56 research outputs found
A polygon model of the functional base-of-support improves the accuracy of balance analysis
No full textMathematical balance models have the potential to identify people at risk of falling before an injury occurs. However, most balance models depend on a model of the base-of-support (BOS) of the feet to calculate how well someone is balancing. Here we evaluate the functional base-of-support (fBOS): the convex polygon on the bottom of the foot that can support a large fraction of the body's weight. First, we develop a geometric model of the fBOS by measuring the center-of-pressure (COP) and kinematic data of the feet of 27 younger adults instructed to move their body mass in large loops without taking a step. We extract a planar convex polygon that contains the COP data. Finally, we compare the area of this fBOS model to a marker-based BOS model before evaluating if the fBOS differs across four everyday conditions: footwear, stance-width, foot dominance, and during single and double stance. We found that the fBOS is much smaller (23% the size) than a marker-based BOS model. Our analysis suggests that using the fBOS, rather than a marker-based BOS, can improve the accuracy of the margin-of-stability by 20% of foot width and 16% of the length. In addition, we found that the fBOS area does not differ across footwear (p=0.88), stance-width (p=0.88), and foot dominance (p=0.68), but during single stance the fBOS is 17% (p=0.0003) larger than during double stance. So that others can use and extend our work, we have made the models, example data and code publicly available
Rollator usage lets young individuals switch movement strategies in sit-to-stand and stand-to-sit tasks
No full textThe transitions between sitting and standing have a high physical and coordination demand, frequently causing falls in older individuals. Rollators, or four-wheeled walkers, are often prescribed to reduce lower-limb load and to improve balance but have been found a fall risk. This study investigated how rollator support affects sit-to-stand and stand-to-sit movements. Twenty young participants stood up and sat down under three handle support conditions (unassisted, light touch, and full support). As increasing task demands may affect coordination, a challenging floor condition (balance pads) was included. Full-body kinematics and ground reaction forces were recorded, reduced in dimensionality by principal component analyses, and clustered by k-means into movement strategies. Rollator support caused the participants to switch strategies, especially when their balance was challenged, but did not lead to support-specific strategies, i.e., clusters that only comprise light touch or full support trials. Three strategies for sit-to-stand were found: forward leaning, hybrid, and vertical rise; two in the challenging condition (exaggerated forward and forward leaning). For stand-to-sit, three strategies were found: backward lowering, hybrid, and vertical lowering; two in the challenging condition (exaggerated forward and forward leaning). Hence, young individuals adjust their strategy selection to different conditions. Future studies may apply this methodology to older individuals to recommend safe strategies and ultimately reduce falls
Active robotic assistance for standing and sitting: experimental evaluation of handle trajectories
No full textBackground
Standing up and sitting down are important activities of daily living, but require large leg moments that often exceed the muscle strength of older adults. Some robotic rollators are designed to provide standing-up and sitting-down assistance through actuated handles or armrests to reduce the loads on the legs, but it is still unclear how they should move. There is limited information on appropriate assistance trajectories and their effects on the body during standing up and sitting down.
Methods
We designed four physiological, scalable and parameterized handle trajectories based on unassisted shoulder movement that can be readily implemented in robotic assistive devices, and evaluated their effect on leg loading, energy input, handle forces and perceived assistance in 15 healthy younger adults. We created a robotic assistance simulator device equipped with moving handles to compare the trajectories to static handles (representing a conventional rollator), and collected full-body motion, ground reaction forces, handle forces and scored perceived assistance.
Results
The proposed handle trajectories substantially decreased leg loads compared to the static handle assistance (non-moving handle), with the two best-performing trajectories reducing the peak hip extension moment by over 70% and the peak knee extension moment by over 50% during standing up and sitting down. This is associated with an increase in peak vertical handle forces of over 30%, with the total bilateral vertical forces reaching up to 60% of body weight, and a decrease in peak horizontal force of more than 50%. The subjective participants’ perception reflected the lower limb mechanical load. The handle velocity was shown to play a secondary role within the investigated range.
Conclusion
The proposed support trajectories can be scaled to the person’s anthropometry and readily implemented in robotic assistive devices, and were shown to substantially reduce leg loading, potentially improving life quality of individuals with difficulties in standing up. However, the large vertical handle forces and thus upper body demand during moving-handle assistance is a trade-off with relieving the lower limb load. This work provides a comprehensive foundation for the design of the necessary further experimental assessments with the target population
Author Correction: Antineoplastic activity of products derived from cellulose‑containing materials: levoglucosenone and structurally‑related derivatives as new alternatives for breast cancer treatment
No full textFil: Delbart, Damian Ignacio. Universidad de Buenos Aires. Instituto de Oncología Ángel H. Roffo. Área Investigación; Argentina.Fil: Giri, Germán Francisco. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario (IQUIR-CONICET); Argentina.Fil: Cammarata, Agostina. Comisión Nacional de Energía Atómica. Gerencia de Investigación y Aplicaciones; Argentina.Fil: Pan, Melisa Denise. Universidad de Buenos Aires. Instituto de Oncología Ángel H. Roffo. Unidad de Transferencia Genética; Argentina.Fil: Bareño, Lizeth Ariza. Universidad de Buenos Aires. Instituto de Oncología Ángel H. Roffo. Área Investigación; Argentina.Fil: Amigo, Natalia Loreley. Universidad de Buenos Aires. Instituto de Oncología Ángel H. Roffo. Área Investigación; Argentina.Fil: Bechis, Andrés. Universidad de Buenos Aires. Instituto de Oncología Ángel H. Roffo. Área Investigación; Argentina.Fil: Suarez, Alejandra Graciela. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario (IQUIR-CONICET); Argentina.Fil: Spanevello, Rolando Ángel. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario (IQUIR-CONICET); Argentina.Fil: Spanevello, Rolando Ángel. Consejo Nacional de Investigaciones Científicas y Técnicas. Scientific Research Career; Argentina.Fil: Villaverde, Marcela Solange. Universidad de Buenos Aires. Instituto de Oncología Ángel H. Roffo. Unidad de Transferencia Genética; Argentina.Fil:Villaverde, Marcela Solange. Consejo Nacional de Investigaciones Científicas y Técnicas. Scientific Research Career; Argentina.Fil: Todaro, Laura Beatriz. Universidad de Buenos Aires. Instituto de Oncología Ángel H. Roffo. Área Investigación; Argentina.Fil: Todaro, Laura Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Scientific Research Career; Argentina.Fil: Urtreger, Alejandro Jorge. Universidad de Buenos Aires. Instituto de Oncología Ángel H. Roffo. Área Investigación; Argentina.Fil: Urtreger, Alejandro Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Scientific Research Career; Argentina
Functional assessment of stretch hyperreflexia in children with cerebral palsy using treadmill perturbations
No full textBackground: As hyperactive muscle stretch reflexes hinder movement in patients with central nervous system disorders, they are a common target of treatment. To improve treatment evaluation, hyperactive reflexes should be assessed during activities as walking rather than passively. This study systematically explores the feasibility, reliability and validity of sudden treadmill perturbations to evoke and quantify calf muscle stretch reflexes during walking in children with neurological disorders. Methods: We performed an observational cross-sectional study including 24 children with cerebral palsy (CP; 6–16 years) and 14 typically developing children (TD; 6–15 years). Short belt accelerations were applied at three different intensities while children walked at comfortable speed. Lower leg kinematics, musculo-tendon lengthening and velocity, muscle activity and spatiotemporal parameters were measured to analyze perturbation responses. Results: We first demonstrated protocol feasibility: the protocol was completed by all but three children who ceased participation due to fatigue. All remaining children were able to maintain their gait pattern during perturbation trials without anticipatory adaptations in ankle kinematics, spatiotemporal parameters and muscle activity. Second, we showed the protocol’s reliability: there was no systematic change in muscle response over time (P = 0.21–0.54) and a bootstrapping procedure indicated sufficient number of perturbations, as the last perturbation repetition only reduced variability by ~ 2%. Third, we evaluated construct validity by showing that responses comply with neurophysiological criteria for stretch reflexes: perturbations superimposed calf muscle lengthening (P < 0.001 for both CP and TD) in all but one participant. This elicited increased calf muscle activity (359 ± 190% for CP and 231 ± 68% for TD, both P < 0.001) in the gastrocnemius medialis muscle, which increased with perturbation intensity (P < 0.001), according to the velocity-dependent nature of stretch reflexes. Finally, construct validity was shown from a clinical perspective: stretch reflexes were 1.7 times higher for CP than TD for the gastrocnemius medialis muscle (P = 0.017). Conclusions: The feasibility and reliability of the protocol, as well as the construct validity—shown by the exaggerated velocity-dependent nature of the measured responses—strongly support the use of treadmill perturbations to quantify stretch hyperreflexia during gait. We therefore provided a framework which can be used to inform clinical decision making and treatment evaluation.Biomechatronics & Human-Machine Contro
Gastrocnemius medialis muscle geometry and extensibility in typically developing children and children with spastic cerebral paresis aged 6 to 13 years
No full textGait of children with spastic paresis (SP) is frequently characterized by a reduced ankle range of motion, presumably due to reduced extensibility of the triceps surae (TS) muscle. Little is known about how morphological muscle characteristics in SP children are affected. The aim of this study was to compare gastrocnemius medialis (GM) muscle geometry and extensibility in children with SP with those of typically developing (TD) children and assess how GM morphology is related to its extensibility. Thirteen children with SP, of which 10 with a diagnosis of spastic cerebral palsy and three with SP of unknown etiology (mean age 9.7 ± 2.1 years; GMFCS: I-III), and 14 TD children (mean age 9.3 ± 1.7 years) took part in this study. GM geometry was assessed using 3D ultrasound imaging at 0 and 4 Nm externally imposed dorsal flexion ankle moments. GM extensibility was defined as its absolute length change between the externally applied 0 and 4 Nm moments. Anthropometric variables and GM extensibility did not differ between the SP and TD groups. While in both groups, GM muscle volume correlated with body mass, the slope of the regression line in TD was substantially higher than that in SP (TD = 3.3 ml/kg; SP = 1.3 ml/kg, p < 0.01). In TD, GM fascicle length increased with age, lower leg length and body mass, whereas in SP children, fascicle length did not correlate with any of these variables. However, the increase in GM physiological cross-sectional area as a function of body mass did not differ between SP and TD children. Increases in lengths of tendinous structures in children with SP exceeded those observed in TD children (TD = 0.85 cm/cm; SP = 1.16 cm/cm, p < 0.01) and even exceeded lower-leg length increases. In addition, only for children with SP, body mass (r = -0.61), height (r = -0.66), muscle volume (r = - 0.66), physiological cross-sectional area (r = - 0.59), and tendon length (r = -0.68) showed a negative association with GM extensibility. Such negative associations were not found for TD children. In conclusion, physiological cross-sectional area and length of the tendinous structures are positively associated with age and negatively associated with extensibility in children with SP.status: Publishe
The size of the functional base of support decreases with age
No full textAbstract Falls occur more often as we age. To identify people at risk of falling, balance analysis requires an accurate base-of-support model. We previously developed a functional base-of-support (fBOS) model for standing young adults and showed that its area is smaller than the footprint area. Our fBOS model is a polygon that contains centre-of-pressure (COP) trajectories recorded as standing participants move their COP in the largest possible loop while keeping their feet flat on the ground. Here we assess how the size of the fBOS changes with age by comparing 38 younger (YA), 14 middle-aged (MA), and 34 older adults (OA). The fBOS area is smaller in older adults: OA area is 58% of the YA area ( ), and 59% of the MA area ( ), with no difference between YA and MA. The reduction in fBOS area among the OA is primarily caused by a reduction in the length of the fBOS. In addition, among older adults smaller fBOS areas correlated with a lower score on the Short Physical Performance Battery ( =0.28, ), a reduced walking speed ( =0.25, ), and a higher frailty level ( ). So that others can extend our work, we have made our fBOS models available online
The size of the functional base of support decreases with age
No full textFalls occur more often as we age. To identify people at risk of falling, balance analysis requires an accurate base-of-support model. We previously developed a functional base-of-support (fBOS) model for standing young adults and showed that its area is smaller than the footprint area. Our fBOS model is a polygon that contains centre-of-pressure trajectories recorded as standing participants move their bodies in the largest possible loop while keeping their feet flat on the ground. Here we assess how the size of the fBOS area changes with age by comparing 38 younger (YA), 14 middle-aged (MA), and 34 older adults (OA).
The fBOS area is smaller in older adults: OA area is 58% of the YA area (p<0.001), and 59% of the MA area (p=0.001), with no difference between YA and MA. The reduction in fBOS area among the OA is primarily caused by a reduction in the length of the fBOS. In addition, among older adults smaller fBOS areas correlated with a lower score on the Short Physical Performance Battery (τ=0.28, p=0.04), a reduced walking speed (τ=0.25, p=0.04), and a higher frailty level (p=0.09). So that others can extend our work, we have made our fBOS models available online
Applying Stretch to Evoke Hyperreflexia in Spasticity Testing: Velocity vs. Acceleration
No full textIn neurological diseases, muscles often become hyper-resistant to stretch due to hyperreflexia, an exaggerated stretch reflex response that is considered to primarily depend on the muscle's stretch velocity. However, there is still limited understanding of how different biomechanical triggers applied during clinical tests evoke these reflex responses. We examined the effect of imposing a rotation with increasing velocity vs. increasing acceleration on triceps surae muscle repsonse in children with spastic paresis (SP) and compared the responses to those measured in typically developing (TD) children. A motor-operated ankle manipulator was used to apply different bell-shaped movement profiles, with three levels of maximum velocity (70, 110, and 150°/s) and three levels of maximum acceleration (500, 750, and 1,000°/s2). For each profile and both groups, we evaluated the amount of evoked triceps surae muscle activation. In SP, we evaluated two additional characteristics: the intensity of the response (peak EMG burst) and the time from movement initiation to onset of the EMG burst. As expected, the amount of evoked muscle activation was larger in SP compared to TD (all muscles: p 0.33-0.36, p ≤ 0.008), but showed no significant effect for acceleration. However, the EMG burst was evoked faster with higher peak acceleration (all muscles p < 0.001) whereas it was delayed in profiles with higher peak velocity (medial gastrocnemius and soleus: p < 0.006). We conclude that while exaggerated response intensity (peak EMG burst) seems linked to stretch velocity, higher accelerations seem to evoke faster responses (time to EMG burst onset) in triceps surae muscles in SP. Understanding and controlling for the distinct effects of different biological triggers, including velocity, acceleration but also length and force of the applied movement, will contribute to the development of more precise clinical measurement tools. This is especially important when aiming to understand the role of hyperreflexia during functional movements where the biomechanical inputs are multiple and changing.sponsorship: This research was financially supported by the KNAW Fund Medical Sciences (Ter Meulen Scholarship), the German CarlZeiss Foundation project HEIAGE and grants from the Research Foundation Flanders (FWO-12R4215N and IWT-TBM 060799) and from the Netherlands Organization for Scientific Research (NWO-016.186.144). (KNAW Fund Medical Sciences (Ter Meulen Scholarship), German CarlZeiss Foundation project HEIAGE, Research Foundation Flanders|FWO-12R4215N, Research Foundation Flanders|IWT-TBM 060799, Netherlands Organization for Scientific Research|NWO-016.186.144)status: Publishe
Aging in 10 Minutes: Do Age Simulation Suits Mimic Physical Decline in Old Age? Comparing Experimental Data with Established Reference Data
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