Compensatory Postural Adjustments Research Articles

Activity of deep trunk muscles for postural control to predictable and unpredictable sagittal plane perturbations: Electromyographic analysis.

The activity of deep trunk muscles (psoas major; PM, quadratus lumborum; QL, transverse abdominis; TrA, and lumbar multifidus; MF) in response to external perturbation is not clearly known. This study aimed to record the onset and amount of activity of the deep trunk muscles during sagittal plane perturbations. Fourteen healthy males participated in this study. The activity of the right deep trunk muscles was recorded using wire electrodes. In standing, the participants performed three tasks: a pendulum impacted from anterior with predictable and unpredictable and posterior with unpredictable. In predictable anterior perturbation, the TrA and PM demonstrated feedforward activation, while all deep trunk muscles demonstrated feedback activation in unpredictable anterior and posterior perturbations. In the anticipatory postural adjustment phase, the activity of the TrA was large in predictable anterior perturbation, while that of all deep trunk muscles was slight in other perturbations. In the compensatory postural adjustment phase, the activity of the PM, QL, and TrA in unpredictable anterior perturbation and those of the PM, QL, and MF in unpredictable posterior perturbation were large. These results showed that the onset and magnitude of deep trunk muscle activity changed depending on both predictable or unpredictable perturbation and the direction of perturbation.

Postural adjustments to self-triggered perturbations under conditions of changes in body orientation

We studied anticipatory and compensatory postural adjustments (APAs and CPAs) associated with self-triggered postural perturbations in conditions with changes in the initial body orientation. In particular, we were testing hypotheses on adjustments in the reciprocal and coactivation commands, role of proximal vs. distal muscles, and correlations between changes in indices of APAs and CPAs. Healthy young participants stood on a board with full support or reduced support area and held a standard load in the extended arms. They released the load in a self-paced manned with a standard small-amplitude arm movement. Electromyograms of 12 muscles were recorded and used to compute reciprocal and coactivation indices between three muscle pairs on both sides of the body. The subject’s body was oriented toward one of three targets: straight ahead, 60° to the left, and 60° to the right. Body orientation has stronger effects on proximal muscle pairs compared to distal muscles. It led to more consistent changes in the reciprocal command compared to the coactivation command. Indices of APAs and CPAs showed positive correlations across conditions. We conclude that the earlier suggested hierarchical relations between the reciprocal and coactivation command could be task-specific. Predominance of negative or positive correlations between APA and CPA indices could also be task-specific.

A 3-DoF robotic platform for the rehabilitation and assessment of reaction time and balance skills of MS patients.

The central nervous system (CNS) exploits anticipatory (APAs) and compensatory (CPAs) postural adjustments to maintain the balance. The postural adjustments comprising stability of the center of mass (CoM) and the pressure distribution of the body influence each other if there is a lack of performance in either of them. Any predictable or sudden perturbation may pave the way for the divergence of CoM from equilibrium and inhomogeneous pressure distribution of the body. Such a situation is often observed in the daily lives of Multiple Sclerosis (MS) patients due to their poor APAs and CPAs and induces their falls. The way of minimizing the risk of falls in neurological patients is by utilizing perturbation-based rehabilitation, as it is efficient in the recovery of the balance disorder. In light of the findings, we present the design, implementation, and experimental evaluation of a novel 3 DoF parallel manipulator to treat the balance disorder of MS. The robotic platform allows angular motion of the ankle based on its anthropomorphic freedom. Moreover, the end-effector endowed with upper and lower platforms is designed to evaluate both the pressure distribution of each foot and the CoM of the body, respectively. Data gathered from the platforms are utilized to both evaluate the performance of the patients and used in high-level control of the robotic platform to regulate the difficulty level of tasks. In this study, kinematic and dynamic analyses of the robot are derived and validated in the simulation environment. Low-level control of the first prototype is also successfully implemented through the PID controller. The capacity of each platform is evaluated with a set of experiments considering the assessment of pressure distribution and CoM of the foot-like objects on the end-effector. The experimental results indicate that such a system well-address the need for balance skill training and assessment through the APAs and CPAs.

The Effect of Additional Leg Supports in Control of Posture in Sitting

The objective of the study was to investigate the effect of leg supports on the anticipatory and compensatory postural adjustments of sitting subjects exposed to external perturbations in the anterior-posterior direction. Ten young participants received perturbations applied to the upper body while sitting on a stool with an anterior or posterior leg support and when using a footrest. Electromyographic activities of the trunk and leg muscles and center of pressure displacements were recorded and analyzed during the anticipatory and compensatory phases of postural control. Anticipatory activities were observed in the tibialis anterior, biceps femoris, and erector spinae muscles in the anterior leg support condition. Early onset of muscle activity was observed in the tibialis anterior, biceps femoris, rectus femoris, and erector spinae muscles in the posterior leg support condition compared to the feet support condition. Moreover, to maintain balance participants utilized co-contraction of muscles as the main mechanism of balance control in sitting regardless of the availability of the anterior or posterior leg support. There was no effect of a leg support on center of pressure displacements. The outcome of the study provides a background for future investigations of the effect of leg supports on control of balance in sitting when perturbed.

Postural adjustment in standing position when catching a ball under unpredictable conditions of the direction to be caught

BackgroundBalanced postural control of the body is associated with two mechanisms: anticipatory postural adjustment and compensatory postural adjustment. Previous studies reported changes in body postural control under unpredictable conditions (interference with closed eyes). Research questionTo ascertain whether in contrast with predictable disturbances, there is a difference in muscle activity and center of pressure displacement changes when the direction of the disturbance is unpredictable. MethodsThree examiners stood at 45° to the left, the front, and 45° to the right of the participant to throw the ball to him. 11 healthy young participants were required to maintain their balance in the standing position after receiving the ball in conditions with and without known catching directions. The anticipatory postural adjustment and compensatory postural adjustment integral changes of the muscle activity in the lower limbs and trunk bilaterally and at the center of pressure displacement in the known and unknown conditions were observed. Two-way ANOVA was used to compare the differences in muscle activity and displacement changes. ResultsResults showed that the center of pressure in the anticipatory postural adjustment and compensatory postural adjustment in the posterior direction with known catching direction was significantly shorter than those without. Integration of electromyogram in anticipatory postural adjustment of the right soleus (p = 0.023) was associated with higher muscle activities in the unknown than known conditions. Integration of electromyogram in compensatory postural adjustment of the right tibial anterior (p = 0.004), right rectus femoris (p = 0.023) and left rectus abdominis (p = 0.038) in unknown catching direction had significantly greater muscle activity than those without. When the direction of the perturbation is unpredictable, the central nervous system may initiate and induce greater center of pressure changes in the posterior direction with changes in several muscular activities to ensure postural control.

An increase in relative contribution of compensatory postural adjustments during voluntary movement while standing in adolescents and young adults with bilateral spastic cerebral palsy.

Previous studies have revealed several deficits in anticipatory postural adjustments (APAs) during voluntary movements while standing in individuals with bilateral spastic cerebral palsy (BSCP). However, it remains unclear whether compensatory postural adjustments (CPAs) during movement increase to compensate for APA deficits. We investigated the anticipatory and compensatory activities of postural muscles during voluntary movement while standing in adolescents and young adults with BSCP. The study included seven participants with BSCP with level II on the Gross Motor Function Classification System (GMFCS), seven with BSCP with level III on the GMFCS, and fourteen healthy controls. The participants stood on a force platform and lifted a load under two weight conditions (light and heavy). The electromyographic activities of postural muscles were analyzed at time intervals typical for APAs and CPAs. The percentage of muscle activity in the CPA time epoch against the total muscle activity during the APA and CPA time epochs was higher in the two BSCP groups than in the control group. In the control group, a load-related modulation was observed only in the APA time epoch, whereas in the BSCP-II group, the load-related increase was observed in both the APA and CPA time epochs. No load-related modulations were observed in the BSCP-III group. These findings suggest that adolescents and young adults with BSCP exhibit an increase in the relative contribution of CPAs during voluntary movement and that there exist severity-related differences in the modulation of APAs and CPAs.

Age-Related Differences in Stepping Reactions to a Balance Perturbation: A Functional Near-Infrared Spectroscopy and Surface Electromyography Study.

We sought to investigate age-related differences in stepping reactions to a sudden balance perturbation, focusing on muscle activity and cortical activation. A total of 18 older healthy adults (older group, OG) and 16 young healthy adults (young group, YG) were recruited into this study. A cable-pull instrument was used to induce a forward perturbation at the waist level among participants, who were required to take the right step to maintain their postural balance. The seven right lower-limb muscle activities during periods of compensatory postural adjustments (CPAs) were recorded by surface electromyography. At the same time, the signals of channels located in the prefrontal, temporal and parietal lobes were recorded by functional near-infrared spectroscopy (fNIRS) during the whole process. Integral electromyograms of the right peroneus muscle, gluteus medius, and lateral gastrocnemius muscles showed greater activity for the OG in the CPA periods. Two channels belonging to the right pre-frontal (PFC) and pre-motor cortex (PMC) revealed lower activation in the OG compared with the YG. These findings can help us to better understand the differences at the peripheral and central levels and may provide some suggestions for future neuromodulation techniques and other clinical treatments.

The effect of the predictability of perturbation magnitudes in older adults with mild cognitive impairment.

Balance impairment is common in older adults with mild cognitive impairment (MCI). The ability to predict the magnitude of the body disturbance is essential to balance maintenance. The purpose of the study was to investigate the effect of the predictability of the perturbation magnitudes on anticipatory (APAs) and compensatory (CPAs) postural adjustments in older adults with MCI and healthy older adults. Fifteen individuals with MCI and fourteen age-matched control participants stood on the force platform and received the pendulum perturbations of small or large magnitudes applied to their upper body. Electromyographic activity of eight leg and trunk muscles and displacements of the center of pressure (COP) were recorded and analyzed during the APA and CPA phases of postural control. Individuals with MCI demonstrated smaller APAs in the conditions of the perturbation of unpredictable magnitude and required more trials to optimize their postural adjustments, as compared to healthy older adults. Moreover, individuals with MCI had reduced postural stability in the conditions of unpredictable magnitude of the perturbation. The findings suggest that cognitive decline adversely affects the ability to predict the magnitude of the perturbations.

Anticipatory and Compensatory Postural Adjustments in Response to Dynamic Platform Perturbation during a Forward Step

We investigated the generation of anticipatory (APAs) and compensatory postural adjustments (CPAs) in preparation for a step during support surface perturbation. Changes in anticipatory muscle activation in the trunk segment were predominantly in the co-contraction indices from −600 t 0 −400 ms to foot-off. Reciprocal indices of the shank muscles were pronounced in the APA intervals. During the CPA intervals, larger reciprocal muscle activities were detected compared to the APA intervals. The results showed subjects co-varied the reciprocal and co-contraction activations in postural muscles to counteract the perturbation and generate mechanical effects sufficient for stepping during the APA and CPA intervals. This study enhances our understanding of the interaction between the APAs and CPAs in balance maintenance.

How Does Lower Limb Respond to Unexpected Balance Perturbations? New Insights from Synchronized Human Kinetics, Kinematics, Muscle Electromyography (EMG) and Mechanomyography (MMG) Data.

Making rapid and proper compensatory postural adjustments is vital to prevent falls and fall-related injuries. This study aimed to investigate how, especially how rapidly, the multiple lower-limb muscles and joints would respond to the unexpected standing balance perturbations. Unexpected waist-pull perturbations with small, medium and large magnitudes were delivered to twelve healthy young adults from the anterior, posterior, medial and lateral directions. Electromyographical (EMG) and mechanomyographical (MMG) responses of eight dominant-leg muscles (i.e., hip abductor/adductors, hip flexor/extensor, knee flexor/extensor, and ankle dorsiflexor/plantarflexors) together with the lower-limb joint angle, moment, and power data were recorded. The onset latencies, time to peak, peak values, and/or rate of change of these signals were analyzed. Statistical analysis revealed that: (1) agonist muscles resisting the delivered perturbation had faster activation than the antagonist muscles; (2) ankle muscles showed the largest rate of activation among eight muscles following both anteroposterior and mediolateral perturbations; (3) lower-limb joint moments that complied with the perturbation had faster increase; and (4) larger perturbation magnitude tended to evoke a faster response in muscle activities, but not necessarily in joint kinetics/kinematics. These findings provided insights regarding the underlying mechanism and lower-limb muscle activities to maintain reactive standing balance in healthy young adults.

Validity and reliability of a smartphone-based assessment for anticipatory and compensatory postural adjustments during predictable perturbations

BackgroundPostural adjustments involve displacements of the center of mass (COM), controlled by the central nervous system (CNS), to maintain equilibrium whilst standing. Postural adjustments can be anticipatory (APAs) or compensatory (CPAs), and are triggered to counteract predictable perturbations. Research questionIs the new smartphone application, Momentum, a valid and reliable tool for the assessment of body balance, by measuring APAs and CPAs using accelerometer readings? Methods20 young adults were exposed to external predictable perturbations induced at the shoulder level, whilst standing. COM linear acceleration was recorded by Momentum (extracting data from a smartphone’s accelerometer) and a 3D motion capture system. ResultsThe key results demonstrated a very high, significant correlation (r ≥ 0.7, p < 0.05) between the two device settings in the APA parameters, which obtained r = 0.65, denoting a high correlation. Considering the reliability, variables that are compensatory in nature are presented on a scale of good to excellent in measurement methods, kinematics, and Momentum. However, the anticipatory variables presented excellent reliability only for the kinematics. SignificanceThese experiments show that Momentum is a valid method for measuring COM acceleration under predictable perturbations and is reliable for compensatory events.

Postural Threat Influences the Coupling Between Anticipatory and Compensatory Postural Adjustments in Response to an External Perturbation

Fear of falling increases conscious control of balance and postural threat warrants accurate anticipatory motor commands for keeping a safe body posture. This study examines the anticipatory (APAs) and compensatory (CPAs) postural adjustments generated in response to an external perturbation while individuals are positioned at two different altitudes (2 cm and 80 cm) from the floor level. The main result indicates that due to the perceived emotional threat, different agonist and antagonist muscles synergies (R and C-Indexes) are manifested, particularly during the anticipatory phase. The results suggest that the CNS sends central commands for anticipating postural adjustments by adopting primarily a muscle reciprocal activation instead of a muscle co-activation strategy. Interestingly, the APAs strategies were modified under different postural threats by controlling the agonist–antagonist muscles at different joints of lower extremity. For CPAs the reciprocal activation was less applied compared to muscles co-activation to unsure larger margin for compensatory adjustments as needed and re-establish the postural stability. The results indicate that when facing to a postural threat, the CNS modulates the anticipatory and compensatory phases of postural adjustments to minimize the risk of falling.

Effects of unilateral and bilateral lower extremity fatiguing exercises on postural control during quiet stance and self-initiated perturbation.

Postural control can be more difficult during muscle fatigue. Anticipatory postural adjustments (APAs) and compensatory postural adjustments (CPAs) are the two main postural strategies controlled by the central nervous system. Unchanged or early anticipatory onset together with altered activation magnitude during the APAs phase is observed in the trunk and thigh muscles following unilateral and bilateral fatiguing exercises. Thus far, no studies have compared the effect of such exercises on APAs and CPAs. This study compared the effects of these exercises performed at the same relative workload on center of pressure (COP)-based postural stability measures during quiet stance and electromyography (EMG)-based APAs and CPAs during self-initiated perturbation. Fifteen young male subjects completed the two separated fatiguing sessions; 50% of maximal voluntary contraction force obtained from the unilateral (dominant) and bilateral legs with five sets of 20 times lower limb exercise was respectively applied as unilateral and bilateral fatiguing protocols. Spatio-temporal COP parameters (sway velocity, total displacement, and envelope area) were used to evaluate postural stability, and spectral analysis was performed to estimate the distributions in COP power spectrum. EMG activities of transversus abdominis/internal oblique (TrA/IO) and lumbar multifidus (LMF) were recorded and analyzed during the APAs and CPAs phases. Increased sway velocity and total displacements occurred following both unilateral and bilateral fatiguing exercises; however, the envelope area was not affected. Further, early anticipatory onset of TrA/IO was found after bilateral than after unilateral fatiguing exercise. Co-activation index of the TrA/IO-LMF muscle pair during the CPAs phase increased following both fatiguing sessions. The results partly confirmed previously reported fatigue effects induced by unilateral and bilateral exercises on postural stability. It was observed that APAs onsets were altered differently following a unilateral or bilateral fatiguing exercise, whereas the alterations of CPAs were independent of fatigue conditions. Repetitive unilateral or bilateral fatiguing exercises in patients or athletes may differently alter the anticipatory component of postural control.

The Effect of Predictability of the Perturbation Magnitude on Anticipatory and Compensatory Postural Adjustments during a Bimanual Load-Lifting Task

Background: To minimize the potential postural disturbance induced by external or self-initiated perturbations, humans generate anticipatory postural adjustments based on their perceived consequences of the body disturbance. Lifting is a common activity that induces a self-initiated perturbation that can compromise balance control. Aim: To assess anticipatory (APAs) and compensatory (CPAs) postural adjustments generated in response to a self-initiated perturbation induced by lifting objects of uncertain mass. Methods: Ten young adults lifted the tray with either light or heavy object placed in it. Electromyographic activity of eight trunk and leg muscles, and center-of-pressure (COP) displacements were recorded and analyzed during the APAs and CPAs phases. Results: When the object mass changed unpredictably, the participants generated APAs based on the most recent experience of lifting and needed three trials of lifting to generate optimal APAs and CPAs. Conclusions: Young adults were able to predict the perturbation magnitude during self-initiated perturbations induced by lifting objects. The outcome provides a foundation for future studies focusing on the role of predictability of perturbation consequences in postural control of older adults and individuals with balance deficit.

The role of predictability of the magnitude of a perturbation in control of vertical posture when catching an object.

The predictability of perturbation magnitude plays an important role in control of standing posture. The aim of the study was to examine anticipatory (APAs) and compensatory (CPAs) postural adjustments in response to catching objects of uncertain mass. Twenty adults caught the same object with either light or heavy weight placed in it. Electromyographic activity of eight trunk and leg muscles, displacements of the center of pressure, and angular displacement of the shoulder joint were recorded and analyzed during the APAs and CPAs intervals. When the subjects experienced repeated catching of the object with the same weight, they estimated the object mass beforehand and generated APAs more precisely. When the object mass changed unpredictably, they generated APAs based on the most recent catch and needed four to six trials to optimize APAs and CPAs. The muscle co-contraction was a primary pattern for catching the object of uncertain mass. The results of the study suggest that catching the object of uncertain mass is a challenging task that involves co-contraction of postural muscles to maintain balance.

Perceptual distortion in virtual reality and its impact on dynamic postural control

BackgroundVoluntary movement such as lifting a foot in preparation to stepping acts as a self-initiated perturbation that disturbs postural equilibrium. To maintain and restore equilibrium, humans utilize early, anticipatory, and compensatory postural adjustments. Despite technological progress in accessible virtual reality (VR) devices, little is known on the usage of VR in control and maintenance of balance while standing. Research questionHow does VR modulate early, anticipatory, and compensatory postural adjustments during a dynamic task of leg lifting while avoiding an obstacle? MethodsFirst, the postural adjustments in a single-leg obstacle avoidance were compared between real and VR settings, where a statistical reanalysis was performed with data subsets that minimize the difference of foot elevation speed. Second, the effect of simple foot elevation was examined to identify the fundamental nature of leg lifting motion as a self-initiated perturbation. Lastly, perceptual distortion in VR was assessed by evaluating how the spatial scale of the virtual scene used in the single-leg obstacle avoidance experiment was recognized by participants. ResultsThe VR setting reduced the activities of lower leg muscles on the supporting side not only in the compensatory phase but also in the preparatory early and anticipatory phases. On the other hand, simple foot elevation resulted in a significant increase of muscle activities with lifting height only found in the compensatory phase. Furthermore, it is suggested that the VR induced perceptual distortion in estimating the sizes of the virtual objects. SignificanceThe findings provide more definitive evidence that VR presentation modulates the components of postural adjustments for maintaining upright stance while being perturbed. One of the potential psychophysical factors is perceptual distortion in VR, and this provides critical information for further development of VR based training system.

Postural Adjustments and Biomechanics During Gait Initiation and Obstacle Negotiation: A Comparison Between Akinetic-Rigid and Hyperkinetic Parkinson's Disease.

Background: Individuals with Parkinson’s disease (PD) exhibit different combinations of motor symptoms. The most frequent subtypes are akinetic-rigid (AK-R) and hyperkinetic (HYP). Motor symptoms, such as rigidity and bradykinesia, can directly affect postural adjustments and performance in daily tasks, like gait initiation and obstacles negotiation, increasing the risk of falls and functional dependence.Objective: To compare postural adjustments and biomechanical parameters during the gait initiation and obstacle negotiation of people with AK-R and HYP PD and correlate with functional mobility and risk of falls.Methods: Cross-sectional study. Thirty-three volunteers with PD were divided into two groups according to clinical motor manifestations: AK-R (n = 16) and HYP (n = 17). We assessed the anticipatory (APA), compensatory (CPA) postural adjustments analyzing kinematic, kinetic and, electromyographic parameters during the gait initiation and obstacle negotiation tests. We applied independent T-tests and Pearson correlation tests for comparisons and correlations, respectively (α = 0.05).Results: In the APA phase of the gait initiation test, compared to the functional HYP group, the AK-R group showed shorter time for single support (p = 0.01), longer time for double support (p = 0.01) accompanied by a smaller first step (size, p = 0.05; height, p = 0.04), and reduced muscle activation of obliquus internus (p = 0.02). Similarly, during the first step in the obstacle negotiation test, the AK-R group showed less step height (p = 0.01) and hip excursion (p = 0.02), accompanied by a reduced mediolateral displacement of the center of pressure (p = 0.02) during APA, and activation of the gluteus medius (p = 0.02) and the anterior tibialis (p = 0.04) during CPA in comparison with HYP group.Conclusion: The findings suggest that people with AK-R present impaired postural adjustments during gait initiation and obstacles negotiation compared to hyperkinetic PD. Based on defined motor symptoms, the proposition presented here revealed consistent postural adjustments during complex tasks and, therefore, may offer new insights onto PD motor evaluation and neurorehabilitation.

A Study on the Relationship between Postural Control and Pain-Related Clinical Outcomes in Patients with Chronic Nonspecific Low Back Pain.

Objectives To explore the relationship between postural control and pain-related clinical outcomes in patients with chronic nonspecific low back pain (cNLBP). Methods Participants with cNLBP and healthy individuals were recruited. Muscle activities were recorded during internal and external perturbation tasks. Postural control capacity was assessed by muscle onset time and integrals of electromyography (iEMGs) of postural muscles during the phases of anticipatory postural adjustments (APAs) and compensatory postural adjustments (CPAs). Correlation analysis was employed to investigate the relationship between postural control capacity, pain, and disability. Results Twenty-seven patients with cNLBP and 27 healthy participants were recruited. Gastrocnemius (GA) muscle onset time was earlier in the cNLBP group than in the control group in the internal perturbation task. The onset time of GA and erector spinae (ES) of the cNLBP group was later than that of the controls in the external perturbation task. Disability level moderately correlated with the iEMGs of rectus abdominis (RA), GA, and external oblique (EO) during APAs. Pain score moderately correlated with the iEMGs of RA, EO, and ES during CPAs of perturbation tasks. Conclusion cNLBP participants had altered muscle activation strategy to maintain postural stability in response to perturbation. This study further discovered that pain-related disabilities of cNLBP participants were likely related to the APAs capacity, whereas the pain intensity may relate to the CPAs capacity. Pain and disability may therefore be related to the control process of the posture-related muscles.

The Effect of Virtual Reality Training on Anticipatory Postural Adjustments in Patients with Chronic Nonspecific Low Back Pain: A Preliminary Study

Objectives This study is aimed at exploring the effects of virtual reality (VR) training on postural control, measured by anticipatory and compensatory postural adjustments (APAs and CPAs, respectively), in patients with chronic nonspecific low back pain (CNLBP) and the potential neuromuscular mechanism of VR training. Methods Thirty-four patients were recruited and randomly assigned to the VR group (n = 11), the motor control exercise group (MCE, n = 12) and the control group (CG, n = 11). The VR group received VR training using Kinect Xbox 360 systems and magnetic therapy. Besides magnetic therapy, the participants in the MCE group performed real-time ultrasound-guided abdominal drawing-in maneuver (ADIM) and four-point kneeling exercise. The CG only received magnetic therapy. Surface muscle electromyography (sEMG) was used to record the muscle activities of transverse abdominis (TrA), multifidus (MF), lateral gastrocnemius (LG), and tibialis anterior (TA) during ball-hitting tasks. The muscle activation time and integrals of the electromyography activities (IEMGs) during the APA and CPA stages were calculated and used in the data analysis. The visual analogue scale (VAS) and Oswestry dysfunction index (ODI) scores were also recorded. Results A significant interaction effect of time × group was observed on the activation time of TrA (p = 0.018) and MF (p = 0.037). The post-intervention activation time of the TrA was earlier in the VR group (p = 0.029). In contrast, the post-intervention activation time of the MF was significantly delayed in the VR group (p = 0.001). The IEMGs of TrA (p = 0.002) and TA (p = 0.007) during CPA1 significantly decreased only in the VR group after the intervention. The VAS scores of three group participants showed significant decreases after intervention (p < 0.001). Conclusions Patients with CNLBP showed reciprocal muscle activation patterns of the TrA and MF muscles after VR training. VR training may be a potential intervention for enhancing the APAs of the patients with CNLBP.

Symptomatic individuals with Lumbar Disc Degeneration use different anticipatory and compensatory kinematic strategies to asymptomatic controls in response to postural perturbation

BackgroundLumbar Disc Degeneration (LDD) is associated with recurrent low back pain (LBP) (symptomatic). However, in some instances of LDD, people do not experience LBP (asymptomatic). Research questionAs a step towards understanding why some people with LDD experience LBP and others do not, the primary aim of this study was to examine differences in anticipatory (APA) and compensatory postural adjustments (CPA), between symptomatic LDD patients (LDD pain) and asymptomatic LDD controls (LDD no pain) during postural perturbation. The secondary aim was to determine simultaneous differences in mental health, disability and quality of life status. Methods3 T MRI was used to acquire T2 weighted images (L1-S1) from LDD no pain (n = 34) and LDD pain groups (n = 34). In this observational study, responses to predicted and unpredicted forward perturbations were examined using three dimensional motion capture. A Mann Whitney U test was conducted to examine group differences in sagittal spine and lower limb kinematics (integrated angular displacements during four established APA and CPA time intervals), anxiety, depression, disability and quality of life. ResultsThe LDD pain group exhibited lower hip and knee displacements (p = 0.049−0.040) than the LDD no pain group during predicted and unpredicted perturbation. The LDD pain group also exhibited higher compensatory lumbar displacement than the LDD no pain group (p = 0.040−0.005) in the predicted condition but there was no difference observed in the unpredicted condition. The LDD pain group experienced higher levels of depression, anxiety and disability (p < 0.0001) and lower quality of life (p = 0.0001) than LDD controls. SignificanceSymptomatic LDD patients are different from LDD controls; they exhibit different kinematic strategies, levels of disability, anxiety, depression and quality of life. Effective care may benefit from evaluating and targeting these differences.