Effectiveness of a Variable-Speed Control Based on Auditory Feedback: Is It Possible?

PURPOSE: Variable-speed control in the field is challenging for motion science. Tests were performed to evaluate speed, Froude number, and oxygen consumption if these varied when using the same frequency of steps. The objective of this study was to evaluate the use of auditory feedback to control variable speed on the treadmill and track during acceleration cycles around the transition speed. METHODS: Twenty-four trained men participated. The protocol was based on 5 ramps of 50 seconds each around 80%, 90%, 100%, 110%, and 120% of the walking-running transition speed, recording the frequency of steps with a mobile phone during the treadmill test. The tests were replicated on the track using auditory feedback. RESULTS: When evaluating each speed of the protocols separately for the same frequency of steps, the average speed on the track was always higher on average at 54.7% compared to the laboratory (P < .050), and on the track, it was 16.2% higher than in the laboratory (P > .050). CONCLUSIONS: It cannot be considered that the same frequency of steps is equivalent to the same speed in the laboratory and on the track. These results point to the importance of reliable speed control during open field tests.

Kinematics and physiological parameters in maximal swimming tests in age-group swimmers / Cinemática y parámetros fisiológicos en pruebas de natación máxima en nadadores de grupos de edad

Objective: The aim of this study was compared and correlate kinematics and physiological parameters in four maximal swimming tests of two groups of young swimmers.Methods: Twelve swimmers, separated in two groups by age (percentile > 50th (n = 6): 15.4 ± 1.11 years old as group 1, and < 50th (n = 6): 12.1 ± 0.83 as group 2) performed four tests during two different sessions. . They performed front crawl trials at maximum intensity: 50 and 200 meters on first day and 100 and 400 m meters on second day. Anthropometric characteristics were measured. Stroke rate, stroke length, stroke index, swimming speed and critical speed were obtained by video analysis. Moreover, were measured the blood lactate concentration, heart rate and rate of perceived exertion.Results: There are no differences at anthropometric characteristics. We found difference between group 1 and group 2. Better results for performance, swimming speed, stroke length and stroke index in group 1. Swimming speed and stroke index show strong correlation in all tests for group 1 and in 50 and 100 meters for group 2. To measure the swimmer profile is essential to verify the benefits that the training program is or is not providing.Conclusion: The parameters evaluated seem related to age and capacities of the swimmers.(AU)

Transfer of strength training to running mechanics, energetics, and efficiency.

To examine the effects of increased strength on mechanical work, the metabolic cost of transport (Cost), and mechanical efficiency (ME) during running. Fourteen physically active men (22.0 ± 2.0 years, 79.3 ± 11.1 kg) were randomized to a strength-training group (SG, n = 7), who participated in a maximal strength training protocol lasting 8 weeks, and a control group (CG, n = 7), which did not perform any training intervention. Metabolic and kinematic data were collected simultaneously while running at a constant speed (2.78 m·s-1). The ME was defined as the ratio between mechanical power (Pmec) and metabolic power (Pmet). The repeated measures two-way ANOVA did not show any significant interaction between groups, despite some large effect sizes (d): internal work (Wint, p = 0.265, d = -1.37), external work (Wext, p = 0.888, d = 0.21), total work (Wtot, p = 0.931, d = -0.17), Pmec (p = 0.917, d = -0.17), step length (SL, p = 0.941, d = 0.24), step frequency (SF, p = 0.814, d = -0.18), contact time (CT, p = 0.120, d = -0.79), aerial time (AT, p = 0.266, d = 1.12), Pmet (p = 0.088, d = 0.85), and ME (p = 0.329, d = 0.54). The exception was a significant decrease in Cost (p = 0.047, d = 0.84) in SG. The paired t-test and Wilcoxon test only detected intragroup differences (pre- vs. post-training) for SG, showing a higher CT (p = 0.041), and a lower Cost (p = 0.003) and Pmet (p = 0.004). The results indicate that improved neuromuscular factors related to strength training may be responsible for the higher metabolic economy of running after 8 weeks of intervention. However, this process was unable to alter running mechanics in order to indicate a significant improvement in ME.

Electromyographical and Physiological Correlation in Patient with Heart Disease

Abstract Background: Walking is an economic activity, the more efficient the mechanical contribution, the less metabolic energy is necessary to keep walking. Patients with chronic heart failure and heart transplant present peripheral musculoskeletal disorders, dyspnea, and fatigue in their activities. Objective: In this scenario, the present study sought to verify the correlations between metabolic and electromyographic variables in chronic heart failure, heart transplant patients, and healthy controls. Methods: Regression and correlation between cost of transport and electromyographic cost, as well as correlation between oxygen consumption and muscle coactivation in patients and controls at five different walking speeds have been performed, with alpha = 0.05. Results: Strong correlation values (r controls: 0.99; chronic heart failure: 0.92; heart transplant: 0.88) indicate a linear relationship between the cost of transport and electromyographic cost. Oxygen consumption was significantly correlated to muscle activation in all groups. Conclusion: These results suggested that dynamic muscle coactivation was an important factor, especially for CHF and HT. These data support the idea that peripheral muscle limitations play an important role in people with CHF and HT. These findings indicate a strong relation between metabolic and electromyographic variables. For chronic heart failure and heart transplant patients, it can help to explain some difficulties in daily activities and aid in physical rehabilitation.

Medidas angulares de la columna vertebral de adultos mayores activos y sedentarios / Spine angular measurements from active and sedentary elderly people

Se considera que la actividad física regulada y sistematizada conlleva beneficios para la salud en diferentes ámbitos para el adulto mayor, ya sean: composición corporal, sistema cardiovascular, nivel metabólico y endócrino, fuerza muscular, huesos, articulaciones y flexibilidad. OBJETIVO: Evaluar y comparar los ángulos de la columna entre dos grupos de adultos mayores: activos y sedentarios, utilizando el método de flexicurva. MÉTODOS: Para este estudio participaron 30 adultos mayores, de los cuales se dividieron en dos grupos: 15 activos y 15 sedentarios (no presentaron diferencias cuanto a características antropométricas), entre 65 y 74 años. Para medir los ángulos de la columna vertebral (cervical, torácica y lumbar) se utiliza la flexicurva y el software Biomec Flex V.3.0. RESULTADOS: Se obtuvo como resultado una diferencia significativa entre grupos en la medida de la columna cervical, donde solo los adultos mayores activos presentan medidas dentro de los parámetros normales, y los sedentarios presentaron hiperlordosis cervical. Las medidas de la columna lumbar presentaron valores de rectificación de la curvatura para ambos grupos (de acuerdo con los valores de referencia de la literatura). CONCLUSIÓN: La curvatura de la columna cervical se mostró afectada en adultos mayores sedentarios del presente estudio, en comparación la curvatura de la columna de los adultos mayores activos. Además la rectificación de la curvatura de la columna lumbar y los cambios debido a esta postura deben ser considerados en la planificación de ejercicio físico en esta población

Regulated and systematized physical activity is considered to have health benefits in different areas for the older adult, like: body composition, cardiovascular system, metabolic and endocrine level, muscle strength, bones, joints and flexibility. Purpose. Evaluate and compare the spinal angles between two groups of elderly people: active and sedentary, using the flexicurve method. METHODS: Participated 30 elderly people, of which they were divided into two groups: 15 active and 15 sedentary (they did not present differences for anthropometric characteristics), between 65 and 74 years old. To measure the angles of the vertebral column (cervical, thoracic and lumbar) the flexicurve and the Biomec Flex software V.3.0 are used. RESULTS: Significant difference was obtained between groups in the measurement of the cervical spine, where only active older adults presented measurements within normal parameters, and sedentary older adults presented cervical hyperlordosis. The lumbar spine measurements presented curvature rectification values ​​for both groups (according to the reference values ​​of the literature). CONCLUSION: The curvature of the cervical spine was affected in sedentary older adults in the present study, compared to the curvature of the spine in active older adults. Furthermore, the rectification of the curvature of the lumbar spine and the changes due to this posture should be considered in the planning of physical exercise in this population

Locomoción humana: modelos y variables biomecánicas / Human locomotion: models and biomechanical variables

Resumen La locomoción con miembros implica diferentes desafíos de tipo mecánico: en cada ciclo, los segmentos deben reposicionarse anatómicamente, con fases de aceleración y deceleración y la consiguiente elevación y descenso del centro de masa. Dentro de la locomoción humana, la marcha y la carrera son actividades fundamentales en todo el ciclo vital humano. En específico, la carrera es una actividad muy estudiada por las ciencias del deporte, medicina, fisioterapia o kinesiología, ingeniería y biología, por el alto impacto articular y muscular que genera, ya que esta trae consigo lesiones y alteraciones en el rendimiento de los pacientes y deportistas. El constante estudio de la locomoción ha reconocido diferentes desafíos de tipo fisiológico y mecánico, tanto en la explicación de fenómenos como en el análisis de estos. Este artículo busca aclarar conceptos a través de textos clásicos, que se consideran básicos e importantes para entender las investigaciones posteriores. Además, se explican diferentes parámetros que sirven para comprender la locomoción, tanto en estudios con humanos como en animales. El objetivo de este trabajo es hacer una revisión de la literatura, que se enfoca en los aspectos mecánicos, energéticos, el efecto del tamaño y los diferentes patrones de la locomoción, con sus modelos mecánicos. Finalmente, los autores esperan que este texto sea un aporte para docentes y estudiantes para la comprensión de la locomoción en idioma español.

Abstract Limbed locomotion involves different mechanical challenges: in each cycle, limbs must be repositioned anatomically, with acceleration and deceleration phases and the consequent raising and lowering of the center of mass. As part of human locomotion, walking and running are fundamental activities throughout the life cycle. In particular, running has been highly studied by sports sciences, medicine, physiotherapy, kinesiology, engineering, and biology due to the high joint and muscular impact it generates, commonly causing injuries and alterations in the performance of patients and athletes. The constant study of locomotion has brought to light the different physiological and mechanical challenges when explaining and analyzing phenomena. Using classical texts, this article aims to clarify concepts considered basic and important to understand further research. In addition, different parameters needed to understand locomotion, both in human and animal studies, are explained. The objective of this paper is to review the literature focused on the mechanical and energetic aspects of locomotion, the effect of size, and the different locomotion patterns and mechanical models. Finally, this paper is presented as a contribution for teachers and students to understand locomotion in the Spanish language.

Resumo A locomoção com membros implica diferentes desafios do tipo mecânico: em cada ciclo, os segmentos devem ser reposicionados anatomicamente, com fases de aceleração e desaceleração e a subsequente elevação e descenso do centro de massa. Dentro da locomoção humana, a marcha e a corrida são atividades fundamentais em todo o ciclo vital humano. Especificamente, a corrida é uma atividade muito estudada pelas ciências do esporte, medicina, fisioterapia ou cinesiologia, engenharia e biologia, devido à geração de alto impacto articular e muscular, trazendo consigo lesões e alterações no rendimento dos pacientes e esportistas. O constante estudo da locomoção reconheceu diferentes desafios de tipo fisiológico e mecânico, tanto na explicação de fenômenos como na análise destes. Este artigo busca aclarar conceitos através de textos clássicos, considerados básicos e importantes para entender as pesquisas posteriores. Além disso, são explicados diferentes parâmetros que servem para compreender a locomoção, tanto em estudos com humanos quanto com animais. O objetivo deste trabalho é fazer uma revisão da literatura, que se enfoca nos aspectos mecânicos, energéticos, no efeito do tamanho e nos diferentes padrões da locomoção, com seus modelos mecânicos. Finalmente, os autores esperam que este texto, em espanhol, seja uma contribuição para docentes e estudantes para a compreensão da locomoção.

Limiting Factors in Walking Performance of Subjects With COPD.

INTRODUCTION: Exercise intolerance is the most predominant symptom in patients with COPD. Nevertheless, it is unclear whether walking economy and gait variability are altered in these patients. Thus, our main objective was to compare the cost of transport and gait variability as a function of speed, including the self-selected walking speed, in subjects with COPD relative to healthy subjects. METHODS: 22 subjects, 11 with COPD (FEV1 = 45 ± 17% of predicted) and 11 age- and sex-matched healthy subjects undertook an evaluation that involved walking on a treadmill at 6 speeds (at 3.2 km/h, at a self-selected walking speed, and at 2 speeds below and 2 speeds above the self-selected walking speed) and measuring the cost of transport (the oxygen consumption normalized by mass and distance), gait variability, perceived dyspnea, and leg fatigue. RESULTS: In subjects with COPD, the cost of transport decreased with increasing walking speed, contrary to healthy subjects, who presented a minimum at the self-selected walking speed. No difference was found in cost of transport between the experimental groups at the same absolute velocity (P = .62). In subjects with COPD, dyspnea sensation rose above the self-selected walking speed, doubling at the maximal walking velocity (P = .03), and gait variability was higher at low speeds. CONCLUSION: Subjects with COPD choose their walking speed so as to keep the dyspnea sensation tolerable and to keep gait variability and cost of transport at an acceptable level. These outcomes suggest that interventions acting on dyspnea and gait pattern may increase patients' self-selected walking speed and improve their quality of life.

Effect of walking speed in heart failure patients and heart transplant patients.

BACKGROUND: Chronic heart failure patients present higher cost of transport and some changes in pattern of walking, but the same aspects have not yet been investigated in heart transplant patients. METHODS: The aim of this study was to investigate both metabolic and mechanicals parameters, at five different walking speeds on treadmill, in chronic heart failure and heart transplant patients. Twelve chronic heart failure patients, twelve healthy controls and five heart transplant patients participated in the study. Tridimensional kinematics data and oxygen uptake were collected simultaneously. FINDINGS: In both experimental groups the self-selected walking speed was lower than in controls, and lower than the expected optimal walking speed. At that speed all groups showed the best ventilatory efficiency. On contrary, chronic heart failure and heart transplant patients reached the minimum cost of transport and the maximum recovery at greater speeds than the self-selected walking speed. Their mechanical efficiency was lower than in controls, while their metabolic cost and mechanical work were on average larger. INTERPRETATION: We conclude that actions, like a physical training, that could increase the self-selected walking speed in these patients, could also increase their economy and optimize the mechanical parameters of walking. We propose a rehabilitation index, based on the theoretical optimal walking speed, to measure the improvements during a physical rehabilitation therapy. These results have an important clinical relevance and can help to improve the quality of life of heart failure and transplant patients.

Electromyography and economy of walking in chronic heart failure and heart transplant patients.

Background Patients with chronic heart failure frequently report intolerance to exercise and present with changes in walk pattern, but information about heart transplant patients is lacking. Alterations of the gait pattern are related to interaction changes between the metabolism, neurological system and the mechanical demands of the locomotor task. The aim of this study was to investigate the electromyographic cost, coactivation and cost of transport of walking of chronic heart failure and heart transplant patients. Design This research was of an exploratory, cross-sectional design. Methods Twelve chronic heart failure patients, twelve healthy controls and five heart transplant patients participated in the study. Electromyographic data and oxygen uptake were collected simultaneously at five walking speeds. Results In the experimental groups, the electromyographic cost, percentage of coactivation in the leg and cost of transport were higher than in controls. The electromyographic cost was in line with the cost of transport. The minimum electromyographic cost matched with the self-selected walking speed in controls, while in chronic heart failure and heart transplant patients, it was reached at speeds higher than the self-selected walking speed. Conclusion The largest postural isometric activation and antagonist activation resulted in the highest metabolic demand. These findings are of great clinical relevance because they support the concept that interventions in order to improve the muscle performance in these patients can increase the self-selected walking speed and therefore the metabolic economy of walking.

VELOCIDADE AUTOSSELECIONADA E IDEAL DA CAMINHADA DE AMPUTADOS TRANSFEMORAIS: SOLO E ESTEIRA / SELF-SELECTED AND OPTIMAL WALKING SPEED OF TRANSFEMORAL AMPUTEES: GROUND VS. TREADMILL / VELOCIDAD AUTOSELECCIONADA E IDEAL EN LA MARCHA DE AMPUTADOS TRANSFEMORALES: SUELO Y CINTA CAMINADORA

RESUMO Introdução: A velocidade de progressão é, em geral, determinada em pesquisas na área da locomoção. Objetivo: Comparar as medidas de velocidade autosselecionada no solo, na esteira rolante e a velocidade ideal estimada pelo número de Froude em sujeitos amputados transfemorais. Método: Primeiramente foi determinada a velocidade no solo; em seguida, realizou-se o teste na esteira, e a velocidade ideal foi estimada a partir dos dados antropométricos. Todos os sujeitos utilizavam joelho hidráulico e pé em fibra de carbono. Para comparação entre as velocidades foi realizada ANOVA de duas vias. Resultados: A velocidade autosselecionada na esteira foi menor (22%) do que no solo. Tanto a velocidade autosselecionada na esteira como a do solo foram 44% e 22% menores do que a velocidade ideal estimada, respectivamente. Conclusão: As velocidades analisadas no presente estudo foram diferentes, provavelmente, devido à variação dos parâmetros cinemáticos.

ABSTRACT Introduction: The speed of progression is generally determined in researches in the field of locomotion. Objective: To compare the self-selected velocity measurements on the ground, on treadmill and the optimal speed estimated by the Froude number in subjects with transfemoral amputation. Methods: First, the ground speed was determined; then the treadmill test was performed, and the optimal speed was estimated from anthropometric data. All subjects had hydraulic knee and carbon fiber foot. To compare the speeds, we used the two-way ANOVA. Results: The self-selected speed in the treadmill was lower (22%) compared with the ground. Both the self-selected speed in treadmill as ground were 44% and 22% lower than the estimated optimum speed, respectively. Conclusion: The speeds analyzed in this study were different, probably due to the variation of the kinematic parameters.

RESUMEN Introducción: La velocidad de progresión es generalmente determinada en investigaciones en el ámbito de la locomoción. Objetivo: Comparar las mediciones de la velocidad autoseleccionada en el suelo, en la cinta caminadora y la velocidad ideal estimada por el número de Froude en sujetos con amputación transfemoral. Métodos: En primer lugar, se determinó la velocidad en el suelo; después, se realizó la prueba en la cinta caminadora, y la velocidad ideal fue estimada a partir de los datos antropométricos. Todos los sujetos tenían rodilla hidráulica y pie en fibra de carbono. Para comparar las velocidades, se utilizó el ANOVA de dos vías. Resultados: La velocidad autoseleccionada en la cinta caminadora fue menor (22%) que en el suelo. Tanto la velocidad autoseleccionada en la cinta caminadora como la del suelo fueron 44% y 22% menores a la velocidad ideal estimada, respectivamente. Conclusión: Las velocidades analizadas en el presente estudio fueron diferentes, probablemente debido a la variación de los parámetros cinemáticos.

The pendular mechanism does not determine the optimal speed of loaded walking on gradients.

The pendular mechanism does not act as a primary mechanism in uphill walking due to the monotonic behavior of the mechanical energies of the center of mass. Nevertheless, recent evidence shows that there is an important minimization of energy expenditure by the pendular mechanism during walking on uphill gradients. In this study, we analyzed the optimum speed (OPT) of loaded human walking and the pendulum-like determining variables (Recovery R, Instantaneous pendular re-conversion Rint, and Congruity percentage %Cong). Ten young men walked on a treadmill at five different speeds and at three different treadmill incline gradients (0, +7 and +15%), with and without a load carried in their backpacks. We used indirect calorimetry and 3D motion analysis, and all of the data were analyzed by computational algorithms. Rint increased at higher speeds and decreased with increasing gradient. R and %Cong decreased with increasing gradient and increased with speed, independent of load. Thus, energy conversion by the pendular mechanism during walking on a 15% gradient is supported, and although this mechanism can explain the maintenance of OPT at low walking speeds, the pendular mechanism does not fully explain the energy minimization at higher speeds.

Ventilatory determinants of self-selected walking speed in chronic heart failure.

PURPOSE: In healthy subjects, the self-selected walking speed (SSWS) corresponds to the lowest cost of transport (CT). This study tested the hypothesis that SSWS could be determined by the work of breathing instead of the CT in patients with chronic heart failure (CHF). METHODS: Seventeen patients with CHF due to left ventricular systolic dysfunction and 17 healthy controls were compared. Both groups were submitted to a walking cost protocol on the treadmill at the SSWS, at two speeds below (-0.5 and -1.0 km·h), and two speeds above (+0.5 and +1.0 km·h). The CT and ventilatory efficiency, as determined by the ventilatory equivalent for carbon dioxide (V˙E/V˙CO2), were compared. RESULTS: CHF patients had a lower SSWS than healthy controls (0.75 ± 0.14 vs 0.98 ± 0.30 m·s, P < 0.01). Among the five speeds, the controls' SSWS was the most economical. For CHF patients, the SSWS was less economical than the higher speeds. However, V˙E/V˙CO2 at the SSWS was lower when compared with other speeds in both groups. CONCLUSIONS: In contrast to what happens with healthy subjects, where the SSWS has the lowest CT, CHF patients choose an SSWS with higher CT, but with lower ventilatory cost. These findings are compatible with the concept that interventions that enhance ventilatory efficiency may increase SSWS in CHF.

Comparação do consumo energético e de aspectos mecânicos da caminhada de amputados transfemurais que utilizam prótese com microprocessador ou convencional: uma revisão / Comparación del consumo de energía e los aspectos mecánicos de la caminata con prótesis transfemoral amputado basado en un microprocesador o convencional: una revisión / Comparison of energy consuption and mechanical aspects of transfemural amputee gait using prosthesis with the microprocessor and conventional knee: a review

A locomoção humana é o resultado de torques advindos de forças externas e internas. É um movimento complexo, cuja otimização minimiza o dispêndio energético. Existem restrições estruturais, como a amputação que influenciam a mecânica da locomoção e, por conseguinte o gasto energético. Neste artigo serão revisados temas relacionados à influência do tipo de prótese no consumo de oxigênio e nos aspectos biomecânicos da caminhada de amputados.