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Song J, Zhu A, Tu Y, Zheng C, Cao G. Magnetorheological Damper With Variable Displacement Permanent Magnet for Assisting the Transfer of Load in Lower Limb Exoskeleton. IEEE Trans Neural Syst Rehabil Eng 2024; 32:43-52. [PMID: 38039179 DOI: 10.1109/tnsre.2023.3338969] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2023]
Abstract
Magnetorheological (MR) fluid exhibits the ability to modulate its shear state through variations in magnetic field intensity, and is widely used for applications requiring damping. Traditional MR dampers use the current in the coil to adjust the magnetic field strength, but the accumulated heat can cause the magnetic field strength to decay if it works for a long time. In order to deal with this shortcoming, a novel MR damper is proposed in this paper, which is based on a variable displacement permanent magnet to adjust the output resistance torque and applied to an exoskeleton joint for human load transfer assistance. A finite element model is used to determine the size parameters of the magnet and separator, so that the maximum output torque is optimal and the torque is uniformly distributed with the magnet displacement. The MR damper was characterized and calibrated on the experimental bench to make it controllable. The novel design enables the torque mass density of the MR damper to reach 8.83Nmm/g, the torque volume density to reach 48.7N/mm2, and has stability for long-term operation. Based on the torque control method proposed, a preliminary human experiment is conducted. The ground reaction force (GRF) data of the subjects is analyzed here, which represents the effect of load transfer to the exoskeleton. Compared with no exoskeleton, the GRF with exoskeleton is significantly reduced: the peak GRF in early stance phase is reduced by 24.14%, and in late stance phase is reduced by 19.77%. Based on our net load benefit (NLB) and net force benefit (NFB) evaluation indicators, the effectiveness of the proposed MR damper exoskeleton for human weight bearing assistance is established.
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Basas C, Ito N, Grävare Silbernagel K, Reyes-Gil F, Basas Á. The Basas Spanish Squat: Superimposition of Electrical Stimulation to Optimize Patellar Tendon Strain: A Case Series. Int J Sports Phys Ther 2023; 18:1299-1307. [PMID: 38050553 PMCID: PMC10693482 DOI: 10.26603/001c.89267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Accepted: 09/24/2023] [Indexed: 12/06/2023] Open
Abstract
Background The Basas Spanish Squat with electrical stimulation (E-stim) has shown promising results as a potential key exercise in treatment of athletes with patellar tendinopathy. Gold standard exercise therapy for tendon injuries consists of tendon loading exercises, or exercises that appropriately applies high levels of mechanical strain to the tendon. The theoretical pathway in which the Basas Spanish Squat with E-stim improves tendinopathy has been speculated to be the additional strain applied through the patellar tendon during superimposition of E-stim. This theory, however, has yet to be confirmed. Purpose The purpose of this case series was to compare patellar tendon strain, during the Basas Spanish Squat with, and without E-stim, and open kinetic chain knee extension. Methods Four healthy participants performed the three exercises while a physical therapist collected simultaneous unilateral ultrasound images from the patellar tendon. Strain was calculated as the change in patellar tendon length during contraction divided by the resting length. Results Amongst all participants, patellar tendon strain was smallest during the Basas Spanish Squat without E-stim, followed by the open kinetic chain knee extension at 60% maximum voluntary isometric contraction. The Basas Spanish Squat with E-stim yielded approximately double or more strain compared to the without E-stim condition and demonstrated higher level of strain compared to open kinetic chain knee extension in all participants. Conclusion The findings reflect a clear trend of increased strain through the patellar tendon when E-stim was superimposed. The results support the theory that the Basas Spanish Squat with E-stim increases patellar tendon strain and could explain the reported clinical benefits in individuals with patellar tendinopathy. Level of Evidence 4, Case series.
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Affiliation(s)
- Carlos Basas
- Department of Physical Therapy Real Federacion Española de Atletismo
| | - Naoaki Ito
- Department of Physical Therapy University of Delaware
- Biomechanics and Movement Science Program University of Delaware
| | - Karin Grävare Silbernagel
- Department of Physical Therapy University of Delaware
- Biomechanics and Movement Science Program University of Delaware
| | | | - Ángel Basas
- Department of Physical Therapy Real Federacion Española de Atletismo
- Department of Physical Therapy University of Delaware
- Biomechanics and Movement Science Program University of Delaware
- Department of Physical Therapy and Sport Science Olympia Medical Center
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Flodin J, Juthberg R, Ackermann PW. Motor point heatmap guide for neuromuscular electrical stimulation of the quadriceps muscle. J Electromyogr Kinesiol 2023; 70:102771. [PMID: 37054655 DOI: 10.1016/j.jelekin.2023.102771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 03/31/2023] [Accepted: 04/04/2023] [Indexed: 04/15/2023] Open
Abstract
PURPOSE To create an anatomical chart that indicates the probability of finding a motor point (MP) in different areas of the quadriceps muscle. METHODS On 31 healthy adults, the individual anatomy of the vastus medialis (VM), rectus femoris (RF) and vastus lateralis (VL) was determined using ultrasound. Thereafter, a 3 Hz neuromuscular electrical stimulation (NMES) MP-search with a MP-pen was performed. The thigh anatomy was normalized and divided into 112 (8x14) 3x3cm areas, and the probability of finding a MP in the different areas was calculated to create a MP heat-map. RESULTS The heat-map displayed the two best 3x3cm areas, over VL and VM respectively, each with a probability greater than 50% of finding a MP and a higher probability compared to all other areas (p <.05). RF exhibited two areas with a 29% probability of finding a MP. A higher number of MPs on the quadriceps, mean (±SD) 9.4 ± 1, was in regression analysis found to be significantly associated with two independent factors higher physical activity level and lower body fat (R2 = 0.42, p=<.0001). CONCLUSION Large inter-individual variations in location, and number of MPs were found, but the heat-map displayed areas with higher probability of finding a MP and can be used to facilitate NMES-application.
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Affiliation(s)
- J Flodin
- Integrative Orthopedic Laboratory, Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden; Department of Trauma, Acute Surgery and Orthopaedics, Karolinska University Hospital, Stockholm, Sweden.
| | - R Juthberg
- Integrative Orthopedic Laboratory, Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden; Department of Trauma, Acute Surgery and Orthopaedics, Karolinska University Hospital, Stockholm, Sweden.
| | - P W Ackermann
- Integrative Orthopedic Laboratory, Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden; Department of Trauma, Acute Surgery and Orthopaedics, Karolinska University Hospital, Stockholm, Sweden.
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Barss TS, Sallis BWM, Miller DJ, Collins DF. Does increasing the number of channels during neuromuscular electrical stimulation reduce fatigability and produce larger contractions with less discomfort? Eur J Appl Physiol 2021; 121:2621-2633. [PMID: 34131798 DOI: 10.1007/s00421-021-04742-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 06/08/2021] [Indexed: 11/27/2022]
Abstract
PURPOSE Neuromuscular electrical stimulation (NMES) is often delivered at frequencies that recruit motor units (MUs) at unphysiologically high rates, leading to contraction fatigability. Rotating NMES pulses between multiple electrodes recruits subpopulations of MUs from each site, reducing MU firing rates and fatigability. This study was designed to determine whether rotating pulses between an increasing number of stimulation channels (cathodes) reduces contraction fatigability and increases the ability to generate torque during NMES. A secondary outcome was perceived discomfort. METHODS Fifteen neurologically intact volunteers completed four sessions. NMES was delivered over the quadriceps through 1 (NMES1), 2 (NMES2), 4 (NMES4) or 8 (NMES8) channels. Fatigability was assessed over 100 contractions (1-s on/1-s off) at an initial contraction amplitude that was 20% of a maximal voluntary contraction. Torque-frequency relationships were characterized over six frequencies from 20 to 120 Hz. RESULTS NMES4 and NMES8 resulted in less decline in peak torque (42 and 41%) over the 100 contractions than NMES1 and NMES2 (53 and 50% decline). Increasing frequency from 20 to 120 Hz increased torque by 7, 13, 21 and 24% MVC, for NMES1, NMES2, NMES4 and NMES8, respectively. Perceived discomfort was highest during NMES8. CONCLUSION NMES4 and NMES8 reduced contraction fatigability and generated larger contractions across a range of frequencies than NMES1 and NMES2. NMES8 produced the most discomfort, likely due to small electrodes and high current density. During NMES, more is not better and rotating pulses between four channels may be optimal to reduce contraction fatigability and produce larger contractions with minimal discomfort compared to conventional NMES configurations.
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Affiliation(s)
- Trevor S Barss
- Human Neurophysiology Laboratory, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, 4-219 Van Vliet Complex, Edmonton, AB, T6G 2H9, Canada.,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Bailey W M Sallis
- Human Neurophysiology Laboratory, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, 4-219 Van Vliet Complex, Edmonton, AB, T6G 2H9, Canada.,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Dylan J Miller
- Human Neurophysiology Laboratory, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, 4-219 Van Vliet Complex, Edmonton, AB, T6G 2H9, Canada.,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - David F Collins
- Human Neurophysiology Laboratory, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, 4-219 Van Vliet Complex, Edmonton, AB, T6G 2H9, Canada. .,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada.
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