How should we quantify intensity load to design core stability training programs?

Many biomechanical studies have been performed to select the most effective and safest core stability exercises (CSE). However, although most of these exercises are commonly used to enhance motor performance and to prevent and treat musculoskeletal injuries, little is known and understood about how CSE intensity should be quantified and modulated to optimize the benefits of CSE training programs. Based on this limitation, two descriptive studies were performed in this doctoral thesis with the main objectives of 1) analyzing the reliability of different posturographic methodologies to assess the intensity of CSE in research and field settings and of 2) establishing difficulty progressions for CSE in young physically active males and females. In both studies, the intensity of some of the most common isometric CSE (bird-dog, front bridge, back bridge and side bridge exercises) was quantified through the evaluation of the postural control demands imposed on the participants when they tried to maintain their spine in neutral position during the exercise execution. In the First Study, 48 males (age: 23.4 ± 3.3 years, mass: 72.4 ± 8.2 kg, height: 175.2 ± 4.8 cm) and 28 females (age: 24.5 ± 2.7 years, mass: 62.2 ± 10.7 kg, height: 163.8 ± 8.6 cm) performed five variations of each of the aforementioned CSE on two synchronized force platforms. The mean velocity and the resultant distance of the center of pressure (CoP) displacement were calculated to assess exercise intensity through the measurement of the participants’ body sway. Unlike the reliability scores of the resultant distance of CoP displacement, the standard error of measurement (SEM) and the intra-class correlation coefficient (ICC3,1) scores obtained by the mean velocity of the CoP displacement were acceptable (most exercise variations obtained SEM values 0.60) to establish intensity progressions for the CSE. The exercise 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 highlights the need to individualize these progressions according to the participants’ training level. In the Second Study, 12 males (age: 23.5 ± 3.6 years; mass: 73.9 ± 6.3 kg; height: 173.9 ± 4.7 cm) and 11 females (age: 24.1 ± 1.5 years; mass: 63.1 ± 8.8 kg; height: 165.0 ± 11.5 cm) performed the same exercise variations also on the two force platforms, but in this case we placed a smartphone accelerometer on the participants’ pelvis to assess pelvic acceleration. Most CSE variations obtained moderate-to-high reliability scores for the pelvic acceleration (0.71 < ICC < 0.88; 13.23% ≤ SEM ≤ 22.99%) and low-to-moderate reliability scores for the mean velocity of the CoP sway (0.24 < ICC < 0.89; 9.88% ≤ SEM ≤ 35.90%). In addition, correlations between these two variables were moderate-to-high (0.52 ≤ r ≤ 0.81). Based on these results, smartphone accelerometers placed on the pelvis provide a more reliable and local measure of postural control during CSE than the MV of CoP sway. Moreover, considering these results and the low-cost, portability and usability of the smartphone accelerometers, these devices seem adequate to quantify the intensity of the CSEs in research and field settings. Overall, this doctoral thesis provides useful information both to guide the design and to control the training intensity of CSE training programs in young physically active individuals.En la actualidad, varios estudios biomecánicos han analizado qué ejercicios de estabilización del tronco (EET) son los más eficaces y seguros. Sin embargo, aunque la mayoría de esos ejercicios se utilizan habitualmente para mejorar el rendimiento motriz, así como la prevención y tratamiento de lesiones músculo esqueléticas, en realidad se sabe poco sobre cómo la intensidad de los EET debería ser cuantificada y manipulada para optimizar los beneficios de los programas de entrenamiento basados en estos ejercicios. En base a esta limitación, en esta tesis se llevaron a cabo dos estudios descriptivos con los objetivos principales de 1) analizar la fiabilidad de distintas metodologías posturográficas para evaluar la intensidad de los EET tanto en laboratorio como en campo y 2) establecer progresiones de dificultad para esos ejercicios en hombres y mujeres físicamente activas. En ambos estudios se cuantificó la intensidad de algunos de los EET isométricos más comunes (perro de muestra, puente frontal, puente dorsal y puente lateral) a través de la evaluación del control postural mostrado por los participantes al intentar mantener la columna vertebral en posición neutra durante la ejecución de dichos ejercicios. En el Primer Estudio, 48 hombres (edad: 23.4 ± 3.3 años, peso: 72.4 ± 8.2 kg, altura: 175.2 ± 4.8 cm) y 28 mujeres (edad: 24.5 ± 2.7 años, peso: 62.2 ± 10.7 kg, altura: 163.8 ± 8.6 cm) realizaron cinco variaciones de cada uno de los ejercicios mencionados anteriormente sobre dos plataformas de fuerzas sincronizadas. Para evaluar la intensidad de los ejercicios, se analizó la oscilación corporal de los participantes mediante el cálculo de la velocidad media y la distancia resultante de la oscilación del centro de presiones (CdP). Contrariamente a lo observado para la distancia resultante, los valores del error estándar de la medida (EEM) y del coeficiente de correlación intra-clase (CCI3,1) mostrados por la velocidad media fueron adecuados (la mayoría de las variaciones de los ejercicios obtuvieron valores de EEM 0.60) para establecer progresiones de intensidad para los EET. Las progresiones obtenidas por hombres y mujeres fueron muy similares. Sin embargo, aquellos participantes con mayor control de tronco mostraron menos diferencias significativas entre las variaciones de los ejercicios que los participantes con menos control de tronco, lo cual destaca la necesidad de individualizar estas progresiones de acuerdo al nivel de entrenamiento de los participantes. En el Segundo Estudio, 12 hombres (edad: 23.5 ± 3.6 años; peso: 73.9 ± 6.3 kg; altura: 173.9 ± 4.7 cm) y 11 mujeres (edad: 24.1 ± 1.5 años; peso: 63.1 ± 8.8 kg; altura: 165.0 ± 11.5 cm) realizaron los mismos ejercicios descritos en el primer estudio sobre dos plataformas de fuerzas, pero en este caso se colocó en un smartphone en la pelvis de los participantes para evaluar la aceleración pélvica a través del acelerómetro que lleva integrado dicho dispositivo. La fiabilidad de la mayoría de las variaciones de los EET fue moderada-alta para la aceleración pélvica (0.71 < CCI < 0.88; 13.23% ≤ EEM ≤ 22.99%) y baja-moderada para la velocidad media del CdP (0.24 < CCI < 0.89; 9.88% ≤ EEM ≤ 35.90%). Además, las correlaciones entre estas dos variables fueron moderadas-altas (0.52 ≤ r ≤ 0.81). En base a estos resultados, los acelerómetros integrados en los smartphones colocados en la pelvis aportan una medida más fiable y local del control postural durante los EET que la oscilación del CdP medida a través de la velocidad media. Asimismo, teniendo en cuenta estos resultados, así como el bajo coste, portabilidad y facilidad de uso de los acelerómetros integrados en los smartphones, estos dispositivos podrían ser una herramienta adecuada para cuantificar la intensidad de los EET tanto en el ámbito de la investigación como en el campo profesional. En general, esta tesis ofrece información útil para guiar en el diseño y control de la intensidad de los programas de entrenamiento de EET en hombres y mujeres jóvenes físicamente activos

Biomechanical Spectrum of Human Sport Performance

Writing or managing a scientific book, as it is known today, depends on a series of major activities, such as regrouping researchers, reviewing chapters, informing and exchanging with contributors, and at the very least, motivating them to achieve the objective of publication. The idea of this book arose from many years of work in biomechanics, health disease, and rehabilitation. Through exchanges with authors from several countries, we learned much from each other, and we decided with the publisher to transfer this knowledge to readers interested in the current understanding of the impact of biomechanics in the analysis of movement and its optimization. The main objective is to provide some interesting articles that show the scope of biomechanical analysis and technologies in human behavior tasks. Engineers, researchers, and students from biomedical engineering and health sciences, as well as industrial professionals, can benefit from this compendium of knowledge about biomechanics applied to the human body

Applied Biomechanics: Sport Performance and Injury Prevention

This Special Issue had, as its main objective, the compilation of biomechanical studies on sports performance and its relationship with musculoskeletal injuries. It is a collection of research on eight different sports (soccer, volleyball, swimming, cycling, skiing, golf, athletics, and hockey) considering injuries in general and specific injuries such as hamstring muscle injury, anterior cruciate ligament of the knee, and pain of the pubic symphysis. Additionally, it is noteworthy that most of the studies considered both men and women. Classical biomechanical tools have been used, such as 2D and 3D motion analysis, force platforms, and electromyography

Physical Diagnosis and Rehabilitation Technologies

The book focuses on the diagnosis, evaluation, and assistance of gait disorders; all the papers have been contributed by research groups related to assistive robotics, instrumentations, and augmentative devices

Validez y fiabilidad de test de campo para evaluar la condición física relacionada con la salud en adultos. Proyecto Adult- Fit

Physical fitness is considered a powerful health marker in different populations (i.e., preschool, childhood, adolescence, adults, and older adults). Epidemiological studies have demonstrated an inverse association between cardiorespiratory and muscular fitness, with morbidity and all-cause mortality. Consequently, physical fitness assessment is considered an important prevention and diagnosis tool. Physical fitness can be objectively and accurately measured through laboratory tests. However, due to their high cost, the necessity of sophisticated instruments, qualified technicians, and time constraints, their use is limited in population-based studies. Field-based physical fitness tests provide a reasonable alternative since they are easy to administer, involve minimal equipment, are low in cost, and a large number of participants can be evaluated in a relatively short period of time and simultaneously. Valid, reliable, feasible, safe, and responsiveness are characteristics that need to be assured for any measurement tool. Longitudinal studies have recently contributed to the existing health-related fitness batteries archiving those characteristics in children and adolescents (The ALPHA Study), and preschool children (The PREFIT Study). However, researchers, clinicians, and sport practitioners do not have enough information about which field-based physical fitness tests are more reliable, valid, and informative from the health point of view to be implemented in adults. Therefore, the general aim of this International Doctoral Thesis was: to propose a battery of field-based tests to assess physical fitness related to health in adults based on scientific evidence, valid (i.e. predictive validity and criterion-related validity) and reliable, depending on sex, age, and physical activity level: The ADULT-FIT project [Plan nacional I+D +i 2017-2020, (ref.: DEP2017-88043-R)]. Likewise, the specific aims were: (i) to comprehensively analyze the predictive validity of the existing motor fitness and flexibility tests in relation to several health outcomes in adults and older adults (study I); (ii) to comprehensively study the criterion-related validity of the existing field-based physical fitness tests used in adults aged 18-64 years (study II), and to identify studies evaluating the criterion-related validity of existing field-based methods and equations for body composition estimation used in adults aged 18-64 years (study III); (iii) to systematically review studies conducted to examine the reliability of field-based physical fitness tests used in adults aged 18-64 years (study IV); (iv) to analyze the criterion-related validity and the reliability of the 2-km walk test and the 20-m shuttle run test for evaluating cardiorespiratory fitness in the adult population, according to sex, age, and physical activity level (study V), and to analyze the criterion-related validity and reliability of the standing long jump test to assess the lower-body explosive muscular fitness in adults, according to sex, age, and physical activity level (study VI). The main results showed that there is strong evidence indicating that: (i) slower gait speed, impaired balance, and worse TUG performance are good indicators of health outcomes in both adults and older adults; and limited evidence about the predictive validity of flexibility tests exists (study I). (ii) To assess cardiorespiratory fitness, the 20-m shuttle run test (using Leger’s equation), 1.5-mile run/walk test, 12-min run/walk test, 6-min walk test, YMCA step test, and the 2-km walk test (using Oja’s equation) are valid; to assess muscular fitness, the handgrip test (using the TKK dynamometer), and the Biering–Sørensen test are valid; to assess flexibility, the sit-and-reach test (and its different versions), and that the toe-to-touch tests are not valid; limited evidence about the criterion-related validity of motor fitness exists (study II). (iii) The field-based methods, waist circumference, body adiposity index, and body mass index are valid indicators of body adiposity in adult population; classical equations, such as Durnin/Womersley equation, Jackson/Pollock equation, Jackson, Pollock and Ward equation, and estimation equations implying skinfolds, alone or combined with circumferences, are most valid to estimate total body fat mass or body fat percentage in adult population (study III). (iv) To assess cardiorespiratory fitness, the 20-m shuttle run test, the step tests and the 6-min walk test are reliable; to assess musculoskeletal fitness, the handgrip test (using a JAMAR dynamometer), back-leg test, Biering-Sørensen (and its modified versions), trunk flexion sustained, 5-reps sit-to-stand, bilateral side and prone bridge, the sit-and-reach (and its modified versions), and the toe-to-touch test are reliable; to assess motor fitness, the T-test (and its modified version) is reliable, and the single- leg stand test (and its modified versions) is not reliable (study IV). (v) The 2-km walk test (using) and the 20-m shuttle run test, as well as their corresponding Oja’s and Leger’s equations, are valid and reliable for estimating cardiorespiratory fitness in adults aged 18-64 years. However, the 20-m shuttle run test obtained slightly greater criterion-related validity and reliability, regardless of sex, age, and physical activity level (study V). (vi) The standing long jump test may be a valid tool to assess the adult population's lower-body explosive muscular fitness, independent of age, and physical activity levels. The standing long jump test may be used when controlling the possible learning effect to provide reliability (study VI). This International Doctoral Thesis provides evidence to propose a battery of field-based tests to assess physical fitness related to health in adults based on valid and reliable scientific evidence, depending on sex, age, and physical activity levels. Future methodological studies are still necessary to establish the validity and/or reliability of those field-based physical fitness tests identified in systematic reviews having insufficient or strong evidence that have not been developed in this International Doctoral Thesis, as well as the feasibility and safety of those field-based physical fitness test identified (in the systematic reviews) as valid and reliable, and the responsiveness of those field-based physical fitness test identified as valid, reliable, feasible and safe, in adult population

Criterios para la toma de decisiones en la determinación de la intensidad y progresión de los ejercicios dirigidos a la mejora de la estabilidad del tronco

La falta de control de la magnitud de la carga de entrenamiento, fundamentalmente la intensidad, es una de las principales limitaciones a la hora de la toma de decisiones para desarrollar programas de ejercicios de estabilización del tronco (ET). Tradicionalmente la intensidad se ha establecido en función de criterios personales de los profesionales que prescriben y dirigen los programas, criterios que no suelen aparecer descritos en los estudios experimentales y que generalmente no han sido validados o sometidos a evaluación. Partiendo de estas limitaciones, los estudios realizados en la presente Tesis Doctoral analizaron diferentes criterios y herramientas para facilitar la toma de decisiones durante el establecimiento de la intensidad de los principales ejercicios de ET y su progresión a lo largo del proceso de entrenamiento. En este sentido, el estudio 1 mostró una alta concordancia inter- e intra-evaluador al utilizar criterios de evaluación observacional basados en la valoración de la dificultad de los participantes para mantener el cuerpo alineado y limitar el movimiento del tronco durante la ejecución de los ejercicios puente frontal, puente dorsal, puente lateral y perro de muestra. Hasta donde conocemos, este es el primer estudio que ha analizado la fiabilidad de criterios de evaluación observacional para la prescripción de la intensidad de los ejercicios de ET. Con objeto de desarrollar criterios objetivos para la prescripción de los ejercicios de ET, en el estudio 1 también se realizaron curvas de rendimiento diagnóstico (conocidas como curvas ROC) para analizar la relación entre las valoraciones de evaluadores expertos y la aceleración de la pelvis medida mediante acelerometría integrada en smartphone como indicador de la intensidad de los ejercicios. Este análisis permitió establecer umbrales de aceleración de la pelvis para los ejercicios referidos que podrían representar los niveles de intensidad mínima necesarios para producir adaptaciones en la ET en personas jóvenes y físicamente activas. Por otro lado, en el estudio 2 se utilizó la acelerometría integrada en smartphone para establecer progresiones en intensidad de diferentes variaciones de los ejercicios puente frontal, puente dorsal, puente lateral y perro de muestra en varones jóvenes y físicamente activos. Los datos obtenidos indican que la realización de puentes largos (con rodillas extendidas) en lugar de puentes cortos (con rodillas flexionadas y apoyadas en el suelo), la reducción del número de apoyos, el apoyo de parte del peso corporal sobre superficies inestables (balón hemiesférico y fitball) y el movimiento de los segmentos en suspensión son criterios a tener en cuenta para incrementar la intensidad de estos ejercicios. Finalmente, los datos obtenidos mostraron también la necesidad de individualizar la prescripción de las progresiones de ejercicios de ET en función del nivel de control postural lumbo-pélvico. Por tanto, en conjunto, los estudios 1 y 2 presentan información relevante para la toma de decisiones de los profesionales del ejercicio físico y la salud durante el diseño de programas dirigidos a la mejora de la ET en personas jóvenes y físicamente activas.The lack of control of the training load magnitude, mainly the intensity, is one of the main limitations when making decisions to develop trunk stability (TS) exercise programs. Traditionally, intensity has been established according to the personal criteria of the professionals who prescribe and conduct the programs, criteria that are not usually described in experimental studies and that have generally not been validated or subjected to evaluation. Based on these limitations, the studies carried out in this Doctoral Thesis analyzed different criteria and tools to facilitate decision-making during the establishment of the intensity of the main TS exercises and their progression throughout the training process. In this sense, study 1 showed a high inter- and intra-evaluator agreement through the use of observational screening guidelines based on the assessment of the participants' difficulty to keep the body aligned and to limit trunk movement during the execution of front bridge, dorsal bridge, side bridge and bird-dog exercises. To our knowledge, this is the first study that has analyzed the reliability of observational screening guidelines for the prescription of the TS exercise intensity. To develop objective criteria for TS exercise prescription, diagnostic performance curves (known as ROC curves) were also performed in study 1 with the aim of analyzing the relationship between expert rater ratings and pelvic accelerations (measured by smartphone accelerometry) as an indicator of exercise intensity. This analysis made it possible to establish pelvic acceleration thresholds for the referred exercises that could represent the minimum intensity levels necessary to proaccelerometry was used to establish intensity progressions of different variations of frontal bridge, dorsal bridge, lateral bridge and bird-dog exercises in young physically active males. The data obtained indicates that performing long bridges (with knees extended) instead of short bridges (with knees bent and resting on the floor), reducing the number of support points, supporting part of the body weight on unstable surfaces (hemisphere ball and fitball) and the movement of the elevated limbs are criteria to be taken into account when aiming to increase the intensity of these exercises. Finally, the data obtained also showed the need to individualize the prescription of TS exercise progressions according to the lumbo-pelvic postural control level. Therefore, overall, studies 1 and 2 present relevant information for decision making by physical exercise and health professionals when designing programs aimed at improving TS in young physically active individuals.duce adaptations in TS in young physically active individuals. On the other hand, in study 2, smartphone accelerometry was used to establish intensity progressions of different variations of frontal bridge, dorsal bridge, lateral bridge and bird-dog exercises in young physically active males. The data obtained indicates that performing long bridges (with knees extended) instead of short bridges (with knees bent and resting on the floor), reducing the number of support points, supporting part of the body weight on unstable surfaces (hemisphere ball and fitball) and the movement of the elevated limbs are criteria to be taken into account when aiming to increase the intensity of these exercises. Finally, the data obtained also showed the need to individualize the prescription of TS exercise progressions according to the lumbo-pelvic postural control level. Therefore, overall, studies 1 and 2 present relevant information for decision making by physical exercise and health professionals when designing programs aimed at improving TS in young physically active individuals