Deletion of a conserved genomic region associated with adolescent idiopathic scoliosis leads to vertebral rotation in mice

Adolescent idiopathic scoliosis (AIS) is the most common form of scoliosis, in which spinal curvature develops in adolescence, and 90% of patients are female. Scoliosis is a debilitating disease that often requires bracing or surgery in severe cases. AIS affects 2%-5.2% of the population; however, the biological origin of the disease remains poorly understood. In this study, we aimed to determine the function of a highly conserved genomic region previously linked to AIS using a mouse model generated by CRISPR-CAS9 gene editing to knockout this area of the genome to understand better its contribution to AIS, which we named AIS_CRMΔ. We also investigated the upstream factors that regulate the activity of this enhancer in vivo, whether the spatial expression of the LBX1 protein would change with the loss of AIS-CRM function, and whether any phenotype would arise after deletion of this region. We found a significant increase in mRNA expression in the developing neural tube at E10.5, and E12.5, for not only Lbx1 but also other neighboring genes. Adult knockout mice showed vertebral rotation and proprioceptive deficits, also observed in human AIS patients. In conclusion, our study sheds light on the elusive biological origins of AIS, by targeting and investigating a highly conserved genomic region linked to AIS in humans. These findings provide valuable insights into the function of the investigated region and contribute to our understanding of the underlying causes of this debilitating disease.

Multimodal sensory control of motor performance by glycinergic interneurons of the mouse spinal cord deep dorsal horn

Sensory feedback is integral for contextually appropriate motor output, yet the neural circuits responsible remain elusive. Here, we pinpoint the medial deep dorsal horn of the mouse spinal cord as a convergence point for proprioceptive and cutaneous input. Within this region, we identify a population of tonically active glycinergic inhibitory neurons expressing parvalbumin. Using anatomy and electrophysiology, we demonstrate that deep dorsal horn parvalbumin-expressing interneuron (dPV) activity is shaped by convergent proprioceptive, cutaneous, and descending input. Selectively targeting spinal dPVs, we reveal their widespread ipsilateral inhibition onto pre-motor and motor networks and demonstrate their role in gating sensory-evoked muscle activity using electromyography (EMG) recordings. dPV ablation altered limb kinematics and step-cycle timing during treadmill locomotion and reduced the transitions between sub-movements during spontaneous behavior. These findings reveal a circuit basis by which sensory convergence onto dorsal horn inhibitory neurons modulates motor output to facilitate smooth movement and context-appropriate transitions.

The effects of trunk repositioning errors on trunk and extremity functions in stroke

AIM

The aim of this study was to analyze the TRE in three directions including forward flexion, lateral flexion to the hemiparetic side, and rotation to the hemiparetic side in patients with stroke and to compare the errors with age- and sex-matched healthy subjects. In addition, it was investigated which functional outcomes were explanatory for TRE in patients with stroke.

METHODS

Forty-one patients with subacute/chronic stroke (age 59 ± 14.5 years) and 41 healthy subjects (age 57 ± 12.8 years) were included in the study. Demographic and clinical data were collected. TREs were measured using an inclinometer. The Trunk Impairment Scale (TIS), Fugl-Meyer Assessment (FMA), Wolf Motor Function Test (WMFT), Timed Up and Go Test, and 10-m walk test (10MWT) were also used to assess trunk control, motor impairment, upper extremity function, and lower extremity function, respectively, in patients with stroke.

RESULTS

TRE scores in three directions were higher in patients with stroke than in healthy subjects (p < 0.001). TREs in three directions were significantly strongly correlated with all functional outcomes (ρ > 0.60, r < 0.001). Multiple regression analysis determined 10MWT, WMFT-Performance, TIS, and FMA-Upper Extremity as explanatory factors for TRE.

CONCLUSION

The model presented in this study could help clinicians and researchers to predict the TRE in patients with stroke. Gait speed, upper extremity motor ability, upper extremity motor impairment, and trunk control should be considered for TRE after a stroke.

Acute and Acclimated Effects of Wearing Compression Garments on Balance Control in Community-Dwelling Older Adults

Falls are very serious health concerns among older adults. Providing additional cutaneous and proprioceptive feedback to older adults may enhance their balance control and therefore reduce the incidents of falls. This study aimed to investigate the acute and acclimated effect of wearing waist-to-above-ankle compression garments (CGs) on balance control in community-dwelling older adults. Thirty-one older adults participated in the study. The Timed Up and Go, Berg Balance Scale, and the Fall Risk Test of the Biodex Balance System were used in a random order to examine balance control in three testing sessions 1 week apart. Results indicated wearing CGs had a significant impact on the Timed Up and Go test (p < .001), Berg Balance Scale (p = .001), and the Fall Risk Test (p = .001). For the Timed Up and Go test, participants exhibited significant improvement in both the acute (8.68 vs. 7.91 s) and acclimated effect (7.91 vs. 7.41 s) of wearing CGs. For the Berg Balance Scale, participants showed significant improvement after wearing CGs for 1 week in comparison to the no CGs condition (55.77 vs. 55.39 points). For the Fall Risk Test, participants showed a significant improvement in the acute effect of wearing CGs in comparison to the no CGs condition (1.55° vs. 1.31°). This exploratory study showed that wearing waist-to-above-ankle CGs provided a positive impact on balance control in healthy community-dwelling older adults. It lays the foundation for future studies with a larger sample size to investigate the potential benefits of wearing CGs in individuals with balance control deficits and/or other comorbidities.

Proprioception and Control of a Soft Pneumatic Actuator Made of a Self-Healable Hydrogel

The current evolutionary trends in soft robotics try to exploit the capacities of smart materials to achieve compact robotics designs with embodied intelligence. In this way, the number of elements that compose the soft robot can be reduced, as the smart material can cover different aspects (e.g., structure and sensorization) all in one. This work follows this tendency and presents a custom-designed hydrogel that exhibits two smart features, self-healing and ionic conductivity, used to build a pneumatic actuator. The self-healing capability provides the actuator's structure with the ability to self-repair from damages (e.g., punctures or cuts), an important quality to prolong the life cycle of the actuator. The ionic conductivity enables the actuator's proprioception: the structure itself serves as a curvature sensor. The behavior of this proprioceptive curvature sensor is analyzed in this work, studying its linearity, stability, and performance after a self-healing process. This sensor is also proposed as feedback in a closed-loop scheme to automatically control the actuator's curvature. A proportional-integral-derivative controller is designed based on an empirical model of the actuator's dynamics, and then validated in experimental tests, proving the proprioceptive sensor as proper feedback. These control tests are performed over undamaged and self-healed actuators, thus demonstrating all the capabilities of our soft material.

The effect of cervical mobilization on joint position sense, balance and gait in patients with multiple sclerosis: a randomized crossover study

OBJECTIVE

To investigate the effect of cervical mobilization on joint position sense, balance and gait in multiple sclerosis (MS) patients.

METHODS

Sixteen MS patients received traditional rehabilitation and traditional rehabilitation+cervical mobilization treatments in different orders, 2 days a week for 4 weeks. For the cervical mobilization, joint traction and shifts with myofascial release techniques were applied. Joint position sense was evaluated from the bilateral knee and ankle joints with a digital goniometer, balanced with the Berg Balance Test (BBT), the Functional Reach Test, and gait with the Dynamic Gait Index (DGI) and the Timed 25-Foot Walk Test.

RESULTS

Improvements were determined in joint position sense, balance, gait with both treatment methods (p < 0.05). With the addition of cervical mobilization to traditional treatment, there was observed to be an increased effect carried over in knee joint position sense and BBT (p < 0.05). The BBT and DGI scores improved in the group applied with cervical mobilization following the washout period (p < 0.05).

CONCLUSIONS

Cervical mobilization could be effective in improving joint position sense, balance and gait, and accelerated improvements in a short time. The application of cervical mobilization could be a supportive treatment method to improve position sense, balance and gait in patients with MS.

Shoulder Proprioception: A Review

The purpose of this review is to provide a comprehensive resource for shoulder proprioception assessment and its integration into clinical decision making as well as targeted rehabilitation protocols. Data for this review were acquired from peer-reviewed articles from computerized online databases, namely PubMed and Medline, published between 1906 and 2021. The development of digital/smart phone goniometers can improve shoulder joint range of motion (ROM) measurements and demonstrate comparable measurement accuracy to the universal standard goniometer. The inclinometer offers a portable and cost-effective method for measuring shoulder joint angles and arcs of motion in the vertical plane. Two types of dynamometers, the computerized isokinetic machine and the handheld hydraulic dynamometer, are reliable tools for objective shoulder rotator cuff strength assessment. Motion analysis systems are highly advanced modalities that create three-dimensional models of motion arcs using a series of cameras and reflective beads, offering unparalleled precision in shoulder proprioception measurement; however, they require time-consuming calibration and skilled operators. Advancements in wearable devices and compact mobile technology such as iPhone applications may make three-dimensional motion analysis more affordable and practical for outpatient settings in the future. The complex interplay between proprioception and shoulder dysfunction is not fully understood; however, shoulder proprioception can likely both contribute to and be caused by shoulder pathology. In patients with rotator cuff tears, glenohumeral osteoarthritis, and shoulder instability, clinicians can track proprioception to understand a patient's disease progression or response to treatment. Finally, rehabilitation programs targeting shoulder proprioception have shown promising initial results in restoring function and returning athletes to play.

Electrophysiological Properties of Proprioception-Related Neurons in the Intermediate Thoracolumbar Spinal Cord

Proprioception, the sense of limb and body position, is required to produce accurate and precise movements. Proprioceptive sensory neurons transmit muscle length and tension information to the spinal cord. The function of excitatory neurons in the intermediate spinal cord, which receive this proprioceptive information, remains poorly understood. Using genetic labeling strategies and patch-clamp techniques in acute spinal cord preparations in mice, we set out to uncover how two sets of spinal neurons, Clarke's column (CC) and Atoh1-lineage neurons, respond to electrical activity and how their inputs are organized. Both sets of neurons are located in close proximity in laminae V-VII of the thoracolumbar spinal cord and have been described to receive proprioceptive signals. We find that a majority of CC neurons have a tonic-firing type and express a distinctive hyperpolarization-activated current (Ih). Atoh1-lineage neurons, which cluster into two spatially distinct populations, are mostly a fading-firing type and display similar electrophysiological properties to each other, possibly due to their common developmental lineage. Finally, we find that CC neurons respond to stimulation of lumbar dorsal roots, consistent with prior knowledge that CC neurons receive hindlimb proprioceptive information. In contrast, using a combination of electrical stimulation, optogenetic stimulation, and transsynaptic rabies virus tracing, we find that Atoh1-lineage neurons receive heterogeneous, predominantly local thoracic inputs that include parvalbumin-lineage sensory afferents and local interneuron presynaptic inputs. Altogether, we find that CC and Atoh1-lineage neurons have distinct membrane properties and sensory input organization, representing different subcircuit modes of proprioceptive information processing.

Sensory deficits of the paretic and non-paretic upper limbs relate with the motor recovery of the poststroke subjects

BACKGROUND

Post stroke, motor paresis has usually been considered to be a crucial factor responsible for the disability; other impairments such as somatosensory deficits may also play a role.

OBJECTIVE

To determine the relation between the sensory deficits (paretic and non-paretic upper limbs) and the motor recovery of the paretic upper limb and to predict the potential of motor recovery based on the sensory deficits among stroke subjects.

METHODS

The study was a cross-sectional study conducted in a rehabilitation institute. Ninety-five poststroke hemiparetic subjects having sensory impairment in any of the modalities were considered for this study. Sensory deficits were assessed on both the upper limbs (paretic and non-paretic) primarily using Erasmus MC modification of the revised version of Nottingham Sensory Assessment (Em-NSA) and Nottingham Sensory Assessment (Stereognosis) (NSA-S). The motor recovery was assessed using the Fugl-Meyer assessment (FMA).

RESULTS

The measures of sensory deficits exhibited weak but significant correlation [the paretic (Em-NSA and NSA; r = .38 to .58; p < .001) and the non-paretic (Em-NSA and NSA; r = .24 to .38; p = .03 to .001)] with the motor recovery of the paretic upper limb as measured by FMA. The potential of favorable recovery of the paretic upper limb may be predicted using the cutoff scores of Em-NSA (30, 21, and 24) and NSA-S (5, 8, and 5) of the paretic side.

CONCLUSION

In stroke, sensory deficits relate weakly with the recovery of the paretic upper limb and can predict recovery potential of the paretic upper limb.

Acute Effect of Kinesiology Taping on Muscle Activation, Functionality and Proprioception in Patients With Knee Osteoarthritis: A Randomized Controlled Trial

Data on the mechanism of kinesiology taping (KT) for providing mechanical support, facilitating or inhibiting muscles, and increasing functionality in the treatment of knee osteoarthritis (OA) have been contradictory, with no study evaluating acute muscle activation. Our aim in this study was to determine the acute effect of KT applied to the rectus femoris muscle on this muscle's activation, functionality and proprioception in patients with knee osteoarthritis. We divided 40 individuals diagnosed with knee osteoarthritis into two groups: (a) KT group (taping with tension facilitation) and (b) a placebo group (taping with no tension facilitation). We applied taping to the participants' left and right side rectus femoris muscles for 30 minutes, but with muscle facilitation in the KT group and without tension in the placebo group. We assessed participants for muscle activation with surface electromyography (sEMG), for functionality with the Timed Up and Go Test (TUG), and for proprioception/joint sense with the Five Times Sit-to-Stand Test (5TSTS) before and after taping. Demographic and clinical characteristics of the groups before these interventions were similar (p > .05). Muscle activation did not change significantly in either group compared to before taping (p > .05), but there were improvements in both knees for proprioception/joint sense (p < .05). Both groups were similar in terms of functionality (5TSTS, TUG) results (p > .05). We concluded that KT applied bilaterally to the rectus femoris did not affect rectus femoris muscle activation and functionality in patients with knee OA, but it did improve proprioception.

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.

Effects of Eccentric Versus Concentric Strengthening in Patients With Subacromial Pain Syndrome: A Randomized Controlled Trial

BACKGROUND

Subacromial pain syndrome (SPS) is the most common cause of shoulder pain. Therapeutic exercise is the first-line treatment for SPS; however, the ideal exercise type remains unclear. Here, we compared the effects of eccentric and concentric strengthening in patients with SPS.

HYPOTHESIS

Adding isolated eccentric strengthening to a multimodal physiotherapy program (MPP) would lead to greater improvements in outcomes compared with either MPP alone or adding isolated concentric strengthening to the MPP.

STUDY DESIGN

Randomized controlled trial.

LEVEL OF EVIDENCE

Level 2.

METHODS

A total of 45 patients were randomized to eccentric strengthening (ESG), concentric strengthening (CSG), and control (CG) groups; all groups received the MPP. The strengthening groups also performed group-specific strengthening. Shoulder pain, abduction and external rotation (ER) strength, joint position sense (JPS), the Constant-Murley Score (CMS), and the Disabilities of the Arm, Shoulder and Hand score were collected at baseline, after 12 weeks of treatment, and at week 24.

RESULTS

For CMS, ESG exhibited a greater, but not clinically meaningful, improvement than CSG and CG (P < 0.05). Eccentric abduction strength increased in ESG compared with CG. From baseline to follow-up, abduction strength increased in ESG compared with CSG and CG. Eccentric abduction strength increased in CSG compared with CG. JPS at abduction improved in the ESG compared with CG. Other between-group comparisons were not significant (P > 0.05).

CONCLUSION

In SPS, eccentric strengthening provided added benefits, improving shoulder abduction strength and JPS at abduction, and was superior to concentric strengthening for improving shoulder abduction strength. Neither strengthening approach had an additional effect on shoulder function, pain, ER strength, or rotational JPS.

CLINICAL RELEVANCE

Clinicians could implement eccentric strengthening as a motor control retraining for strength and proprioception gain rather than for pain relief and reducing disability.

Physiotherapy management focusing on proprioceptive impairment in a patient with gait and balance impairments following stroke: A case report

BACKGROUND

Proprioceptive impairment contributes to gait and balance impairments in patients with stroke. Diagnosis functional impairments and evaluation treatment efficacy require quantitative proprioception assessment. However, proprioception assessment has remained limited to ordinal scale measurement, with a lack of ratio scale measurements.

PURPOSE

This case report describes a physiotherapy management program focusing on proprioceptive impairment in patients with stroke using quantitative tests such as Threshold to Detect Passive Motion (TDPM) and Joint Position Sense (JPS).

CASE DESCRIPTION

A63-year-old male patient with an acute pontine lacunar infarction was admitted to our hospital. His muscle strength, selective movement, and trunk activity were preserved. However, the Berg Balance Scale (BBS) and Gait Assessment andIntervention Tool (GAIT) score were 42 and 9 points, observing balance impairment and the buckling knee pattern with hip ataxia during gait. Based on these, TDPM and JPS using image capture were performed. In physiotherapeuticdiagnosis, proprioceptive impairments in the hip and knee joints were the primary functional impairments related to balance and gait. To address these proprioceptive impairments, a 13-day treatment protocol incorporating transcutaneous electrical nerve stimulation (intensity: sensory threshold, frequency: 100 Hz) targeting the quadriceps femoris was performed.

OUTCOMES

The patient was discharged after achieving independent ambulation and improvement in BBS (56 points) and GAIT (2 points) scores, exceeding the minimum clinically important difference. Recovery of proprioceptive impairment corresponded withimproved balance and gait ability.

CONCLUSION

Quantitatively evaluating proprioceptive impairments may provide novel rehabilitation for patients with stroke who have proprioceptive impairments and contribute to clinical decision-making.

Assessment of lower limb proprioception after fibula free flap harvest: A pilot study

BACKGROUND

After undergoing fibula-free flap harvest, patients may experience complications such as ankle instability. It remains unclear whether these patients have deficits of proprioception, and the recovery process is also uncertain.

OBJECTIVE

This study aimed to objectively evaluate proprioception on the donor and normal side of surgical patients during long-term follow-up using the Pro-kin system.

METHODS

This study enrolled 36 patients who underwent reconstruction of the head and neck using osseous free flaps harvested from the fibula. Each patient underwent pre-operative evaluations and was subsequently evaluated at postoperative months 1, 3, 6, and 12. The study assessed the proprioceptive evaluation of the lower limbs, muscle function, range of motion of the ankle, and donor side complications.

RESULTS

On the donor side, the average trace error (ATE) at postoperative month 1 was significantly higher than pre-operation, postoperative months 6 and 12 (P< 0.05). The test execution time (TTE) at postoperative month 1 was significantly increased by 9.875s compared to the pre-operative levels (P= 0.012, 95% confidence interval [CI] 4: 1.877-17.873) and by 11.583s compared to postoperative month 12 (P= 0.007, 95% CI: 2.858-20.309). The reduction in range of motion of ankle dorsiflexion was most pronounced at postoperative month 1, exhibiting an 11.25∘ decrease compared to pre-operative levels (P< 0.001, 95% CI: 6.304-16.16). Although the range of motion of ankle dorsiflexion gradually improved over time at postoperative months 3, 6, and 12, it remained lower than pre-operative levels (P< 0.05).

CONCLUSION

The study revealed that the patients exhibited proprioceptive disturbances in both lower limbs at postoperative month 1. The proprioceptive function gradually improved over time, with a gradual decrease in donor site complications.

PIEZO ion channels: force sensors of the interoceptive nervous system

Many organs are designed to move: the heart pumps each second, the gastrointestinal tract squeezes and churns to digest food, and we contract and relax skeletal muscles to move our bodies. Sensory neurons of the peripheral nervous system detect signals from bodily tissues, including the forces generated by these movements, to control physiology. The processing of these internal signals is called interoception, but this is a broad term that includes a wide variety of both chemical and mechanical sensory processes. Mechanical senses are understudied, but rapid progress has been made in the last decade, thanks in part to the discovery of the mechanosensory PIEZO ion channels (Coste et al., 2010). The role of these mechanosensors within the interoceptive nervous system is the focus of this review. In defining the transduction molecules that govern mechanical interoception, we will have a better grasp of how these signals drive physiology.

Reduced shoulder proprioception due to fatigue after repeated handball throws and evaluation of test-retest reliability of a clinical shoulder joint position test

Background

Proprioception is vital for motor control and can be disturbed, for example, due to fatigue or injury. Clinical feasible, reliable and valid tests of shoulder proprioception are warranted. The aim was to investigate the effects of local fatigue on shoulder proprioception and the reliability of a feasible joint position sense test using an experimental repeated measures design.

Method

Forty participants repeated a shoulder joint position sense test to assess test-retest reliability. The test was then utilized on a subgroup of handball players who were subjected to five bouts of a repeated throwing task with the dominant hand. The effect of local fatigue was investigated by comparing the fatigued with the non-fatigued shoulder.

Results

There was a significant interaction for the arm × bout (p = 0.028, ηp2 = 0.20) and a significant effect for the arm (p = 0.034, ηp2 = 0.35) with a significant decrease in joint position sense for the throwing arm compared to the non-throwing arm. The intraclass correlation coefficient was 0.78 (95% CI = [0.57; 0.89]). The standard error of measurement between trials was 0.70° (range: 0.57°-0.90°).

Discussion

The results indicate that repeated throwing to fatigue disturbs shoulder joint position sense. Assessment with the modified test showed acceptable reliability and can be a valuable assessment tool in the clinic.

The Effect of Stroboscopic Vision Training on Blind-folded Straight-line Walking

Stroboscopic vision training has shown to improve visual-motor control and dynamic visual acuity in sport performance; however, no studies have considered using this training to enhance kinesthetic awareness during walking, applicable to high fall-risk populations.

Purpose

The purpose of this study was to assess the effect of stroboscopic vision training on blind-folded straight-line walking.

Methods

Thirty-seven college-aged healthy participants (age: 20.14 ± 1.23 years; females: N = 32, males: N = 5) completed this study. In this pre-posttest quasi-experimental investigation, participants with no epileptic or balance disorder history completed a four-week progressive stroboscopic vision training protocol. To assess sensorimotor feedback participants were instructed to walk a 27.5 m straight line while blindfolded. PRE and POST blind-folded straight line walk tests were completed and deviations from endpoint were measured. A paired-samples t-test was used to analyze the calculated deviation angles.

Results

Significant difference was noted from PRE (14.48 ± 5.95) to POST (11.60 ± 6.78) deviation angles (t(36) = 2.71, p = 0.01).

Conclusions

This is the first study to examine the effects of stroboscopic training on a vision restricted walking task, which demands feedback re-weighting. These findings may be valuable for clinical settings or performance where reliance on non-visual systems may be beneficial.

Proprioceptive innervation of the human lips

The objective of this study was to analyze the proprioceptive innervation of human lips, especially of the orbicularis oris muscle, since it is classically accepted that facial muscles lack typical proprioceptors, that is, muscle spindles, but recently this has been doubted. Upper and lower human lips (n = 5) from non-embalmed frozen cadavers were immunostained for detection of S100 protein (to identify nerves and sensory nerve formations), myosin heavy chain (to label muscle fibers within muscle spindles), and the mechano-gated ion channel PIEZO2. No muscle spindles were found, but there was a high density of sensory nerve formations, which were morphologically heterogeneous, and in some cases resemble Ruffini-like and Pacinian sensory corpuscles. The axons of these sensory formations displayed immunoreactivity for PIEZO2. Human lip muscles lack typical proprioceptors but possess a dense sensory innervation which can serve the lip proprioception.

Distribution of nerve endings in human thumb interphalangeal joint

This study aims to quantitatively analyze the distribution of encapsulated nerve endings in the human thumb interphalangeal (IP) joint capsule. There are three types of nerve endings. Type-I nerve endings (Ruffini-like ending) sense pressure changes, Type II (Pacini-like ending) nerve endings contribute to the kinesthetic sense, and Type III (Golgi-like ending) nerve ending provides proprioceptive information. We dissected five right thumbs IP joints from freshly frozen cadavers (5 men). The mean age of the cadavers at the time of death was 63.4 years (55-73). Sections were stained with the hematoxylin-eosin and antiprotein gene product 9.5 (PGP9.5) to identify encapsulated nerve endings. Transverse sections were cut and divided into volar, dorsal, and then into two equal parts, proximal and distal. The density of encapsulated nerve endings compared to volar versus dorsal and proximal versus distal regions was examined. This study showed that type 1 nerve endings were more common in the distal parts of the IP joint (p < 0.05). Also, type 3 nerve endings were observed in the thumb IP joint. There was no difference between regions in type II and type III nerve endings. The current study demonstrates that the distribution of encapsulated nerve endings in the IP joint is different from the PIP and DIP joints. Moreover, further studies are required to understand the thumb's physiology.

Efficacy of Isometric Exercises and Somatosensory Training for Pain, Proprioception, and Balance in Runners with Patellofemoral Pain Syndrome

Background A significant cause of knee pain is patellofemoral pain syndrome (PFPS). Young adults are the most common population to be impacted, and this condition appears to affect both sexes. Patellofemoral joint (PFJ) compression, which is felt around the patella during any physical or athletic activity, usually causes patients to experience pain in the anterior part of the knee. Physiotherapy is essential for patients suffering from this illness, as it can improve their everyday activities and ability to return to their sport. Methodology The study's main goal was to evaluate the effectiveness of somatosensory training and isometric exercises for pain, proprioception, and balance in runners with PFPS. Before- and after-test approaches were used in the investigation. Eighty-five people made up the study, with the inclusion and exclusion criteria used to determine eligibility. Isometric exercises and somatosensory training were given to every individual; the group was not randomly assigned. The patient's diagnosis was made using the patellar grind test. Participants received 30-45 minutes of isometric exercises and 15 minutes of somatosensory training every four days. The visual analog scale, joint position sense test, and Y-balance test were taken as outcome measures to measure PFPS before and after the intervention. Results The result revealed significant (p=0.0001) improvement in PFPS following the intervention. Both the isometric exercises and somatosensory training were found to be significant in reducing the intensity of the pain and improving the proprioception and balance of the individuals. Conclusion Both treatment approaches were beneficial in lowering pain in the joints, developing balance, and helping the patient perceive the position of the joint. Individuals can use both therapy methods to improve their running abilities, and they should become ingrained in daily practice.

Kinematic changes of the trunk and lower limbs during voluntary lateral sway postural control in adults with low back pain

Introduction: Voluntary lateral weight shifting is essential for gait initiation. However, kinematic changes during voluntary lateral weight shifting remain unknown in people with low back pain (LBP). This study aims to explore the differences in kinematics and muscle activation when performing a voluntary lateral weight shifting task between patients with LBP and asymptomatic controls without pain. Methods: Twenty-eight participants volunteered in this study (14 in both the LBP group and the control group). The Sway Discrimination Apparatus (SwayDA) was used to generate a postural sway control task, mimicking lateral weight shifting movements when initiating gait. Kinematic parameters, including range of motion (ROM) and standard deviation of ROM (Std-ROM) of the lumbar spine, pelvis, and lower limb joints, were recorded using a motion capture system during lateral weight shifting. The electroactivity of the trunk and lower limb muscles was measured through surface electromyography using root mean square (RMS). The significant level was 0.05. An independent t-test was employed to compare kinematic parameters, and muscle activation between the LBP group and the control group. A paired-sample t-test, adjusted with Bonferroni correction (significant level of 0.025), was utilized to examine differences between the ipsilateral weight shifting towards side (dominant side) and the contralateral side. Results: The results of kinematic parameters showed significantly decreased ROM and std-ROM of the ipsilateral hip in the transverse plane (tROM = -2.059, p = 0.050; tstd-ROM = -2.670, p = 0.013), as well as decreased ROM of the ipsilateral knee in the coronal plane (t = -2.148, p = 0.042), in the LBP group compared to the control group. For the asymptomatic controls, significantly larger ROM and ROM-std were observed in the hip and knee joints on the ipsilateral side in contrast to the contralateral side (3.287 ≤ t ≤ 4.500, 0.001 ≤ p≤ 0.006), but no significant differences were found between the two sides in the LBP group. In addition, the LBP group showed significantly lower RMS of the biceps femoris than the control group (tRMS = -2.186, p = 0.044). Discussion: Patients with LBP showed a conservative postural control pattern, characterized by reduced ROM of ipsilateral joints and diminished activation of the biceps femoris. These findings suggested the importance of voluntary postural control assessment and intervention to maximize recovery.

Corrigendum: Protocol for a prospective multicenter longitudinal randomized controlled trial (CALIN) of sensory-tonic stimulation to foster parent child interactions and social cognition in very premature infants

[This corrects the article DOI: 10.3389/fped.2022.913396.].

Dancers Show More Accurate Trunk-Pelvic Joint Angle Reproduction While Wearing a Jacket Augmented With Elastic Bands

Purpose: The Backalast® compression jacket is intended to improve posture and proprioception of the trunk and shoulder girdle for dancers and dance students during dance training by way of elastic bands in the rear of the garment (which include bands enclosing the inferior thorax). This study was intended to investigate whether there is evidence to support those objectives. Materials and Methods: Fifteen dance students participated (4 male, mean age 19.9 ± 1.4 years old). The dependent variables of trunk-pelvis angle and proximity of trunk axis to global vertical for each participant were measured using optical motion capture before and after the completion of a series of trunk movements. The Helen Hayes model, which we used to represent the trunk, includes the shoulder girdles as part of the trunk. We compared the effect of the type of garment (Backalast® or control compression shirt) worn upon the 2 dependent variables, within-subject with paired t-tests. The order of whether Backalast® or control compression shirt was worn first was alternated between participants. Results: The pre/posttest difference in trunk proprioception as represented by the construct of ability to reproduce trunk-pelvis angle wearing the Backalast® was 0.8° ± 0.8°, but for the control shirt, the difference was 1.8° ± 1.4°, P = .03. The difference between garments in vertical trunk alignment, measured after the series of trunk movements, was not significant. Conclusion: Our findings suggest that the Backalast® can help enhance trunk proprioception when compared to the control compression shirt, although it did not change the angle at which the participants' held their trunks while standing erect (proximity to global vertical).

Efficacy of scapulothoracic exercises on proprioception and postural stability in cranio-cervico-mandibular malalignment: A randomized, double-blind, controlled trial

BACKGROUND

Cranio-cervico-mandibular (CCM) malalignment is associated with forward head posture (FHP) and temporomandibular joint (TMJ) disorders and affects masticatory muscles.

OBJECTIVE

This randomized, double-blind controlled trial aimed to compare the efficacy of scapula-thoracic (ST) exercises on temporomandibular and cervical joint position sense and postural stability in individuals with CCM malalignment.

METHODS

Fourty-nine participants with CCM malalignment were randomly assigned to the ST exercise group (STEG, n= 24) or the control group (CG, n= 25). STEG included progressive strengthening, proprioceptive, and stabilization exercises. All participants were assessed before treatment, at the end of the 8th week treatment period and at the 12th week post-treatment follow-up. Cranio-vertebral angle measurement, Fonseca's Questionnaire, Helkimo Clinical Dysfunction Index, TMJ position test, cervical joint position error test and postural stability assessment were used.

RESULTS

The TMJ and cervical joint position sense, total sway degree, area gap percentage, sway velocity and antero-posterior body sway results showed significant improvement in the STEG compared to the CG (p< 0.05), however medio-lateral body sway did not differ between groups (p> 0.05).

CONCLUSIONS

Postural stability, TMJ and cervical joint position sense appear to be affected in individuals with CCM malalignment. Our results showed that an exercise program including ST stabilization, proprioception and strengthening of the scapular muscles may be effective in the management of CCM malalignment and will allow clinicians to plan holistic treatment.

The Significance of Proprioceptive Training in the Post-Operative Rehabilitation of Patients Undergoing Achilles Tendon Reconstruction

In the human anatomy, the Achilles tendon (AT) is the strongest and largest tendon. Also, it ruptures the most often. Because it impairs the patient's ability to function adequately, a ruptured AT injury is a serious clinical issue. Reconstruction of the tendon through surgical intervention is the preferred approach to treatment in the case of tendon rupture. Establishing an effective post-operative rehabilitation regimen that mostly consists of functional physiotherapy measures is crucial in the management of AT rupture. In this report, we have presented the case of an AT reconstruction patient who complained of pain in the ankle region, reduced strength and range of the ankle joint, and loss of proprioception. The tailor-made physiotherapy protocol was incorporated, which included strengthening exercises, proprioceptive retraining, cryotherapy, and ambulatory training, which were found to be effective in facilitating early functional recovery.

Rapid Online Corrections for Proprioceptive and Visual Perturbations Recruit Similar Circuits in Primary Motor Cortex

An important aspect of motor function is our ability to rapidly generate goal-directed corrections for disturbances to the limb or behavioral goal. The primary motor cortex (M1) is a key region involved in processing feedback for rapid motor corrections, yet we know little about how M1 circuits are recruited by different sources of sensory feedback to make rapid corrections. We trained two male monkeys (Macaca mulatta) to make goal-directed reaches and on random trials introduced different sensory errors by either jumping the visual location of the goal (goal jump), jumping the visual location of the hand (cursor jump), or applying a mechanical load to displace the hand (proprioceptive feedback). Sensory perturbations evoked a broad response in M1 with ∼73% of neurons (n = 257) responding to at least one of the sensory perturbations. Feedback responses were also similar as response ranges between the goal and cursor jumps were highly correlated (range of r = [0.91, 0.97]) as were the response ranges between the mechanical loads and the visual perturbations (range of r = [0.68, 0.86]). Lastly, we identified the neural subspace each perturbation response resided in and found a strong overlap between the two visual perturbations (range of overlap index, 0.73-0.89) and between the mechanical loads and visual perturbations (range of overlap index, 0.36-0.47) indicating each perturbation evoked similar structure of activity at the population level. Collectively, our results indicate rapid responses to errors from different sensory sources target similar overlapping circuits in M1.

Comparing the efficacy of therapeutic Thai acupressure on plantar acupoints and laser cane therapy on freezing of gait in Parkinson's disease: a randomized non-inferiority trial

Background

ON-freezing of gait (ON-FOG) in Parkinson's disease (PD), often resistant to medication, is linked to sensory deficits and proprioceptive impairment, and results in falls and reduced life quality. While visual cues from a laser cane (LC), which rapidly accesses the motor cortex, are commonly used to compensate for proprioceptive impairment, increased visual reliance may be affected by disease progression. Emerging evidence suggests that modulation of peripheral sensory processing may alleviate ON-FOG, and therapeutic Thai acupressure (TTA) may be a solution. This study aims to evaluate the effect of TTA in alleviating ON-FOG and compare its effectiveness to LC in patients with PD.

Methods

This open-label, non-inferiority trial randomized 90 PD patients with ON-FOG equally into three arms: TTA for plantar nerve stimulation for 96 s, LC for visual cueing, and sham control (SC). Stride length was the primary non-inferiority endpoint [non-inferiority margin: lower limit of 95% confidence interval (CI) above -10 cm in mean change difference in pre- and immediately post-intervention in TTA versus LC (one-sided)]. Secondary outcomes included FOG episodes, double support time, velocity, cadence, step length, timed up and go (TUG) test, and visual analog scale (VAS) score.

Results

TTA showed non-inferiority to LC in stride length (mean = -0.7 cm; 95% CI: -6.55; 5.15) (one-sided). The improvements with TTA and LC versus SC were comparable between (mean = 13.11 cm; 95% CI: 7.26; 18.96) and (mean = 13.8 cm; 95% CI: 7.96; 19.65) (one-sided). Secondary outcomes favored TTA and LC over SC with improved FOG, velocity, step length, and VAS scores, while only TTA resulted in improved double support time, cadence, and TUG test results. No complications occurred.

Conclusion

The efficacy of TTA, which improves stride length, is non-inferior to that of LC and consequently alleviates FOG comparable to LC. TTA might enhance proprioceptive function and reduce visual dependence. Therefore, TTA, characterized by its non-invasive, simple, and safe techniques, is a potential non-pharmacological alternative for ON-FOG treatment and might enhance overall quality of life. However, further research into the mechanism, efficacy, and utilization of TTA is essential.

Clinical trial registration

https://www.thaiclinicaltrials.org/show/TCTR20200317001, identifier TCTR20200317001.

Effects of cervical stabilization with visual feedback on craniovertebral angle and proprioception for the subjects with forward head posture

BACKGROUND

This study aimed to identify the effect of cervical stabilization exercise with visual feedback on the craniovertebral angle and proprioception in subjects with forward head posture.

METHODS

Thirty healthy adults were recruited in the study. Participants were randomly assigned to the stabilization exercise with visual feedback (SE-VF) group (N = 15) or stabilization exercise group (N = 15). The SE-VF group performed cervical stabilization exercise while sitting on a chair without a backrest and checking their side profile in real-time via a monitor 3-m away. The stabilization exercise group performed the same cervical stabilization exercise as the SE-VF group but without visual feedback. Craniovertebral angle (CVA) was measured to quantify forward head posture, and the proprioception of the subjects was evaluated.

RESULTS

There was a significant interaction between group and time in CVA and proprioception (P < .05). Additionally, there was no significant difference pre-intervention between the groups (P > .05); however, there was a significant difference post-intervention (P < .05) in CVA and proprioception.

CONCLUSION

The findings of this study showed that the cervical stabilization exercise with visual feedback was effective for the proprioception of subjects. Moreover, the results suggest that visual feedback is effective in cervical stabilization exercise.

Evaluation of Reliability of the Luna EMG Rehabilitation Robot to Assess Proprioception in the Upper Limbs in 102 Healthy Young Adults

BACKGROUND Proprioception, the body's ability to perceive its own position and movement, is fundamental for motor control and coordination. Reliable assessment tools are essential, particularly for conditions affecting proprioceptive function. This study aimed to evaluate the external and internal compliance of the Luna EMG -multifunction robotic device in assessing proprioception. MATERIAL AND METHODS The study involved 102 healthy students (31 men and 71 women; mean age 22.2±1.46 years), assessing proprioception using the Luna EMG for the upper limbs. Two investigators conducted measurements, which were repeated after 2 weeks under identical conditions. RESULTS Based on the identified values of the interclass correlation coefficient (ICC) (ICC=0.969-0.997), which is a key measure of agreement between 2 assessments, the study shows a high agreement of measurements both between investigators (for right hand: P=0.3484 [Exam 1]; P=1.0000 [Exam 2]; for left hand: P=0.1092 [Exam 1]; P=0.7706 [Exam 2]) and between the examinations (for right hand: 0.1127 [Investigator 1]; 0.2113 [Investigator 2]; for left hand: P=0.0087 [Investigator 1]; P=0.1466 [Investigator 2]). The Bland-Altman analysis showed very small inter-rater deviations, approximately 0.05° in the first examination for the left side and 0.04° for the right side. The highest deviation between the examinations, amounting to 0.08°, was identified for the left side. CONCLUSIONS The study shows that the Luna EMG multifunction robotic device enables a reliable evaluation of upper limb proprioception. Measurements performed using this device show high internal and external consistency in the assessment of the proprioceptive senses of the upper limb in 102 healthy young adults.

Vibration-induced postural reactions: a scoping review on parameters and populations studied

Objective

Mechanical vibration is an effective way for externally activating Ia primary endings of the muscle spindles and skin mechanoreceptors. Despite its popularity in proprioception and postural control studies, there is still no review covering the wide variety of vibration parameters or locations used in studies. The main purpose of this scoping review was thus to give an overview of general vibration parameters and to identify, if available, the rationale for justifying methodological choices concerning vibration parameters.

Methods

Three databases (Pubmed, CINHAL, and SPORTDiscus) were searched from inception to July 2022. Included articles were to focus on the study of muscle spindles and skin mechanoreceptors vibration in humans and assess postural control. Following inclusion, data regarding demographic information, populations, vibration parameters and rationale were extracted and summarized.

Results

One hundred forty-seven articles were included, mostly targeting lower extremities (n = 137) and adults (n = 126). The parameters used varied widely but were most often around 80 Hz, at an amplitude of 1 mm for 10-20 s. Regarding rationales, nearly 50% of the studies did not include any, whereas those including one mainly cited the same two studies, without elaborating specifically on the parameter's choice.

Conclusion

This scoping review provided a comprehensive description of the population recruited and parameters used for vibration protocols in current studies with humans. Despite many studies, there remain important gaps of knowledge that needs to be filled, especially for vibration amplitude and duration parameters in various populations.

Voluntary postural sway control and mobility in adults with low back pain

Introduction

Low back pain (LBP) is associated with altered somatosensory perception, which is involved in both involuntary and voluntary control of posture. Currently, there is a lack of methods and tools for assessing somatosensory acuity in patients with LBP. The purpose of this study was (1) to assess the reliability of the sway discrimination apparatus (SwayDA) (2) to evaluate the differences in somatosensory acuity between patients with LBP and pain-free individuals, and (3) to examine relationships between somatosensory acuity, severity of LBP, and mobility in patients with LBP.

Methods

Twenty participants (10 patients with LBP and 10 matched asymptomatic controls) were recruited in a test-retest reliability test. Another 56 participants were recruited for this study with 28 individuals presenting with LBP and a further twenty-eight being asymptomatic. The SwayDA was custom-built to measure somatosensory perception during voluntary anterior-posterior (SwayDA-AP), medial-lateral to the dominant side (SwayDA-ML-D), and non-dominant side (SwayDA-ML-ND) postural sway control. Participants also completed mobility tests, including 10 times and 1-min sit-to-stand tests (10-STS, 1 m-STS). The area under the receiver operating characteristic curve (AUC) was calculated to quantify somatosensory acuity in discriminating different voluntary postural sway extents.

Results

The ICC (2.1) for the SwayDA-AP, SwayDA-ML-D, and SwayDA-ML-ND were 0.741, 0.717, and 0.805 with MDC95 0.071, 0.043, and 0.050. Patients with LBP demonstrated significantly lower SwayDA scores (tSwayDA-AP = -2.142, p = 0.037; tSwayDA-ML-D = -2.266, p = 0.027) than asymptomatic controls. The AUC values of the SwayDA-AP test were significantly correlated with ODI (rSwayDA-AP-ODI = -0.391, p = 0.039). Performances on the 1 m-STS and the 10-STS were significantly correlated with the AUC scores from all the SwayDA tests (-0.513 ≤ r ≤ 0.441, all p < 0.05).

Discussion

The SwayDA tests evaluated showed acceptable reliability in assessing somatosensory acuity during voluntary postural sway. Somatosensory acuity was diminished in patients with LBP compared to asymptomatic controls. In patients with LBP, lower somatosensory acuity was associated with increased LBP-related disability. Future research could focus on investigating the factors contributing to the decreased somatosensory perception and mobility in individuals with LBP.

Reliability and validity of the trunk position sense and modified functional reach tests in individuals after stroke

The psychometric qualities of the proprioception and dynamic trunk control tests have rarely been studied in individuals after stroke.

OBJECTIVE

To investigate the reliability and validity of the Trunk Position Sense Test (TPS) and Modified Functional Reach Test (MFRT) in persons after stroke.

METHODS

Thirty-two participants were included. The TPS and MFRT were assessed by two physiotherapists during a first session. After resting, a second session was conducted. The intraclass correlation coefficient (ICC) was calculated to assess the test-retest (ICC3,k) and inter-rater reliability (ICC2,k). Pearson correlations coefficients were calculated between TPS/MFRT performances and clinical tests (trunk strength, Timed Up and Go and Balance Assessment in Sitting and Standing Positions - BASSP).

RESULTS

The TPS inter-rater reliability was good for vertical error (ICC = 0.75 [0.50-0.88]) while it was moderate for horizontal error (ICC = 0.48 [0.10-0.75]) as well as for test-retest reliability (0.39 ≤ ICC ≤ 0.59). As for the MFRT, inter-rater (0.76 ≤ ICC ≤ 0.90) and test-retest reliability (0.71 ≤ ICC ≤ 0.91) were good to excellent for anterior, paretic et non-paretic displacements. Horizontal errors for the TPS (-0.26 ≤ r ≤ -0.36) and anterior MFRT (0.38 ≤ r ≤ 0.64) values correlated moderately with trunk strength.

CONCLUSION

The MFRT is a reliable test for persons after stroke with trunk control impairments. The TPS does not appear to be relevant for post-stroke individuals. This can be explained by the fact that its procedure is not easily applied for individuals after stroke - who may have significant motor and cognitive impairments.

Immediate effects of visuomotor tracking with the head on cervical sensorimotor function and pain in chronic neck pain patients

BACKGROUND

Working in awkward and sustained postures is, besides psychosocial risk factors, the most reported physical risk factor for neck pain. Accurate proprioception is fundamental to correcting awkward head-to-trunk positions, but impaired proprioceptive performance has been found in patients with chronic neck pain.

OBJECTIVE

The aim was to compare the effectiveness of two different interventions in a workplace set-up on sensorimotor performance and pain sensitivity in people with chronic neck pain.

METHODS

A total of 25 patients with chronic neck pain participated in this double-blind study. Patients were randomly allocated to the visuomotor tracking task group or the video group (watching a massage video, imagining themselves being massaged). The primary outcomes were cervical joint position sense acuity and pressure pain threshold of the cervical spine, evaluated by a blinded assessor.

RESULTS

There were significant time by group interactions for cervical joint position sense acuity (F1;23: 4.38; p= 0.048) and pressure pain threshold (F1;23: 5.78; p= 0.025), with the tracking task group being more accurate in cervical joint position sense testing and less pain sensitive for pressure pain threshold.

CONCLUSIONS

The visuomotor tracking task improves cervical joint position sense acuity and reduces pressure pain threshold immediately after intervention in people with chronic neck pain.

The mechanosensitive ion channel ASIC2 mediates both proprioceptive sensing and spinal alignment

By translating mechanical forces into molecular signals, proprioceptive neurons provide the CNS with information on muscle length and tension, which is necessary to control posture and movement. However, the identities of the molecular players that mediate proprioceptive sensing are largely unknown. Here, we confirm the expression of the mechanosensitive ion channel ASIC2 in proprioceptive sensory neurons. By combining in vivo proprioception-related functional tests with ex vivo electrophysiological analyses of muscle spindles, we showed that mice lacking Asic2 display impairments in muscle spindle responses to stretch and motor coordination tasks. Finally, analysis of skeletons of Asic2 loss-of-function mice revealed a specific effect on spinal alignment. Overall, we identify ASIC2 as a key component in proprioceptive sensing and a regulator of spine alignment.

Genetic exploration of roles of acid-sensing ion channel subtypes in neurosensory mechanotransduction including proprioception

Although acid-sensing ion channels (ASICs) are proton-gated ion channels responsible for sensing tissue acidosis, accumulating evidence has shown that ASICs are also involved in neurosensory mechanotransduction. However, in contrast to Piezo ion channels, evidence of ASICs as mechanically gated ion channels has not been found using conventional mechanoclamp approaches. Instead, ASICs are involved in the tether model of mechanotransduction, with the channels gated via tethering elements of extracellular matrix and intracellular cytoskeletons. Methods using substrate deformation-driven neurite stretch and micropipette-guided ultrasound were developed to reveal the roles of ASIC3 and ASIC1a, respectively. Here we summarize the evidence supporting the roles of ASICs in neurosensory mechanotransduction in knockout mouse models of ASIC subtypes and provide insight to further probe their roles in proprioception.

Chronic Ankle Instability and Neuromuscular Performance in Prerecruitment Infantry Soldiers

CONTEXT

Ankle instability can describe various impairments, including perceived instability (PI), mechanical instability (MI), and recurrent sprains (RSs), alone or combined.

OBJECTIVE

To examine the prevalence of 8 ankle impairment subgroups and their effect on neuromuscular performance in prerecruitment combat soldiers.

DESIGN

Cross-sectional study.

SETTING

Military infantry basic training base.

PATIENTS OR OTHER PARTICIPANTS

A total of 364 infantry male combat soldiers entering basic training (aged 18-21 years).

MAIN OUTCOME MEASURE(S)

Participants were assessed for PI (via the Cumberland Ankle Instability Tool), MI (using the Anterior Drawer Test and Medial Talar Tilt Test), and RSs (based on history) of their dominant and nondominant legs. Injuries were categorized in 8 subgroups: PI, RSs, PI + RSs, MI, PI + MI, MI + RSs, PI + MI + RSs, and none. Participants were screened for neuromuscular performance (dynamic postural balance, proprioceptive ability, hopping agility, and triceps surae muscle strength) during the first week of military basic training.

RESULTS

For the dominant and nondominant legs, RSs were reported by 18.4% (n = 67) and 20.3% (n = 74) of the participants, respectively; PI was reported by 27.1% (n = 99) and 28.5% (n = 104) of the participants, respectively; and MI was seen in 9.9% (n = 36) and 8.5% (n = 31) of the participants, respectively. A 1-way analysis of variance showed differences in the mean proprioceptive ability scores (assessed using the Active Movement Extent Discrimination Apparatus) of all subgroups with impairments in both the dominant and nondominant legs (F = 6.943, η2 = 0.081, P < .001 and F = 7.871, η2 = 0.091, P < .001, respectively). Finally, differences were found in the mean muscle strength of subgroups with impairment in the nondominant leg (F = 4.884, η2 = 0.056, P = .001).

CONCLUSIONS

A high prevalence of ankle impairments was identified among participants who exhibited reduced abilities in most neuromuscular assessments compared with those who did not have impairments. Moreover, participants with 1 impairment (PI, MI, or RSs) exhibited different neuromuscular performance deficits than those with >1 impairment.

Baseline GABA+ levels in areas associated with sensorimotor control predict initial and long-term motor learning progress

Synaptic plasticity relies on the balance between excitation and inhibition in the brain. As the primary inhibitory and excitatory neurotransmitters, gamma-aminobutyric acid (GABA) and glutamate (Glu), play critical roles in synaptic plasticity and learning. However, the role of these neurometabolites in motor learning is still unclear. Furthermore, it remains to be investigated which neurometabolite levels from the regions composing the sensorimotor network predict future learning outcome. Here, we studied the role of baseline neurometabolite levels in four task-related brain areas during different stages of motor skill learning under two different feedback (FB) conditions. Fifty-one healthy participants were trained on a bimanual motor task over 5 days while receiving either concurrent augmented visual FB (CA-VFB group, N = 25) or terminal intrinsic visual FB (TA-VFB group, N = 26) of their performance. Additionally, MRS-measured baseline GABA+ (GABA + macromolecules) and Glx (Glu + glutamine) levels were measured in the primary motor cortex (M1), primary somatosensory cortex (S1), dorsolateral prefrontal cortex (DLPFC), and medial temporal cortex (MT/V5). Behaviorally, our results revealed that the CA-VFB group outperformed the TA-VFB group during task performance in the presence of augmented VFB, while the TA-VFB group outperformed the CA-VFB group in the absence of augmented FB. Moreover, baseline M1 GABA+ levels positively predicted and DLPFC GABA+ levels negatively predicted both initial and long-term motor learning progress in the TA-VFB group. In contrast, baseline S1 GABA+ levels positively predicted initial and long-term motor learning progress in the CA-VFB group. Glx levels did not predict learning progress. Together, these findings suggest that baseline GABA+ levels predict motor learning capability, yet depending on the FB training conditions afforded to the participants.

Joint position sense error in the hip and knee without reference to the joint angle

BACKGROUND

Joint position reproduction measures the angle acuity of reference angle reproduction using an indicator angle. However, reference angles are often not available.

OBJECTIVE

This study aimed to examine joint position sense at three different targeted joint angles, which were estimated from the maximum range of motion (maxROM) without a reference angle at each targeted joint angle.

METHODS

The maxROM was measured in straight leg raise (SLR) and active knee extension (AKE) positions. In both positions, a targeted joint angle at 75% of the maxROM was assessed first, followed by that at 50% and 25% of the maxROM. A one-sample t-test was used to analyze differences between the targeted and reproduced angles in both positions.

RESULTS

All reproduced angles significantly differed from the targeted angle in both SLR and AKE positions except for the reproduced angle measured at 75% maxROM. Overall, position errors in the AKE position were higher than those in the SLR position.

CONCLUSIONS

Estimating the angle based on the maxROM without a matched reference angle may lead to significant discrepancies in comparison with the targeted joint angle. In clinical settings, if accurate reproduction of motions is required to improve proprioception, providing a reference angle might be helpful.

Afferents to Action: Cortical Proprioceptive Processing Assessed with Corticokinematic Coherence Specifically Relates to Gross Motor Skills

Voluntary motor control is thought to be predicated on the ability to efficiently integrate and process somatosensory afferent information. However, current approaches in the field of motor control have not factored in objective markers of how the brain tracks incoming somatosensory information. Here, we asked whether motor performance relates to such markers obtained with an analysis of the coupling between peripheral kinematics and cortical oscillations during continuous movements, best known as corticokinematic coherence (CKC). Motor performance was evaluated by measuring both gross and fine motor skills using the Box and Blocks Test (BBT) and the Purdue Pegboard Test (PPT), respectively, and with a biomechanics measure of coordination. A total of 61 participants completed the BBT, while equipped with electroencephalography and electromyography, and the PPT. We evaluated CKC, from the signals collected during the BBT, as the coherence between movement rhythmicity and brain activity, and coordination as the cross-correlation between muscle activity. CKC at movements' first harmonic was positively associated with BBT scores (r = 0.41, p = 0.001), and alone showed no relationship with PPT scores (r = 0.07, p = 0.60), but in synergy with BBT scores, participants with lower PPT scores had higher CKC than expected based on their BBT score. Coordination was not associated with motor performance or CKC (p > 0.05). These findings demonstrate that cortical somatosensory processing in the form of strengthened brain-peripheral coupling is specifically associated with better gross motor skills and thus may be considered as a valuable addition to classical tests of proprioception acuity.

Knee movements cause changes in the firing behaviour of muscle spindles located within the mono-articular ankle extensor soleus in the rat

We recently showed that within an intact muscle compartment, changing the length of one muscle affects the firing behaviour of muscle spindles located within a neighbouring muscle. The conditions tested, however, involved muscle lengths and relative positions that were beyond physiological ranges. The aim of the present study was to investigate the effects of simulated knee movements on the firing behaviour of muscle spindles located within rat soleus (SO) muscle. Firing from single muscle spindle afferents in SO was measured intra-axonally for different lengths (static) and during lengthening (dynamic) of the lateral gastrocnemius and plantaris muscles. Also, the location of the spindle within the muscle was assessed. Changing the length of synergistic ankle plantar flexors (simulating different static knee positions, between 45 and 130°) affected the force threshold, but not the length threshold, of SO muscle spindles. The effects on type II afferents were substantially (four times) higher than those on type IA afferents. Triangular stretch-shortening of synergistic muscles (simulating dynamic knee joint rotations of 15°) caused sudden changes in the firing rate of SO type IA and II afferents. Lengthening decreased and shortening increased the firing rate, independent of spindle location. This supports our prediction that the major point of application of forces exerted by connections between adjacent muscles is at the distal end of SO. We conclude that muscle spindles provide the CNS with information about the condition of adjacent joints that the muscle does not span.

Attenuation of muscle spindle firing with artificially increased series compliance during stretch of relaxed muscle

Muscle spindles relay vital mechanosensory information for movement and posture, but muscle spindle feedback is coupled to skeletal motion by a compliant tendon. Little is known about the effects of tendon compliance on muscle spindle feedback during movement, and the complex firing of muscle spindles makes these effects difficult to predict. Our goal was to investigate changes in muscle spindle firing using added series elastic elements (SEEs) to mimic a more compliant tendon, and to characterize the accompanying changes in firing with respect to muscle-tendon unit (MTU) and muscle fascicle displacements (recorded via sonomicrometry). Sinusoidal, ramp-and-hold and triangular stretches were analysed to examine potential changes in muscle spindle instantaneous firing rates (IFRs) in locomotor- and perturbation-like stretches as well as serial history dependence. Added SEEs effectively reduced overall MTU stiffness and generally reduced muscle spindle firing rates, but the effect differed across stretch types. During sinusoidal stretches, peak and mean firing rates were not reduced and IFR was best-correlated with fascicle velocity. During ramp stretches, SEEs reduced the initial burst, dynamic and static responses of the spindle. Notably, IFR was negatively related to fascicle displacement during the hold phase. During triangular stretches, SEEs reduced the mean IFR during the first and second stretches, affecting the serial history dependence of mean IFR. Overall, these results demonstrate that tendon compliance may attenuate muscle spindle feedback during movement, but these changes cannot be fully explained by reduced muscle fascicle length or velocity, or MTU force.

Limitations in utilization and prioritization of standardized somatosensory assessments after stroke: A cross-sectional survey of neurorehabilitation clinicians

BACKGROUND AND PURPOSE

Somatosensory impairments are common after stroke, but receive limited evaluation and intervention during neurorehabilitation, despite negatively impacting functional movement and recovery.

OBJECTIVES

Our objective was to understand the scope of somatosensory assessments used by clinicians in stroke rehabilitation, and barriers to increasing use in clinical practice.

METHODS

An electronic survey was distributed to clinicians (physical therapists, occupational therapists, physicians, and nurses) who assessed at least one individual with stroke in the past 6 months. The survey included questions on evaluation procedures, type, and use of somatosensory assessments, as well as barriers and facilitators in clinical practice.

RESULTS

Clinicians (N = 431) indicated greater familiarity with non-standardized assessments, and greater utilization compared to standardized assessments (p < 0.0001). Components of tactile sensation were the most commonly assessed modality of somatosensation (25%), while proprioception was rarely assessed (1%). Overall, assessments of motor function were prioritized over assessments of somatosensory function (p < 0.0001).

DISCUSSION

Respondents reported assessing somatosensation less frequently than motor function and demonstrated a reliance on rapid and coarse non-standardized assessments that ineffectively capture multi-modal somatosensory impairments, particularly for proprioceptive deficits common post-stroke. In general, clinicians were not familiar with standardized somatosensory assessments, and this knowledge gap likely contributes to lack of translation of these assessments into practice.

CONCLUSIONS

Clinicians utilize somatosensory assessments that inadequately capture the multi-modal nature of somatosensory impairments in stroke survivors. Addressing barriers to clinical translation has the potential to increase utilization of standardized assessments to improve the characterization of somatosensory deficits that inform clinical decision-making toward enhancing stroke rehabilitation outcomes.

Volitional muscle activation intensifies neuronal processing of proprioceptive afference in the primary sensorimotor cortex: an EEG study

Proprioception refers to the ability to perceive the position and movement of body segments in space. The cortical aspects of the proprioceptive afference from the body can be investigated using corticokinematic coherence (CKC). CKC accurately quantifies the degree of coupling between cortical activity and limb kinematics, especially if precise proprioceptive stimulation of evoked movements is used. However, there is no evidence on how volitional muscle activation during proprioceptive stimulation affects CKC strength. Twenty-five healthy volunteers (28.8 ± 7 yr, 11 females) participated in the experiment, which included electroencephalographic (EEG), electromyographic (EMG), and kinematic recordings. Ankle-joint rotations (2-Hz) were elicited through a movement actuator in two conditions: passive condition with relaxed ankle and active condition with constant 5-Nm plantar flexion exerted during the stimulation. In total, 6 min of data were recorded per condition. CKC strength was defined as the maximum coherence value among all the EEG channels at the 2-Hz movement frequency for each condition separately. Both conditions resulted in significant CKC peaking at the Cz electrode over the foot area of the primary sensorimotor (SM1) cortex. Stronger CKC was found for the active (0.13 ± 0.14) than the passive (0.03 ± 0.04) condition (P < 0.01). The results indicated that volitional activation of the muscles intensifies the neuronal proprioceptive processing in the SM1 cortex. This finding could be explained both by peripheral sensitization of the ankle joint proprioceptors and central modulation of the neuronal proprioceptive processing at the spinal and cortical levels.NEW & NOTEWORTHY The current study is the first to investigate the effect of volitional muscle activation on CKC-based assessment of cortical proprioception of the ankle joint. Results show that the motor efference intensifies the neuronal processing of proprioceptive afference of the ankle joint. This is a significant finding as it may extend the use of CKC method during active tasks to further evaluate the motor efference-proprioceptive afference relationship and the related adaptations to exercise, rehabilitation, and disease.

Resting state functional connectivity associated with impaired proprioception post-stroke

Deficits in proprioception, the knowledge of limb position and movement in the absence of vision, occur in ~50% of all strokes; however, our lack of knowledge of the neurological mechanisms of these deficits diminishes the effectiveness of rehabilitation and prolongs recovery. We performed resting-state functional magnetic resonance imaging (fMRI) on stroke patients to determine functional brain networks that exhibited changes in connectivity in association with proprioception deficits determined by a Kinarm robotic exoskeleton assessment. Thirty stroke participants were assessed for proprioceptive impairments using a Kinarm robot and underwent resting-state fMRI at 1 month post-stroke. Age-matched healthy control (n = 30) fMRI data were also examined and compared to stroke data in terms of the functional connectivity of brain regions associated with proprioception. Stroke patients exhibited reduced connectivity of the supplementary motor area and the supramarginal gyrus, relative to controls. Functional connectivity of these regions plus primary somatosensory cortex and parietal opercular area was significantly associated with proprioceptive function. The parietal lobe of the lesioned hemisphere is a significant node for proprioception after stroke. Assessment of functional connectivity of this region after stroke may assist with prognostication of recovery. This study also provides potential targets for therapeutic neurostimulation to aid in stroke recovery.

Proprioceptors in extraocular muscles

Proprioception is the sense that lets us perceive the location, movement and action of the body parts. The proprioceptive apparatus includes specialized sense organs (proprioceptors) which are embedded in the skeletal muscles. The eyeballs are moved by six pairs of eye muscles and binocular vision depends on fine-tuned coordination of the optical axes of both eyes. Although experimental studies indicate that the brain has access to eye position information, both classical proprioceptors (muscle spindles and Golgi tendon organ) are absent in the extraocular muscles of most mammalian species. This paradox of monitoring extraocular muscle activity in the absence of typical proprioceptors seemed to be resolved when a particular nerve specialization (the palisade ending) was detected in the extraocular muscles of mammals. In fact, for decades there was consensus that palisade endings were sensory structures that provide eye position information. The sensory function was called into question when recent studies revealed the molecular phenotype and the origin of palisade endings. Today we are faced with the fact that palisade endings exhibit sensory as well as motor features. This review aims to evaluate the literature on extraocular muscle proprioceptors and palisade endings and to reconsider current knowledge of their structure and function.

Acute effects of an isometric neck warm-up programme on neck performance characteristics and ultrasound-based morphology

OBJECTIVE

Athletic performance can be enhanced immediately after an isometric warm-up, a phenomenon termed post-activation performance enhancement (PAPE). While isometric warm-ups can improve lower extremity sprint and jump performance, neck-specific isometric warm-ups need development and validation for mild traumatic brain disorders and neck pain. This study examined acute effects of isometric warm-ups on neck performance and morphology.

METHODS

Arm 1: Twenty-six adults (13 M:13F) completed neck performance testing before and after a 10-minute neck isometric warm-up or stationary bike (sham) between two visits. Testing included visual-motor reaction time, peak force, rate of force development, force steadiness, and force replication/proprioception measured by a 6-axis load cell. An inclinometer assessed range-of-motion. Paired t-tests and two-way ANOVA examined effects of neck/bike warm-up and interaction effects, respectively. Arm 2: 24 adults (11 M:13F) completed ultrasound scans of cervical muscles: before 20-minute rest (sham), and before/after a 5-min neck isometric warm-up. Longus colli cross-sectional area and sternocleidomastoid/upper trapezius thickness and stiffness, and cervical extensors thickness was assessed. One-way ANOVA compared morphological values at sham, before, and after warm-up. Significance was set at p < 0.05.

RESULTS

Isometric neck warm-up increased rate of force development in flexion (p = 0.022), extension (p = 0.001-0.003), right lateral flexion (p = 0.004-0.032), left lateral flexion (p = 0.005-0.014), while peak force improved only in left lateral flexion (p = 0.032). Lateral flexion range-of-motion increased after neck warm-up (p = 0.003-0.026). Similarly, longus colli cross-sectional area (p = 0.016) and sternocleidomastoid thickness (p = 0.004) increased.

CONCLUSIONS

Increased neck performance characteristics and morphology are likely due to PAPE effects of isometric neck warm-up. For coaches and athletes, simple isometric contractions could be added to existing warm-ups to reduce prevalence, incidence, and severity of mild traumatic brain injuries and neck pain.

A physiologically enhanced muscle spindle model: using a Hill-type model for extrafusal fibers as template for intrafusal fibers

The muscle spindle is an essential proprioceptor, significantly involved in sensing limb position and movement. Although biological spindle models exist for years, the gold-standard for motor control in biomechanics are still sensors built of homogenized spindle output models due to their simpler combination with neuro-musculoskeletal models. Aiming to improve biomechanical simulations, this work establishes a more physiological model of the muscle spindle, aligned to the advantage of easy integration into large-scale musculoskeletal models. We implemented four variations of a spindle model in Matlab/Simulink®: the Mileusnic et al. (2006) model, Mileusnic model without mass, our enhanced Hill-type model, and our enhanced Hill-type model with parallel damping element (PDE). Different stretches in the intrafusal fibers were simulated in all model variations following the spindle afferent recorded in previous experiments in feline soleus muscle. Additionally, the enhanced Hill-type models had their parameters extensively optimized to match the experimental conditions, and the resulting model was validated against data from rats' triceps surae muscle. As result, the Mileusnic models present a better overall performance generating the afferent firings compared to the common data evaluated. However, the enhanced Hill-type model with PDE exhibits a more stable performance than the original Mileusnic model, at the same time that presents a well-tuned Hill-type model as muscle spindle fibers, and also accounts for real sarcomere force-length and force-velocity aspects. Finally, our activation dynamics is similar to the one applied to Hill-type model for extrafusal fibers, making our proposed model more easily integrated in multi-body simulations.

Appropriate Vestibular Stimulation in Children and Adolescents-A Prerequisite for Normal Cognitive, Motor Development and Bodily Homeostasis-A Review

The structural development of the vestibular part of the inner ear is completed by birth but its central connections continue to develop until adolescence. Their development is dependent on vestibular stimulation-vestibular experience. Studies have shown that vestibular function, modulated by experience and epigenetic factors, is not solely an instrument for body position regulation, navigation, and stabilization of the head and images but also influences cognition, emotion, the autonomous nervous system and hormones. To emphasize the importance of appropriate vestibular stimulation, we present a literature review of its effect on bodily homeostasis, cognition and emotion.

Elastic Resistance and Shoulder Movement Patterns: An Analysis of Reaching Tasks Based on Proprioception

This study departs from the conventional research on horizontal plane reach movements by examining human motor control strategies in vertical plane elastic load reach movements conducted without visual feedback. Here, participants performed shoulder presses with elastic resistances at low, moderate, and high intensities without access to visual information about their hand position, relying exclusively on proprioceptive feedback and synchronizing their movements with a metronome set at a 3 s interval. The results revealed consistent performance symmetry across different intensities in terms of the reach speed (p = 0.254-0.736), return speed (p = 0.205-0.882), and movement distance (p = 0.480-0.919). This discovery underscores the human capacity to uphold bilateral symmetry in movement execution when relying solely on proprioception. Furthermore, this study observed an asymmetric velocity profile where the reach duration remained consistent irrespective of the load (1.15 s), whereas the return duration increased with higher loads (1.39 s-1.45 s). These findings suggest that, in the absence of visual feedback, the asymmetric velocity profile does not result from the execution of the action but rather represents a deliberate deceleration post-reach aimed at achieving the target position as generated by the brain's internal model. These findings hold significant implications for interpreting rehabilitation approaches under settings devoid of visual feedback.