An exploration of the motor unit behaviour during the concentric and eccentric phases of a squat task performed at different speeds.

Despite squatting being important in strength training and rehabilitation, few studies have investigated motor unit (MU) behaviour. This study explored the MU behaviour of vastus medialis (VM) and vastus lateralis (VL) during the concentric and eccentric phases of a squat exercise performed at two speeds. Twenty-two participants had surface dEMG sensors attached over VM and VL, and IMUs recorded thigh and shank angular velocities. Participants performed squats at 15 and 25 repetitions per minute in a randomised order, and EMG signals were decomposed into their MU action potential trains. A four factor (muscle × speed × contraction phase × sexes) mixed methods ANOVA revealed significant main effects for MU firing rates between speeds, between muscles and between sexes, but not contraction phases. Post hoc analysis showed significantly greater MU firing rates and amplitudes in VM. A significant interaction was seen between speed and the contraction phases. Further analysis revealed significantly greater firing rates during the concentric compared to the eccentric phases, and between speeds during the eccentric phase only. VM and VL respond differently during squatting depending on speed and contraction phase. These new insights in VM and VL MU behvaviour may be useful when designing training and rehabilitation protocols.

Diagnostics Using the Change-of-Direction and Acceleration Test (CODAT) of the Biomechanical Patterns Associated with Knee Injury in Female Futsal Players: A Cross-Sectional Analytical Study.

The primary aim of this study was to identify kinematic differences at initial contact between female futsal players with and without previous knee injury, using a functional motor pattern test. The secondary aim was to determine kinematic differences between the dominant and non-dominant limb in the whole group, using the same test. A cross-sectional study was performed in 16 female futsal players allocated into two groups: eight females with a previous knee injury, i.e., affected by the valgus collapse mechanism without surgical intervention, and eight with no previous injury. The evaluation protocol included the change-of-direction and acceleration test (CODAT). One registration was made for each lower limb, i.e., the dominant (the preferred kicking limb) and non-dominant limb. A 3D motion capture system (Qualisys AB, Göteborg, Sweden) was used to analyze the kinematics. The Cohen's d effect sizes between the groups demonstrated a strong effect size towards more physiological positions in the non-injured group in the following kinematics in the dominant limb: hip adduction (Cohen's d = 0.82), hip internal rotation (Cohen's d = 0.88), and ipsilateral pelvis rotation (Cohen's d = 1.06). The t-test for the dominant and non-dominant limb in the whole group showed the following differences in knee valgus: dominant limb (9.02 ± 7.31 degrees) and non-dominant limb (1.27 ± 9.05 degrees) (p = 0.049). Conclusions: The players with no previous history of knee injury had a more physiological position for avoiding the valgus collapse mechanism in the hip adduction and internal rotation, and in the pelvis rotation in the dominant limb. All the players showed more knee valgus in the dominant limb, which is the limb at greater risk of injury.

Body mass index and aerobic capacity: The key variables for good performance in soldiers.

Body composition, leg power and aerobic capacity have been shown to be related to performance, although their combined influence in a training task under load carriage in soldiers is still unknown. In this study, the influence of aerobic capacity, body composition and leg strength on performance during an obstacle test with and without combat equipment carriage was analysed. Forty males belonging to the Spanish Army participated in this study. The time needed to complete an obstacle course with and without load, aerobic capacity (20-m shuttle run test), leg power (squat jumps) and body composition variables (body mass index [BMI], fat mass and lean mass) were tested to determine the best predictors of performance. The results indicated that the best predictors of obstacle course performance with and without load carriage are VO2max and BMI. The jump height was not a significant factor in the model. In conclusion, BMI and VO2max are predictors of the obstacle test time with and without load carriage, so it is recommended that both variables are included as criteria for enrolment in the military army to guarantee army members exhibit the highest obstacle course performance possible.HighlightThe VO2max and BMI are the best predictors of an obstacle course performance with/without load carriage.The jump height was not a significant performance factor.The VO2max and BMI are recommended as enrolment criteria for military army.

Are Men and Women Equally Affected by Load Carriage While Landing? Analysis of Balance in Spanish Infantry Soldiers.

In this study, the effect of carrying combat equipment and a backpack on balance between men and women was analyzed by simulating a jump out of an armored fighting vehicle, together with the influence of body composition variables. Thirty-seven men and eight women participated in this study. Three landings were performed by simulating a jump from a wheeled armored vehicle carrying no load, carrying the combat equipment and backpack condition. A force plate was used to measure the amplitude and velocity displacement of the center of pressure and the stabilization time. A significant load effect was found on the total velocity and medial-lateral velocity. The weight of the combat equipment and the body composition variables did not correlate with the balance variables. Male and female soldiers showed similar body balance while carrying military combat equipment.

Chronic Effects of a Training Program Using a Nasal Inspiratory Restriction Device on Elite Cyclists.

This study compared the response of a 9-week cycling training on ventilatory efficiency under two conditions: (i) Combined with respiratory muscle training (RMT) using a new nasal restriction device (FeelBreathe) (FB group) and (ii) without RMT (Control group). Eighteen healthy elite cyclists were randomly separated into the FB group (n = 10) or Control group (n = 8). Gas exchange was measured breath by breath to measure ventilatory efficiency during an incremental test on a cycloergometer before (Pre) and after (Post) the nine weeks of training. The FB group showed higher peak power (Δ (95%HDI) (0.82 W/kg (0.49, 1.17)), VO2max (5.27 mL/kg/min (0.69, 10.83)) and VT1 (29.3 W (1.8, 56.7)) compared to Control at PostFINAL. The FB group showed lower values from Pre to PostPRE in minute ventilation (VE) (-21.0 L/min (-29.7, -11.5)), Breathing frequency (BF) (-5.1 breaths/min (-9.4, -0.9)), carbon dioxide output (VCO2) (-0.5 L/min (-0.7, -0.2)), respiratory equivalents for oxygen (EqO2) (-0.8 L/min (-2.4, 0.8)), heart rate (HR) (-5.9 beats/min (-9.2, -2.5)),, respiratory exchange ratio (RER) (-0.1 (-0.1, -0.0) and a higher value in inspiratory time (Tin) (0.05 s (0.00, 0.10)), expiratory time (Tex) (0.11 s (0.05, 0.17)) and end-tidal partial pressure of CO2 (PETCO2) (0.3 mmHg (0.1, 0.6)). In conclusion, RMT using FB seems to be a new and easy alternative ergogenic tool which can be used at the same time as day-to-day training for performance enhancement.

A Thorax Marker Set Model to Analyse the Kinematics of Walking Without the Need to Place Markers on the Back.

BACKGROUND: Previous thorax models have been proposed for gait analysis, however these require markers to be placed on the back. This presents a limitation in the kinematic analysis of the thorax under load carriage conditions. RESEARCH QUESTION: This study evaluated the validity and reliability of a thorax marker set that does not require markers to be placed on the back (HubemaLab model) when compared to 3 previously published marker set models. METHODS: 17 young adults were evaluated while walking at their self-selected speed. A 12 camera motion capture system was used to acquire the marker position data which was then processed using the respective models using Visual-3D. The level of agreement for the flexion/extension peak, right/left lateral peak and right/left rotation peak of the thorax angle and angular velocity; together with the range of motion and thorax angular velocities in the three planes was found between each thorax marker set, while the reliability was measured using the intraclass correlation coefficient. RESULTS: The ICC results for the thorax angle ROM and the range of thorax angular velocity between the HubemaLab model and the other models showed excellent to good reliability in all three planes. While the ICCs for the peak flexion/extension, peak right/left lateral flexion and peak right/left rotation showed excellent to moderate reliability in all three planes. CONCLUSION: The new model could be potentially valuable for kinematic gait analysis under load carriage conditions which obscure markers placed on the back.

Comparison of three different measurement systems to assess the vertical jump height / Comparação de três sistemas de medição diferentes para avaliar a altura do salto vertical / Comparación de tres sistemas de medición diferentes para evaluar la altura del salto vertical

ABSTRACT Introduction: The numerous instruments used to measure jump height use different technologies and calculations that can provide variable results. Objective: This study compared the countermovement jump (CMJ) height assessed with a wearable 3D inertial measurement unit (IMU), using flight time and the numerical integration method with a force platform and photocells. Methods: Forty CMJs were analysed, starting from an upright standing position with the hands placed on the waist. Twenty healthy volunteers completed 2 CMJs, which were simultaneously assessed using an IMU placed on the subject's sacrum, a force platform (considered the gold standard method) and photocells. The maximum height of each CMJ was measured. Results: The results showed a significant overestimation (p<0.001) in jump height for the IMU using the numerical integration method when compared to the force platform (+7 cm). Excellent intraclass correlation coefficients (ICCs) were obtained with the flight time equations for the different types of measurement equipment. Fair to good ICCs were obtained with the IMU using the numerical integration method and force platform. Conclusion: In conclusion, the jump height obtained with the IMU using the numerical integration method showed the poorest agreement compared to the force platform. Level of evidence III; Prospective comparative study.

RESUMO Introdução: Os numerosos instrumentos usados para medir a altura de salto empregam diferentes tecnologias e cálculos que podem fornecer resultados variáveis. Objetivo: Este estudo comparou a altura de salto contramovimento (SCM) com uma unidade de medida inercial 3D (UMI) portátil, usando o tempo de voo e o método de integração numérica, com plataforma de força e fotocélulas. Métodos: Quarenta SCMs foram analisados a partir da posição ortostática com as mãos na cintura. Vinte voluntários saudáveis concluíram 2 SCMs que foram avaliados simultaneamente com uma UMI colocada no sacro do indivíduo, uma plataforma de força (considerado o método de referência) e fotocélulas. A altura máxima de cada SCM foi medida. Resultados: Os resultados mostraram uma superestimação significativa (p < 0,001) da altura do salto para a UMI com o método de integração numérica, em comparação com a plataforma de força (+7 cm). Foram obtidos excelentes coeficientes de correlação intraclasse (ICCs) com as equações de tempo de voo entre os equipamentos de medição. Foram obtidos resultados de regulares a bons de ICC com a UMI pelo método de integração numérica e a plataforma de força. Conclusão: A altura de salto obtida com a UMI com o método de integração numérica mostrou a pior concordância em comparação com a plataforma de força. Nível de evidência III; Estudo prospectivo comparativo.

RESUMEN Introducción: Los numerosos instrumentos usados para medir la altura del salto emplean diferentes tecnologías y cálculos que pueden suministrar resultados variables. Objetivo: Este estudio comparó la altura del salto contramovimiento (SCM) con una un sistema inercial 3D (IMU) portátil, usando el tiempo de vuelo y el método de integración numérica, con plataforma de fuerza y fotocélulas. Métodos: Cuarenta SCMs fueron analizados a partir de la posición ortostática con las manos en la cintura. Veinte voluntarios saludables concluyeron dos SCMs que fueron evaluados simultáneamente con un IMU colocada en el sacro del individuo, una plataforma de fuerza (considerado el método de referencia) y fotocélulas. Fue medida la altura máxima de cada SCM. Resultados: Los resultados mostraron una sobreestimación significativa (p <0,001) de la altura del salto para la IMU con el método de integración numérica, en comparación con la plataforma de fuerza (+7 cm). Fueron obtenidos excelentes coeficientes de correlación intraclase (ICCs) con las ecuaciones de tiempo de vuelo entre los equipamientos de medición. Fueron obtenidos resultados de regulares a buenos de ICC con la IMU por el método de integración numérica y la plataforma de fuerza. Conclusión: La altura de salto obtenida con la IMU con el método de integración numérica mostró la peor concordancia en comparación con la plataforma de fuerza. Nivel de evidencia III; Estudio prospectivo comparativo.

Gender differences in patients with fibromyalgia: a gait analysis.

This study analysed the spatio-temporal parameters, asymmetry, variability and bilateral coordination of gait in women and men with fibromyalgia and healthy subjects walking at their usual velocity and at a faster walking velocity. Fifty-five women and 12 men with fibromyalgia were analysed. A healthy group of 44 women and 17 men was analysed as the control group. A GAITRite system was used to obtain the spatio-temporal gait parameters for the participants when walking at their usual velocity and at a faster velocity. Coefficients of variation, bilateral coordination and gait asymmetry indexes were calculated. All groups exhibited a significant increase (p < 0.001) in spatio-temporal parameters when walking fast. The fibromyalgia groups showed increased bilateral coordination, asymmetry and variability of stance phase when walking fast. The fibromyalgia women showed significant spatio-temporal, variability and bilateral coordination of gait differences compared with the healthy women. The fibromyalgia men reported significant differences in velocity, cadence, stride length, swing time variability and stance gait asymmetry indices compared with the healthy men. No significant differences were observed between the men and women in the fibromyalgia groups. The findings of the present study did not support gender-specific differences in walking variables and indices in FM patients. The differences found between both genders of FM patients and healthy subjects in walking indices at fast velocities could be a useful tool for diagnoses and evaluation of male and female patients with FM during short-term fast walking tests.

DIFERENCIAS ESPACIO-TEMPORALES DE LA LOCOMOCIÓN EN ADULTOS VARONES CON NORMOPESO Y SOBREPESO / DIFERENÇAS ESPAÇO-TEMPORAIS NA LOCOMOÇÃO DE ADULTOS DO SEXO MASCULINO COM PESO NORMAL E SOBREPESO / SPATIO-TEMPORAL DIFFERENCES OF LOCOMOTION OF ADULT MALES WITH NORMAL WEIGHT AND OVERWEIGHT

RESUMEN Introducción: La obesidad ha estado relacionada con la presencia de adaptaciones estructurales y funcionales que provocan limitaciones en el control del movimiento. Objetivo: Determinar el efecto del exceso de peso sobre las variables espacio-temporales de la locomoción en varones jóvenes y activos. Métodos: Estudio de corte transversal de muestreo no probabilístico con 55 sujetos con normopeso (IMC ≤25) y 22 sujetos con sobrepeso (IMC >25). Se analizó el IMC, % de masa grasa, y el % de masa magra de ambos grupos con un bioimpedanciómetro multifrecuencia (Inbody 230). También se analizaron las variables cinemáticas de la locomoción utilizando una plataforma de presiones GaitRite. Resultados: El grupo con sobrepeso mostró una disminución significativa de la fase de oscilación y fase de apoyo monopodal (p <0,001) junto con un aumento de la fase de apoyo y fase de apoyo bipodal (p <0,001) comparado con el grupo normopeso. Conclusión: La reducción de la fase de oscilación y el incremento de la fase de apoyo y fase de apoyo bipodal que manifestaron el grupo con sobrepeso puede ser consecuencia del aumento de la inestabilidad que se produce durante la marcha debido al sobrepeso.

RESUMO Introdução: A obesidade tem sido relacionada com a presença de adaptações estruturais e funcionais que podem limitar o controle dos movimentos. Objetivo: Determinar o efeito do excesso de peso sobre as variáveis espaço-temporais da locomoção em homens jovens e ativos. Métodos: Estudo transversal de amostragem não probabilística, com 55 indivíduos com peso normal (IMC ≤25) e 22 indivíduos com sobrepeso (IMC >25). Analisaram-se IMC e porcentagem de massa gorda e massa magra em ambos os grupos, com um bioimpedanciômetro multifrequência (Inbody 230). Foram analisadas também as variáveis cinemáticas de locomoção, usando-se um sistema de plataforma de pressão (GaitRite). Resultados: O grupo sobrepeso apresentou diminuição significativa na fase de balanço e fase de apoio monopodal (p <0,001), com aumento da fase de apoio e da fase de apoio bipodal (p <0,001) com relação ao grupo peso normal. Conclusão: A redução da fase de balanço e o aumento da fase de apoio e da fase de apoio bipodal manifestado pelo grupo sobrepeso pode ser resultado do aumento da instabilidade que ocorre durante a marcha, devido ao sobrepeso.

ABSTRACT Introduction: Obesity has been associated with the presence of structural and functional adaptations that may limit movement control. Objective: To determine the effect of overweight on spatio-temporal variables of locomotion in young and active men. Methods: A cross-sectional study of non-probability sampling, with 55 subjects with normal weight (BMI ≤25) and 22 overweight subjects (BMI >25). Body mass index and percentage of fat mass and lean mass were analyzed in both groups, with a multi-frequency bioimpedanciometer (Inbody 230). The kinematic variables of locomotion were also analyzed with a pressure platform system (GaitRite). Results: The overweight group showed a significant decrease in the swing phase and monopodal stance phase (p <0.001) with an increase in the stance phase and double stance phase (p<0.001) in relation to the normal weight group. Conclusion: The reduction of the swing phase and the increase of the stance phase and double stance phase presented by the overweight group may be a result of increased instability that occurs during gait due to overweight.

Pulling a school trolley: A good kinematic option for children.

This study analyzed the kinematic gait parameters associated with pulling a school trolley with different loads and the effects of the type of packing device user (backpack vs. trolley) and body side (loadedunloaded). Methods Fifty-three elementary subjects walked at a selfselected speed under four experimental conditions: without a trolley and pulling a trolley with 10%, 15% and 20% of the subject́s body weight (BW). Averages and standard deviations of spatiotemporal gait parameters and 3D kinematics of the lower limbs and thorax were obtained for the loaded and unloaded sides of the body. Results Spatiotemporal gait parameters were affected by pulling a trolley with a load of 20% BW, although the changes were not important (decrease of 0.02 units in velocity and stride length, decrease of 0.32% in single support and increase of 0.31% in double support). In the 3D kinematics analysis, the main effects of trolley load were observed in the thorax, with increased flexion as the load increased, and in the pelvis between baseline and 10%-15% BW. No interaction was found between kinematic parameters and the type of packing device user (trolley or backpack). Considering the loaded and unloaded sides of the body, the transverse plane of the thorax was the main site affected by the asymmetrical task. Conclusion Although some of the analyzed kinematic parameters were influenced by the use of a school trolley, the adaptations were minimal, and trolleys could be considered a good option for use in the transportation of school supplies.

Children require less gait kinematic adaptations to pull a trolley than to carry a backpack.

To transport school materials, trolleys have been proposed for children as an alternative to carrying a backpack. However, there is limited evidence comparing the adaptations associated with carrying school trolley versus backpack. This study compared the effects of carrying a backpack and pulling a trolley on gait kinematics in children. Fifty-three students were evaluated. Children walked at self-selected speeds across a walkway with no bag (control), carrying a backpack with the 15% of child́s body weight (%BW) and pulling a trolley with the same load. Spatiotemporal gait parameters and 3D kinematics of lower extremities and thorax were computed. No significant differences were obtained in spatiotemporal parameters between pulling a trolley and control. Carrying a backpack resulted in larger kinematics gait alterations than pulling the trolley compared to control. In conclusion, pulling a school trolley (15%BW) was more similar to not carrying a bag than carrying a backpack of the same load during level walking.

Spatio-temporal gait disorder and gait fatigue index in a six-minute walk test in women with fibromyalgia.

BACKGROUND: Gait disorders in fibromyalgia patients affect several gait parameters and different muscle recruitment patterns. The aim of this study was to assess the gait differences observed during a six-minute walk test between fibromyalgia patients and healthy controls. METHODS: Forty-eight women with fibromyalgia and 15 healthy women were evaluated. Fibromyalgia patients met the American College of Rheumatology criteria for fibromyalgia selected of an ambulatory care. Both patients and controls had a negative history of musculoskeletal disease, neurological disorders, and gait abnormalities. The 15 controls were healthy women matched to the patients in age, height and body weight. Spatio-temporal gait variables and the rate of perceived exertion during the six-minute walk test (all subjects) and Fibromyalgia Impact Questionnaire (fibromyalgia subjects) were evaluated. All walking sets on the GaitRITE were collected and the gait variables were selected at three stages during the six-minute walk test: two sets at the beginning, two sets at 3 min and two sets at the end of the test. In addition, the Fibromyalgia Impact Questionnaire was used for the fibromyalgia patients. FINDINGS: Fibromyalgia patients showed a significant decrease in all spatio-temporal gait variables at each of the three stages and had a lower walk distance covered in the six-minute walk test and higher rate of perceived exertion. No correlations were found between the Fibromyalgia Impact Questionnaire and gait variables. The fibromyalgia and control subjects showed lower gait fatigue indices between the middle and last stages. INTERPRETATION: Gait analysis during a six-minute walk test is a good tool to assess the fatigue and physical symptoms of patients with fibromyalgia.

Valoración de la grasa corporal: ultrasonidos frente a sistemas de bioimpedancia tetrapolar y antropometría. Estudio piloto / Valoration of body fat: ultrasounds front of tetrapolar bioimpedance and anthropometrical systems. Pilot study

Objetivos: Para calcular el porcentaje de grasa corporal son numerosos los instrumentos con los que podemos contar, siendo por ello necesario conocer la fiabilidad de los nuevos instrumentos que surjan para dicho fin. El objetivo del trabajo se centra en analizar el nivel de concordancia entre distintos métodos de medida de la grasa corporal: la bioimpedancia, el método antropométrico y un ultrasonido portátil para evaluar el porcentaje graso en personas activas. Material y métodos: En este estudio, han participado 37 sujetos (edad 19,8 ± 9,5 años). Todos los participantes eran individuos activos, practicantes asiduos de actividad física (22 practicantes de natación y 15 asistentes habituales al gimnasio). La medición antropométrica se llevó a cabo siguiendo el protocolo ISAK. Para la bioimpedancia se utilizó un impedanciómetro de 8 electrodos (Inbody Biospace 720) y también se utilizó un aparato de ultrasonido portátil Bodymetrix BX2000. Los resultados fueron analizados utilizando el coeficiente de correlación intraclase (CCI) y el método Bland y Altman para establecer la concordancia entre los distintos métodos de estimación de la grasa corporal utilizados. Resultados: el CCI obtenido cuando se comparó el método antropométrico y el impedanciómetro fue de 0,95. Sin embargo, cuando se comparó al ultrasonido con el método antropométrico y la bioimpedancia, se obtuvo un ICC de 0,73 . Conclusión: Como conclusión destacar que el ultrasonido portable, a pesar de ser una alternativa barata y con ciertas ventajas respecto a otros sistemas de estimación del % de grasa, mostró valores menores de concordancia respecto al método antropométrico y la bioimpedanca

Objectives: To measure the body fat percentage, there are some instruments to assess this. For that reason it is necessary to know the reliability of the new instruments used to this aim. Method: The aim of this study was to assess the level of agreement between the anthropometrical method, the bioimpedance and a portable ultrasound system to evaluate the body fat percentage of physically active people. In the present study, 37 active subjects have participated (age 19,8± 9,5 years). All of them were regular practitioners of physical activity (22 swimmers and 15 regular gym users). Anthropometrical assessment was done according to the ISAK protocol. Bioimpedance was done with an impedanciometre of 8 electrodes (Inbody 720) and it was compared by a portable ultrasound system (Bodymetrix BX2000). To assess the level of agreement, results were analyzed with the intraclass correlation coefficient (ICC) and the Bland Altman method were used. Results: the ICC between anthropometrical method versus bioimpedance was 0,95. The ICC between the ultrasound system and bioimpedance and anthropometrical method was 0,73. Conclusion: In conclusion, the portable ultrasound system, in spite of being a cheap alternative and with certain advantages on other systems to measure the body fat percentage, showed smaller values of agreement compares with the anthropometric method and the bioimpedanciometry

A Comparative Study on the Suitability of Smartphones and IMU for Mobile, Unsupervised Energy Expenditure Calculi.

The metabolic equivalent of task (MET) is currently the most used indicator for measuring the energy expenditure (EE) of a physical activity (PA) and has become an important measure for determining and supervising a person's state of health. The use of new devices which are capable of measuring inertial movements by means of built-in accelerometers enable the PA to be measured objectively on the basis of the reckoning of "counts". These devices are also known as inertial measurement units (IMUs) and each count is an aggregated value indicating the intensity of a movement and can be used in conjunction with other parameters to determine the MET rate of a particular physical activity and thus it's associated EE. Various types of inertial devices currently exist that enable count calculus and physical activity to be monitored. The advent of mobile devices, such as smartphones, with empowered computation capabilities and integrated inertial sensors, has enabled EE to be measure in a distributed, ubiquitous and natural way, thereby overcoming the reluctance of users and practitioners associated with in-lab studies. From the point of view of the process analysis and infrastructure needed to manage data from inertial devices, there are also various differences in count computing: extra devices are required, out-of-device processing, etc. This paper presents a study to discover whether the estimation of energy expenditure is dependent on the accelerometer of the device used in measurements and to discover the suitability of each device for performing certain physical activities. In order to achieve this objective, we have conducted several experiments with different subjects on the basis of the performance of various daily activities with different smartphones and IMUs.