Association between energy cost of walking, muscle activation, and biomechanical parameters in older female fallers and non-fallers

Objective: To determine the nervous activation, muscle strength, and biomechanical parameters that influence the cost of walking in older fallers and non-fallers. Methods: Maximal voluntary isokinetic torque was measured for the hip, knee and ankle of older women. Oxygen consumption was measured at rest and during 8 min of walking at self-selected speed. An additional minute of walking was performed to collect kinematic variables and the electromyographic signal of trunk, hip, knee, and ankle muscles, which was analyzed by the linear envelope. Cost of walking was calculated by subtracting resting body mass-normalized oxygen consumption from walking body mass-normalized oxygen consumption. Stride time and length, and ankle and hip range of motion were calculated from kinematic data. Findings: Older adult fallers had 28% lower knee extensor strength (p = 0.02), 47% lower internal oblique activation at heel contact (p = 0.03), and higher coactivation between tibialis anterior and gastrocnemius lateralis in each of the gait phases (p < 0.05). For fallers, a higher activation of gluteus maximus was associated with a higher cost of walking (r = 0.55, p < 0.05 and r = 0.71, p < 0.01, before and after heel contact, respectively). For non-fallers, an association between cost of walking and age (r = 0.60, p = 0.01) and cost of walking and thigh muscle coactivation (r = 0.53, p = 0.01) existed. Interpretation: This study demonstrated that there may be links between lower-extremity muscle weakness, muscle activation patterns, altered gait, and increased cost of walking in older fallers. © 2013 Elsevier Ltd. All rights reserved.

Characterization of biomechanical parameters during stair ascent

Stair climbing is a functional activity often cited as main complaint by patients with orthopedic – as patellofemoral pain syndrome – or neurologic alterations. Moreover, the stair climbing is usually used as therapeutic resource. However, few studies have been conducted to characterize the movement during the ascent or descent of stairs and these studies concluded that the high variability of the data could not confirm the results [Yu, 1997] . In this way, this study aimed to verify which parameters show less variation and so, are more appropriate to characterize the stair climbing.

Running from Paris to Beijing: biomechanical and physiological consequences.

The purpose of this study was to examine the physiological and biomechanical changes occurring in a subject after running 8,500 km in 161 days (i.e. 52.8 km daily). Three weeks before, 3 weeks after (POST) and 5 months after (POST+5) running from Paris to Beijing, energy cost of running (Cr), knee flexor and extensor isokinetic strength and biomechanical parameters (using a treadmill dynamometer) at different velocities were assessed in an experienced ultra-runner. At POST, there was a tendency toward a 'smoother' running pattern, as shown by (a) a higher stride frequency and duty factor, and a reduced aerial time without a change in contact time, (b) a lower maximal vertical force and loading rate at impact and (c) a decrease in both potential and kinetic energy changes at each step. This was associated with a detrimental effect on Cr (+6.2%) and a loss of strength at all angular velocities for both knee flexors and extensors. At POST+5, the subject returned to his original running patterns at low but not at high speeds and maximal strength remained reduced at low angular velocities (i.e. at high levels of force). It is suggested that the running pattern changes observed in the present study were a strategy adopted by the subject to reduce the deleterious effects of long distance running. However, the running pattern changes could partly be linked to the decrease in maximal strength.

Biomechanical Evaluation of Platform Switching in Different Implant Protocols: Computed Tomography-Based Three-Dimensional Finite Element Analysis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Differences in early biomechanical properties after myopic and hyperopic lasik using mechanical microkeratome Sub-Bowman's Keratomileusis (SBK)

Purpose: To evaluate biomechanical changes measured with the ORA (Ocular Response Analyzer (R); Reichert Ophthalmic Instruments, Buffalo, New York, USA) after Lasik with the Moria One Use Plus and to compare the biomechanics changes after myopic and hyperopic ablations. Methods: Fourteeneyes for hyperopia (H) and 19 eyes for myopia (M) were evaluated with the ORA preoperatively and 1 month after Lasik with thin flap (100 microns) using SBK-OUP (Sub-Bowman Keratomileusis-One Use Plus, Moria (R)). CH (Corneal Hysteresis), CRF (Corneal Resistance Factor), IOPg (gold-standard, Goldmann correlated Intraocular pressure), IOPcc (Corneal compensated Intraocular pressure) and more 38 variables derived from the corneal biomechanical response signal of the ORA were analyzed. The Wilcoxon test was used to assess differences between the variables before and after surgery for each group and the differences between the pre and postoperative (1 month) myopic eyes were compared with those obtained in hyperopic eyes, using the Mann-Whitney test. Results: There was a significant difference before and after Lasik in myopic and hyperopic eyes in IOPg (Wilcoxon, p<0.05), but not in IOPcc. Only myopic eyes showed a significant difference in CH and CRF measurements before and after LASIK, as well as 9 other biomechanical parameters (aspect1, h1, dive1, path1, p1area1, W11, H11, and w2 path11; Wilcoxon, p<0, 05), 8 of these being related to the first sign of flattening. Five parameters related to the sign of the second applanation showed significant variation only in the eyes before and after hyperopic Lasik (aspect2, h2, dive2, mslew2 and H21; Wilcoxon, p<0,05). There was a difference in both myopic and hyperopic on three parameters related to the applanation signal areas (p1area, and p2area p2area1; Wilcoxon, p<0.05). Differences in IOPg and p1area, before and after surgery were significantly higher in myopic eyes than in hyperopic eyes (Mann-Whitey, p<0.05). Conclusion: There are several significant differences in biomechanical parameters after Lasik with Moria OUP_SBK. Overall, the impact of myopic LASIK on corneal biomechanics is higher than of hyperopic Lasik. The parameters derived from the first sign of the ORA are more affected in myopic LASIK, whereas parameters derived from the second applanation are more affected in hyperopic LASIK.

Structural characterization and reliable biomechanical assessment of integrative cartilage repair

Structural and functional characterization of integrative cartilage repair in controlled model systems can play a key role in the development of innovative strategies to improve the long-term outcome of many cartilage repair procedures. In this work, we first developed a method to reproducibly generate geometrically defined disk/ring cartilage composites and to remove outgrown fibrous layers which can encapsulate cartilaginous tissues during culture. We then used the model system to test the hypothesis that such fibrous layers lead to an overestimation of biomechanical parameters of integration at the disk/ring interface. Transmission electron microscopy images of the composites after 6 weeks of culture indicated that collagen fibrils in the fibrous tissue layer were well integrated into the collagen network of the cartilage disk and ring, whereas molecular bridging between opposing disk/ring cartilage surfaces was less pronounced and restricted to regions with narrow interfacial regions (< 2 microm). Stress-strain profiles generated from mechanical push-out tests for composites with the layers removed displayed a single and distinct peak, whereas profiles for composites with the layers left intact consisted of multiple superimposed peaks. As compared to composites with removed layers, composites with intact layers had significantly higher adhesive strengths (161+/-9 vs. 71+/-11 kPa) and adhesion energies (15.0+/-0.7 vs. 2.7+/-0.4 mJ/mm2). By combining structural and functional analyses, we demonstrated that the outgrowing tissue formed during in vitro culture of cartilaginous specimens should be eliminated in order to reliably quantify biomechanical parameters related to integrative cartilage repair.

Biomechanical evaluation of the singing voice

Teaching the adequate use of the singing voice conveys a lot of knowledge in musical performance as well as in objective estimation techniques involving the use of air, muscles, room and body acoustics, and the tuning of a fine instrument as the human voice. Although subjective evaluation and training is a very delicate task to be carried out only by expert singers, biomedical engineering may help contributing with well-funded methodologies developed for the study of voice pathology. The present work is a preliminary study of exploratory character describing the performance of a student singer in a regular classroom under the point of view of vocal fold biomechanics. Estimates of biomechanical parameters obtained from singing voice are given and their potential use is discussed.

Vocal fold biomechanical analysis for the singing voice

Teaching the adequate use of the singing voice conveys a lot of knowledge in musical performance as well as in objective estimation techniques involving the use of air, muscles, room and body acoustics, and the tuning of a fine instrument as the human voice. Although subjective evaluation and training is a very delicate task to be carried out only by expert singers, biomedical engineering may help contributing with well - funded methodologies developed for the study of voice pathology. The present study is a preliminary study of exploratory character describing the performance of a student singer in a regular classroom under the point of view of vocal fold biomechanics. Estimate s of biomechanical parameters obtained from singing voice are given and their use i n the classroom is discussed.

Biomechanical and morphological adaptations in women during pregnancy and the postpartum period in walking

A gravidez é uma fase especial da vida, com diversas alterações nos sistemas hormonais, anatómicos, e na composição corporal da mulher. No entanto, não é claro que alterações biomecânicas tridimensionais ocorrerem. Através do acompanhamento da mulher na gravidez e pós-parto, os objetivos da presente tese foram: 1) determinar os parâmetros temporais e espaciais do ciclo da marcha; 2) descrever a cinemática angular do membro inferior; 3) calcular os momentos e potências articulares do tornozelo, joelho e coxofemoral, utilizando o cálculo por dinâmica inversa; 4) descrever as magnitudes dos picos dos momentos e potências articulares dos membros inferiores; 5) identificar possíveis diferenças entre as fases de recolha relativamente aos parâmetros biomecânicos; 6) descrever longitudinalmente a composição corporal as alterações morfológicas; 7) analisar a influência das alterações antropométricas na cinética articular. Os resultados mostram que as mulheres mantêm os parâmetros temporais e espaciais da marcha. A cinemática angular do membro inferior tem o mesmo padrão, no entanto, a magnitude de alguns picos, especialmente na bacia e coxofemoral durante a fase terminal do apoio, pré-balanço e de balanço, apresentam alterações significativas. A coxofemoral é a articulação com mais alterações na cinética articular, com um aumento da carga interna associada aos momentos articulares da coxofemoral no plano transversal. No entanto, diversos momentos e potências articulares revelam uma diminuição significativa para o final da gravidez e/ou um aumento entre alguns trimestres da gravidez e o pós-parto. Como esperado, a maioria das variáveis associadas à composição corporal e às dimensões corporais tem um aumento significativo durante a gravidez e uma diminuição no pós-parto. Os modelos desenvolvidos para prever a carga interna aplicada ao membro inferior da grávida através de variáveis antropométricas, incluem quatro modelos com variáveis associadas à quantidade de gordura, quatro modelos com variáveis associadas à massa corporal global, três modelos que incluem a massa livre de gordura, e um modelo que inclui a forma do tronco. Os altos valores do R2 ajustado, mostram que as alterações na composição corporal e morfologia, determinam em grande parte a cinética articular da mulher nesta fase particular da vida.

Respostas agudas de parâmetros biomecânicos à utilização de diferentes tamanhos de palmar no nado crawl

Universidade Estadual de Campinas . Faculdade de Educação Física

Análise biomecânica da marcha e funcionalidade em crianças com Paralisia Cerebral: efeito da intervenção da fisioterapia com facilitação em tapete rolante

Introdução: As crianças com Paralisia Cerebral evidenciam frequentemente alterações da sua funcionalidade global, evidenciadas nomeadamente na marcha. Diferentes protocolos de facilitação da marcha em tapete rolante têm vindo a ser alvo de estudos no sentido de clarificar a sua eficácia nesta população. Estes sugerem uma evolução positiva dos diferentes aspectos estudados (funcionalidade global, resistência cardiorespiratória, componentes da marcha), contudo utilizam diferentes metodologias e especificidades do protocolo, não existindo consenso acerca das melhores condições de utilização. Objectivo(s): O presente trabalho teve como objectivo principal avaliar o efeito da aplicação de um protocolo de marcha em tapete rolante (PMTR) em crianças com Paralisia Cerebral (PC) espástica, nos parâmetros biomecânicos da mesma e funcionalidade global. Métodos: Participaram no estudo 9 crianças com PC do tipo diplégico e hemiplégico inscritos na Associação de Paralisia Cerebral de Braga (APCB), com idades compreendidas entre os 3 e os 8 anos de idade. Cada criança foi avaliada antes e após a aplicação do PMTR, através da análise biomecânica da marcha (dinamometria e electromiografia de superfície), bem como da aplicação do teste de medida da função motora (TMFM). A amostra foi dividida em dois grupos – grupo sujeito ao protocolo de marcha em tapete rolante (GPMTR) (n=5) e grupo controlo (GC) (n=4). O protocolo em tapete rolante foi incluído nas sessões de intervenção de fisioterapia, com uma frequência semanal de 2 a 3 vezes por semana, durante um período de 10 semanas consecutivas, após o qual foram repetidas as avaliações iniciais. Resultados: A análise dos resultados permitiu verificar evoluções no GPMTR ao nível do score total da TMFM e especialmente na dimensão E, o que revelou melhorias significativas da funcionalidade motora global neste grupo. Verificaram-se ainda, em termos eletromiográficos um melhor padrão de recrutamento muscular, bem como, no que se refere à análise dinamométrica, evoluções positivas, na componente vertical das forças de reacção do solo.Conclusão: O presente estudo parece sugerir que a inclusão da facilitação da marcha em tapete rolante no plano de intervenção pode contribuir para uma melhoria nos parâmetros biomecânicos da marcha e funcionalidade global de crianças com Paralisia Cerebral do tipo diplégico e hemiplégico, com idades compreendidas entre os 3 e os 8 anos.

Assistive locomotion strategies for active lower limb devices

Dissertação de mestrado integrado em Engenharia Biomédica (área de especialização em Eletrónica Médica)

Conceptual framework for strengthening exercises to prevent hamstring strains

High-speed running accounts for the majority of hamstring strains in many sports. The terminal swing phase is believed to be the most hazardous as the hamstrings are undergoing an active lengthening contraction in a long muscle length position. Prevention-based strength training mainly focuses on eccentric exercises. However, it appears crucial to integrate other parameters than the contraction type. Therefore, the aim of this study is to present a conceptual framework based on six key parameters (contraction type, load, range of motion, angular velocity, uni-/bilateral exercises, kinetic chain) for the hamstring's strength exercise for strain prevention. Based on the biomechanical parameters of sprinting, it is proposed to use high-load eccentric contractions. The movement should be performed at a slow to moderate angular velocity and focused at the knee joint, while the hip is kept in a large flexion position in order to reach a greater elongation stress of the hamstrings than in the terminal swing phase. In this way, we believe that, during sprinting, athletes would be better trained to brake the knee extension effectively in the whole range of motion without overstretch of the hamstrings. Finally, based on its functional application, unilateral open kinetic chain should be preferred.

High-precision satellite positioning system as a new tool to study the biomechanics of human locomotion.

New Global Positioning System (GPS) receivers allow now to measure a location on earth at high frequency (5Hz) with a centimetric precision using phase differential positioning method. We studied whether such technique was accurate enough to retrieve basic parameters of human locomotion. Eight subjects walked on an athletics track at four different imposed step frequencies (70-130steps/min) plus a run at free pace. Differential carrier phase localization between a fixed base station and the mobile antenna mounted on the walking person was calculated. In parallel, a triaxial accelerometer, attached to the low back, recorded body accelerations. The different parameters were averaged for 150 consecutive steps of each run for each subject (total of 6000 steps analyzed). We observed a perfect correlation between average step duration measured by accelerometer and by GPS (r=0.9998, N=40). Two important parameters for the calculation of the external work of walking were also analyzed, namely the vertical lift of the trunk and the velocity variation per step. For an average walking speed of 4.0km/h, average vertical lift and velocity variation were, respectively, 4.8cm and 0.60km/h. The average intra-individual step-to-step variability at a constant speed, which includes GPS errors and the biological gait style variation, were found to be 24. 5% (coefficient of variation) for vertical lift and 44.5% for velocity variation. It is concluded that GPS technique can provide useful biomechanical parameters for the analysis of an unlimited number of strides in an unconstrained free-living environment.

Effects of strontium ranelate and alendronate on bone microstructure in women with osteoporosis. Results of a 2-year study.

A Strontium ranelate appears to influence more than alendronate distal tibia bone microstructure as assessed by high-resolution peripheral quantitative computed tomography (HR-pQCT), and biomechanically relevant parameters as assessed by micro-finite element analysis (mu FEA), over 2 years, in postmenopausal osteoporotic women.Introduction Bone microstructure changes are a target in osteoporosis treatment to increase bone strength and reduce fracture risk.Methods Using HR-pQCT, we investigated the effects on distal tibia and radius microstructure of strontium ranelate (SrRan; 2 g/day) or alendronate (70 mg/week) for 2 years in postmenopausal osteoporotic women. This exploratory randomized, double-blind trial evaluated HR-pQCT and FEA parameters, areal bone mineral density (BMD), and bone turnover markers.Results In the intention-to-treat population (n = 83, age: 64 +/- 8 years; lumbar T-score: -2.8 +/- 0.8 [DXA]), distal tibia Cortical Thickness (CTh) and Density (DCort), and cancellous BV/TV increased by 6.3%, 1.4%, and 2.5%, respectively (all P < 0.005), with SrRan, but not with alendronate (0.9%, 0.4%, and 0.8%, NS) (P < 0.05 for all above between-group differences). Difference for CTh evaluated with a distance transformation method was close to significance (P = 0.06). The estimated failure load increased with SrRan (+2.1%, P < 0.005), not with alendronate (-0.6%, NS) (between-group difference, P < 0.01). Cortical stress was lower with SrRan (P < 0.05); both treatments decreased trabecular stress. At distal radius, there was no between-group difference other than DCort (P < 0.05). Bone turnover markers decreased with alendronate; bALP increased (+21%) and serum-CTX-I decreased (-1%) after 2 years of SrRan (between-group difference at each time point for both markers, P < 0.0001). Both treatments were well tolerated.Conclusions Within the constraints of HR-pQCT method, and while a possible artefactual contribution of strontium cannot be quantified, SrRan appeared to influence distal tibia bone microstructure and FEA-determined biomechanical parameters more than alendronate. However, the magnitude of the differences is unclear and requires confirmation with another method.