Proprioception After Primary Repair of the Anterior Cruciate Ligament.

BACKGROUND: Primary repair of the anterior cruciate ligament (ACL) has some potential advantages over the reconstruction technique, which include but are not limited to better knee sensation due to preservation of the natural ACL tissue in patients compared with tendon graft. Proprioception is impaired after ACL injuries and the sense of the joint position is lost. PURPOSE/HYPOTHESIS: The purpose of this study was to compare arthroscopic ACL primary repair and ACL reconstruction techniques clinically and functionally and analyze the differences in proprioception. It was hypothesized that primary repair would restore knee joint proprioception more successfully because the original tissue of the ACL is preserved. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: A total of 63 patients (34 underwent reconstruction and 29 underwent primary repair between 2017 and 2020) and 33 healthy controls, as well as the healthy knees of the operated groups, were evaluated between 24 and 48 months (mean, 29 months) postoperatively. Patients with proximal femoral avulsion tears and stump quality suitable for repair underwent primary repair, and those with tears outside these criteria underwent reconstruction using hamstring tendon autograft. Proprioception was evaluated using the active joint position sensation method during weightbearing, with a digital inclinometer used to measure differences between the target and achieved flexion angles of 15°, 30°, and 60°. RESULTS: At 15° of knee flexion, the deviation angles for the healthy knee of the reconstruction and primary repair groups were significantly smaller than those of the control group (P < .001), but there was no statistically significant difference between the groups in terms of deviation angle at 30° and 60° of flexion. The deviation angle of the operated knees was statistically significantly larger in the reconstruction group than in the primary repair group at all angles. The deviation angles at 15°, 30°, and 60° were 2.83°, 2.66°, and 2.66° in the reconstruction group and 1.00°, 1.00°, and 1.33° in the primary repair group, respectively (P < .001). There was no statistically significant difference between the reconstruction and primary repair groups in terms of clinical scores. CONCLUSION: Primary ACL repair can preserve proprioception in a well-selected patient group. In short-term follow-up, primary repair of the ACL in patients with proximal femoral avulsion tears and stump quality suitable for repair appears to be proprioceptively protective. Future studies are needed to clarify the long-term consequences of primary repair on proprioception in a larger population.

Impaired proprioception and magnified scaling of proprioceptive error responses in chronic stroke.

BACKGROUND: Previous work has shown that ~ 50-60% of individuals have impaired proprioception after stroke. Typically, these studies have identified proprioceptive impairments using a narrow range of reference movements. While this has been important for identifying the prevalence of proprioceptive impairments, it is unknown whether these error responses are consistent for a broad range of reference movements. The objective of this study was to characterize proprioceptive accuracy as function of movement speed and distance in stroke. METHODS: Stroke (N = 25) and controls (N = 21) completed a robotic proprioception test that varied movement speed and distance. Participants mirror-matched various reference movement speeds (0.1-0.4 m/s) and distances (7.5-17.5 cm). Spatial and temporal parameters known to quantify proprioception were used to determine group differences in proprioceptive accuracy, and whether patterns of proprioceptive error were consistent across testing conditions within and across groups. RESULTS: Overall, we found that stroke participants had impaired proprioception compared to controls. Proprioceptive errors related to tested reference movement scaled similarly to controls, but some errors showed amplified scaling (e.g., significantly overshooting or undershooting reference speed). Further, interaction effects were present for speed and distance reference combinations at the extremes of the testing distribution. CONCLUSIONS: We found that stroke participants have impaired proprioception and that some proprioceptive errors were dependent on characteristics of the movement (e.g., speed) and that reference movements at the extremes of the testing distribution resulted in significantly larger proprioceptive errors for the stroke group. Understanding how sensory information is utilized across a broad spectrum of movements after stroke may aid design of rehabilitation programs.

The effect of joint position sense therapy on chronic shoulder pain with central sensitization.

BACKGROUND: Chronic shoulder pain is a common musculoskeletal problem associated with unreleased pain and functional dysfunction that can evolve into central sensitization. Some forms of manual therapy may exacerbate pain and central sensitization. This study investigated the impact of joint position sense therapy (JPST), a moderate joint proprioception training technique, on central sensitization, shoulder functional dysfunction, and pain in patients with chronic shoulder pain compared with more intense exercises or aggressive manual therapies. METHODS: We assessed the pressure pain threshold (PPT) in 30 patients with and 30 patients without chronic shoulder pain. The assessment focused on 4 muscle sites: deltoid, upper trapezius, brachioradialis, and tibialis anterior. Thirty patients with chronic shoulder pain were randomly divided into the JPST and control groups. The JPST group underwent additional shoulder joint position-sense training. The efficiency outcomes were the disabilities of the arm, shoulder, and hand questionnaire, visual analog scale (VAS), and PPT, evaluated at baseline and after the intervention. RESULTS: Significant differences were observed in the PPT values at the brachioradialis (P < .05), deltoid (P < .01), and trapezius (P < .001) among the non-chronic and chronic groups, but not in the tibialis anterior muscle (P > .05). Although both control and JPST interventions effectively improved the disabilities of the arm, shoulder, and hand questionnaire score, pain intensity, and PPT values in the upper limb, the outcomes in the JPST group were significantly different from those in the control group. CONCLUSIONS: Generalized hyperalgesia changes limited to the upper limbs were observed in patients with chronic shoulder pain. JPST has beneficial effects on pain control and functional dysfunction in patients with chronic shoulder pain.

The Impact of Forward Head Posture on Neck and Ankle Joint Position Sense: A Cross-Sectional Study.

BACKGROUND: Forward head posture (FHP) decreases the neck position sense and creates tension in the neck muscles, which inversely affects the mechanics of the distal joints through body myofascia. Thus, this study investigated the effects of FHP on neck and ankle joint position sense, and conducted a comparison between the joint position sense of the right and left ankle. METHODS: Fifty-seven subjects were assigned according to the craniovertebral angle (CVA) into the FHP group (CVA <49°; n = 27) or the control group (CVA >49°; n = 30). Head and ankle joint repositioning accuracy was measured by using a cervical range-of-motion device and an isokinetic dynamometer, respectively. RESULTS: There was a significant increase in the joint position error (JPE) of the cervical flexion, extension, and right and left side bending motions of the FHP group compared to the control group (P < .05). There were significant increases in the JPE of the right and left ankle dorsiflexion and plantarflexion of the FHP group compared to the healthy group (P < .05). Moreover, the JPE of the right ankle dorsiflexion and plantarflexion of the FHP group were significantly higher than the left ankle (P < .05). CONCLUSIONS: The FHP decreases the position sense of cervical flexion, extension, and right and left side bending motions, and the plantarflexion and dorsiflexion of both ankle joints, especially the right ankle joint.

The effect of 8-week combined balance and plyometric on the dynamic balance and agility of female adolescent taekwondo athletes.

OBJECTIVES: To investigate the effect of combined balance and plyometric training (PT) on the agility and dynamic balance of adolescent taekwondo athletes. METHODS: Thirty female adolescent taekwondo players volunteered to participate and were randomly assigned to the combined balance training and PT (CT; n = 15) and PT (n = 15) groups. The CT group performed balance training combined with PT 3 times a week for 6 weeks (40 minutes of plyometrics and 20 minutes of balance training) while the PT group performed only PT for the same period (3 sets × 8-12 reps for each exercise). Both groups received the same routine technical taekwondo training. RESULTS: Post-intervention assessments revealed that both groups significantly improved their dynamic posture stability index scores (DPSI; forward jump [F-DPSI] and lateral jump [L-DPSI]). However, participants in the CT group achieved notably superior outcomes in the F-DPSI and L-DPSI scores compared with those achieved by their PT counterparts. The center of pressure metrics exhibited improvements post-intervention, with scores of specific measures in the PT group surpassing those in the CT group. Additionally, the 5-0-5 test scores exhibited improvements post-intervention, with scores of specific measures in the PT group surpassing those in the CT group, and the TAST (Taekwondo Specific Agility Test) of the CT group and the PT changed significantly after the intervention. CONCLUSION: An 8-week regimen that integrates balance and plyometric training effectively augments knee function and proprioception in adolescent Taekwondo athletes. This study underscores the potential benefits of a combined training approach, providing coaches and athletes with valuable insights into Taekwondo training.

The reliability and validity of a novel wearable inertial sensor to measure the cervical proprioception.

BACKGROUND: Proprioceptive function assessment is crucial in clinical practice for patients with chronic non-specific neck pain (CNNP) as it is a major issue affecting their condition. PURPOSE: To verify the reliability and validity of baiobit sensor in measuring the neck proprioceptive function of CNNP patients. METHODS: Fifty-three CNNP patients were recruited (36 females, 17 males; age range 21-60 years) and were assessed for cervical joint position error by two blinded raters using the Baiobit sensor and laser pointer devices. The second measurement was conducted by the same rater 48 h later. Intra and inter-rater reliability of the Baiobit sensor was evaluated using the intra-class correlation coefficient (ICC), while the validity of the Baiobit sensor was established using the Spearman correlation coefficient. RESULTS: The Baiobit sensor demonstrated moderate to excellent intra-rater reliability in flexion, extension, left lateral flexion, right lateral flexion, and right rotation (ICCs=0.71∼0.85, 95 %CIs: 0.50∼0.91), left-rotation shows poor to good intra-rater reliability (ICC=0.56, 95 %CI: 0.25∼0.75). The Baiobit sensor also demonstrated moderate to excellent inter-rater reliability in flexion, extension, left lateral flexion, right lateral flexion, and right rotation (ICCs=0.80∼0.88, 95 %CIs: 0.65∼0.91), left-rotation shows poor to good intra-rater reliability (ICC=0.59, 95 %CI: 0.29∼0.76). Validity analysis showed that the Baiobit sensor had a range of low to high validity (r = 0.46∼0.88) for measuring cervical proprioception function, with lower validity observed in the left flexion direction. The Baiobit showed good absolute reliability with low SEM and MDC90 values (0.35°âˆ¼2.42°). CONCLUSION: The new device could be used as an alternative tool to evaluate neck proprioception.

Immediate effect of kinesiology taping on muscle strength, static balance and proprioception after eccentric muscle fatigue on ankle: a randomized cross-over trial.

BACKGROUND: Kinesiology Taping(KT) is commonly used as a physical therapy to prevent exercise-induced fatigue. This study aims to evaluate the immediate effects of KT on muscle strength, static balance, and proprioception after eccentric muscle fatigue on ankle. METHODS: Twenty healthy male university students were recruited. The experimental protocol was structured into four sessions, each separated by a one-week washout period to prevent carryover effects. Participants were randomly allocated to one of four intervention conditions in each session, ensuring no participant received the same intervention twice. These conditions were: no taping(NT),sham taping(ST),athletic taping(AT),and kinesiology taping(KT).Taping was applied immediately following an eccentric muscle fatigue protocol targeting the ankle, and assessments were conducted in the order of proprioception, muscle strength and static balance. Isometric muscle strength and proprioception were evaluated using the Biodex isokinetic system. Static balance was measured using the TecnoBody balance platform. RESULTS: KT had a significantly higher plantarflexion/dorsiflexion peak torque, dorsiflexion average peak torque, and plantarflexion/dorsiflexion average power at 60°/s compared with NT and ST in terms of isometric muscle strength (p < 0.05).Furthermore, the plantarflexion peak torque of KT was significantly greater than AT at 60°/s[p = 0.005,95% confidence interval(CI) = 3.39 to 18.20] and 180°/s[p = 0.006,95%CI(2.62,21.98)]. In terms of proprioception, KT showed a lower absolute error in 25° plantarflexion and 10° dorsiflexion compared to NT, ST and AT. For static balance with eyes-open and eyes-closed conditions, AT and KT had a lower total sway area than NT and ST (p < 0.05). Additionally, a significant difference in total sway length with eyes-open condition was observed between AT and KT[p < 0.001,95%CI(-431.81,-168.25)];total sway area and the center of pressure(COP) velocity in the mediolateral(ML) and anteroposterior(AP) directions with eyes-closed condition were significantly lower in AT compared to KT. CONCLUSION: This study suggests that KT is more effective than other taping conditions in improving muscle strength and proprioception after eccentric muscle fatigue on ankle. However, AT is more helpful in increasing static postural control ability after ankle muscle fatigue than KT. TRIAL REGISTRATION: This study was registered with www.chictr.org.cn (registration number: ChiCTR2300068278) on 13/2/2023.

Task-driven neural network models predict neural dynamics of proprioception.

Proprioception tells the brain the state of the body based on distributed sensory neurons. Yet, the principles that govern proprioceptive processing are poorly understood. Here, we employ a task-driven modeling approach to investigate the neural code of proprioceptive neurons in cuneate nucleus (CN) and somatosensory cortex area 2 (S1). We simulated muscle spindle signals through musculoskeletal modeling and generated a large-scale movement repertoire to train neural networks based on 16 hypotheses, each representing different computational goals. We found that the emerging, task-optimized internal representations generalize from synthetic data to predict neural dynamics in CN and S1 of primates. Computational tasks that aim to predict the limb position and velocity were the best at predicting the neural activity in both areas. Since task optimization develops representations that better predict neural activity during active than passive movements, we postulate that neural activity in the CN and S1 is top-down modulated during goal-directed movements.

Extended physiological proprioception is affected by transhumeral Socket-Suspended prosthesis use.

The objective of this study was to define targeted reaching performance without visual information for transhumeral (TH) prosthesis users, establishing baseline information about extended physiological proprioception (EPP) in this population. Subjects completed a seated proprioceptive targeting task under simultaneous motion capture, using their prosthesis and intact limb. Eight male subjects, median age of 58 years (range 29-77 years), were selected from an ongoing screening study to participate. Five subjects had a left-side TH amputation, and three a right-side TH amputation. Median time since amputation was 9 years (range 3-54 years). Four subjects used a body-powered prosthetic hook, three a myoelectric hand, and one a myoelectric hook. The outcome measures were precision and accuracy, motion of the targeting hand, and joint angular displacement. Subjects demonstrated better precision when targeting with their intact limb compared to targeting with their prosthesis, 1.9 cm2 (0.8-3.0) v. 7.1 cm2 (1.3-12.8), respectively, p = 0.008. Subjects achieved a more direct reach path ratio when targeting with the intact limb compared to with the prosthesis, 1.2 (1.1-1.3) v. 1.3 (1.3-1.4), respectively, p = 0.039 The acceleration, deceleration, and corrective phase durations were consistent between conditions. Trunk angular displacement increased in flexion, lateral flexion, and axial rotation while shoulder flexion decreased when subjects targeted with their prosthesis compared to the intact limb. The differences in targeting precision, reach patio ratio, and joint angular displacements while completing the targeting task indicate diminished EPP. These findings establish baseline information about EPP in TH prosthesis users for comparison as novel prosthesis suspension systems become more available to be tested.

Sensory function and somatosensorial system changes according to visual acuity and throwing techniques in goalball players: A cross-sectional study.

The somatosensory system is a complect sensory system that differentiates individual athletes. The aim of this study is to investigate the effect of visual acuity level on throwing technique, proprioceptive sense of the shoulder joint, light touch and two-point discrimination sense of the upper extremity, and sensory function (postural control and reaction time) in visually impaired goalball players. Goalball players who have different visual acuities B1(unable to perceive light or recognize its shape); B2 (has a visual field of less than 5 degrees and can recognize shapes); B3 (visual field greater than 5 degrees and less than 20 degrees) participated in the study. The sensorial system was evaluated with proprioceptive sense of the shoulder joint and sensory tests (light touch and two-point discrimination sense of the dominant hand.). Sensory function (postural control and reaction time) was evaluated with the flamingo balance test, functional reach test, and pro-agility test. The goalball players' throwing technique was questioned. Seventeen male players, those aged 20-30 (20.8±3.9 years) who have been professionally engaged in goalball for at least three years (58.7-37.8 months) participated. Shoulder internal rotation joint position sense and the flamingo balance test were found to be different in the group with B1 visual acuity than in the group with B3 visual acuity (p = 0.042* and 0.028 respectively). There was no difference between groups with B1-B2 visual acuity (p = 0.394 and p = 0.065) and between groups with B2-B3 visual acuity (p = 0.792 and p = 0.931). There was no difference in the groups in terms of sensory tests and reaction time (p> 0.05). In goalball, joint position sense is related to throwing techniques. Although there is a general acceptance that other sensory systems should work harder to compensate for the sense of vision, fear of falling, athlete's branch year, sports year, muscle strength, and general physical condition of the athlete may affect the measurements made, especially in the dynamic position.

How does a motor or cognitive dual-task affect our sense of upper limb proprioception?

BACKGROUND: Daily upper limb activities require multitasking and our division of attention. How we allocate our attention can be studied using dual-task interference (DTi). Given the vital role proprioception plays in movement planning and motor control, it is important to investigate how conscious upper limb proprioception is impacted by DTi through cognitive and motor interference. PURPOSE: To examine how dual-task interference impacts conscious upper limb proprioception during active joint repositioning tasks (AJRT). METHODS: Forty-two healthy participants, aged between 18 and 35, took part in this cross-sectional study. Participants completed two AJRT during three conditions: baseline (single task), dual-cognitive task (serial subtractions), and dual-motor task (non-dominant hand movements). The proprioceptive error (PE; difference between their estimation and targeted position) was measured using an AJRT of 75% and 90% of maximum internal rotation using the Biodex System IIITM and the Upper Limb Proprioception Reaching Test (PRO-Reach). To determine if PEs differed during dual-task interference, interference change scores from baseline were used with one sample t-tests and analyses of variance. RESULTS: The overall mean PE with the Biodex was 4.1° ± 1.9 at baseline. Mean change scores from baseline reflect a mean improvement of 1.5° ± 1.0 (p < .001) during dual-cognitive task and of 1.5° ± 1.2 (p < .001) during dual-motor task. The overall mean PE with the PRO-Reach was 4.4cm ± 1.1 at baseline. Mean change scores from baseline reflect a mean worsening of 1.0cm ± 1.1 (p < .001) during dual-cognitive task and improvement of 0.8cm ± 0.6 (p < .001) during dual-motor task. Analysis of variance with the Biodex PEs revealed an interference effect (p < .001), with the cognitive condition causing greater PEs compared to the motor condition and a criterion position effect (p = .006), where 75% of maximum IR produced larger PEs during both interference conditions. An interference effect (p = .022) with the PRO-Reach PEs was found highlighting a difference between the cognitive and motor conditions, with decreased PEs during the contralateral motor task. CONCLUSION: Interference tasks did impact proprioception. Cognitive interference produced mixed results, whereas improved proprioception was seen during motor interference. Individual task prioritization strategies are possible, where each person may choose their own attention strategy when faced with dual-task interference.

Perception, action, and the body model.

In 1992, Goodale and Milner proposed to study the visual system based on function, thus dissociating vision for perception (ventral stream) and vision for action (dorsal stream). This became known as the Perception and Action model (PAM). Following the PAM in the visual system, a somatosensory PAM was proposed including a body representation for perception and a separate for action. This review explores the body model of the hand and how it relates to the PAM. The body model refers to the internal representation of the body that is responsible for position sense. Previous research has shown that the representation of the hand features systematic distortions: an overestimation of hand width and an underestimation of finger length. These distortions have been reported using different paradigms, different body parts, and in various settings. Thus, body model distortions appear to be a characteristic of human body representation. If the body model of the hand is distorted, how can actions like reaching and grasping be accurate? We review evidence that body model distortions may in fact provide a functional benefit to our actions, that cortical maps in the somatosensory and motor cortices reflect these distortions, and that actions rely on a distorted body model. We argue that the body model is a product of both the ventral and dorsal somatosensory streams. Further, we suggest that the body model is an example of the inextricable link between the two streams.

Neural correlates of bilateral proprioception and adaptation with training.

Bilateral proprioception includes the ability to sense the position and motion of one hand relative to the other, without looking. This sensory ability allows us to perform daily activities seamlessly, and its impairment is observed in various neurological disorders such as cerebral palsy and stroke. It can undergo experience-dependent plasticity, as seen in trained piano players. If its neural correlates were better understood, it would provide a useful assay and target for neurorehabilitation for people with impaired proprioception. We designed a non-invasive electroencephalography-based paradigm to assess the neural features relevant to proprioception, especially focusing on bilateral proprioception, i.e., assessing the limb distance from the body with the other limb. We compared it with a movement-only task, with and without the visibility of the target hand. Additionally, we explored proprioceptive accuracy during the tasks. We tested eleven Controls and nine Skilled musicians to assess whether sensorimotor event-related spectral perturbations in µ (8-12Hz) and low-ß (12-18Hz) rhythms differ in people with musical instrument training, which intrinsically involves a bilateral proprioceptive component, or when new sensor modalities are added to the task. The Skilled group showed significantly reduced µ and low-ß suppression in bilateral tasks compared to movement-only, a significative difference relative to Controls. This may be explained by reduced top-down control due to intensive training, despite this, proprioceptive errors were not smaller for this group. Target visibility significantly reduced proprioceptive error in Controls, while no change was observed in the Skilled group. During visual tasks, Controls exhibited significant µ and low-ß power reversals, with significant differences relative to proprioceptive-only tasks compared to the Skilled group-possibly due to reduced uncertainty and top-down control. These results provide support for sensorimotor µ and low-ß suppression as potential neuromarkers for assessing proprioceptive ability. The identification of these features is significant as they could be used to quantify altered proprioceptive neural processing in skill and movement disorders. This in turn can be useful as an assay for pre and post sensory-motor intervention research.

Progressive Irreversible Proprioceptive Piezo2 Channelopathy-Induced Lost Forced Peripheral Oscillatory Synchronization to the Hippocampal Oscillator May Explain the Onset of Amyotrophic Lateral Sclerosis Pathomechanism.

Amyotrophic lateral sclerosis (ALS) is a mysterious lethal multisystem neurodegenerative disease that gradually leads to the progressive loss of motor neurons. A recent non-contact dying-back injury mechanism theory for ALS proposed that the primary damage is an acquired irreversible intrafusal proprioceptive terminal Piezo2 channelopathy with underlying genetic and environmental risk factors. Underpinning this is the theory that excessively prolonged proprioceptive mechanotransduction under allostasis may induce dysfunctionality in mitochondria, leading to Piezo2 channelopathy. This microinjury is suggested to provide one gateway from physiology to pathophysiology. The chronic, but not irreversible, form of this Piezo2 channelopathy is implicated in many diseases with unknown etiology. Dry eye disease is one of them where replenishing synthetic proteoglycans promote nerve regeneration. Syndecans, especially syndecan-3, are proposed as the first critical link in this hierarchical ordered depletory pathomechanism as proton-collecting/distributing antennas; hence, they may play a role in ALS pathomechanism onset. Even more importantly, the shedding or charge-altering variants of Syndecan-3 may contribute to the Piezo2 channelopathy-induced disruption of the Piezo2-initiated proton-based ultrafast long-range signaling through VGLUT1 and VGLUT2. Thus, these alterations may not only cause disruption to ultrafast signaling to the hippocampus in conscious proprioception, but could disrupt the ultrafast proprioceptive signaling feedback to the motoneurons. Correspondingly, an inert Piezo2-initiated proton-based ultrafast signaled proprioceptive skeletal system is coming to light that is suggested to be progressively lost in ALS. In addition, the lost functional link of the MyoD family of inhibitor proteins, as auxiliary subunits of Piezo2, may not only contribute to the theorized acquired Piezo2 channelopathy, but may explain how these microinjured ion channels evolve to be principal transcription activators.

The interplay of motor adaptation and groupitizing in numerosity perception: Insights from visual motion adaptation and proprioceptive motor adaptation.

Groupitizing is a well-established strategy in numerosity perception that enhances speed and sensory precision. Building on the ATOM theory, Anobile proposed the sensorimotor numerosity system, which posits a strong link between number and action. Previous studies using motor adaptation technology have shown that high-frequency motor adaptation leads to underestimation of numerosity perception, while low-frequency adaptation leads to overestimation. However, the impact of motor adaptation on groupitizing, and whether visual motion adaptation produces similar effects, remain unclear. In this study, we investigate the persistence of the advantage of groupitizing after motor adaptation and explore the effects of visual motion adaptation. Surprisingly, our findings reveal that proprioceptive motor adaptation weakens the advantage of groupitizing, indicating a robust effect of motor adaptation even when groupitizing is employed. Moreover, we observe a bidirectional relationship, as groupitizing also weakens the adaptation effect. These results highlight the complex interplay between motor adaptation and groupitizing in numerosity perception. Furthermore, our study provides evidence that visual motion adaptation also has an adaptation effect, but does not fully replicate the effects of proprioceptive motor adaptation on groupitizing. In conclusion, our research underscores the importance of groupitizing as a valuable strategy in numerosity perception, and sheds light on the influence of motion adaptation on this strategy.

Comparison of the validity and reliability of three different methods used for wrist proprioception measurement.

BACKGROUND: ː Early detection of loss of proprioception is essential to prevent injury and maintain professional work activities. However, although many different methods are present for wrist proprioception measurement, these methods' validity and reliability studies are quite limited. OBJECTIVE: To compare the validity and reliability of the goniometer, inclinometer, and joint position sense goniometer methods used in measuring wrist active joint position sense (AJPS). METHODS: ː Thirty-two volunteer healthy participants (64 wrists) between the ages of 19-31 (mean age:23,34 ± 3,84) were included in the study. Wrist AJPS was assessed with an isokinetic dynamometer as a reference standard in addition to an inclinometer, goniometer, and joint position sense goniometer (JPSG). Spearman's Correlation Coefficient was used for validity analysis, and Intraclass Correlation Coefficient (ICC3,1) was used to analyze test-retest reliability. RESULTS: ː It was found that the goniometer (p < 0.001, r = 0.529) is a moderately valid method to assess active wrist joint position sense. The JPSG (p < 0.001, r = 0.432) and inclinometer (p = 0.005, r = 0.350) have weak validity. According to the results of ICC3,1 analysis, the goniometer (p < 0.001, ICC3,1 = 0.422) and JPSG (p < 0.001, ICC3,1 = 0.369) were found to have poor reliability in assessing wrist AJPS, and the inclinometer (p = 0,183, ICC3,1 = 0,114) was not found as a reliable method. CONCLUSIONS: ː Our results suggest that the JPSG and inclinometer should not be used in the wrist active joint position sense evaluation because of weak validity and poor reliability. The goniometer can be used in clinics and academic research to evaluate wrist joint position sense if the rater lacks a reliable and valid measurement tool.

Motor neurons generate pose-targeted movements via proprioceptive sculpting.

Motor neurons are the final common pathway1 through which the brain controls movement of the body, forming the basic elements from which all movement is composed. Yet how a single motor neuron contributes to control during natural movement remains unclear. Here we anatomically and functionally characterize the individual roles of the motor neurons that control head movement in the fly, Drosophila melanogaster. Counterintuitively, we find that activity in a single motor neuron rotates the head in different directions, depending on the starting posture of the head, such that the head converges towards a pose determined by the identity of the stimulated motor neuron. A feedback model predicts that this convergent behaviour results from motor neuron drive interacting with proprioceptive feedback. We identify and genetically2 suppress a single class of proprioceptive neuron3 that changes the motor neuron-induced convergence as predicted by the feedback model. These data suggest a framework for how the brain controls movements: instead of directly generating movement in a given direction by activating a fixed set of motor neurons, the brain controls movements by adding bias to a continuing proprioceptive-motor loop.

Relationship between Car-Sickness Susceptibility and Postural Activity: Could the Re-Weighting Strategy between Signals from Different Body Sensors Be an Underlying Factor?

Postural control characteristics have been proposed as a predictor of Motion Sickness (MS). However, postural adaptation to sensory environment changes may also be critical for MS susceptibility. In order to address this issue, a postural paradigm was used where accurate orientation information from body sensors could be lost and restored, allowing us to infer sensory re-weighting dynamics from postural oscillation spectra in relation to car-sickness susceptibility. Seventy-one participants were standing on a platform (eyes closed) alternating from static phases (proprioceptive and vestibular sensors providing reliable orientation cues) to sway referenced to the ankle-angle phases (proprioceptive sensors providing unreliable orientation cues). The power spectrum density (PSD) on a 10 s sliding window was computed from the antero-posterior displacement of the center of pressure. Energy ratios (ERs) between the high (0.7-1.3 Hz) and low (0.1-0.7 Hz) frequency bands of these PSDs were computed on key time windows. Results showed no difference between MS and non-MS participants following loss of relevant ankle proprioception. However, the reintroduction of reliable ankle signals led, for the non-MS participants, to an increase of the ER originating from a previously up-weighted vestibular information during the sway-referenced situation. This suggests inter-individual differences in re-weighting dynamics in relation to car-sickness susceptibility.

Stimulated cervical afferent input increases postural instability in older people with chronic neck pain: a cross-sectional study.

BACKGROUND: Several potential causes can impair balance in older people. The neck torsion maneuver may be useful in demonstrating impaired balance caused by the stimulation of cervical proprioceptive input. Whereas evidence suggests impaired standing balance in older people with chronic neck pain, balance impairment during the neck torsion position and its relationship with clinical characteristics have not yet been investigated in this population. The aims of this study were to investigate whether the neck torsion position could significantly influence balance responses in older people with chronic non-specific neck pain and to determine the relationships between the balance responses and characteristics of neck pain. METHODS: Sixty-eight older people (34 with chronic non-specific neck pain and 34 controls) participated in the study. Balance was tested using a force plate during comfortable stance with eyes open under four conditions: neutral head on a firm surface, neutral head on a soft surface, neck torsion to left and right on a firm surface and neck torsion to left and right on a soft surface. Balance outcomes were anterior-posterior (AP) and medial-lateral (ML) displacements, sway area and velocity. Characteristics of neck pain were intensity, duration and disability. RESULTS: Overall, the neck pain group exhibited greater AP and ML displacements, sway area and velocity in the neck torsion position on firm and soft surfaces compared to controls (partial eta squared (η²p) = 0.06-0.15, p < 0.05). The neck pain group also had greater AP displacement, sway area and velocity in the neutral position on a soft surface compared to controls (η²p = 0.09-0.16, p < 0.05). For both groups, the neck torsion position displayed overall greater postural sway compared to the neutral position (η²p = 0.16-0.69, p < 0.05). There were no relationships between the postural sway outcomes and characteristics of neck pain (p > 0.05). CONCLUSION: The neck torsion maneuver, stimulating the receptors resulted in increased postural sway in older people, with a more pronounced effect in those with neck pain. The study provides evidence supporting the use of neck torsion for assessing impaired balance related to abnormal cervical input in older people with chronic non-specific neck pain.