Force and pressure analysis during occasional loaded gait

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The influence of differente speeds on backpacker's gait kinectics

This study analyzed the influence of different speeds on ground reaction force’s (GRF), impulses and mean vertical force during gait of people submitted to occasional overload (backpack). A force plate was used to record the GRF data of 60 young adult subjects walking in two different cadences: 69 steps/min (slow gait) and 120 steps/min (fast gait). During the slow gait, the impact and propulsive impulses of vertical GRF, propulsive impulse of anterior-posterior GRF, impulse of medial-lateral GRF and duration of stance phase were larger than during the fast gait; the mean vertical force was the only variable that showed larger values during fast gait. Therefore, slow gait may present a larger possibility of blister development and gait unbalance, while the fast gait, even presenting a small impulse, seems to be more harmful to the musculoskeletal system.

Estudo comparativo entre criança com e sem joelhos valgos praticantes de hóquei em patins utilizando diferentes sistemas de análise

O presente estudo tem como objetivo comparar experimentalmente duas crianças praticantes de Hóquei em Patins, uma normal e uma com a patologia dos joelhos valgos, avaliando qualitativamente as diferenças posturais, estáticas e dinâmicas, decorrentes da utilização dos patins específicos desta modalidade, através do sistema de análise da Força de Reação do Solo (FRS), de Eletromiografia (EMG), de captura de movimento, e de modelação e simulação. Para atingir o objetivo definiu-se um protocolo de ensaios com as seguintes tarefas: repouso com e sem patins, marcha, corrida, deslizar com os dois pés apoiados e deslizar com o pé esquerdo levantado. No repouso avaliou-se a variação do ponto de aplicação da FRS da criança normal e patológica, com e sem patins. Ainda na tarefa de repouso avaliou-se também as componentes médio-lateral, antero-posterior individualmente e a componente vertical da FRS, juntamente com a atividade muscular dos músculos Gastrocnémio Medial (GM), Recto Femoral (RF), Vasto Medial (VM), Vasto Lateral (VL), Bicípete Femoral (BF), Semitendinoso (ST), Tensor da Fascia Lata (TFL), Gastrocnémio Lateral (GL), de forma a comparar os valores de intensidade de FRS e da atividade muscular dos diferentes instantes de tempo desta tarefa. Para as restantes tarefas apenas se avaliou individualmente as componentes médio-lateral e antero-posterior da FRS e a componente vertical da FRS juntamente com a atividade muscular dos referidos músculos, salientando as diferenças evidentes entre as curvas da criança normal e as curvas da criança patológica durante os diferentes instantes do movimento. Todas as tarefas referidas, exceto a tarefa de repouso com patins, foram ainda simuladas recorrendo a modelos músculo-esqueléticos. A partir destas simulações do movimento obtiveram-se os ângulos articulares e efetuou-se a respetiva análise. No final dos resultados obtidos apresentou-se uma tabela de resumo com o cálculo dos coeficientes de variação de cada grandeza, exceto nos gráficos da posição no espaço da FRS, onde se constatou que existe uma grande variabilidade inter-individuo em cada tarefa. A análise dos resultados de cada tarefa permite concluir que a utilização de patins pode trazer uma maior ativação muscular para a criança patológica, embora se verifique instabilidade articular. Apesar dessa instabilidade pode-se inferir que, uma maior ativação muscular decorrente da utilização de patins, tal como acontece na prática do hóquei em patins, pode trazer uma melhoria, a longo prazo, na estabilidade da articulação do joelho e na sustentação corporal, proporcionada pelo fortalecimento muscular.

Interlimb relation during the double support phase of gait: an electromyographic, mechanical and energy based analysis

The purpose of this study is to analyse the interlimb relation and the influence of mechanical energy on metabolic energy expenditure during gait. In total, 22 subjects were monitored as to electromyographic activity, ground reaction forces and VO2 consumption (metabolic power) during gait. The results demonstrate a moderate negative correlation between the activity of tibialis anterior, biceps femoris and vastus medialis of the trailing limb during the transition between midstance and double support and that of the leading limb during double support for the same muscles, and between these and gastrocnemius medialis and soleus of the trailing limb during double support. Trailing limb soleus during the transition between mid-stance and double support was positively correlated to leading limb tibialis anterior, vastus medialis and biceps femoris during double support. Also, the trailing limb centre of mass mechanical work was strongly influenced by the leading limbs, although only the mechanical power related to forward progression of both limbs was correlated to metabolic power. These findings demonstrate a consistent interlimb relation in terms of electromyographic activity and centre of mass mechanical work, being the relations occurred in the plane of forward progression the more important to gait energy expenditure.

Interlimb coordination during the stance phase of gait in subjects with stroke

Objective: To analyze the relation between contralesional and ipsilesional limbs in subjects with stroke during step-to-step transition of walking. Design: Observational, transversal, analytical study with a convenience sample. Setting: Physical medicine and rehabilitation clinic. Participants: Subjects (nZ16) with poststroke hemiparesis with the ability to walk independently and healthy controls (nZ22). Interventions: Not applicable. Main Outcome Measures: Bilateral lower limbs electromyographic activity of the soleus (SOL), gastrocnemius medialis, tibialis anterior, biceps femoris, rectus femoris, and vastus medialis (VM) muscles and the ground reaction force were analyzed during double-support and terminal stance phases of gait. Results: The propulsive impulse of the contralesional trailing limb was negatively correlated with the braking impulse of the leading limb during double support (rZ .639, PZ.01). A moderate functional relation was observed between thigh muscles (rZ .529, PZ.035), and a strong and moderate dysfunctional relation was found between the plantar flexors of the ipsilesional limb and the vastus medialis of the contralesional limb, respectively (SOL-VM, rZ .80, P<.001; gastrocnemius medialis-VM, rZ .655, PZ.002). Also, a functional moderate negative correlation was found between the SOL and rectus femoris muscles of the ipsilesional limb during terminal stance and between the SOL (rZ .506, PZ.046) and VM (rZ .518, PZ.04) muscles of the contralesional limb during loading response, respectively. The trailing limb relative impulse contribution of the contralesional limb was lower than the ipsilesional limb of subjects with stroke (PZ.02) and lower than the relative impulse contribution of the healthy limb (PZ.008) during double support. Conclusions: The findings obtained suggest that the lower performance of the contralesional limb in forward propulsion during gait is related not only to contralateral supraspinal damage but also to a dysfunctional influence of the ipsilesional limb.

Ground reaction forces and plantar pressure distribution during occasional loaded gait

This study compared the ground reaction forces (GRF) and plantar pressures between unloaded and occasional loaded gait. The GRF and plantar pressures of 60 participants were recorded during unloaded gait and occasional loaded gait (wearing a backpack that raised their body mass index to 30); this load criterion was adopted because is considered potentially harmful in permanent loaded gait (obese people). The results indicate an overall increase (absolute values) of GRF and plantar pressures during occasional loaded gait (p < 0.05); also, higher normalized (by total weight) values in the medial midfoot and toes, and lower values in the lateral rearfoot region were observed. During loaded gait the magnitude of the vertical GRF (impact and thrust maximum) decreased and the shear forces increased more than did the proportion of the load (normalized values). These data suggest a different pattern of GRF and plantar pressure distribution during occasional loaded compared to unloaded gait.

Gait Selection for Quadruped Legged Robots

This paper studies periodic gaits of quadruped locomotion systems. The purpose is to determine the best set of gait and locomotion variables for different robot velocities based on the system dynamics during walking. In this perspective, several performance measures are formulated and a set of experiments reveals the influence of the gait and locomotion variables upon those proposed indices. The results show that the locomotion parameters (β, LS and HB) should be adapted to the walking velocity in order to optimize the robot performance. Furthermore, for the case of a quadruped robot, we concluded that the gait should be adapted to VF .

Gait Analysis of Natural and Artificial Walking Systems

This paper studies periodic gaits of multi-legged locomotion systems based on dynamic models. The purpose is to determine the system performance during walking and the best set of locomotion variables. For that objective the prescribed motion of the robot is completely characterized in terms of several locomotion variables such as gait, duty factor, body height, step length, stroke pitch, foot clearance, legs link lengths, foot-hip offset, body and legs mass and cycle time. In this perspective, we formulate three performance measures of the walking robot namely, the mean absolute energy, the mean power dispersion and the mean power lost in the joint actuators per walking distance. A set of model-based experiments reveals the influence of the locomotion variables in the proposed indices.

Ankle anticipatory postural adjustments during gait initiation in healthy and post-stroke subjects

Background: Anticipatory postural adjustments during gait initiation have an important role in postural stability but also in gait performance. However, these first phase mechanisms of gait initiation have received little attention, particularly in subcortical post-stroke subjects, where bilateral postural control pathways can be impaired. This study aims to evaluate ankle anticipatory postural adjustments during gait initiation in chronic post-stroke subjects with lesion in the territory of middle cerebral artery. Methods: Eleven subjects with post-stroke hemiparesis with the ability to walk independently and twelve healthy controls participated in this study. Bilateral electromyographic activity of tibialis anterior, soleus and medial gastrocnemius was collected during gait initiation to assess the muscle onset timing, period of activation/deactivation and magnitude of muscle activity during postural phase of gait initiation. This phase was identified through centre of pressure signal. Findings: Post-stroke group presented only half of the tibialis anterior relative magnitude observed in healthy subjects in contralesional limb (t=2.38, p=0.027) and decreased soleus deactivation period (contralesional limb, t=2.25, p=0.04; ipsilesional limb, t=3.67, p=0.003) as well its onset timing (contralesional limb, t=3.2. p=0.005; ipsilesional limb, t=2.88, p=0.033) in both limbs. A decreased centre of pressure displacement backward (t=3.45, p=0.002) and toward the first swing limb (t=3.29, p=0.004) was observed in post-stroke subjects. Interpretation: These findings indicate that chronic post-stroke subjects with lesion at middle cerebral artery territory present dysfunction in ankle anticipatory postural adjustments in both limbs during gait initiation.

Reliability of Two Methods for Identifying the Postural Phase of Gait Initiation in Healthy and Post-stroke Subjects

This study aims to compare two methods of assessing the postural phase of gait initiation as to intrasession reliability, in healthy and post-stroke subjects. As a secondary aim, this study aims to analyse anticipatory postural adjustments during gait initiation based on the centre of pressure (CoP) displacements in post-stroke participants. The CoP signal was acquired during gait initiation in fifteen post-stroke subjects and twenty-three healthy controls. Postural phase was identified through a baseline-based method and a maximal displacement based method. In both healthy and post-stroke participants higher intra-class correlation coefficient and lower coefficient of variation values were obtained with the baseline-based method when compared to the maximal displacement based method. Post-stroke participants presented decreased CoP displacement backward and toward the first swing limb compared to controls when the baseline-based method was used. With the maximal displacement based method, there were differences between groups only regarding backward CoP displacement. Postural phase duration in medial-lateral direction was also increased in post-stroke participants when using the maximal displacement based method. The findings obtained indicate that the baseline-based method is more reliable detecting the onset of gait initiation in both groups, while the maximal displacement based method presents greater sensitivity for post-stroke participants.

Interlimb Coordination During Step-to-Step Transition and Gait Performance

Most energy spent in walking is due to step-to-step transitions. During this phase, the interlimb coordination assumes a crucial role to meet the demands of postural and movement control. The authors review studies that have been carried out regarding the interlimb coordination during gait, as well as the basic biomechanical and neurophysiological principles of interlimb coordination. The knowledge gathered from these studies is useful for understanding step-to-step transition during gait from a motor control perspective and for interpreting walking impairments and inefficiency related to pathologies, such as stroke. This review shows that unimpaired walking is characterized by a consistent and reciprocal interlimb influence that is supported by biomechanical models, and spinal and supraspinal mechanisms. This interlimb coordination is perturbed in subjects with stroke.

The influence of gait cadence on the ground reaction forces and plantar pressures during load carriage of young adults

Biomechanical gait parameters—ground reaction forces (GRFs) and plantar pressures—during load carriage of young adults were compared at a low gait cadence and a high gait cadence. Differences between load carriage and normal walking during both gait cadences were also assessed. A force plate and an in-shoe plantar pressure system were used to assess 60 adults while they were walking either normally (unloaded condition) or wearing a backpack (loaded condition) at low (70 steps per minute) and high gait cadences (120 steps per minute). GRF and plantar pressure peaks were scaled to body weight (or body weight plus backpack weight). With medium to high effect sizes we found greater anterior-posterior and vertical GRFs and greater plantar pressure peaks in the rearfoot, forefoot and hallux when the participants walked carrying a backpack at high gait cadences compared to walking at low gait cadences. Differences between loaded and unloaded conditions in both gait cadences were also observed.