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1.
J Sports Sci ; 38(5): 542-551, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31924128

RESUMO

Males and females demonstrate unique running mechanics that may contribute to sex-related differences in common running related injuries. Understanding differences in muscle forces during running may inform intervention approaches, such as gait retraining addressing muscle force distribution. The purpose of this study was to compare muscle force characteristics and inter-trial variability between males and females during running. Twenty female and 14 male collegiate cross-country runners were examined. Three-dimensional kinetic and kinematic data were collected during overground running and used to estimate muscle forces via musculoskeletal modelling. Principle components analysis was used to capture the primary sources of variance from the muscle force waveforms. The magnitude of the forces for the hamstrings, gastrocnemius, and soleus muscles were higher across the majority of stance in male runners regardless of footstrike pattern. Males also demonstrated greater inter-trial variability in the timing of the peak gluteus maximus force and the magnitude of local peaks in the gastrocnemius force waveform. Male and female collegiate cross-country runners appear to employ unique lower extremity muscle force characteristics during overground running.


Assuntos
Músculo Esquelético/fisiologia , Corrida/fisiologia , Adolescente , Fenômenos Biomecânicos/fisiologia , Feminino , Marcha/fisiologia , Músculos Isquiotibiais/fisiologia , Humanos , Extremidade Inferior/fisiologia , Masculino , Análise Multivariada , Músculo Quadríceps/fisiologia , Fatores Sexuais , Adulto Jovem
2.
J Sports Sci ; 38(5): 518-527, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31900052

RESUMO

The purpose of this study was to investigate the effects of slope on three-dimensional running kinematics at high speed. Thirteen male sprinters ran at high speed (7.5 m/s) on a motorised treadmill in each a level and a 5.0% slope condition. Three-dimensional motion analysis was conducted to compare centre of mass (CoM) energetics, pelvis segment and lower limb joints kinematics. We found that contact time was not affected by the slope, whereas flight time and step length were significantly shorter in uphill compared to level running. Uphill running reduced negative CoM work and increased positive CoM work compared to level running. Ankle, knee and hip joints were more flexed at initial ground contact, but only the knee was more extended at the end of stance in uphill compared to level running. Additionally, the hip joint was more abducted, and the free leg side of the pelvis was more elevated at the end of stance in uphill running. Our results demonstrate that joint motion must be developed from a more flexed/adducted position at initial contact through a greater range of motion compared to level running in order to meet the greater positive CoM work requirements in uphill running at high speed.


Assuntos
Articulação do Tornozelo/fisiologia , Articulação do Quadril/fisiologia , Articulação do Joelho/fisiologia , Corrida/fisiologia , Fenômenos Biomecânicos/fisiologia , Teste de Esforço , Marcadores Fiduciais , Marcha , Humanos , Imagem Tridimensional , Masculino , Movimento/fisiologia , Amplitude de Movimento Articular/fisiologia , Adulto Jovem
3.
World Neurosurg ; 133: 343-357.e1, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31550538

RESUMO

BACKGROUND: The center of rotation (COR), instantaneous center of rotation (ICR), instantaneous axis of rotation, instantaneous helical axis, finite helical axis, and helical axis of motion are important kinematic parameters for evaluating the quality of intervertebral motion of the cervical spine (QIMC). These parameters embody different concepts and are calculated using various methods. In this review, the distinctions and connections between these kinematic parameters are analyzed according to the concepts, research, and measurement techniques to provide a theoretic basis for future research and new research directions. METHODS: The PubMed/MEDLINE databases were searched for studies published in English related to the concepts, research, and calculation of these parameters. The included studies were classified according to the different research or calculation methods, and the proportion of each study type was calculated and analyzed. RESULTS: Forty articles were selected. The methods for analyzing the QIMC include in vivo and in vitro studies and finite element analysis. The primary methods for calculating these parameters include the method of perpendicular bisectors and the finite helical axis method. CONCLUSIONS: COR was the simplest but not the most accurate parameter to evaluate the QIMC. Conversely, instantaneous helical axis/helical axis of motion were the most accurate, but relatively complex parameters to evaluate the QIMC. ICR showed dynamic changes during flexion-extension motion, but not the three-dimensional kinematic motion of the cervical spine. These parameters were equivalent only in certain situations but cannot be substituted for each other in the clinic. A dynamic radiographic in vivo study was the most convenient and frequently used research method to calculate COR, but failed to describe the dynamic movement. The method of perpendicular bisectors was widely used to calculate the COR or ICR. Therefore, a combination of new research and calculation methods to simply and effectively evaluate the QIMC requires further investigation.


Assuntos
Vértebras Cervicais/fisiologia , Disco Intervertebral/fisiologia , Amplitude de Movimento Articular/fisiologia , Fenômenos Biomecânicos/fisiologia , Humanos , Rotação
4.
Int J Sports Med ; 41(1): 21-26, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31756737

RESUMO

The aim of the study was to verify the relative contributions of energetic and kinematic parameters to the performance in 400-m front crawl test. Fourteen middle-distance swimmers participated in the study. Oxygen consumption was measured directly and blood samples were collected to assay lactate concentration. Both oxygen consumption and lactate concentration were used to calculate the: (i) overall energy expenditure, (ii) anaerobic (alactic and lactic) and (iii) aerobic contributions. The mean centre of mass speed and intracycle velocity variation were determined through three-dimensional kinematic analysis. Mean completion time was 315.64±26.91s. Energetic contributions were as follows: 6.1±0.28% from alactic anaerobic metabolism, 5.9±0.63% from anaerobic lactic and 87.8±0.88% from aerobic. Mean intracycle velocity variation was 0.14±0.03. The results indicated that performance of 400-m test relies predominantly on aerobic power. Parameters such as lactate, mean speed, anaerobic lactic and alactic (kW) correlated with performance of 400-m test (p <0.05). Multiple linear regressions indicated that mean centre of mass speed and anaerobic alactic (kW) determined the 400-m test performance (R2=0.92). Even though the T400 is characterized by aerobic metabolism, the anaerobic alactic component cannot be negligible at this competition level.


Assuntos
Metabolismo Energético/fisiologia , Teste de Esforço/métodos , Natação/fisiologia , Fenômenos Biomecânicos/fisiologia , Comportamento Competitivo/fisiologia , Humanos , Ácido Láctico/sangue , Masculino , Oxigênio/sangue , Consumo de Oxigênio , Estudos de Tempo e Movimento , Gravação em Vídeo , Adulto Jovem
5.
Forensic Sci Int ; 306: 110060, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31785511

RESUMO

In order to investigate potential causal relations between the shaking of infants and injuries, biomechanical studies compare brain and skull dynamic behavior during shaking to injury thresholds. However, performing shaking tolerance research on infants, either in vivo or ex vivo, is extremely difficult, if not impossible. Therefore, infant injury thresholds are usually estimated by scaling or extrapolating adult or animal data obtained from crash tests or whiplash experiments. However, it is doubtful whether such data accurately matches the biomechanics of shaking in an infant. Hence some thresholds may be inappropriate to be used for the assessment of inflicted head injury by shaking trauma in infants. A systematic literature review was conducted to 1) provide an overview of existing thresholds for head- and neck injuries related to violent shaking, and 2) to identify and discuss which thresholds have been used or could be used for the assessment of inflicted head injury by shaking trauma in infants. Key findings: The majority of studies establishing or proposing injury thresholds were found to be based on loading cycle durations and loading cycle repetitions that did not resemble those occurring during shaking, or had experimental conditions that were insufficiently documented in order to evaluate the applicability of such thresholds. Injury thresholds that were applied in studies aimed at assessing whether an injury could occur under certain shaking conditions were all based on experiments that did not properly replicate the loading characteristics of shaking. Somewhat validated threshold scaling methods only exist for scaling concussive injury thresholds from adult primate to adult human. Scaling methods that have been used for scaling other injuries, or for scaling adult injury thresholds to infants were not validated. There is a clear and urgent need for new injury thresholds established by accurately replicating the loading characteristics of shaking.


Assuntos
Fenômenos Biomecânicos/fisiologia , Síndrome do Bebê Sacudido/fisiopatologia , Aceleração , Animais , Lesão Axonal Difusa/fisiopatologia , Medicina Legal/métodos , Traumatismos Cranianos Fechados/fisiopatologia , Humanos , Lactente , Hemorragias Intracranianas/fisiopatologia , Modelos Biológicos , Lesões do Pescoço/fisiopatologia , Hemorragia Retiniana/fisiopatologia
6.
DNA Cell Biol ; 39(2): 159-166, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31821009

RESUMO

Hippo signaling regulates the balance between cell proliferation and apoptosis to control the size of organs during development. Appropriate Hippo signaling is associated with stem cell differentiation, and inappropriate signaling can result in tumorigenesis and cancer. Hippo signaling activity is influenced not only by biochemical signals but also by mechanical force and the cytoskeleton transmitted through cell-cell junctions and cell-matrix adhesions. In this review, we describe the evidence for the regulation of Hippo signaling by the spatial reorganization of signaling components, mechanical force, and the cytoskeleton. Although our understanding of the relationship between Hippo signal transduction and mechanical force and the cytoskeleton is developing rapidly, many unresolved questions remain.


Assuntos
Citoesqueleto/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Serina-Treonina Quinases/fisiologia , Animais , Fenômenos Biomecânicos/fisiologia , Carcinogênese/metabolismo , Diferenciação Celular , Proliferação de Células , Humanos , Microtúbulos/metabolismo , Transdução de Sinais/fisiologia
7.
Accid Anal Prev ; 134: 105297, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31683233

RESUMO

The motorcyclist is exposed to the risk of falling and impacting ground head-first at a wide range of travelling speeds - from a speed limit of less than 50 km/h on the urban road to the race circuit where speed can reach well above 200 km/h. However, motorcycle helmets today are tested at a single and much lower impact speed, i.e. 30 km/h. There is a knowledge gap in understanding the dynamics and head impact responses at high travelling speeds due to the limitation of existing laboratory rigs. This study used a finite element head model coupled with a motorcycle helmet model to simulate head-first falls at travelling speed (or tangential velocity at impact) from 0 to 216 km/h. The effect of different falling heights (1.6 m and 0.25 m) and coefficient of frictions (0.20 and 0.45) between the helmet outer shell and ground were also examined. The simulation results were analysed together with the analytical model to better comprehend rolling and/or sliding phenomena that are often observed in helmet oblique impacts. Three types of helmet-to-ground interactions are found when the helmet impacts ground from low to high tangential velocities: (1) helmet rolling without slipping; (2) a combination of sliding and rolling; and (3) continuous sliding. The tangential impulse transmitted to the head-helmet system, peak angular head kinematics and brain strain increase almost linearly with the tangential velocity when the helmet rolls but plateaus when the helmet slides. The critical tangential velocity at which the motion transit from the rolling regime to the sliding regime depends on both the falling height and friction coefficient. Typically, for a fall height of 1.63 m and a friction coefficient of 0.45, the rolling/sliding transition occurs at a tangential velocity of 10.8 m/s (38.9 km/h). Low sliding resistance in helmet design, i.e. by the means of a lower friction coefficient between the helmet outer shell and ground, has shown a higher reduction of brain tissue strain in the sliding regime than in the rolling regime. This study uncovers the underlying dynamics of rolling and sliding phenomena in high-speed oblique impacts, which largely affect head impact biomechanics. Besides, the study highlights the importance of testing helmets at speeds covering both the rolling and sliding regime since potential designs for improved head protection at high-speed impacts can be more distinguishable in the sliding regime than in the rolling regime.


Assuntos
Fricção , Dispositivos de Proteção da Cabeça , Motocicletas/estatística & dados numéricos , Aceleração , Acidentes de Trânsito/classificação , Fenômenos Biomecânicos/fisiologia , Traumatismos Craniocerebrais/etiologia , Traumatismos Craniocerebrais/prevenção & controle , Humanos , Fatores de Risco
8.
Dev Sci ; 23(1): e12873, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31144771

RESUMO

Body movements, as well as faces, communicate emotions. Research in adults has shown that the perception of action kinematics has a crucial role in understanding others' emotional experiences. Still, little is known about infants' sensitivity to body emotional expressions, since most of the research in infancy focused on faces. While there is some first evidence that infants can recognize emotions conveyed in whole-body postures, it is still an open question whether they can extract emotional information from action kinematics. We measured electromyographic (EMG) activity over the muscles involved in happy (zygomaticus major, ZM), angry (corrugator supercilii, CS) and fearful (frontalis, F) facial expressions, while 11-month-old infants observed the same action performed with either happy or angry kinematics. Results demonstrate that infants responded to angry and happy kinematics with matching facial reactions. In particular, ZM activity increased while CS activity decreased in response to happy kinematics and vice versa for angry kinematics. Our results show for the first time that infants can rely on kinematic information to pick up on the emotional content of an action. Thus, from very early in life, action kinematics represent a fundamental and powerful source of information in revealing others' emotional state.


Assuntos
Fenômenos Biomecânicos/fisiologia , Eletromiografia/métodos , Emoções/fisiologia , Expressão Facial , Adulto , Ira , Músculos Faciais , Medo , Feminino , Felicidade , Humanos , Lactente , Masculino
9.
Clin Podiatr Med Surg ; 37(1): 1-22, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31735261

RESUMO

In trying to explain the myriad of foot deformities and symptoms that have slow onset and/or are considered to be overuse syndromes, clinicians have been trying to develop quantitative examinations to describe the cause of the patient's problems and to better individualize treatment modalities. This type of examination is called a biomechanical examination. This article discusses some of the more common portions of a biomechanical examination of the foot and lower extremity. It will also point out some ways that the information from a biomechanical examination can be applied in clinically treating patients.


Assuntos
Deformidades do Pé/terapia , Extremidade Inferior/fisiopatologia , Fenômenos Biomecânicos/fisiologia , Deformidades do Pé/diagnóstico , Deformidades do Pé/etiologia , Humanos , Exame Físico
10.
J Sports Sci ; 38(5): 486-493, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31865835

RESUMO

Biomechanical analysis has typically been confined to a laboratory setting. While attempts have been made to take laboratory testing into the field, this study was designed to assess whether augmented reality (AR) could be used to bring the field into the laboratory. This study aimed to measure knee load in volleyball players through a jump task incorporating AR while maintaining the perception-action couplings by replicating the visual features of a volleyball court. Twelve male volleyball athletes completed four tasks: drop landing, hop jump, spike jump, and spike jump while wearing AR smart glasses. Biomechanical variables included patellar tendon force, knee moment and kinematics of the ankle, knee, hip, pelvis and thorax. The drop landing showed differences in patellar tendon force and knee moment when compared to the other conditions. The hop jump did not present differences in kinetics when compared to the spike conditions, instead of displaying the greatest kinematic differences. As a measure of patellar tendon loading the AR condition showed a close approximation to the spike jump, with no differences present when comparing landing forces and mechanics. Thus, AR may be used in a clinical assessment to better replicate information from the competitive environment.


Assuntos
Desempenho Atlético/fisiologia , Realidade Aumentada , Voleibol/fisiologia , Adolescente , Articulação do Tornozelo/fisiologia , Fenômenos Biomecânicos/fisiologia , Articulação do Quadril/fisiologia , Humanos , Articulação do Joelho/fisiologia , Masculino , Ligamento Patelar/fisiologia , Reprodutibilidade dos Testes , Adulto Jovem
11.
PLoS One ; 14(12): e0219333, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31887218

RESUMO

BACKGROUND: Successful hand-object interactions require precise hand-eye coordination with continual movement adjustments. Quantitative measurement of this visuomotor behaviour could provide valuable insight into upper limb impairments. The Gaze and Movement Assessment (GaMA) was developed to provide protocols for simultaneous motion capture and eye tracking during the administration of two functional tasks, along with data analysis methods to generate standard measures of visuomotor behaviour. The objective of this study was to investigate the reproducibility of the GaMA protocol across two independent groups of non-disabled participants, with different raters using different motion capture and eye tracking technology. METHODS: Twenty non-disabled adults performed the Pasta Box Task and the Cup Transfer Task. Upper body and eye movements were recorded using motion capture and eye tracking, respectively. Measures of hand movement, angular joint kinematics, and eye gaze were compared to those from a different sample of twenty non-disabled adults who had previously performed the same protocol with different technology, rater and site. RESULTS: Participants took longer to perform the tasks versus those from the earlier study, although the relative time of each movement phase was similar. Measures that were dissimilar between the groups included hand distances travelled, hand trajectories, number of movement units, eye latencies, and peak angular velocities. Similarities included all hand velocity and grip aperture measures, eye fixations, and most peak joint angle and range of motion measures. DISCUSSION: The reproducibility of GaMA was confirmed by this study, despite a few differences introduced by learning effects, task demonstration variation, and limitations of the kinematic model. GaMA accurately quantifies the typical behaviours of a non-disabled population, producing precise quantitative measures of hand function, trunk and angular joint kinematics, and associated visuomotor behaviour. This work advances the consideration for use of GaMA in populations with upper limb sensorimotor impairment.


Assuntos
Medições dos Movimentos Oculares/normas , Movimentos Oculares/fisiologia , Mãos/fisiologia , Adulto , Fenômenos Biomecânicos/fisiologia , Medições dos Movimentos Oculares/instrumentação , Feminino , Fixação Ocular/fisiologia , Força da Mão/fisiologia , Humanos , Masculino , Movimento/fisiologia , Desempenho Psicomotor , Amplitude de Movimento Articular/fisiologia , Reprodutibilidade dos Testes , Extremidade Superior/fisiologia
12.
Hum Mov Sci ; 68: 102539, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31683085

RESUMO

OBJECTIVE: Gait variability is a measure of gait disturbance, and therefore constitutes a useful parameter for gait assessment as well as planning of therapeutic and medical interventions. To date, variability during walking has not been adequately analyzed in amputees. The aim of this examination was to evaluate trunk and pelvic movement variability in transfemoral amputees. The effect of different types of walking surfaces on variability in trunk and pelvic movement was also studied. METHOD: This prospective clinical examination compares 20 transfemoral amputees (17 ♂, 42 ±â€¯16 years; 3 ♀, 48 ±â€¯3 years) with a group of 20 age and mass matched healthy controls regarding the extent of variability in trunk and pelvic movement. Kinematic data of trunk and pelvic movement during walking on level, uneven ground and slope was captured by eight infrared cameras (Vicon Nexus ™, Oxford, UK). Variability in trunk and pelvic movement was analyzed. Univariate ANCOVA and ANOVA with repeated measures and post hoc tests were used for statistical comparison. Fall history was retrospectively collected from medical history to assess the association between falls and variability in trunk and pelvic movement. RESULTS: Trunk and pelvic movement variability in amputees was significantly higher during walking on uneven ground and slope compared to healthy controls (p ≤ 0.05). Variability in trunk and pelvic movement was increased during walking on uneven ground and slope compared to even ground for both groups (p ≤ 0.05). CONCLUSION: Amputees showed increased trunk and pelvic movement variability during walking on uneven ground and slope, indicating an affected gait pattern in comparison to healthy controls. Therefore, trunk and pelvic movement variability could be a potential marker for gait quality with diagnostic implications.


Assuntos
Amputados , Fêmur/cirurgia , Transtornos Neurológicos da Marcha/fisiopatologia , Adulto , Fenômenos Biomecânicos/fisiologia , Estudos de Casos e Controles , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Pelve/fisiopatologia , Estudos Prospectivos , Estudos Retrospectivos , Tronco/fisiopatologia , Caminhada/fisiologia
13.
Hum Mov Sci ; 68: 102528, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31706119

RESUMO

The objective of this study was to characterize joint angle variation across strides. Specifically, the statistical persistence of variations were quantified using the Hurst exponent. If a time series exhibits statistical persistence, then a parameter which is smaller (or larger) than average will tend to be followed by additional values that are also smaller (or larger) than average. Human walking has statistical persistence between stride durations. Variation in stride duration must arise from variation in the motion of the leg segments during walking. It is unclear, however, if the joint angle variation also exhibits statistical persistence. This study examined kinematic data collected from nine healthy adults walking for 10 min at a self-selected comfortable speed on a treadmill. The joint angle variation in the lower limbs was parameterized using first-order Fourier series which in turn were described by frequency and magnitude coefficients for each stride. To determine if the joint angle variation exhibited statistical persistence, the Hurst exponent was found for each coefficient at each joint. The mean Hurst exponents were 0.54 for the frequency coefficients and 0.61 for the magnitude coefficients. Neither the frequency or magnitude coefficients exhibited statistically significant persistence, although some of the magnitude coefficients were close to reaching statistical significance. This suggests that joint angle variability in healthy adults does not directly produce the statistical persistence observed in stride duration fluctuations.


Assuntos
Articulação do Quadril/fisiologia , Caminhada/fisiologia , Adolescente , Adulto , Articulação do Tornozelo/fisiologia , Fenômenos Biomecânicos/fisiologia , Teste de Esforço/métodos , Feminino , Marcha/fisiologia , Humanos , Articulação do Joelho/fisiologia , Extremidade Inferior/fisiologia , Masculino , Amplitude de Movimento Articular/fisiologia , Adulto Jovem
14.
Hum Mov Sci ; 68: 102522, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31707313

RESUMO

Individuals with stroke often present functional impairment and gait alteration. Among different aspects, intralimb coordination of these individuals is one of the key points that should be considered before implementing any gait intervention protocol. The purpose of this study was to investigate the effects of stroke on intralimb gait coordination of the lower limbs using a vector coding technique. Twenty-five individuals with stroke and 18 non-disabled individuals (control), between 46 and 71 years old, participated in this study. A computerized analysis system registered data from reflective markers placed on specific body landmarks to define thigh, shank, and foot of both body sides, as participants walked at self-selected comfortable speed. Coordination modes, such as in-phase, anti-phase, proximal-segment-phase, and distal-segment-phase, and variability of thigh-shank, and shank-foot were analyzed for the paretic, non-paretic and control limbs during the stance and swing periods, and the entire gait cycle using the vector coding technique. During the stance period, individuals with stroke presented higher frequency of thigh-phase and lower frequency of shank-phase for the thigh-shank coupling and higher frequency of shank-phase for the shank-foot coupling compared to non-disabled controls, indicating that the proximal segment of each pair leads the movement. During the swing period, the paretic limb presented higher frequency for in-phase than non-paretic and control limbs for the thigh-shank coupling. Adaptations in the non-paretic limb were observed in the swing period, with higher frequency than paretic and control limbs in the thigh-phase for the thigh-shank coupling, and higher frequency than the paretic limb in the foot-phase for the shank-foot coupling. No differences in coordination variability were found between paretic, non-paretic, and control limbs. The vector coding technique constitutes a useful tool for identifying gait alterations in intralimb coordination of individuals with stroke. Our coordination results demonstrate a shift from distal to more proximal control during the stance phase in both legs for the individuals with stroke and an inability to decouple segment coordination during the swing phase in the paretic limb. The results indicate that it is more suitable to consider the stance and swing periods separately instead of considering the entire gait cycle to investigate intralimb gait coordination of individuals with stroke.


Assuntos
Marcha/fisiologia , Extremidade Inferior/fisiopatologia , Acidente Vascular Cerebral/fisiopatologia , Idoso , Fenômenos Biomecânicos/fisiologia , Estudos de Casos e Controles , Feminino , Pé/fisiopatologia , Transtornos Neurológicos da Marcha/etiologia , Transtornos Neurológicos da Marcha/fisiopatologia , Humanos , Masculino , Pessoa de Meia-Idade , Paresia/etiologia , Paresia/fisiopatologia , Desempenho Psicomotor/fisiologia , Acidente Vascular Cerebral/complicações , Coxa da Perna/fisiopatologia , Caminhada/fisiologia
15.
Hum Mov Sci ; 68: 102542, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31710922

RESUMO

Sensations of knee instability are self-reported in 60-80% of individuals with knee osteoarthritis. These sensations are most often reported during walking; however, it remains unclear how they affect knee joint biomechanics and muscle activation patterns as indicators of joint function. Perturbation paradigms may provide insight into how the knee joint responds to walking challenges. Thus, the purpose of this study was to determine how individuals with moderate medial compartment knee osteoarthritis respond to unexpected, 3 cm medial walkway surface translations during gait compared to an asymptomatic control group. It is hypothesized that individuals with knee osteoarthritis will demonstrate altered biomechanics, and elevated and prolonged muscle activation compared to the asymptomatic group. Twenty asymptomatic individuals and 20 individuals with knee osteoarthritis walked on a dual-belt instrumented treadmill. Participants experienced 24 unexpected medial/lateral, 1 cm/3 cm walkway translations during mid-stance on each leg. Joint motions, moments and maximal voluntary isometric contraction amplitude normalized muscle activations were analyzed for the 3 cm walkway translations. Discrete measures were extracted from each biomechanical waveform and Principal Component Analysis (PCA) was used to determine knee joint muscle activation patterns. PCA is a factorization method to reduce dimensionality of EMG envelopes into linearly uncorrelated principal patterns (PP1, PP2, PP3) that explain the largest possible variance in the dataset. PP1 is often interpreted as a feature that explains the overall amplitude, while PP2 and PP3 are features that explain the variance in temporal activation patterns (i.e. how activation patterns change over the gait cycle). Statistical significance was determined using Analysis of Covariance models (alpha = 0.05). In response to the medial 3 cm walkway translation, increased activation amplitudes in the hamstring and gastrocnemius, captured by PP1 were found in both groups, as well as alterations in temporal activation patterns (captured by combinations of PP2 and PP3 patterns) across all muscle sites (p < 0.05). No group differences were demonstrated in joint motion and moment discrete metrics (p > 0.05) in response to the 3 cm translation. These findings suggest that the medial 3 cm walkway translation posed a challenged to knee function, however the biomechanical and neuromuscular response was similar between individuals with moderate knee osteoarthritis and asymptomatic individuals.


Assuntos
Articulação do Joelho/fisiopatologia , Osteoartrite do Joelho/fisiopatologia , Caminhada/fisiologia , Idoso , Fenômenos Biomecânicos/fisiologia , Estudos de Casos e Controles , Eletromiografia/métodos , Teste de Esforço/métodos , Feminino , Marcha/fisiologia , Análise da Marcha/métodos , Músculos Isquiotibiais/fisiopatologia , Humanos , Contração Isométrica , Instabilidade Articular/etiologia , Instabilidade Articular/fisiopatologia , Masculino , Pessoa de Meia-Idade , Músculo Esquelético/fisiopatologia , Osteoartrite do Joelho/complicações , Análise de Componente Principal
16.
J Sports Med Phys Fitness ; 59(10): 1684-1690, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31694362

RESUMO

BACKGROUND: Athletes in jumping and running sports have a high incidence of Achilles tendon (AT) injuries. We compared AT loading during jumping and landing phases in anteroposterior (AP) and mediolateral (ML) directions. METHODS: Sixteen males (age: 21.6±1.8 years, height: 178.4±6.4 cm, weight: 76.4±11.2 kg) performed single leg AP and ML jump-landings during both propulsive (jump) and braking (land) phases. Inverse dynamics and static optimization were used to determine muscle forces. AT cross sectional area was measured with ultrasound. AT force was divided by cross sectional area to determine stress while strain was determined from previous data. Two-way repeated measures analysis of variance (α=0.05) compared several variables (vertical ground reaction force (VGRF), ankle and knee angle, ankle joint muscle moment arm, external ankle moment arm, AT tendon force, stress, and strain) between movements (jump-landings) and directions (AP/ML). RESULTS: AT loading was higher during jump than land in the ML compared to AP direction. VGRF was higher during land versus jump with no direction effect (AP/ML). An interaction showed a higher VGRF during the AP land and ML jump. The ankle joint moment arm was lower in jump and AP direction at peak tendon stress. External ankle moment arm at peak tendon stress was higher in jump and ML direction with an interaction. A larger external ankle moment arm occurred in ML but the change was less in the jump. CONCLUSIONS: Higher tendon loading occurred during the jump and ML direction. This may provide insight into both injuries and rehabilitation efforts.


Assuntos
Tendão do Calcâneo/química , Tendão do Calcâneo/fisiologia , Adulto , Traumatismos do Tornozelo , Articulação do Tornozelo/fisiologia , Atletas , Fenômenos Biomecânicos/fisiologia , Humanos , Articulação do Joelho/fisiologia , Masculino , Movimento , Corrida , Adulto Jovem
18.
PLoS Comput Biol ; 15(11): e1007444, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31751339

RESUMO

It is widely held that quadrupeds choose steady gaits that minimize their energetic cost of transport, but it is difficult to explore the entire range of possible footfall sequences empirically. We present a simple model of a quadruped that can spontaneously produce any of the thousands of planar footfall sequences available to quadrupeds. The inelastic, planar model consists of two point masses connected with a rigid trunk on massless legs. It requires only center of mass position, hind and forelimb proportions and a stride-length to speed relationship as input. Through trajectory optimization of a work and force-rate cost, and a large sample of random initial guesses, we provide evidence for the global optimality of symmetrical four-beat walking at low speeds and two beat running (trotting) at intermediate speeds. Using input parameters based on measurements in dogs (Canis lupus familiaris), the model predicts the correct phase offset in walking and a realistic walk-trot transition speed. It also spontaneously reproduces the double-hump ground reaction force profile observed in walking, and the smooth single-hump profile observed in trotting. Actuation appears elastic, despite the model's lack of springs, suggesting that spring-like locomotory behaviour emerges as an optimal tradeoff between work minimization and force-rate penalties.


Assuntos
Metabolismo Energético/fisiologia , Previsões/métodos , Marcha/fisiologia , Animais , Fenômenos Biomecânicos/fisiologia , Cães , Locomoção , Modelos Biológicos , Modelos Teóricos , Corrida/fisiologia , Caminhada/fisiologia
19.
Hum Mov Sci ; 68: 102524, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31733429

RESUMO

In computational models of human walking, both magnitude and timing of locomotor propulsion are important for mechanical and metabolic efficiency, suggesting that these are likely tightly controlled by the neuromuscular system. Studies of actual human walking have focused primarily on magnitude-related measures of propulsion, often ignoring its timing. The purpose of this study was to quantify the timing of onset and peak propulsion relative to contralateral heel strike (HS) in healthy, young adults walking at multiple speeds. Propulsion was quantified at the ground-level using the anterior component of the anteroposterior ground reaction force, the limb-level using individual limb power, and the joint-level using ankle power. Contrary to common computational models, most of our timing-related measures indicated that propulsion occurred after contralateral HS. Timing-related measures of propulsion also changed with walking speed - as speed increased, individuals initiated propulsion earlier in the support phase. Timing of locomotor propulsion is theoretically important for walking performance, especially metabolic efficiency, and could therefore provide important clinical information. This study provides a set of relatively simple metrics that can be used to quantify propulsion and benchmark data that can be used for future comparisons with individuals or populations with gait impairments.


Assuntos
Caminhada/fisiologia , Adulto , Articulação do Tornozelo/fisiologia , Fenômenos Biomecânicos/fisiologia , Teste de Esforço/métodos , Feminino , Calcanhar/fisiologia , Humanos , Masculino , Velocidade de Caminhada/fisiologia , Adulto Jovem
20.
Hum Mov Sci ; 68: 102520, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31654912

RESUMO

In this study we investigated motor variability in individuals who showed (responders) and who did not show (non-responders) a behavioural phenomenon termed repeated bout rate enhancement. The phenomenon is characterized by an increase of the freely chosen index finger tapping rate during the second of two consecutive tapping bouts. It was hypothesized that responders would perform (i) tapping with a lower magnitude, but more complex structure of variability than non-responders and (ii) bout 2 with a lower magnitude and increased complexity of variability than bout 1, as opposed to non-responders. Individuals (n = 102) performed two 3-min tapping bouts separated by 10 min rest. Kinetic and kinematic recordings were performed. Standard deviation (SD), coefficient of variation (CV), and sample entropy (SaEn), representing magnitude and complexity of variability, were computed. For responders, SaEn of vertical displacement of the index finger was higher than for non-responders (p = .046). Further, SaEn of vertical force and vertical displacement was higher in bout 2 than in bout 1 for responders (p < .001 and p = .006, respectively). In general, SD of vertical displacement was lower in bout 2 than in bout 1 (p < .001). SaEn of vertical force was higher in bout 2 than in bout 1 (p = .009). The present lower SD and higher SaEn values of vertical force and displacement time series in bout 2 as compared to bout 1 suggest differences in the dynamics of finger tapping. Further, it is possible that the increases in SaEn of vertical displacement reflected a greater adaptability in the dynamics of motor control among responders compared with non-responders.


Assuntos
Dedos/fisiologia , Desempenho Psicomotor/fisiologia , Adulto , Fenômenos Biomecânicos/fisiologia , Entropia , Feminino , Humanos , Cinética , Masculino , Movimento/fisiologia , Fatores de Tempo , Adulto Jovem
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