Timely Revisit of Proprioceptive Deficits in Adolescent Idiopathic Scoliosis: A Systematic Review and Meta-Analysis

STUDY DESIGN

Systematic review and meta-analysis.

OBJECTIVES

The present review aimed to summarize the evidence regarding differences in proprioception between children with and without adolescent idiopathic scoliosis (AIS).

METHODS

Seven electronic databases were searched from their inception to April 10, 2021. Articles were included if they involved: (1) AIS patients aged between 10 and 18 years, (2) measurements of proprioceptive abilities, and (3) comparisons with non-AIS controls. Animal studies, case reports, commentaries, conference proceedings, research protocols, and reviews were excluded. Two reviewers independently conducted literature screening, data extraction, risks of bias assessments, and quality of evidence evaluations. Relevant information was pooled for meta-analyses.

RESULTS

From 432 identified citations, 11 case-control studies comprising 1121 participants were included. The meta-analyses showed that AIS participants displayed proprioceptive deficits as compared to non-AIS controls. Moderate evidence supported that AIS participants showed significantly larger repositioning errors than healthy controls (pooled mean difference = 1.27 degrees, P < .01). Low evidence substantiated that AIS participants had significantly greater motion detection threshold (pooled mean difference = 1.60 degrees, P < .01) and abnormal somatosensory evoked potentials (pooled mean difference = .36 milliseconds, P = .01) than non-AIS counterparts.

CONCLUSIONS

Consistent findings revealed that proprioceptive deficits occurred in AIS patients. Further investigations on the causal relationship between AIS and proprioception, and the identification of the subgroup of AIS patients with proprioceptive deficit are needed.

Prospective comparative study between knee alignment-oriented static and dynamic balance exercise in patellofemoral pain syndrome patients with dynamic knee valgus

Exercise therapy has been reported as an effective treatment method for patellofemoral pain syndrome (PFPS). However, there is a lack of studies regarding the effectiveness of balance exercise in the treatment of patients with PFPS. This study aimed to prospectively compare changes in proprioception, neuromuscular control, knee muscle strength, and patient-reported outcomes between patients with PFPS treated with knee alignment-oriented static balance exercise (SBE) and dynamic balance exercise (DBE). The participants were divided into 2 groups: 17 knee alignment-oriented SBE group and 19 knee alignment-oriented DBE group. Proprioception was assessed by dynamic postural stability using postural stabilometry. Neuromuscular control and knee muscle strength were measured for acceleration time and peak torque in quadriceps muscle using an isokinetic device. Patient-reported outcomes were evaluated using a visual analog scale for pain and the Kujala Anterior Knee Pain Scale. There was greater improvement in dynamic postural stability (0.9 ± 0.3 vs 1.2 ± 0.5; 95% confidence interval [CI]: 0, 0.6; Effect size: 0.72; P = .021) and quadriceps AT (40.5 ± 14.3 vs 54.1 ± 16.9; 95% CI: 2.9, 24.2; Effect size: 0.86; P = .014) in the DBE group compared to the SBE group. Knee alignment-oriented DBE can be more effective in improving dynamic postural stability and quadriceps muscle reaction time compared with the knee alignment-oriented SBE in PFPS patients with dynamic knee valgus.

Mobile-Bearing Total Ankle Replacement In Vivo Kinematic Assessment: A Prospective Study Protocol

Total ankle prosthesis as a surgical solution in the case of end-stage osteoarthritis has seen a considerable increase in the last two decades. This study protocol arises from the need to understand the in vivo kinematics of mobile-bearing, flat tibial component total ankle replacement, evaluating the real range of motion and the reciprocal relationships between the components during normal motor tasks through the use of model-based radio-stereometric analysis (MB-RSA). In addition, pre- and post-operative evaluation of walking kinematics with inertial motion sensors, proprioception through a dedicated workstation, and clinical outcomes are discussed. We expect that based on our study protocol researchers will be able to improve future prosthetic designs and validate the setup of MB-RSA, as well as to understand "how an ankle prosthesis moves" once implanted in the patient.

Effects of a Novel Proprioceptive Rehabilitation Device on Shoulder Joint Position Sense, Pain and Function

Background and Objectives: Shoulder disorders are associated with pain, restricted range of motion and muscular strength, moderate disability and diminished proprioception. This study aimed to compare the effectiveness of an innovative technology-supported and a classical therapist-based proprioceptive training program in addition to conventional physiotherapy, on joint position sense (JPS), pain and function, in individuals with different musculoskeletal shoulder disorders, such as rotator cuff tear, subacromial impingement syndrome and superior labrum anterior and posterior tear. The innovative element of the proprioceptive training programme consists of the use of the Kinesimeter, a device created for both training and assessing shoulder JPS. Materials and Methods: The shoulder JPS test and the DASH outcome questionnaire were applied to fifty-five individuals (28 females, 27 males, mean age 56.31 ± 6.75), divided into three groups: 17 in the conventional physiotherapy group (control group); 19 in the conventional physiotherapy + classical proprioceptive training program group (CPT group); and 19 in the conventional physiotherapy + innovative proprioceptive training program group (KPT group). Assessments were performed before and after a four-week rehabilitation program, with five physiotherapy sessions per week. Results: When baseline and post-intervention results were compared, the value of the shoulder JPS and DASH outcome questionnaire improved significantly for the KPT and CPT groups (all p < 0.001). Both KPT and CPT groups showed statistically significant improvements in JPS, pain and function, compared to the control group which received no proprioceptive training (all p < 0.05). However, the KPT group showed no significant benefits compared to the CPT group. Conclusions: Our findings indicate that using the Kinesimeter device as a novel, innovative proprioceptive training tool has similar effects as the classical proprioceptive training programs among individuals with different non-operated musculoskeletal shoulder disorders such as: rotator cuff tear, subacromial impingement syndrome, and superior labrum anterior and posterior tear.

Proprioceptive art: How should it be defined, and why has it become so popular?

In recent years, there has been something of an explosion of interest in those artworks and installations that directly foreground the bodily senses. Often referred to as proprioceptive (or prop.) art, the question to be addressed in this narrative historical review is how it should be defined, and why has it become so popular? A contrast is drawn with examples of sculpture and/or tactile art. The entertainment/experiential element of such works cannot be denied, especially in an era where funding in the arts sector is so often linked to footfall. At the same time, however, a number of the works appear to be about little more than entertainment/amusement. One might wonder why such "edutainment" should be placed in the art gallery rather than, say, in a museum of science or illusion. Nevertheless, in the best cases, the foregrounding, or removal, of bodily sensations that proprioceptive artworks deliver can potentially help to connect people in an increasingly digital, online, mostly audiovisual, and hence in some sense disembodied contemporary existence. These issues are discussed in the context of the works of Carsten Höller, a prolific German installation and object artist.

In the back of your mind: Cortical mapping of paraspinal afferent inputs

Topographic organisation is a hallmark of vertebrate cortex architecture, characterised by ordered projections of the body's sensory surfaces onto brain systems. High-resolution functional magnetic resonance imaging (fMRI) has proven itself as a valuable tool to investigate the cortical landscape and its (mal-)adaptive plasticity with respect to various body part representations, in particular extremities such as the hand and fingers. Less is known, however, about the cortical representation of the human back. We therefore validated a novel, MRI-compatible method of mapping cortical representations of sensory afferents of the back, using vibrotactile stimulation at varying frequencies and paraspinal locations, in conjunction with fMRI. We expected high-frequency stimulation to be associated with differential neuronal activity in the primary somatosensory cortex (S1) compared with low-frequency stimulation and that somatosensory representations would differ across the thoracolumbar axis. We found significant differences between neural representations of high-frequency and low-frequency stimulation and between representations of thoracic and lumbar paraspinal locations, in several bilateral S1 sub-regions, and in regions of the primary motor cortex (M1). High-frequency stimulation preferentially activated Brodmann Area (BA) regions BA3a and BA4p, whereas low-frequency stimulation was more encoded in BA3b and BA4a. Moreover, we found clear topographic differences in S1 for representations of the upper and lower back during high-frequency stimulation. We present the first neurobiological validation of a method for establishing detailed cortical maps of the human back, which might serve as a novel tool to evaluate the pathological significance of neuroplastic changes in clinical conditions such as chronic low back pain.

The effects of close kinetic chain exercises on proprioception and physical activity level in pediatric patients with hemophilia

INTRODUCTION

Knee joint proprioception is affected, and lower extremity functioning declines over time in patients with hemophilia A.

AIM

To investigate the effects of a structured exercise programme consisting of the close kinetic chain (CKC) exercises on proprioception and physical activity level in pediatric patients with hemophilia.

METHODS

A total of 21 patients with hemophilia A who had at least one target knee joint were randomized into three groups: Study Group (SG, n = 7), Conventional Treatment Group (CTG, n = 7) and Control Group (CG, n = 7). The SG received a structured, lower limb-specific exercise protocol consisting of CKC exercises 2 days a week for 12 weeks, in addition to prophylactic treatment. The CTG received exercise training as described in the published literature. The CG continued to receive prophylactic treatment during the study period. Proprioception was measured using a digital goniometer before and after treatment in open and closed kinetic chain positions (CKCPs). The Five Times Sit to Stand (STS), Timed Up and Go (TUG) and Functional Independence Score in Hemophilia were used for the assessment of physical activity level.

RESULTS

A significant pre/post-treatment difference was found among the groups in proprioception (p = .001) and physical activity level (TUG p = .008, STS p = .001, FISH p = .006). Improvements in proprioception and physical activity level were greater in the SG compared to the other two groups (p < .05).

CONCLUSION

Compared to conventional exercise, the structured exercise protocol consisting of CKC exercise training produced improvements in proprioception and physical activity in patients with hemophilia A.

Impairments in trunk muscles performance and proprioception in older adults with hyperkyphosis

BACKGROUND AND OBJECTIVES

Thoracic hyperkyphosis is one of the most common postural deformities in the geriatric population. This study investigated whether trunk proprioception, muscle strength, and endurance differ between older adults with hyperkyphosis and the age-matched control group. This study also aimed to explore the association of kyphotic posture with muscle performance, position sense, and force sense.

METHODS

Ninety-seven elderly volunteers (61 with hyperkyphosis and 36 normal controls) participated in this cross-sectional study. The kyphosis degree, trunk position sense, force sense, back muscle strength, and endurance were assessed in all participants.

RESULTS

The results showed lower back extensor strength and endurance, also higher force and position sense error in the hyperkyphotic group than the control group. In addition, the findings revealed that back extensor strength and endurance, as well as trunk position sense, were associated with kyphotic posture in older adults.

DISCUSSION AND IMPLICATIONS

This study suggests that back extensor strength and endurance and trunk position sense and force sense are potentially modifiable impairments associated with thoracic kyphosis in older adults with hyperkyphosis. It seems monitoring these potentially contributing factors would be helpful in the assessment and treatment of hyperkyphotic older individuals.

Know Your Movements: Poorer Proprioceptive Accuracy is Associated With Overprotective Avoidance Behavior

Pain-related avoidance of movements that are actually safe (ie, overprotective behavior) plays a key role in chronic pain disability. Avoidance is reinforced through operant learning: after learning that a certain movement elicits pain, movements that prevent pain are more likely to be performed. Proprioceptive accuracy importantly contributes to motor learning and memory. Interestingly, reduced accuracy has been documented in various chronic pain conditions, prompting the question whether this relates to avoidance becoming excessive. Using robotic arm-reaching movements, we tested the hypothesis that poor proprioceptive accuracy is associated with excessive pain-related avoidance in pain-free participants. Participants first performed a task to assess proprioceptive accuracy, followed by an operant avoidance training during which a pain stimulus was presented when they performed one movement trajectory, but not when they performed another trajectory. During a test phase, movements were no longer restricted to 2 trajectories, but participants were instructed to avoid pain. Unbeknownst to the participants, the pain stimulus was never presented during this phase. Results supported our hypothesis. Furthermore, exploratory analyses indicated a reduction in proprioceptive accuracy after avoidance learning, which was associated with excessive avoidance and higher trait fear of pain. PERSPECTIVE: This study is the first to show that poorer proprioceptive accuracy is associated with excessive pain-related avoidance. This finding is especially relevant for chronic pain conditions, as reduced accuracy has been documented in these populations, and points toward the need for research on training accuracy to tackle excessive avoidance.

Evidence of distorted proprioception and postural control in studies of experimentally induced pain: a critical review of the literature

OBJECTIVES

Deficits in proprioception and postural control are common in patients with different musculoskeletal pain syndromes. It has been proposed that pain can negatively affect proprioception and postural control at a peripheral level, however research is limited to animal studies. Human studies have shown that it is more likely, that the link between pain and proprioceptive deficits, lies within changes in the central nervous system where noxious and non-noxious stimuli may overlap. In clinical studies, causality cannot be determined due to other factors which could confound the assessment such as pathophysiological features of the underlying musculoskeletal disorder and different psycho-social influences especially in patients with chronic pain. On the other hand, experimentally induced pain in healthy participants is able to control most of these confounding factors and perhaps offers an assessment of the effects of pain on proprioception and postural control. The aim of this paper is to critically appraise the literature related to the effect of experimentally induced pain on proprioception and postural control. Results from these studies are discussed and limitations are highlighted for future research.

METHODS

A search of databases (Medline, Scopus, PubMed) was conducted as well as reference check from relevant articles published since 2000. Fifteen studies which explored the effect of experimentally induced pain on postural control and ten studies which explored the effect of experimentally induced pain on proprioception were included.

RESULTS

We found that in the majority of the studies, postural control was negatively affected by experimentally induced pain. Results for proprioception were mixed depending on the body region and the way the painful stimuli were delivered. Kinesthesia was negatively affected in two studies, while in one study kinesthesia was enhanced. Joint position sense was not affected in four out of five studies. Finally, force sense was affected in three out of four studies.

CONCLUSIONS

From a clinical point of view, findings from the available literature suggest that experimentally induced pain impairs postural control and could potentially increases the risk for falls in patients. Interventions aiming to reduce pain in these patients could lead to preservation or improvement of their balance. On the other hand, the same conclusion cannot be drawn for the effect of experimentally induced pain on kinesthesia and joint position sense due to the limited number of studies showing such an effect.

I Can Step Clearly Now, the TENS Is On: Transcutaneous Electric Nerve Stimulation Decreases Sensorimotor Uncertainty during Stepping Movements

Transcutaneous electric nerve stimulation (TENS) is a method of electrical stimulation that elicits activity in sensory nerves and leads to improvements in the clinical metrics of mobility. However, the underlying perceptual mechanisms leading to this improvement are unknown. The aim of this study was to apply a Bayesian inference model to understand how TENS impacts sensorimotor uncertainty during full body stepping movements. Thirty healthy adults visited the lab on two occasions and completed a motor learning protocol in virtual reality (VR) on both visits. Participants were randomly assigned to one of three groups: TENS on first visit only (TN), TENS on second visit only (NT), or a control group where TENS was not applied on either visit (NN). Using methods of Bayesian inference, we calculated the amount of uncertainty in the participants' center of mass (CoM) position estimates on each visit. We found that groups TN and NT decreased the amount of uncertainty in the CoM position estimates in their second visit while group NN showed no difference. The least amount of uncertainty was seen in the TN group. These results suggest that TENS reduces the amount of uncertainty in sensory information, which may be a cause for the observed benefits with TENS.

Non-linear multimodal integration in a distributed premotor network controls proprioceptive reflex gain in the insect leg

Producing context-appropriate motor acts requires integrating multiple sensory modalities. Presynaptic inhibition of proprioceptive afferent neurons^1-4 and afferents of different modalities targeting the same motor neurons (MNs)^5-7 underlies some of this integration. However, in most systems, an interneuronal network is interposed between sensory afferents and MNs. How these networks contribute to this integration, particularly at single-neuron resolution, is little understood. Context-specific integration of load and movement sensory inputs occurs in the stick insect locomotory system,^6,8-12 and both inputs feed into a network of premotor nonspiking interneurons (NSIs).⁸ We analyzed how load altered movement signal processing in the stick insect femur-tibia (FTi) joint control system by tracing the interaction of FTi movement^13-15 (femoral chordotonal organ [fCO]) and load^13,15,16 (tibial campaniform sensilla [CS]) signals through the NSI network to the slow extensor tibiae (SETi) MN, the extensor MN primarily active in non-walking animals.^17-19 On the afferent level, load reduced movement signal gain by presynaptic inhibition. In the NSI network, graded responses to movement and load inputs summed nonlinearly, increasing the gain of NSIs opposing movement-induced reflexes and thus decreasing the SETi and extensor tibiae muscle movement reflex responses. Gain modulation was movement-parameter specific and required presynaptic inhibition. These data suggest that gain changes in distributed premotor networks, specifically the relative weighting of antagonistic pathways, could be a general mechanism by which multiple sensory modalities are integrated to generate context-appropriate motor activity.

Human muscle spindles are wired to function as controllable signal-processing devices

Muscle spindles are encapsulated sensory organs found in most of our muscles. Prevalent models of sensorimotor control assume the role of spindles is to reliably encode limb posture and movement. Here, I argue that the traditional view of spindles is outdated. Spindle organs can be tuned by spinal γ motor neurons that receive top-down and peripheral input, including from cutaneous afferents. A new model is presented, viewing γ motor activity as an intermediate coordinate transformation that allows multimodal information to converge on spindles, creating flexible coordinate representations at the level of the peripheral nervous system. That is, I propose that spindles play a unique overarching role in the nervous system: that of a peripheral signal-processing device that flexibly facilitates sensorimotor performance, according to task characteristics. This role is compatible with previous findings and supported by recent studies with naturalistically active humans. Such studies have so far shown that spindle tuning enables the independent preparatory control of reflex muscle stiffness, the selective extraction of information during implicit motor adaptation, and for segmental stretch reflexes to operate in joint space. Incorporation of advanced signal-processing at the periphery may well prove a critical step in the evolution of sensorimotor control theories.

Relationship between Cervicocephalic Kinesthetic Sensibility Measured during Dynamic Unpredictable Head Movements and Eye Movement Control or Postural Balance in Neck Pain Patients

Cervical afferent input is believed to affect postural balance and oculomotor control in neck pain patients, but its relationship to cervicocephalic kinesthesia, describing movement sense, has not yet been studied. The aim of this study was to analyze the relationship of two aspects of cervicocephalic kinesthesia to postural balance and oculomotor control in neck torsion positions. Forty-three idiopathic neck pain patients referred from orthopedic outpatient clinics and forty-two asymptomatic controls were enrolled in the study. A force plate was used to measure center-of-pressure movements during parallel stances under neutral and neck torsion maneuvers. Video-oculography was used to assess eye movements during smooth pursuit neck torsion test (SPNTT), while kinesthetic awareness was measured using the Butterfly test and head-to-neutral relocation test. Multiple regression was used to describe relationships between tests. Body sway in the anterior-posterior direction was related to Butterfly parameters but less to the head-to-neutral test. A medium relationship between Butterfly parameters and gain during SPNTT, with less SPNT-difference, was observed, but not for the head-to-neutral test. It can be concluded that specific aspect of neck kinesthetic functions (i.e., movement sense) importantly contributes towards oculomotor and balance control, which is more evident under neck torsion positions in neck pain patients, but is less pronounced in asymptomatic individuals.

The efficacy of balance and proprioception exercises in female patients with knee osteoarthritis: A randomized controlled study

OBJECTIVE

Loss of proprioception and balance disorders are commonly observed in patients with knee osteoarthritis. In this study, we aimed to investigate the effects of balance and proprioception exercises in patients with knee osteoarthritis.

DESIGN

A single-center randomized trial with three parallel arms.

SETTING

A tertiary health care facility in Turkey.

PARTICIPANTS

Female patients with knee osteoarthritis aged 40-70 years.

INTERVENTIONS

Ten-week exercise program in Biodex training, classical balance training and isometric strengthening groups.

MAIN MEASURES

Dynamic balance (overall stability index and the modified Clinical Test of Sensory Interaction and Balance), pain (visual analogue scale), physical function (30-s chair stand test and 40-meter fast-paced walk test) and quality of life (Knee Injury and Osteoarthritis Outcome Score).

RESULTS

Eighty-nine patients enrolled in the study. The Biodex training group, the classical training group, and the control group had overall stability index values of 1.0 ± 0.07, 1.4 ± 0.07 and 1.4 ± 0.07, and the Modified Clinical Test of Sensory Interaction and Balance - Condition-3 values of 0.7 ± 0.04, 0.9 ± 0.04 and 0.9 ± 0.04 respectively, at the end of treatment. In terms of pain scores on movement, each group showed significant improvement compared to their baseline, and the classical balance training group had better scores than the control group. No other significant difference was found between the groups. Physical function and quality of life outcomes showed significant main effects only in the time factor.

CONCLUSIONS

Balance and proprioception exercises may have positive effects on dynamic balance and pain. The effects on physical function and quality of life should be investigated in further studies with larger sample.

Proprioceptive and Dual-Task Training: The Key of Stroke Rehabilitation, A Systematic Review

This systematic review aims to reveal the effectiveness of proprioceptive exercise combined with dual-task training in stroke patients. The research was conducted using PubMed, Cochrane Library, Web of Science, and Scopus databases to evaluate studies of rehabilitation interventions with proprioceptive and dual-task exercises in patients with stroke. The keywords for the search were: "stroke" AND "proprioception" OR "proprioceptive" AND "rehabilitation" OR "training" OR "exercises" AND "dual-task" OR "task-performance" with the following inclusion criteria: comparative studies of rehabilitation interventions with proprioceptive and dual-task exercises in stroke patients. Of the 104,014 studies identified, 23 were included according to the inclusion criteria. Proprioceptive and dual-task exercises stimulate and promote postural balance, gait, and quality of life and reduce the risk of falls in stroke patients compared with traditional rehabilitation programs. In conclusion, this systematic review suggests that proprioceptive exercise combined with dual-task training is needed to improve balance and recover gait. Moreover, it provides a comprehensive overview of the literature on the various proprioceptive treatments with contextual dual-task exercises for imbalance after stroke, providing a guide for choosing a complete rehabilitation protocol that combines these two techniques.

The effect of methocarbamol and mexiletine on murine muscle spindle function

INTRODUCTION/AIMS

The muscle relaxant methocarbamol and the antimyotonic drug mexiletine are widely used for the treatment of muscle spasms, myotonia, and pain syndromes. To determine whether these drugs affect muscle spindle function, we studied their effect on the resting discharge and on stretch-induced action potential frequencies of proprioceptive afferent neurons.

METHODS

Single unit action potential frequencies of proprioceptive afferents from muscle spindles in the murine extensor digitorum longus muscle of adult C57BL/6J mice were recorded under resting conditions and during ramp-and-hold stretches. Maximal tetanic force of the same muscle after direct stimulation was determined. High-resolution confocal microscopy analysis was performed to determine the distribution of Na_v 1.4 channels, a potential target for both drugs.

RESULTS

Methocarbamol and mexiletine inhibited the muscle spindle resting discharge in a dose-dependent manner with IC₅₀ values around 300 μM and 6 μM, respectively. With increasing concentrations of both drugs, the response to stretch was also affected, with the static sensitivity first followed by the dynamic sensitivity. At high concentrations, both drugs completely blocked muscle spindle afferent output. Both drugs also reversibly reduced the specific force of the extensor digitorum longus muscle after tetanic stimulation. Finally, we present evidence for the presence and specific localization of the voltage-gated sodium channel Na_v 1.4 in intrafusal fibers.

DISCUSSION

In this study we demonstrate that both muscle relaxants affect muscle spindle function, suggesting impaired proprioception as a potential side effect of both drugs. Moreover, our results provide additional evidence of a peripheral activity of methocarbamol and mexiletine.

Elbow Joint Position and Force Senses in Young and Adult Untrained People and Gymnasts

Joint position (JPS) and force senses (FS) are the proprioception modalities. While the development of JPS was investigated both in children/adult and athlete/untrained conditions, there is a lack of insight into the development of FS. Overall, 28 gymnasts and 25 untrained controls underwent proprioception testing. They were divided into two groups: 9 to 11-year-old boys (13 gymnasts and 10 non-athletes) and 18 to 25-year-old adults (15 gymnasts and 15 non-athletes). The testing was performed at an isokinetic dynamometer and included elbow JPS and FS (20% and 50% maximal voluntary contraction) tasks. Children had two times higher error in JPS (p < 0.01) and 50% higher errors in FS of both flexor (p < 0.001) and extensor muscles (p < 0.05) in comparison with adults. Only in the 50% maximal voluntary contraction task, gymnasts showed 33% lower error than the controls (p < 0.01). Untrained boys presented 54%, 132%, and 169% higher error for elbow flexor performance than young gymnasts, untrained adults, and adult gymnasts, respectively (p < 0.01). The 9 to 11-year-old participants were characterized by a lower precision of JPS and FS performance in comparison with adults. Gymnastic training can possibly accelerate the development of FS when higher loads are considered.

Skeletal muscle function underpins muscle spindle abundance

Muscle spindle abundance is highly variable within and across species, but we currently lack any clear picture of the mechanistic causes or consequences of this variation. Previous use of spindle abundance as a correlate for muscle function implies a mechanical underpinning to this variation, but these ideas have not been tested. Herein, we use integrated medical imaging and subject-specific musculoskeletal models to investigate the relationship between spindle abundance, muscle architecture and in vivo muscle behaviour in the human locomotor system. These analyses indicate that muscle spindle number is tightly correlated with muscle fascicle length, absolute fascicle length change, velocity of fibre lengthening and active muscle forces during walking. Novel correlations between functional indices and spindle abundance are also recovered, where muscles with a high abundance predominantly function as springs, compared to those with a lower abundance mostly functioning as brakes during walking. These data demonstrate that muscle fibre length, lengthening velocity and fibre force are key physiological signals to the central nervous system and its modulation of locomotion, and that muscle spindle abundance may be tightly correlated to how a muscle generates work. These insights may be combined with neuromechanics and robotic studies of motor control to help further tease apart the functional drivers of muscle spindle composition.

Could Proprioceptive Stimuli Change Saddle Pressure on Male Cyclists during Different Hand Positions? An Exploratory Study of the Effect of the Equistasi® Device

When pedaling, the excessive pressure on the seat has the potential to produce injuries and this can strongly affect sport performance. Recently, a large effort has been dedicated to the reduction of the pressure occurring at the saddle region. Our work aims to verify the possibility of modifying cyclists’ pedaling posture, and consequently the pressure on the saddle, by applying a proprioceptive stimulus. Equistasi® (Equistasi srl, Milano, Italy) is a wearable device that emits focal mechanical vibrations able to transform the body temperature into mechanical vibratory energy via the embedded nanotechnology. The data acquired through a pressure mapping system (GebioMized®) on 70 cyclists, with and without Equistasi®, were analyzed. Pedaling in three positions was recorded on a spin trainer: with hands on the top, hands on the drop handlebar, and hands on the lever. Average force, contact surface, and average and maximum pressure each in different regions of the saddle were analyzed, as well as integral pressure time and center of pressure. In the comparisons between hands positions, overall pressure and force variables were significantly lower in the drop-handlebar position at the rear saddle (p < 0.03) and higher in hand-on-lever and drop-handlebar positions at the front saddle (p < 0.01). When applying the Equistasi device, the contact surface was significantly larger in all hand positions (p < 0.05), suggesting that focal stimulation of the lumbar proprioceptive system can change cyclists’ posture.

Changes in Dynamic Postural Stability After ACL Reconstruction: Results Over 2 Years of Follow-up

Background:

The anterior cruciate ligament (ACL) is crucial for knee proprioception and postural stability. While ACL reconstruction (ACLR) and rehabilitation improve postural stability, the timing in improvement of dynamic postural stability after ACLR remains relatively unknown.

Purpose:

To evaluate changes in dynamic postural stability after ACLR out to 24 months postoperatively.

Study Design:

Case series; Level of evidence, 4.

Methods:

Patients undergoing ACLR were prospectively enrolled, and dynamic postural stability was assessed within 2 days before surgery, at 3-month intervals postoperatively to 18 months, then at 24 months. Measurements were made on a multidirectional platform tracking the patient’s center of mass based on pelvic motion. The amount of time the patient was able to stay on the platform was recorded, and a dynamic motion analysis score, reflecting the patient’s ability to maintain one’s center of mass, was generated overall and in 6 independent planes of motion.

Results:

A total of 44 patients with a mean age of 19.7 ± 6.2 years completed the study protocol. Overall mean dynamic postural stability improved significantly at 3, 6, 9, and 12 months after surgery, with continued improvement out to 24 months. Notable improvements occurred in medial/lateral and anterior/posterior stability from baseline to 6 months postoperatively, while internal/external rotation and flexion/extension stability declined initially after surgery from baseline to 3 months postoperatively before stabilizing to the end of the study period.

Conclusion:

Overall dynamic postural stability significantly improved up to 12 months after ACLR. Improvement in postural stability occurred primarily in the medial/lateral and anterior/posterior planes of motion, with initial decreases in the flexion/extension and internal/external rotational planes of motion.

Delayed detection of passive motion in shoulders with a rotator cuff tear

The aim of this study was to test whether or not the threshold to the detection of passive motion (TTDPM) and passive joint position sense on the affected shoulder of patients with rotator cuff tear (RCT) was impaired compared to those on the unaffected side and to investigate the relationship between the tear size and changes in the TTDPM and passive joint position sense induced by RCT. This study included 21 patients with unilateral RCT before arthroscopic rotator cuff repair. To investigate proprioception in this study, we measured the TTDPM and passive joint position sense in abduction and external rotation using an isokinetic dynamometer. The tear size was evaluated intraoperatively under direct arthroscopic visualization. The TTDPM in abduction and external rotation was significantly longer on the affected side than on the unaffected side. However, the angular absolute error in passive joint position sense in abduction and external rotation was not significantly different between the limbs. A comparison according to the tear size impaired proprioception of the TTDPM in the larger tear group showed significantly longer values than in the smaller group. There was impaired proprioception of TTDPM in patients with RCT, and the impaired proprioception was related to tear severity. Impaired proprioception of TTDPM may inhibit consistent muscle recruitment to achieve precise control. Our results suggest that clinicians should consider proprioceptive exercises for impaired proprioception in their treatment for conservative or postoperative patients.

Significantly Delayed Medium-Latency Response of the Stretch Reflex in Delayed-Onset Muscle Soreness of the Quadriceps Femoris Muscles Is Indicative of Sensory Neuronal Microdamage

Unaccustomed or strenuous eccentric exercise is known to cause delayed-onset muscle soreness. A recent hypothesis postulated that mechano-energetic microinjury of the primary afferent sensory neuron terminals in the muscle spindles, namely a transient Piezo2 channelopathy, could be the critical cause of delayed-onset muscle soreness in the form of a bi-phasic non-contact injury mechanism. This theory includes that this microlesion could delay the medium-latency response of the stretch reflex. Our aim with this study was to investigate this hypothesis. According to our knowledge, no study has examined the effect of delayed-onset muscle soreness on the medium-latency response of the stretch reflex. Our findings demonstrated that a significant delay in the medium-latency stretch reflex could be observed right after a multi-stage fitness test in the quadriceps femoris muscles of Hungarian professional handball players who consequently experienced delayed-onset muscle soreness. The long-latency stretch reflex and most likely short-latency stretch reflex were unaffected by delayed-onset muscle soreness in our study, which is in line with earlier findings. We translate these findings as indicative of proprioceptive Type Ia terminal microdamage in the muscle spindle in line with the aforementioned new acute non-contact compression axonopathy theory of delayed-onset muscles soreness.

Factors affecting the performance of the deep cervical flexors in young people using smartphones

OBJECTIVE

To determine the factors affecting the performance of the deep cervical flexors (DCFs) in young people using smartphones.

METHODS

Eighty-six individuals were enrolled in this study. Joint position sense errors, forward head and protracted shoulder posture, DCFs, and the superficial cervical muscles were evaluated. Smartphone Addiction Scale, State-Trait Anxiety Inventory, and International Physical Activity Questionnaire were used.

RESULTS

Regression analysis indicated that smartphone addiction and superficial cervical muscle strengths affect the performance of DCFs independently (p < 0.05). SAS was correlated with JPSE-flexion (r = 0.408), DCF activity/performance score (r = -0.453/r = -0.431), forward head posture (r = -0.412), and cervical flexor/extensor muscle strengths (r = -0.313/r = -0.319).

CONCLUSION

Smartphone addiction and cervical superficial muscles are related to the performance of the DCFs in young people. Using smartphones causes impaired joint position sense in flexion, decreased DCF activity, and forward head posture.

Novel Soft Haptic Biofeedback-Pilot Study on Postural Balance and Proprioception

Sensory feedback is critical in proprioception and balance to orchestrate muscles to perform targeted motion(s). Biofeedback plays a significant role in substituting such sensory data when sensory functions of an individual are reduced or lost such as neurological disorders including stroke causing loss of sensory and motor functions requires compensation of both motor and sensory functions. Biofeedback substitution can be in the form of several means: mechanical, electrical, chemical and/or combination. This study proposes a soft monolithic haptic biofeedback device prototyped and pilot tests were conducted with healthy participants that balance and proprioception of the wearer were improved with applied mechanical stimuli on the lower limb(s). The soft monolithic haptic biofeedback device has been developed and manufactured using fused deposition modelling (FDM) that employs soft and flexible materials with low elastic moduli. Experimental results of the pilot tests show that the soft haptic device can effectively improve the balance of the wearer as much as can provide substitute proprioceptive feedback which are critical elements in robotic rehabilitation.

Differences in Postural Balance, Pain Sensitivity and Depression between Individuals with Acute and Chronic Back Pain

To compare differences in postural balance, pain and depression in patients with chronic and acute low back pain, twenty patients with chronic and twenty patients with acute low back pain from the Edward Francis Small Hospital (Banjul, Gambia), as well as 20 age-matched healthy controls participated in the study. A modified Romberg test was used to assess postural balance during one minute with closed eyes. Body sway in the anteroposterior and mediolateral axes was video-recorded during test performance and further analyzed with an open source software for movement analyses (CvMob). Pain sensitivity was assessed by means of pressure pain thresholds and depression by a self-report questionnaire (PHQ-9). As results, patients with chronic low back pain displayed higher body sway in the anteroposterior and mediolateral axes, as well as faster body sway than patients with acute low back pain and healthy controls. Nevertheless, group differences disappeared when depression was introduced as a covariate, indicating a major role of depression in postural balance deficits of patients with pain disorders. As conclusions, the assessment of postural balance and depression should be implemented in the clinical routine for the design of tailored interventions in pain conditions.

Effect of a semi-rigid backpack type thoracolumbar orthosis on thoracic kyphosis angle and muscle performance in older adults with hyperkyphosis: a randomized controlled trial

PURPOSE

To investigate the effect of a semi-rigid backpack type thoracolumbar orthosis (TLO) on thoracic kyphosis angle (TKA) and potentially contributing factors of hyperkyphosis, including position sense and back muscle strength and endurance.

METHOD

This randomized, controlled trial was conducted on 48 older adults with hyperkyphosis, randomly allocated to an experimental or control group. The experimental group wore a semi-rigid TLO for 3 consecutive months. The control group received no external support or exercise. Thoracic kyphosis angle (TKA), joint position sense, back muscle strength and endurance were evaluated at the baseline and at the end of week 6 and week 12.

RESULTS

The two-way (group × time) interactions were significant in terms of TKA (F = 37.88, p ≤ 0.001, η_p² = 0.45), muscle strength (F = 26.005, p ≤ 0.001, η_p² = 0.36), muscle endurance measured via load cell (F = 3.417, p = 0.039, η_p² = 0.06), and endurance holding time of Ito test (F = 3.629, p = 0.045, η_p² = 0.07). A further analysis using one-way repeated measures of ANOVA showed that TKA, muscle strength and endurance were significantly improved in the experimental group. Also, two-way interactions were significant for absolute error and variable error of trunk neutral repositioning test from a trunk flexed and/or extended position for global components and horizontal components trunk repositioning test.

CONCLUSION

Wearing a semi-rigid backpack type TLO even from an unknown brand for short periods during the day (e.g., 2-4 h) over 3 months not only modifies kyphotic posture but also can enhance back muscle performance in older adults with hyperkyphosis. IMPLICATIONS FOR REHABILITATIONPrescription of a semi-rigid backpack type thoracolumbar orthosis for older adults has no adverse effects such as muscle weakness if it is applied for short periods during the day.A semi-rigid backpack thoracolumbar orthosis can prevent position sense degradation in older adults with hyperkyphosis.A semi-rigid backpack type thoracolumbar orthosis may counteract trunk flexion and kyphotic posture by applying the biomechanical principles of the three-point pressure system.Improvement in spinal alignment resulting from wearing thoracolumbar orthosis should not occur in exchange for muscle deconditioning.

Newly identified axon types of the facial nerve unveil supplemental neural pathways in the innervation of the face

INTRODUCTION

Neuromuscular control of the facial expressions is provided exclusively via the facial nerve. Facial muscles are amongst the most finely tuned effectors in the human motor system, which coordinate facial expressions. In lower vertebrates, the extracranial facial nerve is a mixed nerve, while in mammals it is believed to be a pure motor nerve. However, this established notion does not agree with several clinical signs in health and disease.

OBJECTIVES

To elucidate the facial nerve contribution to the facial muscles by investigating axonal composition of the human facial nerve. To reveal new innervation pathways of other axon types of the motor facial nerve.

METHODS

Different axon types were distinguished using specific molecular markers (NF, ChAT, CGRP and TH). To elucidate the functional role of axon types of the facial nerve, we used selective elimination of other neuronal support from the trigeminal nerve. We used retrograde neuronal tracing, three-dimensional imaging of the facial muscles, and high-fidelity neurophysiological tests in animal model.

RESULTS

The human facial nerve revealed a mixed population of only 85% motor axons. Rodent samples revealed a fiber composition of motor, afferents and, surprisingly, sympathetic axons. We confirmed the axon types by tracing the originating neurons in the CNS. The sympathetic fibers of the facial nerve terminated in facial muscles suggesting autonomic innervation. The afferent fibers originated in the facial skin, confirming the afferent signal conduction via the facial nerve.

CONCLUSION

These findings reveal new innervation pathways via the facial nerve, support the sympathetic etiology of hemifacial spasm and elucidate clinical phenomena in facial nerve regeneration.

Interrelationships of Touch and Proprioception with Motor Impairments in Individuals with Cerebral Palsy: A Systematic Review

Considering that somatosensory impairments may impact motor performance in individuals with cerebral palsy (CP), a better understanding of these relations is relevant to planning interventions. To synthesize research evidence to date on the interrelationships between the somatosensory functions of touch and proprioception with motor functions in persons with CP, we systematically searched Embase, CINAHL, PsycINFO, and Medline databases for studies relating these variables that were published in English from the inception of these databases to November 2020. We targeted the following content categories in our literature search: (a) cerebral palsy; (b) sensory functions; (c) tactile functions; (d) proprioception functions; and (e) motor functions. The selection, data extraction, and methodological quality assessment of these studies were performed in duplicate. We retrieved and analyzed information regarding the studies' methodological approaches and synthesized results. The 11 studies that met our inclusion criteria showed that, in individuals with CP, impairments in tactile discrimination, proprioception, and stereognosis are related to motor functions in terms of overall manual ability, grip strength, postural control and locomotion. Thus, clinical practitioners should attend to somatosensory aspects of motor impairment in individuals with CP. More research is needed to clarify the direction of these associations.

The myokinetic stimulation interface: activation of proprioceptive neural responses with remotely actuated magnets implanted in rodent forelimb muscles

OBJECTIVE

Proprioception is the sense of one's position, orientation, and movement in space, and it is of fundamental importance for motor control. When proprioception is impaired or absent, motor execution becomes error-prone, leading to poorly coordinated movements. The kinaesthetic illusion, which creates perceptions of limb movement in humans through non-invasively applying vibrations to muscles or tendons, provides an avenue for studying and restoring the sense of joint movement (kinaesthesia). This technique, however, leaves ambiguity between proprioceptive percepts that arise from muscles versus those that arise from skin receptors. Here we propose the concept of a stimulation system to activate kinaesthesia through the untethered application of localized vibration through implanted magnets.

APPROACH

In this proof-of-concept study, we use two simplified 1-DoF systems to show the feasibility of eliciting muscle-sensory responses in an animal model across multiple frequencies, including those that activate the kinaesthetic illusion (70 - 115 Hz). Furthermore, we generalized the concept by developing a 5-DoF prototype system capable of generating directional, frequency-selective vibrations with desired displacement profiles.

MAIN RESULTS

In-vivo tests with the 1-DoF systems demonstrated the feasibility to elicit muscle sensory neural responses in the median nerve of an animal model. Instead, in-vitro tests with the 5-DoF prototype demonstrated high accuracy in producing directional and frequency selective vibrations along different magnet axes.

SIGNIFICANCE

These results provide evidence for a new technique that interacts with the native neuro-muscular anatomy to study proprioception and eventually pave the way towards the development of advanced limb prostheses or assistive devices for the sensory impaired.

Linear Motor Driven Leg-Press Dynamometer for Testing, Training, and Rehabilitation: A Scoping Review with a Focus on the Concept of Serial Stretch Loading

Background: The purpose of this scoping review was to analyze the evidence of acute and long-term effects of the application of leg-press strength training with or without serial stretch-loading stimuli on various biomechanical and physiological outcomes. Methods: This review was performed in accordance with PRISMA for Scoping Reviews recommendations, and two researchers independently searched the following databases: PubMed, Web of Science, Scopus, ScienceDirect, ProQuest, Cochrane, and Google Scholar. All studies that used unique leg-press device for testing, acute responses and long-term adaptation were included in this review, irrespective of the measured outcomes. A total of 13 studies were included in this review, with 5 focused on the testing capabilities of the device and acute training responses and 8 focused on the long-term adaptations in various physical and physiological outcomes. Results: Regarding the acute responses after leg-press strength training with or without serial stretch-loading stimuli, visible changes were observed in the muscle force, rate of force development, and hormonal concentrations between pre- and postmenopausal women (only one study). Long-term studies revealed different training adaptations after performing leg-press strength training with unique serial stretch-loading stimuli. A positive trend for leg-press strength training with serial stretch-loading was recorded in the young population and athletes; however, more variable training effects favoring one or the other approach were achieved in the older population. Conclusions: In summary, this review shows the uniqueness and usability of a leg-press device that is capable of various exercising modes, including special serial stretch-loading stimuli. The use of this device can serve as a positive addition to training regiments, and the main application appears to be suitable for rehabilitation needs.

Levels of Gnostic Functions in Top Karate Athletes-A Pilot Study

High-quality sensory perception and body scheme (somatognosis) are important aspects for sport performance. This study compares stereognosis, body scheme, and kinesthesia in a group of 36 competitive karate athletes against a control group of 32 general population participants. The stereognosis Petrie test, two body scheme tests, and three kinesthesia tests served as outcome measurement tools. No significant difference was found in the stereognosis Petrie test, for the dominant (p = .389) or the nondominant (p = .791) hand, nor in the kinesthesia test (dominant, p = .661 and nondominant, p = .051). Karate athletes performed significantly better in the body scheme tests, that is, fist width estimation (p = .024) and shoulder width estimation (p = .019), as well as in karate-specific kinesthesia tests, that is, single punch (p = .010) and triple punch (p = .001). This study confirms competitive karate athletes have significantly better somatognosis, and better accuracy when performing quick dynamic movements compared with the general population.

The Effect of Proprioception Training on Pain Intensity in Thumb Basal Joint Osteoarthritis: A Randomized Controlled Trial

A randomized controlled trial of forty-five females over 18 years of age with diagnosis of thumb basal osteoarthritis in their dominant hand and with a minimum pain rating of 4/10 on the Visual Analogue Scale (VAS) during activities of daily living (ADLs) were recruited from March to June 2021. The group receiving proprioception training was compared to routine conservative physiotherapy treatment. The main purpose of this clinical trial is to test the effect of proprioception training on pain intensity in subjects with thumb osteoarthritis. Primary outcome was joint position sense (JPS) for the assessment of CMC proprioception and secondary outcomes were Visual Analogue Scale (VAS) and Canadian Occupational Performance Measure (COPM) for the assessment of patient satisfaction and the Quick-DASH which assessed upper limb function. A block randomization was carried out for the control group (n = 22) and experimental group (n = 23). Participants and evaluator were blinded to the group assignment. Proprioception training produced a statistically significant reduction in pain post intervention, but this reduction was small (d = 0.1) at the 3-month follow-up. JPS accuracy demonstrated statistically significant differences between the groups (p = 0.001) post-intervention and at the 3-month follow-up (p < 0.003). Statistically significant differences between means were found in both the Quick-Dash and COPM post intervention (both, p < 0.001), as well as at the 3-month follow-up (both, p < 0.001). There was a significant time factor for the reduction of pain intensity over time but effect sizes between groups was small at the 3-month follow-up period. Proprioceptive training improves thumb JPS accuracy; however, it does not contribute to a reduction in pain intensity in the long term. The inclusion of a proprioceptive program may be beneficial for improving individuals with thumb CMC OA sensorimotor performance. The study was registered at ClinicalTrials.gov NCT04738201. No funding was provided for this study.

The effects of eccentric exercise-induced fatigue on position sense during goal-directed movement

We investigated the impairment of position sense associated with muscle fatigue. In Exp. 1, participants performed learned eccentric extension (22 °/s) movements of the elbow as the arm was pulled through the horizontal plane without vision of the arm. They opened their closed right hand when they judged it to be passing through a target. Dynamic position sense was assessed via accuracy of limb position to the target at time of hand opening. Eccentric movements were performed against a flexion load (10% of flexion MVC). We investigated performance under conditions with and without biceps vibration, as well as before and after eccentric exercise. In Exp. 2, a motor was used to extend the participant's limb passively. We compared conditions with and without vibration of the lengthening but passive biceps, before and after exercise. In Exp. 1, vibration of the active biceps resulted in participants opening their hand earlier ( [95% CI] -5.52° [-7.40, -3.63]) compared to without vibration. Exercise reduced flexion MVCs by ~44%, and participants undershot the target more (-5.51° [-9.31, -1.70]) in the post-exercise block during control trials. Exercise did not influence the persistence of the vibratory illusion. In Exp. 2, vibration resulted in greater undershooting (-2.99° [-3.99, -1.98]) compared to without vibration, before and after exercise. Although exercise reduced MVCs by ~50%, the passive task showed no effects of exercise. We suggest that the CNS continues to rely on muscle spindles for limb position sense, even when they reside in a muscle exposed to fatiguing eccentric contractions.

Electromyostimulation Application on Peroneus Longus Muscle Improves Balance and Strength in American Football Players

PURPOSE

The aim of this study was to evaluate the effect of 5 weeks of electromyostimulation (EMS) of the peroneus longus muscle on balance and muscle strength in American Football (AmF) players.

METHODS

Thirty-two healthy male athletes (4 American Football team training sessions per week, college level) were randomly divided into the EMS and control groups. The EMS applications were conducted on the dominant peroneus longus muscle 3 times per week for 5 weeks, with each application lasting 25 minutes. Before and after the interventions, the strength of ankle dorsiflexion-plantar flexion and foot eversion-inversion was measured with isometric dynamometer and anterior-posterior sway, mediolateral sway, perimeter, and ellipse area were measured with the Technobody Balance System in unilateral stance positions, while eyes were open.

RESULTS

Changes between initial and final tests for dorsiflexion and eversion strength, and mediolateral sway for dynamic balance in the groups were significantly different (P = .039, P = .027, P = .030, respectively).

CONCLUSION

The EMS application had positive effects on muscle strength and dynamic balance of AmF players. The EMS can be used to improve isometric strength and dynamic balance in AmF players.

Pain in relationship to Tinnitus and Hearing Loss

INTRODUCTION

Cervical and lower back pain are noteworthy in the manner of development of tinnitus.

OBJECTIVES

The focus of this research was to indicate the consequence of the severity of neck pain and pain of the lower back and/or lower limbs in tinnitus patients.

DESIGN

A retrospective analysis of 61 patients with tinnitus as main complaint during a three month period.

RESULTS

In this study, we found two groups of tinnitus patients defined by the existence of postural instability. Patients with tinnitus and postural unsteadiness were characterized by predominant female, self-perceived hearing loss, a higher intensity of tinnitus, cervical pain, and pain of the lower back and/or of the lower limbs, and more hearing deficit from 250 Hz to 4 kHz.

CONCLUSIONS

In patients with tinnitus one should be aware that hearing loss can be a consequence of high intensity cervical pain. Stimulation of the proprioceptive input pathways due to cervical pain can result in a higher intensity of tinnitus and a hearing loss in the range of 250 Hz to 4 kHz.

Distortion of mental body representations

Our body is central to our sense of self, and distorted body representations are found in several serious medical conditions. This paper reviews evidence that distortions of body representations are also common in healthy individuals, and occur in domains including tactile spatial perception, proprioception, and the conscious body image. Across domains, there is a general tendency for body width to be overestimated compared to body length. Intriguingly, distortions in both eating disorders and chronic pain appear to be exaggerations of this baseline pattern of distortions, suggesting that these conditions may relate to dysfunction of mechanisms for body perception. Distortions of body representations provide a revealing window into basic aspects of self-perception.

Alteration of Ligamento-Muscular Reflex Patterns After Cutaneous and Periarticular Desensitization of the Basal Thumb Joint: An Electromyographic Study

PURPOSE

Stimulation of the dorsoradial ligament (DRL) of the first carpometacarpal joint (CMC-1) has shown a ligamento-muscular reflex pathway between the DRL and CMC-1 stabilizing muscles in healthy volunteers. However, it remains unclear how this ligamento-muscular reflex pattern is altered after anesthetizing sensory skin receptors and administering a further periarticular block around the CMC-1 joint, which may influence the dynamic aspects of joint stability.

METHODS

Ligamento-muscular reflexes were obtained from the extensor pollicis longus, abductor pollicis longus, abductor pollicis brevis, and the first dorsal interosseous muscles in 10 healthy participants after establishing superficial anesthesia of the skin around the CMC-1. The DRL was stimulated with a fine wire electrode while EMG activities were recorded during isometric tip, key, and palmar pinch. The measurements were repeated after an additional periarticular CMC-1 block using 5 ml of 1% lidocaine. Average EMG values were analyzed to compare the prestimulus and poststimulus activity.

RESULTS

Statistically significant changes in poststimulus EMG activity were observed in all 4 muscles and all 3 tested thumb positions. A markedly reduced activity in all 4 muscles was observed in the palmar position, followed by the tip and key pinch positions. Almost no reactions were observed in the first 20 ms poststimulus for all muscles in all positions.

CONCLUSIONS

Superficial skin anesthesia and an additional periarticular CMC-1 block anesthesia resulted in a reduced ligamento-muscular reflex pattern in all 4 muscles.

CLINICAL RELEVANCE

Ligamento-muscular reflexes play an important role in dynamic CMC-1 joint stability. The elimination of early reactions, those considered joint-protective reflexes, is a potential risk factor for developing osteoarthritis or injury because it results in an inability to adequately protect and stabilize the joint in sudden movements.

Exploring Sex Differences and Force Level Effects on Grip Force Perception in Healthy Adults

This study aimed to explore the effect of sex and force level on grip force reproduction in healthy adults by conducting a force reproduction task. Participants (n = 28) were instructed to replicate a range of reference grip force levels (10-130 N in 10 N increments). We found that women (absolute error: 16.2 ± 8.7 N) replicated these force levels more accurately than men (absolute error: 23.1 ± 9.5 N) at higher force levels (90-130 N). Furthermore, the force reproductions were most accurate at the 30-50 N range for men and the 50-60 N range for women. These results may offer significant insights into the higher rates of musculoskeletal disorders among women, enabling researchers and clinicians to design novel interventions and tools that can improve grip force perception and reduce hand injury rates in both men and women.

Proprioception: a new look at an old concept

Proprioception, which can be defined as the awareness of the mechanical and spatial state of the body and its musculoskeletal parts, is critical to motor actions and contributes to our sense of body ownership. To date, clinical proprioceptive tests have focused on a person's ability to detect, discriminate or match limb positions or movements, and reveal that the strength of the relationship between deficits in proprioception and physical function varies widely. Unfortunately, these tests fail to assess higher-level proprioceptive abilities. In this Perspective, we propose that to understand fully the link between proprioception and function, we need to look beyond traditional clinical tests of proprioception. Specifically, we present a novel framework for human proprioception assessment that is divided into two categories: low-level and high-level proprioceptive judgments. Low-level judgments are those made in a single frame of reference and are the types of judgments made in traditional proprioceptive tests (i.e. detect, discriminate or match). High-level proprioceptive abilities involve proprioceptive judgments made in a different frame of reference. For example, when a person indicates where their hand is located in space. This framework acknowledges that proprioception is complex and multifaceted, and that tests of proprioception should not be viewed as interchangeable, but rather as complimentary. Crucially, it provides structure to the way researchers and clinicians can approach proprioception and its assessment. We hope this Perspective serves as the catalyst for discussion and new lines of investigation.

The Role of Even-Skipped in Drosophila Larval Somatosensory Circuit Assembly

Proper somatosensory circuit assembly is critical for processing somatosensory stimuli and for responding accordingly. In comparison to other sensory circuits (e.g., olfactory and visual), somatosensory circuits have unique anatomy and function. However, understanding of somatosensory circuit development lags far behind that of other sensory systems. For example, there are few identified transcription factors required for integration of interneurons into functional somatosensory circuits. Here, as a model, we examine one type of somatosensory interneuron, Even-skipped (Eve) expressing laterally placed interneurons (ELs) of the Drosophila larval nerve cord. Eve is a highly conserved, homeodomain transcription factor known to play a role in cell fate specification and neuronal axon guidance. Because marker genes are often functionally important in the cell types they define, we deleted eve expression specifically from EL interneurons. On the cell biological level, using single neuron labeling, we find eve plays several previously undescribed roles in refinement of neuron morphogenesis. Eve suppresses aberrant neurite branching, promotes axon elongation, and regulates dorsal-ventral dendrite position. On the circuit level, using optogenetics, calcium imaging, and behavioral analysis, we find eve expression is required in EL interneurons for the normal encoding of somatosensory stimuli and for normal mapping of outputs to behavior. We conclude that the eve gene product coordinately regulates multiple aspects of EL interneuron morphogenesis and is critically required to properly integrate EL interneurons into somatosensory circuits. Our data shed light on the genetic regulation of somatosensory circuit assembly.

Clinical effects of glabellar botulinum toxin injections on borderline personality disorder: A randomized controlled trial

BACKGROUND

Inhibition of frowning via injections of botulinum toxin A (BTX) into the glabellar region has shown beneficial effects in the treatment of major depression. Preliminary research suggests that improvements in the affective domain are not depression-specific, but may also translate to other psychiatric disorders.

AIM

This 16-week, single-blind, two-center randomized controlled trial investigated the influence of BTX on clinical symptoms of borderline personality disorder (BPD).

METHODS

Fifty-four patients with BPD were randomly assigned to treatment with BTX (n = 27) or a minimal acupuncture (ACU) control condition (n = 27). Clinical outcomes were followed at 2, 4, 6, 8, 12, and 16 weeks. Primary endpoint was the relative score change on the Zanarini Rating Scale for Borderline Personality Disorder (ZAN-BPD) 8 weeks after baseline relative to the control group and adjusted for treatment center. Secondary and additional outcome variables were self-rated borderline symptoms, comorbid symptoms of depression, psychological distress, and clinical global impression.

RESULTS

Participants showed significant improvements at the primary efficacy endpoint in both treatment groups (BTX: M = -0.39, SD = 0.39; ACU: M = -0.35, SD = 0.42), but no superior effect of the BTX condition in comparison with the control intervention was found-F(1,5323) = 0.017, p = 0.68). None of the secondary or additional outcomes yielded significant group differences. Side effects were mild and included headache, transient skin or muscle irritations, and dizziness.

CONCLUSION

Evidence regarding the efficacy of BTX for BDP remains limited, and the design of adequate control conditions presents an opportunity for further research.ClinicalTrials.gov registry: Botulinum Toxin A for Emotional Stabilization in Borderline Personality Disorder (BPD), NCT02728778, https://clinicaltrials.gov/ct2/show/NCT02728778.

Neuregulin 1 Drives Morphological and Phenotypical Changes in C2C12 Myotubes: Towards De Novo Formation of Intrafusal Fibres In Vitro

Muscle spindles are sensory organs that detect and mediate both static and dynamic muscle stretch and monitor muscle position, through a specialised cell population, termed intrafusal fibres. It is these fibres that provide a key contribution to proprioception and muscle spindle dysfunction is associated with multiple neuromuscular diseases, aging and nerve injuries. To date, there are few publications focussed on de novo generation and characterisation of intrafusal muscle fibres in vitro. To this end, current models of skeletal muscle focus on extrafusal fibres and lack an appreciation for the afferent functions of the muscle spindle. The goal of this study was to produce and define intrafusal bag and chain myotubes from differentiated C2C12 myoblasts, utilising the addition of the developmentally associated protein, Neuregulin 1 (Nrg-1). Intrafusal bag myotubes have a fusiform shape and were assigned using statistical morphological parameters. The model was further validated using immunofluorescent microscopy and western blot analysis, directed against an extensive list of putative intrafusal specific markers, as identified in vivo. The addition of Nrg-1 treatment resulted in a 5-fold increase in intrafusal bag myotubes (as assessed by morphology) and increased protein and gene expression of the intrafusal specific transcription factor, Egr3. Surprisingly, Nrg-1 treated myotubes had significantly reduced gene and protein expression of many intrafusal specific markers and showed no specificity towards intrafusal bag morphology. Another novel finding highlights a proliferative effect for Nrg-1 during the serum starvation-initiated differentiation phase, leading to increased nuclei counts, paired with less myotube area per myonuclei. Therefore, despite no clear collective evidence for specific intrafusal development, Nrg-1 treated myotubes share two inherent characteristics of intrafusal fibres, which contain increased satellite cell numbers and smaller myonuclear domains compared with their extrafusal neighbours. This research represents a minimalistic, monocellular C2C12 model for progression towards de novo intrafusal skeletal muscle generation, with the most extensive characterisation to date. Integration of intrafusal myotubes, characteristic of native, in vivo intrafusal skeletal muscle into future biomimetic tissue engineered models could provide platforms for developmental or disease state studies, pre-clinical screening, or clinical applications.

Measuring the force perception in knee flexor/ extensor muscles in patients with anterior cruciate ligament injury and healthy subjects

BACKGROUND

Force perception as a contributor to the neuromuscular control of the knee joint may be altered after anterior cruciate ligament (ACL) injury.

OBJECTIVE

This study aimed to compare the force perception accuracy in the knee joints of patients with ACL injury and healthy subjects.

METHODS

Twenty-six patients with ACL injury and 26 healthy subjects participated in this case-control study. Participants were asked to produce 50% of the maximum voluntary isometric contraction of the knee muscles as a target force and reproduce it in their limbs in flexion and extension directions.

RESULTS

There were significant interactions between group and condition as well as group, condition, and limb in the force perception error respectively (P< 0.05). The highest amount of error was seen in the contralateral limb of the ACL injury group when the reference force was produced in the injured limb (P< 0.05).

CONCLUSION

The findings revealed that the force perception accuracy in the knee flexor/extensor muscles of individuals with ACL injury is impaired. Moreover, error is most evident when the patient produces force in the injured limb and replicates it in the uninjured limb in both flexion and extension directions. Therefore, the rehabilitation programs should encompass neuromuscular training in both quadriceps and hamstrings after ACL injury.

3D Stereophotogrammetric Quantitative Evaluation of Posture and Spine Proprioception in Subacute and Chronic Nonspecific Low Back Pain

The literature shows that low back pain causes a reduced lumbar range of movement, affecting patients’ proprioception and motor control. Nevertheless, studies have found that proprioception and motor control of the spine and posture are vague and individually expressed even in healthy young adults. This study aimed to investigate the standing posture and its modifications induced by an instinctive self-correction manoeuvre in subacute and chronic nonspecific low back pain (NSLBP) patients to clarify how NSLBP relates to body upright posture, proprioception, and motor control and how these are modified in patients compared to healthy young adults (121 healthy young adults: 57 females and 64 males). A cohort of 83 NSLBP patients (43 females, 40 males) were recruited in a cross-sectional observational study. Patients’ entire body posture, including 3D spine shape reconstruction, was measured using a non-ionising 3D optoelectronic stereophotogrammetric approach. Thirteen quantitative biomechanical parameters describing the nature of body posture were computed. The statistical analysis was performed using multivariate methods. NSLBP patients did not present an altered proprioception and motor control ability compared to healthy young adults. Furthermore, as for healthy subjects, NSLBP patients could not focus and control their posture globally. Proprioception and motor control in natural erect standing are vague for most people regardless of gender and concurrent nonspecific low back pain. Self-correction manoeuvres improving body posture and spine shape must be learned with specific postural training focusing on the lumbar spine.

Anterior Cruciate Ligament Reconstructed Patients Who Recovered Normal Postural Control Have Dissimilar Brain Activation Patterns Compared to Healthy Controls

Simple Summary

We report that patients with anterior cruciate ligament reconstruction have similar postural control but different cortical activation patterns in several regions of the brain when compared to healthy controls. This is significant because dissimilar cortical activation patterns indicate that neural adaptation in the brain is responsible for motor coordination, possibly due to altered proprioception, despite having a surgical reconstruction after an anterior cruciate ligament injury. Such neuroplasticity in ACLR patients may imply compensatory neural protective mechanisms in order to sustain postural control, which is a fundamental functional skill in daily activities. We believe that our findings will elucidate other researchers and clinicians about the effects of a peripheral joint injury on the brain’s function during postural control.

Abstract

Postural control, which is a fundamental functional skill, reflects integration and coordination of sensory information. Damaged anterior cruciate ligament (ACL) may alter neural activation patterns in the brain, despite patients’ surgical reconstruction (ACLR). However, it is unknown whether ACLR patients with normal postural control have persistent neural adaptation in the brain. Therefore, we explored theta (4–8 Hz) and alpha-2 (10–12 Hz) oscillation bands at the prefrontal, premotor/supplementary motor, primary motor, somatosensory, and primary visual cortices, in which electrocortical activation is highly associated with goal-directed decision-making, preparation of movement, motor output, sensory input, and visual processing, respectively, during first 3 s of a single-leg stance at two different task complexities (stable/unstable) between ACLR patients and healthy controls. We observed that ACLR patients showed similar postural control ability to healthy controls, but dissimilar neural activation patterns in the brain. To conclude, we demonstrated that ACLR patients may rely on more neural sources on movement preparation in conjunction with sensory feedback during the early single-leg stance period relative to healthy controls to maintain postural control. This may be a compensatory protective mechanism to accommodate for the altered sensory inputs from the reconstructed knee and task complexity. Our study elucidates the strategically different brain activity utilized by ACLR patients to sustain postural control.

Association between Kinesiophobia and Knee Pain Intensity, Joint Position Sense, and Functional Performance in Individuals with Bilateral Knee Osteoarthritis

In current clinical practice, fear of movement has been considered a significant factor affecting patient disability and needs to be evaluated and addressed to accomplish successful rehabilitation strategies. Therefore, the study aims (1) to establish the association between kinesiophobia and knee pain intensity, joint position sense (JPS), and functional performance, and (2) to determine whether kinesiophobia predicts pain intensity, JPS, and functional performance among individuals with bilateral knee osteoarthritis (KOA). This cross-sectional study included 50 participants (mean age: 67.10 ± 4.36 years) with KOA. Outcome measures: The level of kinesiophobia was assessed using the Tampa Scale of Kinesiophobia, pain intensity using a visual analog scale (VAS), knee JPS using a digital inclinometer, and functional performance using five times sit-to-stand test. Knee JPS was assessed in target angles of 15°, 30°, and 60°. Pearson’s correlation coefficients and simple linear regressions were used to analyze the data. Significant moderate positive correlations were observed between kinesiophobia and pain intensity (r = 0.55, p < 0.001), JPS (r ranged between 0.38 to 0.5, p < 0.05), and functional performance (r = 0.49, p < 0.001). Simple linear regression analysis showed kinesiophobia significantly predicted pain intensity (B = 1.05, p < 0.001), knee JPS (B ranged between 0.96 (0° of knee flexion, right side) to 1.30 (15° of knee flexion, right side)), and functional performance (B = 0.57, p < 0.001). We can conclude that kinesiophobia is significantly correlated and predicted pain intensity, JPS, and functional performance in individuals with KOA. Kinesiophobia is a significant aspect of the recovery process and may be taken into account when planning and implementing rehabilitation programs for KOA individuals.

Impaired wrist position sense is linked to motor abnormalities in young adults with a probable developmental coordination disorder

Proprioceptive deficits have been found to underlie motor abnormalities in individuals with movement disorders. This study investigated wrist proprioceptive acuity in young adults with and without probable developmental coordination disorder (DCD) and examined how proprioceptive acuity is linked to different domains of motor function. Thirty participants were included in this study (age, 19-22 years), ten with probable DCD and 20 controls. Wrist proprioceptive acuity was assessed using a joint position sense paradigm under contralateral and ipsilateral conditions. The Bruininks-Oseretsky Test of Motor Proficiency 2^nd Edition (BOT-2) was used to measure different domains of motor ability. Compared to the control group, young adults with probable DCD exhibited significantly increased proprioceptive error variability in contralateral (p < 0.0001) and ipsilateral conditions (p < 0.05). Furthermore, wrist proprioceptive error variability was significantly associated with the levels of body coordination measured by BOT-2 (r = - 0.55). This study verified impaired wrist proprioceptive function in young adults with probable DCD, which is likely to contribute to motor impairment in adults with DCD.