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)

Test de camp per valorar la resistència dels músculs del tronc

El test Biering-Sorensen (BST), el test Side Bridge (SBT) i el test Ito (IT) són tres dels tests de camp més utilitzats per mesurar la resistència dels músculs del tronc. L’objectiu d’aquest estudi va ser analitzar la fiabilitat absoluta i relativa dels tests referits, així com valorar-ne l’efecte en el rendiment de l’antropometria dels participants en les proves. En l’estudi van participar 27 joves homes (23,5 ± 4,0 anys) i físicament actius. Els participants van fer dues sessions de registre en què van executar els tres tests (recuperació de 8 min entre proves) i on es van mesurar diverses variables antropomètriques. La fiabilitat relativa va ser bona, amb ICC majors de 0,80 en tots els tests, però la fiabilitat absoluta no, amb SEM que van oscil·lar entre 13,36 % en el BST i 19,89 % en l’IT. L’IT va mostrar una correlació negativa amb la massa (r = – ,475; p = ,014) i el diàmetre bileocrestal (r = – ,404; p = ,040), i el SBT una correlació negativa amb la massa (r = – ,610; p = ,001), el diàmetre bileocrestal (r = – ,546; p = ,004), el diàmetre biacromial (r = – ,456; p = ,019) i l’índex acromioilíac (r = – ,413; p = ,036). Les dades de fiabilitat absoluta qüestionen la utilitat d’aquestes proves en programes d’entrenament on els participants tenen poc marge de millora. A més a més, si es fan comparacions entre subjectes és important tenir en compte les seves diferències antropomètriques, ja que durant l’execució dels tests el cos s’utilitza com a instrument de mesura

Test de campo para valorar la resistencia de los músculos del tronco

El Biering-Sorensen test (BST), el Side Bridge test (SBT) y el Ito test (IT) son tres de los test de campo más utilizados para medir la resistencia de los músculos del tronco. El objetivo de este estudio fue analizar la fiabilidad absoluta y relativa de los test referidos, así como valorar el efecto de la antropometría de los participantes en el rendimiento en las pruebas. En el estudio participaron 27 jóvenes varones (23,5 ± 4,0 años) y físicamente activos. Los participantes realizaron dos sesiones de registro en las que ejecutaron los tres test (recuperación de 8 min entre pruebas) y donde se midieron diversas variables antropométricas. La fiabilidad relativa fue buena, con ICC mayores de 0.80 en todos los test, pero no así la fiabilidad absoluta, con SEM que oscilaron entre el 13,36 % en el BST y el 19,89 % en el IT. El IT mostró una correlación negativa con la masa (r= – ,475; p= ,014) y el diámetro bileocrestal (r = – ,404; p = ,040) y el SBT una correlación negativa con la masa (r = –,610; p = ,001), el diámetro bileocrestal (r = –,546; p = ,004), el diámetro biacromial (r= - ,456; p = ,019) y el índice acromioiliaco (r= –,413; p = ,036). Los datos de fiabilidad absoluta cuestionan la utilidad de estas pruebas en programas de entrenamiento donde los participantes tienen poco margen de mejora. Además, si se realizan comparaciones entre sujetos es importante tener en cuenta sus diferencias antropométricas, ya que durante la ejecución de los test el cuerpo se utiliza como instrumento de medida

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

Aplicación de la dinamometría isocinética para establecer perfiles de riesgo de lesión isquiosural en futbolistas profesionales. [The use of isokinetic dynamometry to establish risk profiles of hamstring injury in professional football players].

<p align="justify">Las lesiones en la musculatura isquiosural son frecuentes en el fútbol profesional y han sido relacionadas con el desequilibrio entre la fuerza de los flexores y extensores de rodilla. El objetivo de nuestro estudio fue comprobar si la ratio de fuerza máxima excéntrica de flexores/concéntrica de extensores (ratio Flexexc30/Extcon240) y el ángulo de rodilla donde la musculatura isquiosural alcanza su máximo momento de fuerza, son variables útiles para establecer perfiles de riesgo de lesión isquiosural en futbolistas profesionales. Veinte jugadores de un equipo de la Segunda División de la Liga de Fútbol Profesional realizaron bilateralmente un test isocinético de flexión excéntrica de rodilla a 30º/s y extensión concéntrica de rodilla a 240º/s durante la pretemporada. Tras calcular la ratio Flexexc30/Extcon240 y el ángulo de máximo momento de fuerza, se registraron las lesiones sufridas por los jugadores a lo largo de la temporada. Los resultados mostraron que dos de los cinco jugadores lesionados presentaron ratios Flexexc30/Extcon240 menores de 0.89, valor que ha sido utilizado previamente para determinar el desequilibrio entre la musculatura flexora y extensora de rodilla y el riesgo de lesión (Croisier, Ganteaume, Binet, Genty, y Ferret, 2008). Además, otros dos de los jugadores lesionados obtuvieron ratios entre 0.93 y 1.00. Por otro lado, no se encontraron diferencias en el ángulo de máximo momento de fuerza entre jugadores lesionados y no lesionados. Estos resultados indican que la ratio Flexexc30/Extcon240 puede ser un índice útil para determinar el riesgo de lesión isquiosural en futbolistas profesionales.</p>Abstract<p align="justify">Hamstring injuries are common in professional football and have been related to the imbalance between knee flexor and extensor strength. The aim of our study was to establish whether the flexor eccentric/extensor concentric strength ratio (Flexexc30/Extcon240 ratio) and the knee angle where the peak torque of the hamstring musculature was found, are useful variables to establish risk profiles for hamstring injury in professional football players. Twenty players of a Second Division team of the Liga de Fútbol Profesional bilaterally performed an isokinetic test of eccentric knee flexion at 30º/s and concentric knee extension at 240º/s during the pre-season. The Flexexc30/Extcon240 ratio and the knee angle of peak torque were calculated, and the players’ injuries were registered throughout the season. The results showed that two of the five injured players had Flexexc30/Extcon240 ratios lower than 0.89, value that has been previously used to determine the imbalance between knee flexor and extensor strength and the risk of injury (Croisier, Ganteaume, Binet, Genty, and Ferret, 2008). In addition, another two injured players obtained ratios between 0.93 and 1.00. On the other hand, no differences in the knee angle of peak torque between injured and non-injured players were found. These results indicate that the Flexexc30/Extcon240 ratio may be a useful index to determine the risk of hamstring injury in professional football players.</p>http://dx.doi.org/10.5232/ricyde2013.0340

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

Reliability assessment and correlation analysis of 3 protocols to measure trunk muscle strength and endurance

Different methods have been developed to quantify trunk muscle strength and endurance. However, some important protocol characteristics are still unclear, hindering the selection of the most suitable tests in each specific situation. The aim of this study was to examine the reliability and the relationship between 3 representative tests of the most common type of protocols used to assess trunk muscle strength and endurance. Twenty-seven healthy men performed each test twice spaced 1 month apart. Trunk strength and endurance were evaluated with an isokinetic dynamometer and 2 field tests including Biering-Sørensen test and Flexion–rotation trunk test. All tests showed a good relative consistency (intraclass correlation coefficient [ICC]> 0.75), except for the isokinetic endurance variables which had low–moderate reliability (0.37 0.65). Absolute reliability seemed slightly better in the isokinetic protocol than in the field tests, which showed about 12% of test–retest score increase. No significant correlations were found between test scores. After a familiarisation period for the field tests, the 3 protocols can be used to obtain reliable measures of trunk muscle strength and endurance. Based on the correlation analysis, these measures are not related, which highlights the importance of selecting the most suitable trunk test for each situation

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

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