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1.
PLoS One ; 15(11): e0241969, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33175905

RESUMO

Goal-kicking is an important skill in Australian Football (AF). This study examined whether kinematic differences exist between accurate and inaccurate goal-kicks and determined the relationships between technical factors and accuracy. Eighteen elite to sub-elite AF players performed 15 x 30 m goal-kicks on an AF training ground, with three-dimensional kinematics collected using the Xsens inertial measurement system (Xsens Technologies B.V., Enschede, the Netherlands). A general linear mixed modelling approach and regression-based statistics were employed to quantify differences between accurate and inaccurate goal kicks and the relationships between technical factors and accuracy. Accurate goal-kicks were characterised by a straighter approach line, with less kick-leg joint range of motion (knee and hip), lower linear velocity (centre of mass, foot speed), angular velocity (knee and shank), and less support-leg knee flexion during the kicking phase compared to inaccurate goal-kicks. At the end of the follow through, players produced greater ankle plantarflexion and a straighter-leg line in accurate goal-kicks. Findings in this research indicated that many factors interact with goal-kicking accuracy in AF, ranging from the players' approach line path, their support-leg mechanics, the kick-leg swing motion, to the final position of the kicker during their follow through.


Assuntos
Fenômenos Biomecânicos/fisiologia , Futebol Americano/fisiologia , Futebol/fisiologia , Adolescente , Tornozelo/fisiologia , Articulação do Tornozelo/fisiologia , Desempenho Atlético/fisiologia , Austrália , Pé/fisiologia , Humanos , Joelho/fisiologia , Articulação do Joelho/fisiologia , Perna (Membro)/fisiologia , Extremidade Inferior/fisiologia , Masculino , Movimento/fisiologia , Amplitude de Movimento Articular/fisiologia
2.
PLoS One ; 15(11): e0242454, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33186397

RESUMO

BACKGROUND: The ability to balance on one foot for a certain time is a widely used clinical test to assess the effects of age and diseases like peripheral neuropathy on balance. While state-space methods have been used to explore the mechanical demands and achievable accelerations for balancing on two feet in the sagittal plane, less is known about the requirements for sustaining one legged balance (OLB) in the frontal plane. RESEARCH QUESTION: While most studies have focused on ankle function in OLB, can age and/or disease-related decreases in maximum hip abduction strength also affect OLB ability? METHODS: A two-link frontal plane state space model was used to define and explore the 'feasible balance region' which helps reveal the requirements for maintaining and restoring OLB, given the adverse effects of age and peripheral neuropathy on maximum hip and ankle strengths. RESULTS: Maintaining quasistatic OLB required 50%-106% of the maximum hip abduction strength in young and older adults, and older patients with peripheral neuropathy. Effectiveness of a 'hip strategy' in recovering OLB was heavily dependent on the maximum hip abduction strength, and for healthy older women was as important as ankle strength. Natural reductions of strength due to healthy aging did not show a meaningful reduction in meeting the strength requirement of clinical OLB. However deficits in hip strength typical of patients with peripheral neuropathy did adversely affect both quasistatic OLB and recoverable OLB states. SIGNIFICANCE: The importance of hip muscle strength has been underappreciated in the clinical OLB test. This is partly because the passive tissues of the hip joint can mask moderate deficits in hip abduction strength until it is needed for recovering OLB. Adding a follow up OLB test with a slightly raised pelvis would be a simple way to check for adequate hip abductor muscle strength.


Assuntos
Quadril/fisiologia , Equilíbrio Postural/fisiologia , Tornozelo , Articulação do Tornozelo/fisiologia , Fenômenos Biomecânicos/fisiologia , Articulação do Quadril/fisiologia , Humanos , Perna (Membro)/fisiologia , Modelos Teóricos , Força Muscular/fisiologia , Músculo Esquelético/fisiologia , Pelve , Coxa da Perna/fisiologia
5.
Fisioterapia (Madr., Ed. impr.) ; 42(5): 277-280, sept.-oct. 2020. tab, ilus
Artigo em Espanhol | IBECS | ID: ibc-195144

RESUMO

ANTECEDENTES: La cervicalgia crónica (CC) es una afección frecuente, siendo una de las principales causas de discapacidad. Dentro de los tratamientos fisioterapéuticos más utilizados se encuentran el ejercicio y la movilización manual vertebral (MMV). No obstante, la aplicación de MMV se basa en fundamentos artrocinemáticos y no en el propósito directo de favorecer la ejecución de un ejercicio específico. OBJETIVO: Describir el efecto de un programa de fisioterapia a corto y medio plazo basado en MMV destinada a favorecer el ejercicio de flexión cráneo-cervical (EFCC). Descripción de los casos: Se evaluaron la intensidad de dolor, el umbral de dolor a la presión, el rango de movimiento, el control neuromuscular y la discapacidad cervical en 12 mujeres con CC al inicio, al término y a 3 meses de finalizada la intervención. Intervención: Se ejecutó un programa de 10 sesiones de tratamiento basadas en EFCC y MMV. RESULTADOS: Todas las participantes experimentaron una mejoría clínicamente relevante de su condición a corto plazo, la que se mantuvo 3 meses postintervención. CONCLUSIÓN: El EFCC sumado a una técnica de MMV que busca potenciar la ejecución del ejercicio presentó resultados positivos en mujeres con CC a corto y medio plazo


BACKGROUND: Chronic neck pain is a frequent condition, considered one of the main causes of disability. Among the most used physiotherapeutic treatments are exercise and vertebral manual mobilisation (VMM). However, the application of VMM is based on arthrokinematic fundamentals and not on directly favouring the execution of a specific exercise. OBJECTIVE: to describe the effect of a short- and medium-term physiotherapy programme based on VMM aimed at promoting the exercise of cranio-cervical flexion (CCFE). Cases description: Pain intensity, pressure pain threshold, range of motion, neuromuscular control and cervical disability were evaluated in 12 women with chronic neck pain at the beginning, end and 3 months after the intervention. Intervention: A programme of 10 treatment sessions based on CCFE and VMM was executed. RESULTS: all participants experienced a clinically relevant improvement of their condition in the short term, which remained 3 months post-intervention. CONCLUSION: The CCFE added to a VMM, which seeks to enhance the execution of the exercise, presented positive results in women with chronic neck pain in the short and medium term


Assuntos
Humanos , Feminino , Adolescente , Adulto Jovem , Adulto , Pessoa de Meia-Idade , Cervicalgia/reabilitação , Cervicalgia/terapia , Fenômenos Biomecânicos/fisiologia , Modalidades de Fisioterapia , Dor Crônica/reabilitação , Medição da Dor , Dor Crônica/terapia , Doenças Neuromusculares/reabilitação , Monitoração Neuromuscular
6.
Proc Natl Acad Sci U S A ; 117(43): 26600-26607, 2020 10 27.
Artigo em Inglês | MEDLINE | ID: mdl-33028678

RESUMO

When pollen grains become exposed to the environment, they rapidly desiccate. To protect themselves until rehydration, the grains undergo characteristic infolding with the help of special structures in the grain wall-apertures-where the otherwise thick exine shell is absent or reduced in thickness. Recent theoretical studies have highlighted the importance of apertures for the elastic response and the folding of the grain. Experimental observations show that different pollen grains sharing the same number and type of apertures can nonetheless fold in quite diverse fashions. Using the thin-shell theory of elasticity, we show how both the absolute elastic properties of the pollen wall and the relative elastic differences between the exine wall and the apertures play an important role in determining pollen folding upon desiccation. Focusing primarily on colpate pollen, we delineate the regions of pollen elastic parameters where desiccation leads to a regular, complete closing of all apertures and thus to an infolding which protects the grain against water loss. Phase diagrams of pollen folding pathways indicate that an increase in the number of apertures leads to a reduction of the region of elastic parameters where the apertures close in a regular fashion. The infolding also depends on the details of the aperture shape and size, and our study explains how the features of the mechanical design of apertures influence the pollen folding patterns. Understanding the mechanical principles behind pollen folding pathways should also prove useful for the design of the elastic response of artificial inhomogeneous shells.


Assuntos
Pólen/química , Pólen/fisiologia , Fenômenos Biomecânicos/fisiologia , Dessecação , Elasticidade/fisiologia , Pólen/anatomia & histologia , Pólen/metabolismo , Stachys/citologia , Stachys/fisiologia
7.
Proc Biol Sci ; 287(1937): 20201748, 2020 10 28.
Artigo em Inglês | MEDLINE | ID: mdl-33081609

RESUMO

Musculoskeletal systems cope with many environmental perturbations without neurological control. These passive preflex responses aid animals to move swiftly through complex terrain. Whether preflexes play a substantial role in animal flight is uncertain. We investigated how birds cope with gusty environments and found that their wings can act as a suspension system, reducing the effects of vertical gusts by elevating rapidly about the shoulder. This preflex mechanism rejected the gust impulse through inertial effects, diminishing the predicted impulse to the torso and head by 32% over the first 80 ms, before aerodynamic mechanisms took effect. For each wing, the centre of aerodynamic loading aligns with the centre of percussion, consistent with enhancing passive inertial gust rejection. The reduced motion of the torso in demanding conditions simplifies crucial tasks, such as landing, prey capture and visual tracking. Implementing a similar preflex mechanism in future small-scale aircraft will help to mitigate the effects of gusts and turbulence without added computational burden.


Assuntos
Aves/fisiologia , Voo Animal/fisiologia , Asas de Animais/fisiologia , Animais , Fenômenos Biomecânicos/fisiologia
8.
Sci Rep ; 10(1): 15698, 2020 09 24.
Artigo em Inglês | MEDLINE | ID: mdl-32973276

RESUMO

Juvenile bone growth is well described (physiological and anatomical) but there are still lacks of knowledge on intrinsic material properties. Our group has already published, on different samples, several studies on the assessment of intrinsic material properties of juvenile bone compared to material properties of adult bone. The purpose of this study was finally to combine different experimental modalities available (ultrasonic measurement, micro-Computed Tomography analysis, mechanical compression tests and biochemical measurements) applied on small cubic bone samples in order to gain insight into the multiparametric evaluation of bone quality. Differences were found between juvenile and adult groups in term of architectural parameters (Porosity Separation), Tissue Mineral Density (TMD), diagonal stiffness coefficients (C33, C44, C55, C66) and ratio between immature and mature cross-links (CX). Diagonal stiffness coefficients are more representative of the microstructural and biochemical parameters of child bone than of adult bone. We also found that compression modulus E was highly correlated with several microstructure parameters and CX in children group while it was not at all correlated in the adult group. Similar results were found for the CX which was linked to several microstructure parameters (TMD and E) only in the juvenile group. To our knowledge, this is the first time that, on a same sample, ultrasonic measurements have been combined with the assessment of mechanical and biochemical properties. It appears that ultrasonic measurements can provide relevant indicators of child bone quality (microstructural and biochemical parameters) which is promising for clinical application since, B-mode ultrasound is the preferred first-line modality over other more constraining imaging modalities (radiation, parent-child accessibility and access to the patient's bed) for pediatric patients.


Assuntos
Desenvolvimento Ósseo/fisiologia , Osso e Ossos/diagnóstico por imagem , Idoso , Idoso de 80 Anos ou mais , Fenômenos Biomecânicos/fisiologia , Densidade Óssea/fisiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Ultrassonografia , Microtomografia por Raio-X
9.
Sci Rep ; 10(1): 15425, 2020 09 22.
Artigo em Inglês | MEDLINE | ID: mdl-32963292

RESUMO

This study examined the relationships between the foot bone morphologies and sprint performance in sprinters. Foot images in 56 male sprinters obtained using magnetic resonance imaging. The relative lengths of the forefoot bones of the big and second toes, which were calculated as total lengths of the forefoot bones for each toe normalized to the foot length, correlated significantly with personal best 100-m sprint time (r = - 0.293 and - 0.459, both Ps < 0.05). The relative lengths of the rearfoot talus and calcaneus normalized to the foot length also correlated significantly with the sprint performance (r = - 0.378 and - 0.496, both Ps < 0.05). Furthermore, the relative height of the calcaneus, but not the talus, normalized to body height correlated significantly with sprint performance (r = - 0.690, P < 0.001). Additionally, the relative calcaneus height correlated significantly with the foot arch height index (r = 0.420, P = 0.001), and the foot arch height index correlated significantly with sprint performance (r = - 0.517, P < 0.001). These findings suggest that the taller calcaneus may be a key morphological factor for achieving superior sprint performance, potentially via modeling the longer forefoot and rearfoot bones and functional foot morphology in sprinters.


Assuntos
Desempenho Atlético/fisiologia , Calcâneo/fisiologia , Corrida/fisiologia , Adulto , Fenômenos Biomecânicos/fisiologia , Pé/fisiologia , Ossos do Pé/fisiologia , Humanos , Masculino , Músculo Esquelético/fisiologia , Dedos do Pé/fisiologia , Adulto Jovem
10.
Sci Rep ; 10(1): 15275, 2020 09 17.
Artigo em Inglês | MEDLINE | ID: mdl-32943736

RESUMO

Considering the interplay between orbital bones and intraorbital soft tissues, commonly accepted patterns of the blow-out type of trauma within the human orbit require more thorough investigation to assess the minimal health-threatening impact value. Two different three-dimensional finite element method (FEM) models of the human orbital region were developed to simulate the pure "buckling" mechanism of orbital wall fracture in two variants: the model of orbital bone elements and the model of orbital bone, orbit and intraorbital tissue elements. The mechanical properties of the so-defined numerical skull fragment were applied to the model according to the unique laboratory tensile stress tests performed on small and fragile specimens of orbital bones as well as using the data available in the literature. The nonlinear transient analysis of the contact problem between bodies that differ substantially in terms of the Young's modulus was carried out to investigate the interaction of different bodies within an instant injury. Potential damage areas were found within the lower orbital wall as well as the destructive load values for both FEM skull models (7,660 N and 8,520 N). Moreover, numerical simulations were validated by comparing them with computed tomography scans of real injuries.


Assuntos
Órbita/lesões , Fraturas Orbitárias/patologia , Ferimentos e Lesões/patologia , Adulto , Fenômenos Biomecânicos/fisiologia , Simulação por Computador , Módulo de Elasticidade , Feminino , Análise de Elementos Finitos , Humanos , Masculino , Pessoa de Meia-Idade , Modelos Biológicos , Dinâmica não Linear , Crânio/lesões , Estresse Mecânico , Tomografia Computadorizada por Raios X/métodos , Adulto Jovem
11.
Proc Natl Acad Sci U S A ; 117(41): 25532-25542, 2020 10 13.
Artigo em Inglês | MEDLINE | ID: mdl-32989126

RESUMO

The actin cytoskeleton assembles into diverse load-bearing networks, including stress fibers (SFs), muscle sarcomeres, and the cytokinetic ring to both generate and sense mechanical forces. The LIM (Lin11, Isl- 1, and Mec-3) domain family is functionally diverse, but most members can associate with the actin cytoskeleton with apparent force sensitivity. Zyxin rapidly localizes via its LIM domains to failing SFs in cells, known as strain sites, to initiate SF repair and maintain mechanical homeostasis. The mechanism by which these LIM domains associate with stress fiber strain sites (SFSS) is not known. Additionally, it is unknown how widespread strain sensing is within the LIM protein family. We identify that the LIM domain-containing region of 18 proteins from the Zyxin, Paxillin, Tes, and Enigma proteins accumulate to SFSS. Moreover, the LIM domain region from the fission yeast protein paxillin like 1 (Pxl1) also localizes to SFSS in mammalian cells, suggesting that the strain sensing mechanism is ancient and highly conserved. We then used sequence and domain analysis to demonstrate that tandem LIM domains contribute additively, for SFSS localization. Employing in vitro reconstitution, we show that the LIM domain-containing region from mammalian zyxin and fission yeast Pxl1 binds to mechanically stressed F-actin networks but does not associate with relaxed actin filaments. We propose that tandem LIM domains recognize an F-actin conformation that is rare in the relaxed state but is enriched in the presence of mechanical stress.


Assuntos
Proteínas com Domínio LIM/metabolismo , Proteínas com Domínio LIM/fisiologia , Fibras de Estresse/metabolismo , Fibras de Estresse/fisiologia , Sequência de Aminoácidos , Animais , Fenômenos Biomecânicos/fisiologia , Linhagem Celular , Sequência Conservada , Evolução Molecular , Proteínas com Domínio LIM/química , Camundongos , Miosinas/química , Miosinas/metabolismo , Ligação Proteica/fisiologia , Fibras de Estresse/química , Estresse Mecânico , Leveduras
12.
PLoS One ; 15(9): e0233475, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32946458

RESUMO

We aimed to compare the match-play and kinematic demands of the translation and rotation movements of elite wheelchair padel players as a function of match results. Twenty-two elite male players were video-analysed with a two-dimensional direct linear transformation (DLT) -corrected video system across seven matches of a professional tournament. Distance, turns, changes of direction, linear and angular speed, acceleration and the players' heart rate (HR) were recorded. Losing couples in wheelchair padel covered greater distances than winners (P <0.001; r = 0.024) and did so at a higher speed (P <0.001; r = 0.06), while making greater efforts by accelerating (P <0.001; ∅ = -0.021), braking (P <0.001; ∅ = -0.014), and remaining less time stationary (P <0.001; ∅ = 0.059). In addition, losers performed more turns per rally (P <0.001; r = 0.04) at a faster speed, greater angular accelerations (P <0.001; V = 0.06) and greater average (P = 0.007; d = 0.91) and maximum (P = 0.20; d = 0.69) HR values. These data suggest that winner couples performed a better court positioning and employed a strategy to move the opponent during rallies in order to avoid them optimally reaching the ball.


Assuntos
Desempenho Atlético/fisiologia , Paratletas , Esportes/fisiologia , Cadeiras de Rodas , Aceleração , Adulto , Fenômenos Biomecânicos/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade , Estudos de Tempo e Movimento , Gravação em Vídeo
13.
PLoS One ; 15(9): e0239471, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32946493

RESUMO

Humans can innately track a moving target by anticipating its future position from a brief history of observations. While ballistic trajectories can be readily extrapolated, many natural and artificial systems are governed by more general nonlinear dynamics and, therefore, can produce highly irregular motion. Yet, relatively little is known regarding the behavioral and physiological underpinnings of prediction and tracking in the presence of chaos. Here, we investigated in lab settings whether participants could manually follow the orbit of a paradigmatic chaotic system, the Rössler equations, on the (x,y) plane under different settings of a control parameter, which determined the prominence of transients in the target position. Tracking accuracy was negatively related to the level of unpredictability and folding. Nevertheless, while participants initially reacted to the transients, they gradually learned to anticipate it. This was accompanied by a decrease in muscular co-contraction, alongside enhanced activity in the theta and beta EEG bands for the highest levels of chaoticity. Furthermore, greater phase synchronization of breathing was observed. Taken together, these findings point to the possible ability of the nervous system to implicitly learn topological regularities even in the context of highly irregular motion, reflecting in multiple observables at the physiological level.


Assuntos
Dinâmica não Linear , Análise e Desempenho de Tarefas , Adulto , Sistema Nervoso Autônomo/fisiologia , Fenômenos Biomecânicos/fisiologia , Eletroencefalografia , Eletromiografia , Força da Mão/fisiologia , Humanos , Cinética , Aprendizagem/fisiologia , Movimento (Física) , Contração Muscular/fisiologia , Adulto Jovem
14.
PLoS One ; 15(9): e0239148, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32936793

RESUMO

Lower limb exoskeletons and lower limb prostheses have the potential to reduce gait limitations during stair ambulation. To develop robotic assistance devices, the biomechanics of stair ambulation and the required transitions to level walking have to be understood. This study aimed to identify the timing of these transitions, to determine if transition phases exist and how long they last, and to investigate if there exists a joint-related order and timing for the start and end of the transitions. Therefore, this study analyzed the kinematics and kinetics of both transitions between level walking and stair ascent, and between level walking and stair descent (12 subjects, 25.4 yrs, 74.6 kg). We found that transitions primarily start within the stance phase and end within the swing phase. Transition phases exist for each limb, all joints (hip, knee, ankle), and types of transitions. They have a mean duration of half of one stride and they do not last longer than one stride. The duration of the transition phase for all joints of a single limb in aggregate is less than 35% of one stride in all but one case. The distal joints initialize stair ascent, while the proximal joints primarily initialize the stair descent transitions. In general, the distal joints complete the transitions first. We believe that energy- and balance-related processes are responsible for the joint-specific transition timing. Regarding the existence of a transition phase for all joints and transitions, we believe that lower limb exoskeleton or prosthetic control concepts should account for these transitions in order to improve the smoothness of the transition and to thus increase the user comfort, safety, and user experience. Our gait data and the identified transition timings can provide a reference for the design and the performance of stair ambulation- related control concepts.


Assuntos
Articulação do Tornozelo/fisiologia , Marcha/fisiologia , Articulação do Quadril/fisiologia , Articulação do Joelho/fisiologia , Subida de Escada/fisiologia , Adulto , Membros Artificiais , Fenômenos Biomecânicos/fisiologia , Exoesqueleto Energizado , Humanos , Extremidade Inferior , Masculino , Equilíbrio Postural/fisiologia , Desenho de Prótese/métodos , Amplitude de Movimento Articular/fisiologia , Fatores de Tempo , Adulto Jovem
15.
J Vis Exp ; (162)2020 08 25.
Artigo em Inglês | MEDLINE | ID: mdl-32925877

RESUMO

Gait termination caused by unexpected stimulus is a common occurrence in everyday life. This study presents a protocol to investigate the lower-limb biomechanical changes that occur during unplanned gait termination (UGT) under different walking speeds. Fifteen male participants were asked to perform UGT on a walkway at normal walking speed (NWS) and fast walking speed (FWS), respectively. A motion analysis system and plantar pressure platform were applied to collect lower-limb kinematic and plantar pressure data. Paired-sampled T-test was used to examine the differences in lower-limb kinematics and plantar pressure data between two walking speeds. The results showed larger range of motion in the hip, knee, and ankle joints in the sagittal plane as well as plantar pressure in forefoot and heel regions during UGT at FWS when compared with NWS. With the increase in walking speed, subjects exhibited different lower-limb biomechanical characteristics that show FWS associated with greater potential injury risks.


Assuntos
Extremidade Inferior/fisiologia , Velocidade de Caminhada/fisiologia , Adulto , Fenômenos Biomecânicos/fisiologia , Calibragem , Humanos , Masculino , Movimento (Física) , Pressão , Amplitude de Movimento Articular
16.
Sci Rep ; 10(1): 15085, 2020 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-32934249

RESUMO

This study was designed to investigate the effects of anxiety and dual-task on reach and grasp motor control in chronic stroke survivors compared with age- and sex-matched healthy subjects (HC). Reach and grasp kinematic data of 68 participants (high-anxiety stroke (HA-stroke), n = 17; low-anxiety stroke (LA-stroke), n = 17; low-anxiety HC, n = 17; and high-anxiety HC, n = 17) were recorded under single- and dual-task conditions. Inefficient reach and grasp of stroke participants, especially HA-stroke were found compared with the control groups under single- and dual-task conditions as evidenced by longer movement time (MT), lower and earlier peak velocity (PV) as well as delayed and smaller hand opening. The effects of dual-task on reach and grasp kinematic measures were similar between HCs and stroke participants (i.e., increased MT, decreased PV that occurred earlier, and delayed and decreased hand opening), with greater effect in stroke groups than HCs, and in HA-stroke group than LA-stroke group. The results indicate that performing a well-learned upper limb movement with concurrent cognitive task leads to decreased efficiency of motor control in chronic stroke survivors compared with HCs. HA-stroke participants were more adversely affected by challenging dual-task conditions, underlying importance of assessing anxiety and designing effective interventions for it in chronic stroke survivors.


Assuntos
Ansiedade/fisiopatologia , Ansiedade/psicologia , Córtex Motor/fisiopatologia , Acidente Vascular Cerebral/fisiopatologia , Acidente Vascular Cerebral/psicologia , Extremidade Superior/fisiopatologia , Adulto , Idoso , Fenômenos Biomecânicos/fisiologia , Feminino , Força da Mão/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade , Movimento/fisiologia , Recuperação de Função Fisiológica/fisiologia , Reabilitação do Acidente Vascular Cerebral/psicologia , Sobreviventes
17.
Artigo em Inglês | MEDLINE | ID: mdl-32933208

RESUMO

Backward jump-landing during sports performance will result in dynamic postural instability with a greater risk of injury, and most research studies have focused on forward landing. Differences in kinematic temporal characteristics between single-leg and double-leg backward jump-landing are seldom researched and understood. The purpose of this study was to compare and analyze lower extremity kinematic differences throughout the landing phases of forward and backward jumping using single-leg and double-leg landings (FS and BS, FD and BD). Kinematic data were collected during the landing phases of FS and BS, FD and BD in 45 participants. Through statistical parametric mapping (SPM) analysis, we found that the BS showed smaller hip and knee flexion and greater vertical ground reactive force (VGRF) than the FS during 0-37.42% (p = 0.031), 16.07-32.11% (p = 0.045), and 23.03-17.32% (p = 0.041) landing phases. The BD showed smaller hip and knee flexion than the FD during 0-20.66% (p = 0.047) and 0-100% (p < 0.001) landing phases. Most differences appeared within a time frame during the landing phase at 30-50 ms in which non-contact anterior cruciate ligament (ACL) injuries are thought to occur and are consistent with the identification of risk in biomechanical analysis. A landing strategy that consciously increases the knee and hip flexion angles during backward landing should be considered for people as a measure to avoid injury during the performance of this type of physical activity.


Assuntos
Lesões do Ligamento Cruzado Anterior , Desempenho Atlético/fisiologia , Traumatismos do Joelho/prevenção & controle , Perna (Membro)/fisiologia , Extremidade Inferior/fisiologia , Movimento/fisiologia , Equilíbrio Postural/fisiologia , Adulto , Atletas , Fenômenos Biomecânicos/fisiologia , Humanos , Articulação do Joelho/fisiologia
18.
Proc Natl Acad Sci U S A ; 117(37): 23085-23095, 2020 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-32873637

RESUMO

Animals use active sensing to respond to sensory inputs and guide future motor decisions. In flight, flies generate a pattern of head and body movements to stabilize gaze. How the brain relays visual information to control head and body movements and how active head movements influence downstream motor control remains elusive. Using a control theoretic framework, we studied the optomotor gaze stabilization reflex in tethered flight and quantified how head movements stabilize visual motion and shape wing steering efforts in fruit flies (Drosophila). By shaping visual inputs, head movements increased the gain of wing steering responses and coordination between stimulus and wings, pointing to a tight coupling between head and wing movements. Head movements followed the visual stimulus in as little as 10 ms-a delay similar to the human vestibulo-ocular reflex-whereas wing steering responses lagged by more than 40 ms. This timing difference suggests a temporal order in the flow of visual information such that the head filters visual information eliciting downstream wing steering responses. Head fixation significantly decreased the mechanical power generated by the flight motor by reducing wingbeat frequency and overall thrust. By simulating an elementary motion detector array, we show that head movements shift the effective visual input dynamic range onto the sensitivity optimum of the motion vision pathway. Taken together, our results reveal a transformative influence of active vision on flight motor responses in flies. Our work provides a framework for understanding how to coordinate moving sensors on a moving body.


Assuntos
Drosophila/fisiologia , Voo Animal/fisiologia , Visão Ocular/fisiologia , Vias Visuais/fisiologia , Animais , Fenômenos Biomecânicos/fisiologia , Movimentos da Cabeça/fisiologia , Mecanorreceptores/fisiologia , Movimento (Física) , Asas de Animais/fisiologia
19.
Sensors (Basel) ; 20(18)2020 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-32899946

RESUMO

Gait deterioration caused by prolonged walking represents one of the main consequences of multiple sclerosis (MS). This study aims at proposing quantitative indices to measure the gait deterioration effects. The experimental protocol consisted in a 6-min walking test and it involved nine patients with MS and twenty-six healthy subjects. Pathology severity was assessed through the Expanded Disability Status Scale. Seven inertial units were used to gather lower limb kinematics. Gait variability and asymmetry were assessed by coefficient of variation (CoV) and symmetry index (SI), respectively. The evolution of ROM (range of motion), CoV, and SI was computed analyzing data divided into six 60-s subgroups. Maximum difference among subgroups and the difference between the first minute and the remaining five were computed. The indices were analyzed for intra- and inter-day reliability and repeatability. Correlation with clinical scores was also evaluated. Good to excellent reliability was found for all indices. The computed standard deviations allowed us to affirm the good repeatability of the indices. The outcomes suggested walking-related fatigue leads to an always more variable kinematics in MS, in terms of changes in ROM, increase of variability and asymmetry. The hip asymmetry strongly correlated with the clinical disability.


Assuntos
Fadiga/fisiopatologia , Transtornos Neurológicos da Marcha/diagnóstico , Marcha/fisiologia , Esclerose Múltipla/diagnóstico , Índice de Gravidade de Doença , Caminhada/fisiologia , Adulto , Idoso , Fenômenos Biomecânicos/fisiologia , Estudos de Casos e Controles , Avaliação da Deficiência , Progressão da Doença , Teste de Esforço/métodos , Feminino , Transtornos Neurológicos da Marcha/etiologia , Indicadores Básicos de Saúde , Humanos , Masculino , Pessoa de Meia-Idade , Esclerose Múltipla/patologia , Esclerose Múltipla/fisiopatologia , Reprodutibilidade dos Testes , Projetos de Pesquisa , Fatores de Tempo
20.
Artigo em Inglês | MEDLINE | ID: mdl-32867383

RESUMO

BACKGROUND AND AIM: To identify kinematic variables related to short course 100 m breaststroke performance. METHODS: An automatic race analysis system was utilized to obtain start (0-15 m), turn (5 m before the wall until 10 m out), finish (95-100 m), and clean swimming (the rest of the race) segment times as well as cycle rate and cycle length during each swimming cycle from 15 male swimmers during a 100 m breaststroke race. A bivariate correlation and a partial correlation were employed to assess the relationship between each variable and swimming time. RESULTS: Turns were the largest time contributor to the finishing time (44.30 ± 0.58%), followed by clean swimming (38.93 ± 0.50%), start (11.39 ± 0.22%), and finish (5.36 ± 0.18%). The finishing time was correlated (p < 0.001) with start segment time (r = 0.979), clean swimming time (r = 0.940), and 10 m turn-out time (r = 0.829). The clean swimming time was associated with the finishing time, but cycle rate and cycle length were not. In both start and turns, the peak velocity (i.e., take-off and push-off velocity) and the transition velocity were related to the segment time (r ≤ -0.673, p ≤ 0.006). CONCLUSIONS: Breaststroke training should focus on: (I) 15 m start with generating high take-off velocity, (II) improving clean swimming velocity by finding an optimal balance between cycle length and rate, (III) 10 m turn-out with maintaining a strong wall push-off, and (IV) establishing a high transition velocity from underwater to surface swimming.


Assuntos
Desempenho Atlético/fisiologia , Tempo de Reação/fisiologia , Natação/fisiologia , Desempenho Atlético/psicologia , Fenômenos Biomecânicos/fisiologia , Humanos , Manutenção , Masculino
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