RESUMEN
Interlimb temporal synchrony and spatial symmetry of centre of pressure (COP) displacements may be vital contributors to standing balance control. In previous work among stroke survivors, low-frequency COP displacements (< 0.4 Hz) were proposed to arise from centre of mass (COM) dynamics, or from proactive exploratory processes. COP displacements among higher frequencies (>0.4 Hz), in contrast, have been attributed to corrective balance responses to internal perturbations. The present study extends this work to explore age-related alterations in such stability control processes during standing balance. The combined COP displacements from both limbs (COPnet) in addition to individual-limb COP timeseries were calculated from synchronous force platform data obtained from 19 younger adults and 19 older adults during a 60 s trial of quiet standing. The discrete wavelet transform was used to decompose the anteroposterior and mediolateral COPnet, in addition to the individual-limb timeseries, into low-frequency and high-frequency bandwidths. Root-mean-squared (RMS) amplitudes of high- and low-frequency COPnet displacements were calculated. The cross-correlation coefficient was used to assess the extent of between-limb temporal synchronization, while the ratio of individual-limb RMS amplitudes was used to assess between-limb spatial symmetry within each high- and low-frequency bandwidth. We observed greater high-frequency anteroposterior COPnet displacements among older adults, without age related differences in the lower frequency bandwidth or in the mediolateral direction. Further, older adults exhibited greater high-frequency anteroposterior between-limb synchronization, without age-related differences in the low frequency bandwidth, or among any of the spatial symmetry variables. The present age-related alterations in COPnet could represent a conservative strategy to ensure stability, whereby age-related challenges in stability maintenance during standing are offset by greater demands on stability control. Further, increased high frequency between-limb temporal synchronization among older adults may suggest a loss of adaptability in balance corrective responses during standing.
Asunto(s)
Postura , Accidente Cerebrovascular , Humanos , Anciano , Postura/fisiología , Equilibrio Postural/fisiología , Extremidades , EnvejecimientoRESUMEN
BACKGROUND: Previous work has linked the eccentricity of the net ground reaction force (GRFnet) to increased mediolateral instability during single-step voluntary and compensatory stepping responses. The present work sought to understand the extent to which such control mechanisms for mediolateral stability are present during gait. RESEARCH QUESTION: How do gait velocity and step width constraints influence the kinetic control of mediolateral stability control among healthy participants? METHODS: 25 participants performed three walking conditions - normal walking with self-selected speed and foot-placement, fast walking with self-selected foot-placement, and narrowbase walking - across a 10-meter walkway. Lateral instability was quantified by the mediolateral margin of stability (MoSML). The frontal-plane eccentricity of the GRFnet was calculated as the difference between GRFnet vector orientation and that of a line joining the coordinates of COPnet and COM. Two discrete time-points (P1 and P2) following foot-contact were examined, as they have been suggested to be indicative of proactive and reactive COM control, respectively. Task-related differences in the magnitude and timing of kinematic and kinetic outcome variables were analysed using one-way ANOVAs with repeated-measures. RESULTS: With constraints on step-width in narrow-base walking, participants exhibited reduced stability as evidenced by reduced MoSML, alongside reductions in the peak GRFnet eccentricity (θd) at P1. Participants exhibited no reduction in stability during fast walking, as revealed by the MoSML in part because of a similar onset of P1 within the gait cycle. P2 magnitude was larger in narrow-base walking relative to fast-walking, and occurred at an earlier point in the gait cycle. SIGNIFICANCE: Findings suggest proactive mechanisms (i.e. P1) may predominantly regulate mediolateral stability during walking. Reactive mechanisms (i.e. P2), however, may be capable of offsetting instability in situations where proactive mechanisms are insufficient.
Asunto(s)
Equilibrio Postural , Caminata , Fenómenos Biomecánicos , Pie , Marcha , HumanosRESUMEN
BACKGROUND: Effective fall prevention exercise for community-dwelling older adults requires (i) challenging balance exercise, (ii) offered at least 3 hrs/ week, and (iii) on an ongoing basis, to reduce falls. Community exercise programs are a potential implementation strategy for fall prevention exercise; however, the extent to which they address balance and include effective fall prevention exercise is unknown. Study objectives were to describe program delivery, exercise design, and assessment characteristics of older adult community exercise programs in Winnipeg, Canada; determine if they included effective fall prevention exercise; determine the balance challenge and components of postural control addressed in the most- and least-frequently reported exercises. METHODS: A public inventory of older adult community exercise programs served as the sampling frame for cross-sectional telephone questionnaires exploring program, exercise, and assessment characteristics. Exercises were coded independently by two investigators for balance challenge level and components of postural control. Programs were categorized by number of effective fall prevention exercise components established by evidence-based recommendations. Descriptive statistics were calculated. RESULTS: Thirty-three eligible programs were identified and nine individuals participated. Most programs (n = 5, 56%) identified as general exercise, and two (22%) as fall prevention exercise. Most programs (n = 5, 56%) were offered two or more times/ week and reported exercise intensity as somewhat challenging. Exercise time offered ranged between 1 and 3 h/ week. Assessments were conducted in two programs (22%). Only one program (general exercise) included all components of effective fall prevention exercise. Two programs (22%) included the component of being offered at least 3 hrs/ week. Three programs (33%) included the component of being offered on an ongoing basis. Seven programs (78%) prescribed mostly moderate challenge balance exercise, and one program (11%) prescribed mostly high challenge exercise. Most of the 19 most-frequently prescribed exercises (n = 17, 89%) targeted static stability and none targeted reactive postural control. CONCLUSIONS: Most of the older adult community exercise programs participating in this study did not focus on fall prevention, and did not include all components of effective fall prevention exercise. Future studies should focus on fall prevention programs and explore factors influencing implementation of effective fall prevention exercise components to facilitate planning.
Asunto(s)
Accidentes por Caídas/prevención & control , Terapia por Ejercicio/tendencias , Ejercicio Físico/fisiología , Vida Independiente/tendencias , Equilibrio Postural/fisiología , Autoinforme , Anciano , Estudios Transversales , Ejercicio Físico/psicología , Terapia por Ejercicio/métodos , Terapia por Ejercicio/psicología , Femenino , Humanos , Vida Independiente/psicología , Masculino , Manitoba/epidemiología , Resultado del TratamientoRESUMEN
BACKGROUND: The specific mechanisms responsible for age-related decline in forward stability control remain unclear. Previous work has suggested reactive control of net ground reaction force (GRFnet) eccentricity may be responsible for age-related challenges in mediolateral stability control during the restabilisation phase of forward compensatory stepping responses. RESEARCH QUESTIONS: Does reactive control of GRFnet eccentricity play a role in managing forward stability control during the restabilisation phase of a forward stepping response to external balance perturbation? METHODS: Healthy younger (YA) (n = 20) and older adults (OA) (n = 20) were tethered to a rigid frame, via adjustable cable. Participants were released from a standardised initial forward lean and regained their balance using a single step. Whole-body motion analysis and four force platforms were utilised for data acquisition. Forward instability was quantified as centre of mass (COM) incongruity - the difference between the first local peak and final stable anterior COM positions. The extent of GRFnet eccentricity was quantified as the sagittal-plane angle of divergence of the line of action of the GRFnet relative to the COM. Two discrete points during restabilisation were examined (P1 and P2), which have been suggested to be indicative of proactive and reactive COM control, respectively. Age-related differences in magnitude, timing and trial-to-trial variability of kinematic and kinetic outcome variables were analysed using two-factor ANOVAs with repeated-measures. RESULTS: OA exhibited greater COM incongruity magnitude and variability - both were reduced with trial-repetition. There were no age-related differences in the magnitude or timing of P2. Instead, OA exhibited a reduced magnitude of GRFnet eccentricity at P1. There was a positive correlation between AP COM incongruity magnitude and P1 magnitude. SIGNIFICANCE: Different from mediolateral stability control, the present results suggest that OA may experience forward stability control challenges as a function of insufficient preparatory lower limb muscle activation prior to foot-contact.
Asunto(s)
Adaptación Fisiológica , Envejecimiento/fisiología , Pie/fisiología , Equilibrio Postural/fisiología , Propiocepción/fisiología , Anciano , Fenómenos Biomecánicos/fisiología , Femenino , Humanos , Masculino , Adulto JovenRESUMEN
BACKGROUND: Locomotion on stairs is challenging for balance control and relates to a significant number of injurious falls. The visual system provides relevant information to guide stair locomotion and there is evidence that peripheral vision is potentially important. RESEARCH QUESTION: This study investigated the role of the lower visual field information for the control of stair walking. It was hypothesized that restriction in the lower visual field (LVF) would significantly impact gaze and locomotor behaviour specifically during descent and during transition phases emphasizing the importance of the LVF information during online control. METHODS: Healthy young adults (n = 12) ascended and descended a 7-step staircase while wearing customized goggles that restricted the LVF. Three visual conditions were tested: full field of view (FULL); 30° (MILD), and 15° (SEVERE) of lower field of view available. Stride time, head pitch angle and handrail use were assessed during approach, transition steps (two steps at the top and bottom of the stairs) and middle step phases. RESULTS: Transient downward head pitch angle increased with LVF restriction, while walk speed decreased and handrail use increased. Occlusion impaired stair descent more strongly than ascent reflected by a larger downward head pitch angles and slower walk times. LVF restriction had a greater influence on stride time and head angle during the approach and first transition compared to other stair regions. SIGNIFICANCE: Information from the lower visual field is important to guide stair walking and particularly when negotiating the first few steps of a staircase. Restriction in the lower visual field during stair walking results in more cautious locomotor behaviour such as walking slower and using the handrails. In daily activities, tasks or conditions that restrict or alter the lower visual field information may elevate the risk for missteps and falls.
Asunto(s)
Subida de Escaleras/fisiología , Campos Visuales/fisiología , Adulto , Fenómenos Biomecánicos , Femenino , Marcha/fisiología , Voluntarios Sanos , Humanos , Masculino , Velocidad al Caminar/fisiología , Adulto JovenRESUMEN
OBJECTIVE: To determine whether quiet standing measures at specific frequency levels (representative of reactive control) differed between individuals with stroke based on their ability to recover balance (Failed or Successful Responses to external perturbations). METHODS: Individuals with stroke completed a clinical assessment, including 30 s of quiet standing and lean-and-release postural perturbations, at admission to in-patient rehabilitation. Quiet standing centre of pressure (COP) signals were calculated and discrete wavelet decomposition was performed. Net COP amplitude, between-limb synchronization, and ratios of individual-limb COP were determined for each frequency level of interest, and for the non-decomposed signal (all frequency levels). Outcome measures were compared between individuals who exhibited Failed and Successful Responses during (a) unconstrained and (b) encouraged-use lean-and-release trials. RESULTS: Individuals with Failed Responses during the unconstrained lean-and-release trials displayed greater net COP amplitude than those with Successful Responses, specifically within a frequency range of 0.40-3.20Hz. CONCLUSIONS: Reduced ability to recover balance among individuals with stroke may be reflected in impaired reactive control of quiet standing. SIGNIFICANCE: These results provide insight into the mechanism by which reactive control of quiet standing is impaired in individuals with stroke, and may inform assessment and rehabilitation strategies for post-stroke reactive balance control.
Asunto(s)
Equilibrio Postural , Rehabilitación de Accidente Cerebrovascular , Accidente Cerebrovascular/fisiopatología , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Masculino , Persona de Mediana Edad , Postura , Accidente Cerebrovascular/diagnósticoRESUMEN
Anticipatory balance control optimizes balance reactions to postural perturbations. Predictive control is dependent on the ability of the central nervous system to modulate gain in accordance with specific task demands. Inter-limb synchronization is a sensitive measure of individual limb contributions to balance control and may reflect the coordination of gain modulation in preparation for instability. The purpose of the study was to determine whether gain modulation in advance of predictable bouts of instability was reflected in the extent of inter-limb synchronization. Two adjacent force plates were used to collect center of pressure (COP) data from 12 healthy young adults (27.5±3.4 years). Participants prepared for internal and external balance perturbations using a cueing paradigm with three auditory warning tones followed by an imperative tone. Perturbations were delivered in blocked and randomized conditions with two perturbation magnitudes (small and large). Inter-limb synchrony was calculated using the cross-correlation function of the COP excursions from the left and right foot for three seconds prior to perturbation onset in the anteroposterior (AP) and mediolateral (ML) direction. Inter-limb synchrony decreased in the AP and ML directions as perturbation magnitude became more unpredictable. The need to take a step or not knowing whether a step was required prior to postural instability reduced ML inter-limb synchrony. No differences were found between internal and external perturbations. Modulation of postural set was evident in the extent of inter-limb synchrony.
Asunto(s)
Extremidad Inferior/fisiología , Equilibrio Postural/fisiología , Postura/fisiología , Adulto , Señales (Psicología) , Femenino , Pie , Humanos , Masculino , Adulto JovenRESUMEN
Age-related mediolateral instability during forward stepping reactions evoked by whole-body perturbation is believed to occur independent of the initial temporospatial parameters prior to step-contact. Recent research is beginning to explore the restabilisation phase, following step-contact, as the origin of such instability. This work sought to uncover potential mechanisms underlying age-related mediolateral instability during restabilisation by examining whole-body centre of mass (COM) kinematics and the orientation of the net ground reaction force relative to the COM. Healthy younger (n=20) and older adults (n=20) were anchored to a rigid frame, via adjustable cable. After establishing a standardised initial forward lean, cable release occurred with pseudorandom timing. Participants regained their balance using a single self-selected step. The potential for lateral instability was quantified by COM kinematics. The angle of divergence of the line of action of the net ground reaction force relative to the COM was quantified and examined at three discrete points during restabilisation, as indices of COM control. Age-related differences in magnitude and trial-to-trial variability were analysed. Older adults exhibited increased ML COM incongruity and trial-to-trial variability, which were reduced with trial repetition. Older adults required an increased time to reorient the net ground reaction force, which was correlated with the increased lateral COM displacement during restabilisation. The present results support the idea that age-related mediolateral instability occurs during restabilisation and may be linked to the reactive control of the orientation of the net ground reaction force with respect to the centre of mass.
Asunto(s)
Envejecimiento/fisiología , Locomoción/fisiología , Equilibrio Postural/fisiología , Adulto , Anciano , Fenómenos Biomecánicos , Femenino , Humanos , Masculino , Adulto JovenRESUMEN
Background Poststroke lower-limb spasticity (LLS) has been shown to degrade standing balance control by disrupting the temporal synchronization between individual limb centers of pressure (COPs). Time-varying changes in standing balance control associated with alterations in the extent of LLS have yet to be documented and are important to informing treatment strategies to improve such functional outcomes. Objective The present work aimed to understand the natural recovery of standing balance control among stroke survivors with LLS using limb-specific indices of standing balance control. Furthermore, we sought to understand if time-varying changes in LLS were associated with alterations in standing balance control. Methods A retrospective analysis of 92 participants was performed; 47 participants never exhibited LLS during the study (No_LLS), and 45 participants exhibited LLS during at least 1 testing session (LLS). Quiet standing for a duration of 30 s on 2 force platforms was recorded. Temporal synchrony and spatial symmetry of COP displacements were assessed, along with interlimb weight-bearing symmetry. Results All variables, except spatial symmetry, indicated initial improvement followed by deceleration in the rate of balance control recovery. Limb-specific measures indicated that individuals with LLS exhibited deficits in balance control. The recovery trajectories were not different between groups, suggesting a similar rate, but reduced extent, of balance control recovery among the LLS relative to the No_LLS group. Only temporal synchrony was altered by time-varying changes in spasticity. Conclusions The present results suggest that the reduction in spasticity may be beneficial to balance control recovery.
Asunto(s)
Extremidad Inferior/fisiopatología , Equilibrio Postural/fisiología , Postura , Cuadriplejía/etiología , Recuperación de la Función/fisiología , Accidente Cerebrovascular/complicaciones , Anciano , Anciano de 80 o más Años , Estudios de Cohortes , Femenino , Humanos , Funciones de Verosimilitud , Masculino , Persona de Mediana Edad , Índice de Severidad de la Enfermedad , Navegación Espacial , Factores de Tiempo , Soporte de PesoRESUMEN
This study examined the control of standing balance while wearing construction stilts. Motion capture data were collected from nine expert stilt users and nine novices. Three standing conditions were analysed: ground, 60 cm stilts and an elevated platform. Each task was also performed with the head extended as a vestibular perturbation. Both expert and novice groups exhibited lower displacement of the whole body centre of mass and centre of pressure on construction stilts. Differences between the groups were only noted in the elevated condition with no stilts, where the expert group had lower levels of medial-lateral displacement of the centre of pressure. The postural manipulation revealed that the expert group had superior balance to the novice group. Conditions where stilts were worn showed lower levels of correspondence to the inverted pendulum model. Under normal conditions, both expert and novice groups were able to control their balance while wearing construction stilts. PRACTITIONER SUMMARY: This work investigated the effects of experience on the control of balance while using construction stilts. Under normal conditions, expert and novice stilt users were able to control their balance while wearing construction stilts. Differences between the expert and novice users were revealed when the balance task was made more difficult, with the experts showing superior balance in these situations.
Asunto(s)
Industria de la Construcción/instrumentación , Aparatos Ortopédicos , Equilibrio Postural/fisiología , Postura/fisiología , Adulto , Fenómenos Biomecánicos , Voluntarios Sanos , Humanos , Competencia ProfesionalRESUMEN
Lower limb spasticity is a common sensorimotor consequence post-stroke, which further complicates stability control by altering the temporal relationship between individual-limb centre of pressure (COP) displacements. The present work employed the discrete wavelet transform to better understand the influence of lower limb spasticity on the control of standing balance, which occurs across multiple timescales. An 8-level decomposition of the individual-limb COP was performed, using retrospective data from 91 stroke survivors with (n = 29) and without (n = 56) lower limb spasticity. Inter-limb temporal synchrony and spatial symmetry at each timescale were evaluated by the cross correlation coefficient at zero phase-lag and the root mean square ratio, respectively, using the reconstructed time series at each timescale. Reduced temporal synchrony was observed among individuals with lower limb spasticity at frequencies down to 0.20 Hz. The present results suggest that the additional balance control challenges associated with post-stroke lower limb spasticity may be linked to the ability to temporally co-modulate the more rapid COP displacements. This may be particularly problematic if individuals are faced with balance perturbations, which require rapid reactive balance corrections to regain stability.
Asunto(s)
Articulación del Tobillo/fisiopatología , Espasticidad Muscular/fisiopatología , Músculo Esquelético/fisiopatología , Equilibrio Postural , Postura , Accidente Cerebrovascular/fisiopatología , Anciano , Simulación por Computador , Femenino , Humanos , Masculino , Persona de Mediana Edad , Modelos Biológicos , Espasticidad Muscular/etiología , Presión , Accidente Cerebrovascular/complicacionesRESUMEN
Research examining age-related changes in dynamic stability during stepping has recognised the importance of the restabilisation phase, subsequent to foot-contact. While regulation of the net ground reaction force (GRFnet) line of action is believed to influence dynamic stability during steady-state locomotion, such control during restabilisation remains unknown. This work explored the origins of age-related decline in mediolateral dynamic stability by examining the line of action of GRFnet relative to the centre of mass (COM) during restabilisation following voluntary stepping. Healthy younger and older adults (n=20 per group) performed three single-step tasks (varying speed and step placement), altering the challenge to stability control. Age-related differences in magnitude and intertrial variability of the angle of divergence of GRFnet line of action relative to the COM were quantified, along with the peak mediolateral and vertical GRFnet components. The angle of divergence was further examined at discrete points during restabilisation, to uncover events of potential importance to stability control. Older adults exhibited a reduced angle of divergence throughout restabilisation. Temporal and spatial constraints on stepping increased the magnitude and intertrial variability of the angle of divergence, although not differentially among the older adults. Analysis of the time-varying angle of divergence revealed age-related reductions in magnitude, with increases in timing and intertrial timing variability during the later phase of restabilisation. This work further supports the idea that age-related challenges in lateral stability control emerge during restabilisation. Age-related alterations during the later phase of restabilisation may signify challenges with reactive control.
Asunto(s)
Envejecimiento/fisiología , Pie/fisiología , Equilibrio Postural/fisiología , Caminata/fisiología , Adulto , Anciano , Femenino , Humanos , Cinética , Modelos Lineales , Locomoción/fisiología , Masculino , Factores de TiempoRESUMEN
BACKGROUND: Challenges in stability control are common post-stroke. Although lower-limb spasticity is a common sensorimotor consequence post-stroke, its potential to further complicate stability control among stroke-survivors remains largely unknown. Advancing such understanding can help inform strategies to reduce fall risk and increase independence among these individuals. The purpose of this study was to characterise the extent of limb-specific dyscontrol among individuals with spasticity. METHODS: A retrospective analysis of 131 patients assessed for spasticity was performed. Patients selected for inclusion were categorised into two groups, with (n=19) or without (n=63) unilateral lower-limb spasticity. Two force platforms were used to determine the individual-limb and net centres of pressure in both anteroposterior and mediolateral directions during 30s of quiet standing. Limb-specific dyscontrol was assessed by calculating weight-bearing symmetry ratios, cross-correlation coefficients at zero phase-shift (temporal synchrony) and ratios of individual-limb root-mean-square displacements (spatial symmetry). Total body postural control was assessed by examining the root-mean-square of the net centre of pressure displacement. FINDINGS: The group with spasticity bore less weight on the affected limb and exhibited reduced temporal synchrony of centre of pressure displacements. There were no differences in inter-limb root-mean-square centre of pressure ratios or in the root-mean-square of the net centre of pressure displacement. INTERPRETATION: Individuals with lower-limb spasticity may have additional challenges with stability control, specifically linked to the ability to modify the location of the centre of pressure beneath the affected limb, in a time-sensitive manner so as to contribute beneficially to the control of whole body stability.
Asunto(s)
Trastornos Neurológicos de la Marcha/etiología , Trastornos Neurológicos de la Marcha/fisiopatología , Espasticidad Muscular/complicaciones , Espasticidad Muscular/fisiopatología , Equilibrio Postural/fisiología , Accidente Cerebrovascular/complicaciones , Soporte de Peso/fisiología , Adulto , Anciano , Femenino , Marcha/fisiología , Trastornos Neurológicos de la Marcha/rehabilitación , Humanos , Masculino , Persona de Mediana Edad , Espasticidad Muscular/rehabilitación , Presión , Estudios Retrospectivos , Factores de TiempoRESUMEN
The control of mediolateral dynamic stability during stepping can be particularly challenging for older adults and appears to be related to falls and hip fracture. The specific mechanisms or control challenges that lead to mediolateral instability, however, are not fully understood. This work focussed on the restabilisation phase of volitional forward stepping, subsequent to foot contact, which we believe to be a principal determinant of mediolateral dynamic stability. Twenty younger (age 24±5 years; 50% women) and 20 older participants (age 71±5 years; 50% women) performed three different single-step tasks of various speed and step placement, which varied the challenge to dynamic stability. The trajectory of the total body centre of mass (COM) was quantified. Mediolateral COM incongruity, defined as the difference between the peak lateral and final COM position, and trial-to-trial variability of incongruity were calculated as indicators of dynamic stability. Older adults exhibited increased instability compared to young adults, as reflected by larger COM incongruity and trial-to-trial variability. Such increases among older adults occurred despite alterations in COM kinematics during the step initiation and swing phases, which should have led to increased stability. Task related increases in instability were observed as increased incongruity magnitude and trial-to-trial variability during the two rapid stepping conditions, relative to preferred speed stepping. Our findings suggest that increased COM incongruity and trial-to-trial variability among older adults signify a reduction in dynamic stability, which may arise from difficulty in reactive control during the restabilisation phase.
Asunto(s)
Envejecimiento/fisiología , Marcha/fisiología , Equilibrio Postural/fisiología , Accidentes por Caídas , Adulto , Anciano , Fenómenos Biomecánicos , Femenino , Humanos , Masculino , Adulto JovenRESUMEN
This work sought to advance the understanding of dynamic stability control during stepping. The specific intention was to better understand the control of the centre of mass during voluntary stepping, by characterizing its trajectory and intertrial variability. Young participants (n=10) performed five different stepping tasks to vary the challenge to COM control: (1) preferred step, (2) long step, (3) wide step, (4) long and wide step and (5) rapid step. The trajectory of the total body COM during the restabilisation phase was assessed by quantifying the magnitude of incongruity between the peak and final COM position. The intertrial variability of incongruity and the extent to which incongruity was reduced with trial repetition were also evaluated. Interestingly, incongruity was typical during preferred stepping, with a strong bias toward overshoot. In the frontal plane, the magnitude of incongruity and the incidence of overshoot were greater in trials with increased step width. The variability of incongruity did not vary by condition nor was there evidence of adaptive changes. Together, these results suggest that overshoots may represent a strategy linked to gait initiation or to the simplification of reactive control during the restabilisation phase. Further insight into these mechanisms will be gained by examining the kinetic determinants of dynamic stability control.
Asunto(s)
Marcha/fisiología , Equilibrio Postural/fisiología , Adulto , Fenómenos Biomecánicos , Humanos , Masculino , Adulto JovenRESUMEN
The present study sought to use stilt walking as a model to uncover modifications to gait dynamics caused by changes in lower limb anthropometrics. We examined 10 novice and 10 expert stilt walkers, each walking with and without stilts, to determine the specific adaptations brought about by experience. Three-dimensional kinematics and force platform data were used to calculate the intersegmental forces, net joint moments and moment powers at the ankle, knee and hip. Spatio-temporal data were computed to aid the interpretation of these data. Non-dimensional scaling was used to facilitate comparison between stilt- and normal-walking. In general, the stilts induced largely the same alterations in the locomotor patterns of both novices and experts, which did not allow for the conclusion that the experts employed locomotor dynamics that were better suited to the challenges imposed by alterations to limb length, mass and mass moment of inertia induced by the stilts. Nevertheless, the experts exhibited a lesser reduction in dimensionless stride length and velocity and generated larger concentric knee flexor and hip extensor powers, relative to the novices, which may be indicative of enhanced dynamic stability control.
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Atención/fisiología , Fenómenos Biomecánicos/fisiología , Estatura/fisiología , Marcha/fisiología , Distorsión de la Percepción/fisiología , Caminata/fisiología , Adulto , Antropometría , Articulación de la Cadera/fisiología , Humanos , Interpretación de Imagen Asistida por Computador , Imagenología Tridimensional , Cinética , Articulación de la Rodilla/fisiología , Masculino , Destreza Motora/fisiología , Plasticidad Neuronal/fisiología , Práctica Psicológica , Adulto JovenRESUMEN
BACKGROUND: Knee bracing has been shown to alter lower limb joint mechanics, which may protect the anterior cruciate ligament. The effect of brace alignment and brace type, however, remains largely unknown. This study was conducted to determine whether the use of a functional knee brace, the type of brace used or its alignment relative to the knee causes biomechanical alterations to gait. METHODS: Ten healthy participants took part in two walking conditions (aligned brace and misaligned brace) for two different types of brace (sleeve brace with bilateral hinges and hinge-post-shell). A non-braced condition was included as a baseline measure. Three-dimensional kinematics and force platform data were used to calculate the joint intersegmental forces and net joint moments of the ankle, knee and hip. FINDINGS: In comparison to non-braced walking, the shell brace in its aligned position significantly reduced the peak ankle plantarflexor moment. There was a decreased peak knee flexion angle with both the aligned shell and sleeve braces. The shell brace in its aligned position significantly increased peak knee adduction and reduced peak knee internal rotation. INTERPRETATION: In this sample of healthy participants, functional knee bracing failed to alter lower limb mechanics in such a way that would reduce the force transmitted to the anterior cruciate ligament. In addition, although there were brace induced changes in lower limb kinematics with 2cm of distal hinge misalignment, it is unlikely that hinge misalignment of this magnitude is detrimental to an uninjured knee joint during walking.