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The Iowa Orthopaedic Journal 2024Walking is a vital activity often compromised in individuals with neuropathic conditions. Charcot-Marie-Tooth (CMT) disease and Cerebral Palsy (CP) are two common...
BACKGROUND
Walking is a vital activity often compromised in individuals with neuropathic conditions. Charcot-Marie-Tooth (CMT) disease and Cerebral Palsy (CP) are two common neurodevelopmental disabilities affecting gait, predisposing to the risk of falls. With guiding scientific evidence limited, there is a critical need to better understand how surgical correction affects mobility, balance confidence, and gait compared to ankle foot orthosis (AFO) bracing. A systematic approach will enable rigorous collaborative research to advance clinical care.
METHODS
Key elements of this vision include 1) prospective studies in select patient cohorts to systematically compare conservative vs. surgical management, 2) objective laboratory-based evaluation of patient mobility, balance, and gait using reliable methods, and 3) use of patient-centric outcome measures related to health and mobility.
RESULTS
Valid and reliable standardized tests of physical mobility and balance confidence have been described in the literature. They include 1) the four-square step test, a widely used test of balance and agility that predicts fall risk, 2) the self-selected walking velocity, a measure of general mobility able to detect function change with orthosis use, and 3) the activity specific balance confidence scale, a survey instrument that assesses an individual's level of balance confidence during activity. Additionally, motion capture and ground reaction force data can be used to evaluate whole-body motion and loading, with discriminative biomechanical measures including toe clearance during the swing phase of gait, plantarflexion at 50% of swing, peak ankle plantarflexor moment, and peak ankle push-off power.
CONCLUSION
The tools needed to support evidence-based practice and inform clinical decision making in these challenging patient populations are all available. Research must now be conducted to better understand the potential benefits and limitations of AFO use in the context of mobility and balance during gait for individuals with neuropathic conditions, particularly relative to those offered by surgical correction.
CLINICAL RELEVANCE
Following this path of research will provide comparative baseline data on mobility, balance confidence, and gait that can be used to inform an objective criterion-based approach to AFO prescription and the impact of surgical intervention.
Topics: Humans; Postural Balance; Charcot-Marie-Tooth Disease; Foot Orthoses; Cerebral Palsy; Orthotic Devices; Gait Disorders, Neurologic; Gait; Walking
PubMed: 38919344
DOI: No ID Found -
Journal of Neurophysiology Jun 2024Previous research has shown that action effects of self-generated movements are internally predicted before outcome feedback becomes available. To test whether these...
Previous research has shown that action effects of self-generated movements are internally predicted before outcome feedback becomes available. To test whether these sensorimotor predictions are used to facilitate visual information uptake for feedback processing, we measured eye movements during the execution of a goal-directed throwing task. Participants could fully observe the effects of their throwing actions (ball trajectory, and either hitting or missing a target) in most of the trials. In a portion of the trials, the ball trajectory was not visible, and participants only received static information about the outcome. We observed a large proportion of predictive saccades, shifting gaze toward the goal region before the ball arrived and outcome feedback became available. Fixation locations after predictive saccades systematically covaried with future ball positions in trials with continuous ball flight information, but notably also in trials with static outcome feedback and only efferent and proprioceptive information about the movement that could be used for predictions. Fixation durations at the chosen positions after feedback onset were modulated by action outcome (longer durations for misses than for hits) and outcome uncertainty (longer durations for narrow vs. clear outcomes). Combining both effects, durations were longest for narrow errors and shortest for clear hits, indicating that the chosen locations offer informational value for feedback processing. Thus, humans are able to use sensorimotor predictions to direct their gaze toward task-relevant feedback locations. Outcome-dependent saccade latency differences (miss vs. hit) indicate that also predictive valuation processes are involved in planning predictive saccades.
PubMed: 38919149
DOI: 10.1152/jn.00052.2024 -
Journal of the Royal Society, Interface Jun 2024Virtual balancing tasks facilitate the study of human motion control: human reaction to the change of artificially introduced parameters can be studied in a computer...
Virtual balancing tasks facilitate the study of human motion control: human reaction to the change of artificially introduced parameters can be studied in a computer environment. In this article, the dynamics of human stick balancing are generalized using fractional-order derivatives. Reaction delay sets a strong limitation on the length of the shortest stick that human subjects can balance. Human processing of visual input also exhibits a memory effect, which can be modelled by fractional-order derivatives. Therefore, we hypothesize a delayed fractional-order PD control of the unstable fractional-order process. The resulting equation of motion is investigated in a dimensionless framework, and stabilizability limits are determined as a function of the dynamics's order. These theoretical limits are then compared with the results of a systematic series of virtual balancing tests performed by 18 subjects. The comparison shows that the theoretical stabilizability limits for controllers with fixed fractional order correspond to the measured data points. The best fit is obtained if the fractional order of the underlying control law is 0.475.
Topics: Humans; Female; Male; Adult; Postural Balance; Models, Biological; Reaction Time
PubMed: 38919061
DOI: 10.1098/rsif.2023.0685 -
Experimental Brain Research Jun 2024The purpose of the present study was to elucidate whether an external reference frame contributes to tactile localization in blindfolded healthy humans. In a session,...
The purpose of the present study was to elucidate whether an external reference frame contributes to tactile localization in blindfolded healthy humans. In a session, the right forearm was passively moved until the elbow finally reached to the target angle, and participants reached the left index finger to the right middle fingertip. The locus of the right middle fingertip indicated by the participants deviated in the direction of the elbow extension when vibration was provided to the biceps brachii muscle during the passive movement. This finding indicates that proprioception contributes to the identification of the spatial coordinate of the specific body part in an external reference frame. In another session, the tactile stimulus was provided to the dorsal of the right hand during the passive movement, and the participants reached the left index finger to the spatial locus at which the tactile stimulus was provided. Vibration to the biceps brachii muscle did not change the perceived locus of the tactile stimulus indicated by the left index finger. This finding indicates that an external reference frame does not contribute to tactile localization during the passive movement. Humans may estimate the spatial coordinate of the tactile stimulus based on the time between the movement onset and the time at which the tactile stimulus is provided.
PubMed: 38918211
DOI: 10.1007/s00221-024-06877-w -
Journal of Athletic Training Jun 2024
Topics: Humans; Foot; Postural Balance; Electric Stimulation; Male; Biomechanical Phenomena; Young Adult; Female
PubMed: 38918008
DOI: 10.4085/1062-6050-1004.24 -
The Journal of Sports Medicine and... Jul 2024Interventions on ankle motor control are important to prevent recurrent ankle sprains. Training using whole-body vibration may easily and effectively improve ankle motor... (Randomized Controlled Trial)
Randomized Controlled Trial
BACKGROUND
Interventions on ankle motor control are important to prevent recurrent ankle sprains. Training using whole-body vibration may easily and effectively improve ankle motor control, but the effects have not been investigated. Therefore, this study aimed to clarify the effects of 6 weeks of training with whole-body vibration on ankle motor control in a dynamic movement task among healthy participants.
METHODS
Twenty healthy university students (6 males and 14 females) were randomly allocated to whole-body vibration training and control groups, with 10 participants in each group. The training was performed twice a week for 6 weeks in both groups. Primary outcome was mean ankle angular jerk cost in the star excursion balance test. Secondary outcomes were maximum ankle motion angle and maximum reach distance in the star excursion balance test, ankle proprioception, and range of ankle dorsiflexion motion in the loaded position.
RESULTS
There was a significant group × period (pre- and postintervention) interaction for mean ankle angular jerk cost in the direction of ankle abduction/adduction during posterolateral reaching, which was significantly lower at postintervention than that at preintervention in the whole-body vibration group In the whole-body vibration group, the maximum ankle dorsiflexion motion angle during anterior and posterolateral reaching was significantly higher at postintervention than that at preintervention.
CONCLUSIONS
Training with whole-body vibration improves ankle motor control in dynamic movement tasks, although the direction of reach and plane of motion are limited. Additionally, training with whole-body vibration is also effective in increasing the ankle dorsiflexion angle during dynamic movement tasks.
Topics: Humans; Vibration; Female; Male; Young Adult; Proprioception; Range of Motion, Articular; Ankle Injuries; Postural Balance; Ankle Joint; Adult; Ankle
PubMed: 38916091
DOI: 10.23736/S0022-4707.24.15788-X -
BioRxiv : the Preprint Server For... Jun 2024Spinal cord stimulation (SCS) has emerged as a therapeutic tool for improving motor function following spinal cord injury. While many studies focus on restoring...
Spinal cord stimulation (SCS) has emerged as a therapeutic tool for improving motor function following spinal cord injury. While many studies focus on restoring locomotion, little attention is paid to enabling standing which is a prerequisite of walking. In this study, we fully characterize a new type of response to SCS, a long extension activated post-stimulation (LEAP). LEAP is primarily directed to ankle extensors and hence has great clinical potential to assist postural movements. To characterize this new response, we used the decerebrate cat model to avoid the suppressive effects of anesthesia, and combined EMG and force measurement in the hindlimb with intracellular recordings in the lumbar spinal cord. Stimulation was delivered as five-second trains via bipolar electrodes placed on the cord surface, and multiple combinations of stimulation locations (L4 to S2), amplitudes (50-600 uA), and frequencies (10-40 Hz) were tested. While the optimum stimulation location and frequency differed slightly among animals, the stimulation amplitude was key for controlling LEAP duration and amplitude. To study the mechanism of LEAP, we performed in vivo intracellular recordings of motoneurons. In 70% of motoneurons, LEAP increased at hyperpolarized membrane potentials indicating a synaptic origin. Furthermore, spinal interneurons exhibited changes in firing during LEAP, confirming the circuit origin of this behavior. Finally, to identify the type of afferents involved in generating LEAP, we used shorter stimulation pulses (more selective for proprioceptive afferents), as well as peripheral stimulation of the sural nerve (cutaneous afferents). The data indicates that LEAP primarily relies on proprioceptive afferents and has major differences from pain or withdrawal reflexes mediated by cutaneous afferents. Our study has thus identified and characterized a novel postural motor response to SCS which has the potential to expand the applications of SCS for patients with motor disorders.
PubMed: 38915687
DOI: 10.1101/2024.06.13.598885 -
PeerJ 2024Low energy availability (LEA) causes pathophysiology of the female athlete's body affecting the bone and reproductive health and was observed to have a high prevalence...
BACKGROUND
Low energy availability (LEA) causes pathophysiology of the female athlete's body affecting the bone and reproductive health and was observed to have a high prevalence in recreational female athletes previously. The aim of this study was to analyse the relationship between low energy availability in females questionnaire (LEAF-Q), bone mineral density (BMD), and postural stability in recreational athletes.
METHODS
Recreational female athletes ( = 24, age: 23.71 ± 2.94, Tier I) completed LEAF-Q, postural stability measurement during quiet stance (Zebris platform FDM; GmbH) and their BMD was measured using DXA (Hologic QDR Horizon A). Non-parametric statistical tests were used to analyse the relationships between LEAF-Q, BMD, and postural stability and to compare differences between participants divided by the LEAF-Q score and its subscales.
RESULTS
Risk of LEA was observed in 50% of recreational athletes participating in this study. Up to 46% of participants perceived menstrual bleeding changes related to training and 37.50% experienced menstrual dysfunction. Body composition and body weight fluctuations were observed to affect postural stability and BMD. With the risk score for LEA, the BMD and postural stability were not negatively affected in recreational athletes. However, the high number of recreational athletes in the risk score for LEA and menstrual dysfunctions highlights the need for public health programs aimed to increase awareness of LEA and its health consequences and for open communication about the menstrual cycle. Future longitudinal studies observing LEA, BMD, menstrual function, postural stability, and their interrelationship in female athletes are needed to increase the knowledge of this topic.
Topics: Humans; Female; Bone Density; Athletes; Young Adult; Adult; Postural Balance; Surveys and Questionnaires; Athletic Injuries; Relative Energy Deficiency in Sport; Body Composition; Absorptiometry, Photon
PubMed: 38915384
DOI: 10.7717/peerj.17533 -
Journal of Neuroengineering and... Jun 2024Impaired ankle proprioception strongly predicts balance dysfunction in chronic stroke. However, only sparse data on ankle position sense and no systematic data on ankle...
BACKGROUND
Impaired ankle proprioception strongly predicts balance dysfunction in chronic stroke. However, only sparse data on ankle position sense and no systematic data on ankle motion sense dysfunction in stroke are available. Moreover, the lesion sites underlying impaired ankle proprioception have not been comprehensively delineated. Using robotic technology, this study quantified ankle proprioceptive deficits post-stroke and determined the associated brain lesions.
METHODS
Twelve adults with chronic stroke and 13 neurotypical adults participated. A robot passively plantarflexed a participant's ankle to two distinct positions or at two distinct velocities. Participants subsequently indicated which of the two movements was further/faster. Based on the stimulus-response data, psychometric just-noticeable-difference (JND) thresholds and intervals of uncertainty (IU) were derived as measures on proprioceptive bias and precision. To determine group differences, Welch's t-test and the Wilcoxon-Mann-Whitney test were performed for the JND threshold and IU, respectively. Voxel-based lesion subtraction analysis identified the brain lesions associated with observed proprioceptive deficits in adults with stroke.
RESULTS
83% of adults with stroke exhibited abnormalities in either position or motion sense, or both. JND and IU measures were significantly elevated compared to the control group (Position sense: + 77% in JND, + 148% in IU; Motion sense: +153% in JND, + 78% in IU). Adults with stroke with both impaired ankle position and motion sense had lesions in the parietal, frontal, and temporoparietal regions.
CONCLUSIONS
This is the first study to document the magnitude and frequency of ankle position and motion sense impairment in adults with chronic stroke. Proprioceptive dysfunction was characterized by elevated JND thresholds and increased uncertainty in perceiving ankle position/motion. Furthermore, the associated cortical lesions for impairment in both proprioceptive senses were largely overlapping.
Topics: Humans; Male; Robotics; Proprioception; Female; Middle Aged; Stroke; Ankle; Aged; Adult; Chronic Disease; Brain; Stroke Rehabilitation
PubMed: 38915064
DOI: 10.1186/s12984-024-01396-9 -
Nature Communications Jun 2024Neuromuscular control of bionic arms has constantly improved over the past years, however, restoration of sensation remains elusive. Previous approaches to reestablish...
Neuromuscular control of bionic arms has constantly improved over the past years, however, restoration of sensation remains elusive. Previous approaches to reestablish sensory feedback include tactile, electrical, and peripheral nerve stimulation, however, they cannot recreate natural, intuitive sensations. Here, we establish an experimental biological sensorimotor interface and demonstrate its potential use in neuroprosthetics. We transfer a mixed nerve to a skeletal muscle combined with glabrous dermal skin transplantation, thus forming a bi-directional communication unit in a rat model. Morphological analyses indicate reinnervation of the skin, mechanoreceptors, NMJs, and muscle spindles. Furthermore, sequential retrograde labeling reveals specific sensory reinnervation at the level of the dorsal root ganglia. Electrophysiological recordings show reproducible afferent signals upon tactile stimulation and tendon manipulation. The results demonstrate the possibility of surgically creating an interface for both decoding efferent motor control, as well as encoding afferent tactile and proprioceptive feedback, and may indicate the way forward regarding clinical translation of biological communication pathways for neuroprosthetic applications.
Topics: Animals; Bionics; Rats; Muscle, Skeletal; Feedback, Sensory; Proprioception; Ganglia, Spinal; Mechanoreceptors; Muscle Spindles; Male; Female; Touch; Skin
PubMed: 38914540
DOI: 10.1038/s41467-024-49580-8