Are trunk stability and endurance determinant factors for whole-body dynamic balance in physically active young males? A multidimensional analysis.

OBJECTIVES: Determine if (a) a better trunk stability and endurance are associated with an improved whole-body dynamic balance, and if (b) the assessment tests can be interchanged within each capability. METHODS: Sixty-three physically active young males performed three trunk stability (i.e., the lumbopelvic stability, the unstable sitting and the sudden loading sitting tests), three trunk muscle endurance (i.e., the Biering-Sørensen, the side bridge and the front bridge tests) and four whole-body dynamic balance (i.e., the tandem and the single-leg stance, the Y-Balance, and the single-leg triple hop tests) tests two times. After assessing the reliability of the variables, a Pearson correlation analysis was performed. RESULTS: The correlations between trunk stability and endurance tests with dynamic balance tests were non-significant except for the unstable sitting test with both the tandem (r = 0.502) and the single-leg stance (r = 0.522) tests. Moreover, no relationships were observed between the trunk stability and the trunk muscle endurance tests. Interestingly, no relationships were found between most tests within each capability (i.e., trunk stability, trunk endurance, and dynamic balance) except: (i) the front bridge stability test and the back (r = 0.461) and the side (r = 0.499) bridge stability tests; (ii) the two side bridge endurance tests (r = 0.786); (iii) the tandem and the single-leg stance tests (0.439 ≤ r ≤ 0.463); (iv) the Y-Balance and the single-leg triple hop tests (0.446 ≤ r ≤ 0.477). CONCLUSION: Better trunk function does not seem to be a relevant factor for dynamic balance in young active males. In this population, specific measures are needed as the test interchangeability is questioned.

Postural control strategies are revealed by the complexity of fractional components of COP.

The complexity of the center of pressure (COP) provides important information regarding the underlying mechanisms of postural control. The relationships between COP complexity and balance performance are not fully established and might depend on the task constraints and the filtering decomposition of the COP signal. This study assessed COP complexity under different task constraints and it was assessed if emergent dynamics of COP fluctuations differ according to fractional components of COP related to peripheral or central adjustments. One hundred and sixty-two participants performed two sitting balance tasks. Accuracy was required by following a target that moved in the mediolateral (ML) or in the anteroposterior (AP) axis. Complexity dynamics of COP were addressed through detrended fluctuation analysis (DFA) in the axis constrained by accuracy requirements and in the one nonconstrained. Decomposition of COP components was applied by low-pass, band-pass, and high-pass filters. DFA of low-pass and band-pass components of COP in the constrained axis were small-to-moderately related (r = 0.190-0.237) to balance performance. DFA of the high-pass component of the COP exhibited the opposite relationship (r = -0.283 to -0.453) in both axes (constrained and nonconstrained). This study evidences that COP complexity is linked to better performance. This positive relationship complexity/performance is observed in the low- and mid-frequency components of the COP. These components might be related to central mechanisms of postural control. The lack of relationships between the different frequencies analyzed in the study suggests that they are capturing different components of postural control.NEW & NOTEWORTHY The relationship between the complexity of the center of pressure (COP) and balance performance is not fully established. The task constraints and the filtering decomposition of the COP could influence this relationship. COP complexity is related to a better balance performance only in low frequencies and midfrequencies of the COP. The different frequencies measure different postural control components. Filtering decomposition should be explored in future studies to address the underlying mechanisms of postural control.

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. LEVEL OF EVIDENCE: III.

Comparisons of hip strength and countermovement jump height in elite tennis players with and without acute history of groin injuries.

BACKGROUND: Despite the high groin-injury (GI) prevalence in tennis, no studies have assessed the extent to which intrinsic groin injury risk factors, such as hip muscle strength, have recovered in elite tennis players with a history of previous GI. OBJECTIVE: To investigate whether elite tennis players with a history of GI show differences in hip strength and jump height between injured and uninjured limbs and compared with dominant limb in tennis players without history of acute groin-injuries (NGI). DESIGN: Cohort study. PARTICIPANTS: Sixty-one tennis players completed this study: 17 in the GI group and 44 in the NGI. Isometric adductor and abductor hip strength were assessed with a handheld dynamometer, and unilateral counter-movement jump tests were performed on a contact mat connected to an Ergo tester. Paired t-tests were conducted to identify differences between injured and non-injured limbs in the GI group, and independent measures t-tests were conducted to compare between GI and NGI groups. RESULTS: Isometric adductor strength and adductor/abductor strength ratios were lower in the injured limb (16.4% and 20.1%, respectively) compared with uninjured side within the GI group, and lower than the dominant side in the NGI group. No significant differences were found for unilateral jump heights between sides in the GI, nor isometric abductor strength, when comparing GI to NGI groups. CONCLUSIONS: Isometric adductor weakness and adductor/abductor strength ratio deficits suggest that adductor muscle strength is not fully recovered in these athletes, potentially increasing their risk of a repeat groin injury.

Core stability: evaluación y criterios para su entrenamiento / / Core stability: avaliação e critérios para treinamento / Core stability: evaluation and training criteria

El objetivo de este trabajo fue revisar las características de los métodos utilizados para valorar la estabilidad de la zona central del cuerpo (core stability), así como las características más importantes de los programas de ejercicios de estabilización del tronco. Los resultados de la revisión indican que métodos biomecánicos, como la aplicación controlada de cargas o descargas súbitas, el paradigma del asiento inestable y la modelación matemática, han permitido analizar el efecto de numerosos factores sobre la estabilidad del raquis. Por otro lado, los test de campo utilizados habitualmente para valorar la core stability (test de condición muscular, test de equilibrio corporal en apoyo monopodal, test de control postural del raquis lumbar y la pelvis, etc.) presentan limitaciones importantes, principalmente debido a la falta de estudios sobre la validez de estas medidas. Finalmente, existe una gran cantidad de información en relación con la eficacia y la seguridad de los ejercicios de estabilización, pero carecemos de información suficiente sobre otras características de la carga de entrenamiento (AU)

The aim of this study was to review both the characteristics of the tests used to assess core stability and the most important features of trunk stabilization exercise programs. The results of this review suggest that biomechanical methods such as sudden and controlled trunk loading and unloading, unstable sitting paradigm and mathematical modeling, have allowed us to analyze the effect of several factors on spine stability. In addition, field tests commonly used to assess core stability (muscle condition tests, single leg stance balance tests, postural control of lumbar spine and pelvis tests, etc.) have important limitations, mainly due to the absence of studies on the validity of these measurements. Finally, there is a lot of information regarding the effectiveness and safety of the stabilization exercises, but we lack enough information on other training load characteristics (AU)

O objetivo desse trabalho foi revisar as características dos métodos utilizados para avaliar a estabilidade da zona central do corpo ("core estability"), assim como as características mais importantes dos programas de exercícios de estabilização do tronco. Os resultados da revisão indicam que métodos biomecânicos como a aplicação controlada de cargas ou descargas súbitas, o paradigma do assento estável e a modelação matemática, tem permitido analisar o efeito de numerosos fatores sobre a estabilidade da coluna. Por outro lado, os testes de campo utilizados habitualmente para avaliar a estabilidade do core (teste de condição muscular, teste de equilíbrio corporal em apoio monopodal, teste de controle postural da coluna lombar e da pelve, etc.) apresentam limitações importantes, principalmente devido a falta de estudos sobre a validade dessas medidas. Finalmente, existe uma grande quantidade de informação em relação à eficácia e à segurança dos exercícios de estabilização, mas carecemos de informação suficiente sobre outras características da carga de treinamento

Core stability. Concepto y aportaciones al entrenamiento y la prevención de lesiones / / «Core stability». Conceito e contribuições no treinamento e a prevenção de lesões / «Core stability». Concept and contributions to training and injury prevention

En este trabajo presentamos una revisión de la literatura científica sobre la estabilidad de la zona central del cuerpo (core stability) con el objeto de clarificar el significado de este concepto y su relación con el rendimiento y las lesiones deportivas. Los resultados de la revisión indican que el uso del término core stability es ambiguo, existiendo una gran confusión terminológica tanto en la literatura científica como en el ámbito profesional. Diversos estudios biomecánicos y epidemiológicos sugieren que el déficit en el control neuromuscular de la core stability está relacionado con el síndrome de dolor lumbar y lesiones de los miembros inferiores. Sin embargo, a pesar de que los ejercicios de core stability son elementos habituales dentro de los programas de entrenamiento deportivo, no existen evidencias suficientes para establecer una relación clara entre la práctica de estos ejercicios y la mejora del rendimiento en el deporte (AU)

In this work we present a scientific literature review on core stability with the aim of clarifying the meaning of this concept and its relation with sport performance and injury. The results of this review show that the use of the term core stability is ambiguous, as there is a great terminological confusion in both scientific literature and professional fields. Several biomechanical and epidemiological studies suggest that the neuromuscular control deficit of core stability is related to low back pain and lower limb injuries. Nevertheless, despite the fact that core stability exercises are key elements in sport training programs,there isnot enoughevidence to establisha clear relationbetweenthe practice ofthese exercises and the improvement in sport performance (AU)

Neste trabalho apresentamos uma revisão da literatura científica sobre a estabilidade da zona central do corpo (core stability), com o objetivo de esclarecer o significado do conceito e sua relação com o rendimento e lesões desportivas. Os resultados desta revisão indicam que o uso do termo core stability é ambíguo, existindo uma grande confusão terminológica tanto na literatura científica como no âmbito profissional. Diversos estudos biomecânicos e epidemiológicos sugerem que o déficit no controle neuromuscular da core stability está relacionado com a síndrome da dor lombar e lesões dos membros inferiores. No entanto, apesar dos exercícios de core stability serem elementos habituais dentro dos programas de treinamento desportivo, não existem evidências suficientes para estabelecer uma relação clara entre a prática dos exercícios e a melhora do rendimento no esporte (AU)

El procesado del desplazamiento del centro de presiones para el estudio de la relación complejidad/rendimiento observada en el control postural en bipedestación / Center of pressure preprocessing methods to analyze complexity/performance relation in quiet standing

Objetivo. Este estudio evalúa la relación entre complejidad y dispersión del centro de presiones (COP) en una tarea de equilibrio en bipedestación, observando cómo la frecuencia de registro, las características estacionarias y el uso de distintos análisis afectan a la misma. Método. Se registró el desplazamiento del COP de 21 voluntarios que se mantuvieron de pie durante 30 segundos sobre una superficie estable. Se analizó la desviación típica (DT) y la complejidad de las fluctuaciones del COP mediante SampleEntropy (SampEn) y Detrended Fluctuation Analysis (DFA), a diferentes frecuencias (1000,100 y 20 Hz) y en función de la eliminación de la tendencia de la señal. Resultados. La frecuencia de registro afecta a los valores de SampEn y DFA, disminuyendo y aumentando, respectivamente, al aumentar la frecuencia de registro. Sin embargo, el tratamiento del COP no muestra ninguna influencia. Existe una correlación negativa entre la DT y el SampEn en ambos ejes. No obstante, la relación entre la DT y el DFA se modifica en función del eje, siendo negativa en el eje AP y positiva en el ML. Conclusión. La frecuencia de registro no influye de manera determinante en las variables no lineales, pero las frecuencias cercanas a las de la dinámica del COP maximizan las diferencias existentes en el DFA. Por otro lado, se recomienda la eliminación de la tendencia de la señal para mejorar el análisis de la estructura de la variabilidad del desplazamiento del COP. Los resultados obtenidos respaldan la existencia de la relación entre el rendimiento y la complejidad del COP(AU)

Objective. The aim of this study is to analyze the relationship between the complexity and postural balance in a standing balance task. In this way, this study assesses the effect of the sample frequency, the stationarity of center of pressure (COP) and the used of different analysis. Method. Twenty-one volunteers were asked to stand still for 30 s on a stable surface. Displacement of COP was measured. The performance was assessed through the standard deviation (SD) of COP. Complexity of COP was measured through Sample Entropy (SampEn) and Detrended Fluctuation Analysis (DFA). All variables were analyzed on three different frequencies (20,100 and 1000 Hz) and on two signal treatment (the original and detrended signal). Results. The sample frequency influences the values of SampEn and DFA. However, these values keep the trend shown between experimental conditions. SD values are negatively related with SampEn of COP data in both axes. Nevertheless, the relationship between SD and DFA varies by axis; this relationship is negative in the AP axis and positive in the ML axis. Conclusion. The sample frequency has a significant influence in the results, but frequencies close to the dynamics of COP enhance the differences. On the other hand, we suggest to detrend the signal to improve the analysis of dynamics of COP. The results support the direct relationship between performance and complexity of COP(AU)