based on personal criteria rather than on objective parameters. To develop exercise progressions for four of the most common CSEs based on the postural control challenge imposed on the participants, and to analyze the effect of participants’ sex and postural control level on these progressions. Methods Seventy-six males and females performed five variations of front bridge, back bridge, side bridge and bird-dog exercises on two force platforms. The mean velocity of the center of pressure displacement was calculated to assess exercise intensity through the measurement of the participants’ body sway (PBS). Results In general, long bridges produced higher PBS than short bridges, bridging with single leg support produced higher PBS than bridging with double leg support and bridging on a hemisphere ball produced higher PBS than bridging on the floor. The most difficult bridging variations were those performed on a hemisphere ball with single leg support. Regarding the bird-dog, two-point positions produced higher PBS than three-point positions and the positions performed on a hemisphere ball produced higher PBS than those performed on the floor. Conclusion The CSE progressions obtained by males and females were very similar. However, the participants with high trunk control showed less significant differences between exercise variations than the participants with low trunk control, which shows the need to individualize the progressions according to the participants’ training level. Overall, this study provides useful information to guide the prescription of CSE progressions in young physically active individuals

Different neuromuscular parameters influence dynamic balance in male and female football players

Purpose To analyse the relationship between several parameters of neuromuscular performance with unilateral dynamic balance measured through the Y-Balance test, as well as to determine the possible sex-related differences. Methods The Y-Balance test, isokinetic (concentric and eccentric) knee flexion and extension strength, isometric hip abduction and adduction strength, lower extremity joint range of motion (ROM) (hip, knee and ankle) and core stability were assessed in male (n = 88) and female (n = 44) professional football players. A stepwise multivariate linear least square regression with backward elimination analysis was carried out to identify a group of factors that were independently associated with balance performance in both sexes. Results Passive hip flexion and ankle dorsiflexion with knee flexed ROM were the main factors that retained a significant association to dominant (R2 = 23.1) and non-dominant (R2 = 33.5) balance scores for males. For females, core stability, hip abduction isometric peak torque, passive hip abduction and ankle dorsiflexion with knee flexed ROM variables retained a significant association with balance scores for both, dominant (R2 = 38.2) and non-dominant (R2 = 46.9) legs. Conclusions Training interventions aimed at improving or maintaining unilateral dynamic balance in male football players should include, among other things, stretching exercises for the posterior chain of the lower extremity. However, females should also include exercises for strength and mobility of the hip abductors and core stability (especially in the frontal plane). This knowledge would allow clinicians and sport practitioners to develop more effective and tailored unilateral dynamic balance training interventions in male and female football players, possibly improving performance and reducing the risk of injury

Condición muscular y estabilidad del tronco en judocas de nivel nacional e internacional

Antecedentes: Desde un punto de vista teórico, el desarrollo de la capacidad para estabilizar el tronco podría mejorar el rendimiento del judoca a través del desarrollo del control del equilibrio corporal y la optimización de la transmisión de fuerzas desde los miembros inferiores hacia los miembros superiores. Sin embargo, carecemos de evidencias científicas que permitan establecer una relación clara entre la estabilidad del tronco y el rendimiento en judo. Objetivo: El objetivo principal del estudio fue determinar si la valoración de la estabilidad del tronco y la fuerza y resistencia muscular permitían diferenciar entre judocas de categoría nacional (n = 7) e internacional (n = 6). Asimismo, se analizó la relación entre la estabilidad del tronco y la fuerza y resistencia de la musculatura implicada en el control de la estabilidad. Método: Para valorar la estabilidad del tronco se analizó tanto la respuesta del tronco ante cargas súbitas aplicadas mediante un mecanismo de tracción neumática, como el control postural del tronco mediante el paradigma del asiento inestable. Para valorar la fuerza y resistencia muscular se realizó un test de flexión y extensión del tronco en un dinamómetro isocinético. Resultados/Conclusiones: Los judocas de categoría internacional mostraron menor desplazamiento del CoP en la tarea más compleja sobre el asiento inestable (7.00±1.19 vs 8.93±1.45 mm; p=.025) y mayor momento de fuerza relativo de la musculatura extensora (7.05±0.87 vs 5.74±0.72 Nm; p=.013) que los judocas de categoría nacional. Según estos resultados, la condición muscular y la estabilidad del tronco son cualidades a tener en cuenta en la preparación física de los judocas. El análisis correlacional no encontró relación entre las variables analizadas, por lo que la fuerza y resistencia muscular no parecen tener un efecto importante sobre el rendimiento en los test de estabilidad del tronco

Muscular condition and trunk stability in judoka of national and international level

[ES] Antecedentes: Desde un punto de vista teórico, el desarrollo de la capacidad para estabilizar el tronco podría mejorar el rendimiento del judoca a través del desarrollo del control del equilibrio corporal y la optimización de la transmisión de fuerzas desde los miembros inferiores hacia los miembros superiores. Sin embargo, carecemos de evidencias científicas que permitan establecer una relación clara entre la estabilidad del tronco y el rendimiento en judo. Objetivo: El objetivo principal del estudio fue determinar si la valoración de la estabilidad del tronco y la fuerza y resistencia muscular permitían diferenciar entre judocas de categoría nacional (n = 7) e internacional (n = 6). Asimismo, se analizó la relación entre la estabilidad del tronco y la fuerza y resistencia de la musculatura implicada en el control de la estabilidad. Método: Para valorar la estabilidad del tronco se analizó tanto la respuesta del tronco ante cargas súbitas aplicadas mediante un mecanismo de tracción neumática, como el control postural del tronco mediante el paradigma del asiento inestable. Para valorar la fuerza y resistencia muscular se realizó un test de flexión y extensión del tronco en un dinamómetro isocinético. Resultados/Conclusiones: Los judocas de categoría internacional mostraron menor desplazamiento del CoP en la tarea más compleja sobre el asiento inestable (7.00±1.19 vs 8.93±1.45 mm; p=.025) y mayor momento de fuerza relativo de la musculatura extensora (7.05±0.87 vs 5.74±0.72 Nm; p=.013) que los judocas de categoría nacional. Según estos resultados, la condición muscular y la estabilidad del tronco son cualidades a tener en cuenta en la preparación física de los judocas. El análisis correlacional no encontró relación entre las variables analizadas, por lo que la fuerza y resistencia muscular no parecen tener un efecto importante sobre el rendimiento en los test de estabilidad del tronco.[EN] Background:It is theorized that the development of the ability to stabilize the trunk may improve the performance of a judoka because it improves body balance control and optimizes force transmission from the lower extremities to the upper limbs. However, there is a lack of scientific evidence to establish a clear relationship between trunk stability and performance in judo.Aim: The purpose of this study was to determine whether the quantification of trunk stability and muscular strength and endurance allowed differentiation between national level (n = 7) and international level judoka (n = 6). In addition, the relationship between trunk stability and muscular strength and endurance of the muscles involved in trunk stability control was analyzed. Method: To assess trunk stability, trunk responses to sudden loads applied by a pneumatic mechanism were analyzed, as well as trunk postural control through an unstable sitting paradigm. Muscular strength and endurance were assessed via a flexion and extension trunk test using an isokinetic dynamometer. Results/Conclusions: International level judokas showed lower CoP displacement in the most complex task in unstable seat (7.00 ± 1.19 vs 8.93 ± 1.45 mm, T = .025) and higher absolute and relative peak torque in extensor muscles (7.05 ± 0.87 vs 5.74 ± 0.72 Nm, T = .013) than national level judoka. According to these results, core stability and trunk muscular condition are important qualities in the physical training of elite judoka. Correlational analysis found no relation between the analyzed variables, thus muscular strength and endurance appear to have a non‐significant effect on performance in the trunk stability tests.[PT] Antecedentes: Do ponto de vista teórico, o desenvolvimento da capacidade para estabilizar o tronco pode melhorar o rendimento do judoca através do desenvolvimento do controlo do equilíbrio corporal e a otimização da transmissão de forças dos membros inferiores e dos membros superiores. Contudo, carecem as evidências que permitem estabelecer uma clara relação entre a estabilidade do tronco e o rendimento no judo.Objetivo: O objetivo do estudo foi o determinar se a valorização da estabilidade do tronco e da força e resistência muscular permitiam diferenciar entre judocas de categoria nacional (n = 7) e judocas de categoria internacional (n = 6). Assim mesmo, analisou‐se a relação entre a estabilidade do tronco e a força e a resistência muscular implicada e o controlo da estabilidade. Método: Para medir a estabilidade do tronco, analisou‐se a resposta do tronco antes das cargas súbitas aplicadas mediante um mecanismo de tração neumática, bem como o controlo postural do tronco mediante o paradigma da posição instável. Para medir a força e a resistência muscular, realizou‐se um teste de flexão e extensão do tronco com um dinamómetro isocinético. Resultados/Conclusões: Os judocas de categoria internacional mostraram menor deslizamento do CoP na tarefa mais complexa sobre a posição instável (7.00±1.19 vs 8.93±1.45 mm; p=.025) e maior momento de força relativa à musculatura extensora (7.05±0.87 vs 5.74±0.72 Nm; p=.013) do que os judocas de categoria nacional. Segundo estes resultados, a condição muscular e a estabilidade do tronco são qualidades a ter em conta na preparação física dos judocas. A análise correlacionada não encontrou relação entre as variáveis analisadas, na medida em que a força e a resistência muscular não parecem ter um efeito importante sobre o rendimento nos testes de estabilidade do tronco