Torque responses to in-place-perturbations in people with multiple sclerosis

BackgroundAutomatic postural responses are critical to prevent falls after a loss of balance. Although responses have been shown to be delayed in people with multiple sclerosis (PwMS), the degree to which other aspects of these movements are impacted by MS remains unknown.Research QuestionDo responses to in-place support-surface perturbations differ in PwMS compared to neurotypical adults? Are these responses related to a functional measure of postural response performance- center of mass (COM) displacement?.Method52 PwMS and 20 neurotypical, age-matched adults (NA) experienced backward support surface perturbations resulting in forward loss of balance and requiring an in-place response. Center of pressure (COP) and torque were calculated from force plates while center of mass (COM) approximations were collected via motion capture. Primary outcomes were maximal torque production at the foot and its timing, rate, and onset.ResultsPwMS and NA demonstrated no differences in maximal torque production (p = 0.79), timing of maximal torque (p = 0.29), rate of torque development (p = 0.76), or the onset of AP COP movement (p = 0.44). There was a significant negative association between the rate of torque development and forward COM displacement in both groups (Control: r=-0.64, p = 0.002; MS: r=-0.35, p = 0.01). Larger maximal torque production was also associated with smaller COM displacement in PwMS (r=-0.33, p = 0.02).ConclusionTorque profiles in response to backward support surface translations resulting in feet in-place responses were similar in people with mild MS and neurotypical adults. The rate of development and maximal torque were however correlated to functional postural response outcomes. These findings suggest that while not worse in PwMS during in-place perturbations, force-responses seem to be important predictors of the effectiveness of reactive postural control responses.     

Evaluating the contribution of reactive balance to prediction of fall rates cross-sectionally and longitudinally in persons with multiple sclerosis

BackgroundFalls are common in persons with multiple sclerosis (PwMS). Reactive postural control—one’s response to a balance perturbation—is likely an aspect of fall risk; however, the relationship between reactive posture and falls is poorly understood in PwMS.ObjectiveWe evaluated tibialis anterior muscle onset latency (TA latency) after balance perturbations as a predictor of fall rates in PwMS, controlling for clinical, functional, sensory, psychological, and cognitive factors.MethodAt baseline of the 18-month cohort study, 122 participants with MS (EDSS = 2.23) were included. Assessments were conducted every 6 months.ResultsOf the original 122 participants at the baseline collection, data were available from 41, 39, and 34 people at the 6, 12, and 18 month follow-ups, respectively. Percent fallers at the four time points were 35.3%, 12.2%, 15.4%, and 20.5%. Cross-sectionally (i.e., at baseline), the Timed Up-and-Go, Falls Efficacy Scale – International (FES-I), and TA latency after perturbations were significant predictors of retrospective falls rates using negative binomial regression. Longitudinally, random-effects negative binomial regression found that trait-level FES-I, Stroop Color-Word, and TA latency were significant predictors for falls rates.ConclusionDelays in automatic postural responses seem to account uniquely for fall rates in PwMS—beyond clinical, balance, or mobility measures. These delays may contribute to the increased fall rate in PwMS. In addition to brief self-report instruments (FES-I) and cognitive assessments, muscle onset after balance perturbations may be a valuable tool for predicting falls in those with MS.     

Effects of light finger touch on the regularity of center-of-pressure fluctuations during quiet bipedal and single-leg postural tasks

BackgroundThe use of extra sources of sensory information associated with light fingertip touch to enhance postural steadiness has been associated with increased attentional demands, whereas the regularity of center of pressure (COP) fluctuations has been interpreted as a marker of the amount of attention invested in posture control.Research questionThis study addressed whether increased attentional demands associated with postural tasks involving light finger touch might be reflected by measures of COP regularity.MethodsThe experiments involved quiet bipedal stance (n = 8 participants) and single-legged stance (n = 14 participants). Each participant was instructed to stand as quietly as possible on a force plate, either touching an external rigid surface (applied force < 1 N, light touch condition), or not (no touch condition). Postural steadiness was assessed by traditional COP measurements (COP Area, RMS, and velocity), whereas the regularity of postural sway was based on estimates of the sample entropy (SaEn) of the COP time series.ResultsTraditional parameters of postural sway and COP regularity (inversely related to SaEn COP measurements) were reduced during the touch conditions as compared to the no-touch conditions, for both bipedal quiet stance and single-legged stance. Decreased COP regularity with light touch was mainly reflected in the direction of the largest postural sway (i.e. in the sagittal plane for bipedal stance and in the frontal plane for single-legged stance).SignificanceThe present results suggest that actively touching an external surface with the fingertip, besides increasing postural steadiness, generated an externally oriented (presumably cognitive-dependent) focus of attention, so that participants invested less attention on the postural task per se (as suggested by increased SaEn), which might be associated with a more “automatic” control of posture.     

Use of time-to-boundary to assess postural instability and predict functional mobility in people with diabetes mellitus and peripheral neuropathy

BackgroundPeople with diabetes mellitus and peripheral neuropathy (DMPN) often have balance and mobility deficits. Time-to-boundary (TTB) is a parameter of postural control that combines position and velocity center of pressure data. While not previously investigated, assessment of TTB may provide new insight regarding postural control in people with DMPN.Research questionIs TTB reduced and related to a measure of mobility in people with DMPN?MethodsThirteen people with DMPN without fall history and 13 healthy matched controls participated in this case-control study. Participants stood in double-limb stance on a force plate. The anterior-posterior and medial-lateral center of pressure position and velocity relative to the boundaries of the base of support were used to calculate TTB (s). Lower values indicate less postural control. Time-to-failure during single-limb stance was a secondary measure of postural control. Time to complete the Timed Up and Go (TUG) was our measure of mobility. Longer TUG times correspond to decreased mobility, strength, and balance. Independent t-tests or Mann-Whitney U tests were conducted to assess group differences. Bivariate correlations between task outcomes were conducted.ResultsAnterior-posterior TTB and single-limb stance times were shorter in people with DMPN (p ≤ 0.04). TUG times were longer in the DMPN group (p = 0.04). In the DMPN group, inverse relationships were observed between TTB and TUG (anterior-posterior R² = .34; medial-lateral R² = .49; both p = 0.01), but not between single-limb stance times and TTB or TUG.SignificanceTTB was a sensitive measure of postural control in people with DMPN. The detected relationship between TTB and TUG newly establishes TTB as a clinically meaningful indicator of balance and function. Study findings may serve to further guide balance screening and rehabilitation efforts in people with DMPN.     

Intrinsic foot muscles act to stabilise the foot when greater fluctuations in centre of pressure movement result from increased postural balance challenge

BackgroundIncreased postural balance challenge is associated with more fluctuations in centre of pressure movement, indicating increased interference from the postural control system. The role of intrinsic foot muscles in balance control is relatively understudied and whether such control system interference occurs at the level of these muscles is unknown.Research QuestionDo fewer fluctuations in intrinsic foot muscle excitation occur in response to increased postural balance challenge?MethodsSurface EMGs were recorded using a grid of 13 × 5 channels from the plantar surface of the foot of 17 participants, who completed three balance tasks: bipedal stance; single leg stance and bipedal tip-toe. Centre of pressure (CoP) movement was calculated from simultaneously recorded force plate signals. Fluctuations in CoP and EMGs for each task were quantified using a sample entropy based metric, Entropy Halflife (EnHL). Longer EnHL indicates fewer signal fluctuations.ResultsThe shortest EMG EnHL, 9.27 ± 3.34 ms (median ± interquartile range), occurred during bipedal stance and the longest during bipedal tip-toe 15.46 ± 11.16 ms, with 18.80 ± 8.00 ms recorded for single leg stance. Differences were statistically significant between bipedal stance and both bipedal tip-toe (p < 0.001) and single leg stance (p < 0.001). CoP EnHL for both anterior-posterior and medial-lateral movements also differed significantly between tasks (p < 0.001, both cases). However, anterior-posterior CoP EnHL was longest for bipedal stance 259.84±230.22 ms and shortest for bipedal tip-toe 146.25±73.35 ms. Medial-lateral CoP EnHL was also longest during bipedal stance 215.73±187.58 ms, but shortest for single leg stance 113.48±83.01 ms.SignificanceFewer fluctuations in intrinsic foot muscle excitation occur in response to increased postural balance challenge. Fluctuations in CoP movement during balance must be predominantly driven by excitation of muscles extrinsic to the foot. Intrinsic foot muscles therefore likely play a greater role in stabilisation of the foot than balance control during the postural tasks studied.     

Relation between physical exertion and postural stability in hemiparetic participants secondary to stroke

IntroductionChronic hemiparetic stroke individuals are at a higher risk of falling. This may be due to balance impairments, cardiovascular deconditioning, and muscle weakness associated with stroke effects. Postural instability associated with fatigue would likely be attained more rapidly for stroke individuals than for healthy individuals.ObjectiveTo determine the effects of physical exertion induced by walking on postural stability in hemiparetic stroke participants.MethodsTwelve hemiparetic participants and 12 control participants walked over-ground for a duration of 6 min and 18 min at their comfortable speed. Postural stability was assessed using centre of pressure related parameters during double-legged stance and tasks before the walk, immediately after the walk, 15 min post-walk, and 30 min post-walk. Measures of physical exertion during walking were also obtained from cardiorespiratory parameters, time-distance parameters, and subjective scales. Variables on postural stability and on physical exertion were analyzed using two-way repeated measures ANOVA and Generalized Estimating Equations.ResultsPhysical exertion measures significantly increased when the duration of walk was increased from 6 min to 18 min in both control and hemiparetic participants. For postural stability measures, increasing the duration of walking led to a significant increase of postural sway in double-legged stance and sit-to-stand for the hemiparetic participants only. This effect on balance of hemiparetic participants was observed immediately after the end of the walk.ConclusionThis study demonstrated that physical exertion can increase postural sway in hemiparetic participants which could possibly lead to an increased risk of falling in these individuals.     

Time-to-boundary analysis of postural control following acute lateral ankle sprain

BackgroundAcute lateral ankle sprain (ALAS) impairs unipedal balance both with the injured and uninjured limb, suggesting that balance during bipedal stance may also be compromised. However, a previous study failed to find such impairment because of poorly sensitive balance outcomes. Time-to-boundary (TTB) analysis may be sensitive enough for detecting latent deficits in bipedal balance following ALAS.Research questionWe aimed to examine postural stability during bipedal stance in patients with ALAS using TTB outcomes, and to determine bilateral deficits in unipedal balance.MethodsTwenty-seven patients with ALAS and 26 persons without a history of ALAS participated. ALAS was operationally defined as a traumatic injury to the lateral ligaments of the ankle joint occurring within 24–72 h. Both limbs of the control group were side-matched to those of the patients as either injured or uninjured limbs. All participants performed 3 trials of bipedal stance with eyes open and closed. Next, they completed 3 trials of unipedal stance on both the injured and uninjured limbs in both visual conditions. Order of limb and visual condition for each limb was randomly selected. Means and standard deviations of TTB minima in the anteroposterior and mediolateral directions were computed to assess balance, with lower values indicating poorer balance.ResultsIndependent t-tests revealed significant group differences for almost all measures (p=<0.001 to 0.021), indicating that the ALAS group presented poorer bipedal balance. For unipedal balance, there were no significant group-by-limb interactions for all measures (p > 0.05), indicating no side-to-side differences in the ALAS group. However, group main effects were found for all measures (p=<0.001 to 0.048), showing poorer unipedal balance in the ALAS group.SignificanceTTB analysis revealed impaired balance during both unipedal and bipedal stance conditions following ALAS. These results support the emerging hypothesis that centrally mediated changes in postural control may occur following ALAS.     

Functional limits of stability and standing balance in people with Parkinson’s disease with and without freezing of gait using wearable sensors

BackgroundPeople with from Parkinson’s disease (PD) and freezing of gait (FoG) have more frequent falls compared to those who do not freeze but there is no consensus on which, specific objective measures of postural instability are worse in freezers (PD + FoG) than non-freezers (PD-FoG).Research questionAre functional limits of stability (fLoS) or postural sway during stance measured with wearable inertial sensors different between PD + FoG versus PD-FoG, as well as between PD versus healthy control subjects (HC)?MethodsSixty-four PD subjects with FoG (MDS-UPDRS Part III: 45.9 ± 12.5) and 80 PD subjects without FoG (MDS-UPDRS Part III: 36.2 ± 10.9) were tested Off medication and compared with 79 HC. Balance was quantified with inertial sensors worn on the lumbar spine while performing the following balance tasks: 1) fLoS as defined by the maximum displacement in the forward and backward directions and 2) postural sway area while standing with eyes open on a firm and foam surface. An ANOVA, controlling for disease duration, compared postural control between groups.ResultsPD + FoG had significantly smaller fLoS compared to PD-FoG (p = 0.004) and to healthy controls (p < 0.001). However, PD-FoG showed similar fLoS compared to healthy controls (p = 0.48). Both PD+FoG and PD-FoG showed larger postural sway on a foam surface compared to healthy controls (p = 0.001) but there was no significant difference in postural sway between PD+FoG and PD-FoG.SignificancePeople with PD and FoG showed task-specific, postural impairments with smaller fLoS compared to non-freezers, even when controlling for disease duration. However, individuals with PD with or without FoG had similar difficulties standing quietly on an unreliable surface compared to healthy controls. Wearable inertial sensors can reveal worse fLoS in freezers than non-freezers that may contribute to FoG and help explain their more frequent falls.     

The correlation between dental occlusion and posture is different in trained versus nontrained subjects

A relationship between postural control and occlusion is known and the postural variation after a change in occlusion might be different in athletes compared to sedentary subjects. Ten healthy sedentary subjects (nontrained group) and ten healthy athletic subjects (athlete group) were studied by static posturography with and without the interposition of cotton rolls between opposing teeth. Postural control was only slightly modified by the change in occlusion in the nontrained group (p ns) while postural strategies in the athlete group changed significantly (p < 0.001). In the athlete group, the change in occlusion resulted in sensory reorganization with an increase in the visual component and a reduction in the somatosensory component.     

Exercise training improves postural steadiness in cancer survivors undergoing chemotherapy

BackgroundCancer and cancer treatments negatively affect somatosensory, vestibular, and visual inputs that regulate postural stability and balance, increasing the risk of falling. Exercise training has been shown to mitigate other negative side effects of cancer treatments, such as reducing peripheral neuropathy.Research QuestionHow does 12 weeks of supervised exercise training influence postural stability in cancer survivors who receive chemotherapy?MethodsPostural stability of cancer survivors (n = 25; mass = 79.0 ± 22.6 kg; height = 1.66 ± 0.08 m; age = 61 ± 10 years) receiving chemotherapy was assessed prior to and following a 12-week individualized exercise training program by quantifying changes in center of pressure data. A series of 2-factor (pre/post x condition) analysis of variance with repeated measures were used to identify differences between conditions and pre- and post- training program on time and frequency domain measures.ResultsMediolateral root mean square excursion (p = 0.040; es = 0.20) and resultant mean frequency (p = 0.044; es = 0.29) of the center of pressure trajectory were found to be significantly different between pre- and post-training program. Further, participants dealt better with perturbations after completing the training program by reducing mediolateral root mean square excursion and 95 % confidence ellipse when visual stimulus was removed.SignificanceSupervised exercise training in cancer patients undergoing chemotherapy improves postural stability in the mediolateral direction. Given that mediolateral movement of the center of pressure has previously been associated with fallers in other populations, exercise training during cancer treatments may be beneficial.     

Vestibular training promotes adaptation of multisensory integration in postural control

BackgroundPostural stability depends on the integration of the multisensory system to produce motor outputs. When visual and somatosensory input is reliable, this reduces reliance on the vestibular system. Despite this, vestibular loss can still cause severe postural dysfunction. Training one or more of the three sensory systems through vestibular habituation and adaptation can alter sensory weighting and change postural behavior.AimThe purpose of this study was to assess sensory reweighting of postural control processing after combined vestibular activation with voluntary weight shift training in healthy adults.MethodsThirty-three healthy individuals (18–35 y.o.) were randomly assigned to one of three groups: No training (control), visual feedback weight shift training (WST) coupled with an active horizontal headshake (HS) activity to elicit a vestibular perturbation, or the same WST without HS (NoHS). Training was performed 2x/day, every other day (M, W, F), totaling six sessions. Pre- and post- assessments on the Sensory Organization Test (SOT) were performed. Separate between- and within- repeated measures ANOVAs were used to analyze the six SOT equilibrium scores, composite scores, sensory ratios and center of pressure (COP) variables by comparing baseline to post-training. Alpha level was set at p < .05.ResultsThere was a significant group x session x condition change (p = .012) in the COP multiscale entropy (MSE) velocity sway in the HS group during SOT conditions 5 and 6. Similarly, COP medio-lateral standard deviation sway (ML Std) showed group x session x visual condition (p = .028), due to HS in condition 6 relative to other two groups.ConclusionPostural training can alter sensory organization after a visual feedback-vestibular activation training protocol, suggesting a possible sensory reweighting through vestibular adaptation and/or habituation.SignificanceTranslating these findings into a vestibular-impaired population can stimulate the design of a rehabilitation balance protocol.     

Impact of orthognathic surgery on the body posture

BackgroundPostural control is classically described as being based on the visual, vestibular, and proprioceptive musculo-articular sensory systems. The influence of mandibular proprioception on postural stabilization remains controversial. Most previous studies analyzed how postural stability is influenced by partial changes in mandibular proprioception (dental occlusion and jaw position).Research QuestionIn the present experiment, we asked whether drastic mandibular changes, resulting from orthognathic surgery (including dental, joint and muscular efferents), modify postural control.MethodsThe analyzes were performed in 22 patients tested before, and 2.5 months, after orthognathic surgery for treatment of dysmorphic jaws. Experiments were performed under 4 experimental conditions: 2 visual conditions: Eyes Open (EO) and Eyes Closed (EC), and 2 occlusal conditions: Occlusion (OC: mandible positioned by the contact of the teeth), and Rest Position (RP: mandible positioned by the muscles without tooth contact). The analyses focused on head orientation in the frontal plane and on postural stabilization in a static task, consisting of standing upright.ResultsThe results show that, 2.5 months after orthognathic surgery, head orientation in the frontal plane was improved, since patient’s external intercanthal lines became closer to the true horizontal line when they were tested EC and in OC condition. Postural responses, based on the wavelet transformation data, highlight an improvement in maintaining an upright stance for all the tested sensory conditions. However, such improvement was greater in the EC and RP conditions.SignificanceThese results show, for the first time, that after drastic mandibular changes, the weight of proprioceptive cues linked to the mandibular system may be so enhanced that it may constitute a new reference frame to orient the head in space, in darkness, and improve static postural stabilization, even in the presence of visual cues.     

Out of balance – Postural control in cancer patients before and after neurotoxic chemotherapy

BackgroundChemotherapy-induced peripheral neuropathy (CIPN) is a serious side effect deriving from neurotoxic chemotherapeutic agents. The underlying nerve injury can affect proprioception causing impaired postural control, gait difficulties and a higher risk of falling. Overall, the symptoms and functional limitations negatively affect patients’ independence and quality of life.Research questionOur objective was to analyze postural control in cancer patients before and after neurotoxic chemotherapy and to compare these data to healthy controls.MethodsParticipants were 35 cancer patients (PAT) and 35 healthy, one-to-one gender, age, height, and weight matched controls (HMC). Postural control of HMC was tested once, whereas PAT were tested prior to (PAT_pre) and three weeks after completion of neurotoxic chemotherapy (PAT_post). Temporal, spatial and frequency domain measures of the center of pressure (COP) were calculated using a force plate. The following balance conditions were analyzed: bipedal stance with open (BP_EO) and closed eyes (BP_EC), semi-tandem (ST_EO, ST_EC) and monopedal stance (MP_EO). CIPN was assessed clinically (Total Neuropathy Score) and via questionnaire. Time and group differences were determined by using Wilcoxon-signed-rank tests. Spearman correlation was applied to analyze associations between severity of CIPN and postural control.ResultsPAT_post showed significantly increased temporal and spatial measures of the COP (p < .05) – both after neurotoxic chemotherapy (PAT_pre–PAT_post) and in comparison to HMC. Withdrawal of visual control resulted in greater temporal and spatial COP displacements in PAT_post than in the comparative groups (PAT_pre, HMC). Correlation analyzes revealed moderate associations of COP measures with clinical CIPN measures and low to none for the questionnaires.SignificanceThree weeks after completion of neurotoxic chemotherapy, PAT_post showed significant balance deficits compared to PAT_pre and HMC. Especially the deficits in the standing conditions with closed eyes may indicate an impaired proprioception. This hypothesis is supported by the finding that stronger CIPN symptoms were associated with poorer postural control. However, future studies need to take further influencing factors on postural control into account (e.g. strength) in order to generate efficacious rehabilitation measures.     

Postural stability after treadmill and overground walking in young and elderly

BackgroundAgeing commonly disrupts the balance control and compensatory postural responses that contribute to maintaining balance and preventing falls during perturbation of posture. Improvement of compensatory postural responses during walking is one of the main goals in fall prevention programs which often include treadmill walking training. However, during treadmill walking, there is a sensory (visualsomatosensory and vestibular-somatosensory) conflict that can evoke aftereffects of self-motion sensation and could alter postural stability after training.Research questionThe aim of this study was to compare the effect of overground and treadmill walking on postural stability in healthy young and elderly subjects. Methods: Postural responses of 31 Young and 19 healthy Elderly before and after overground and treadmill walking were assessed by a force platform in four stance conditions: firm and foam surface with eyes open and eyes closed.ResultsIn Elderly group, velocity parameters significantly increased after treadmill walking but not after overground walking. This increase was found particularly in the conditions with eyes open in both types of surfaces (firm, foam). The velocity parameters values (expect Vx) were significantly increased in Elderly compared to Young almost in all four conditions after treadmill and overground walking. Significance: Our study suggests that Elderly become more unstable after treadmill walking and have greater difficulties to adapt to new balance circumstances caused by sensory conflict associated with treadmill walking. It seems that during treadmill walking and subsequent stance, vision is the major factor contributing to posture stabilization. Thus, the suitability of treadmill walking as a part of training programs for elderly adults with higher fall risk should be seriously considered.     

Gathering your ‘sea legs’: Extended durations in an offshore environment increases postural sway excursions

BackgroundMal de debarquement (MdD), or often called ‘sea legs’, is the perception of self-motion after exposure to passive movement such as being on a boat at sea. Previous studies highlight sensory re-organization difficulties and postural control impairments after disembarking from sea travel in experienced crew members. However, the impact of MdD in individuals with minimal offshore experience, defined as participating in less than 2 offshore excursions per year, has not been investigated.Research questionDoes exposure to boat motion while at sea alter static postural control after disembarking in individuals with minimal offshore experience?MethodsHealthy adults (n = 24) with minimal offshore experience had their static balance assessed on a force platform before (PRE) and after (POST) a 7-h deep sea fishing excursion. Static balance was tested in eyes open (EO), eyes closed (EC), eyes open on a foam surface (EOF), and eyes closed on a foam surface (ECF) conditions. Sway excursions, sway velocity and sway variability in the medial-lateral (ML) and anterior-posterior (AP) directions were computed and then compared PRE/POST using a paired t-test (p < 0.05).ResultsSignificant increases in ML sway excursion (p = 0.004), ML sway range (p < 0.001), ML sway variability (p < 0.001), AP sway excursion (p = 0.045), AP sway range (p = 0.020), and AP sway variability (p = 0.030) were observed at POST during EOF. Significant increases in ML sway excursion (p = 0.027), AP sway excursion (p = 0.020), and AP sway variability (p = 0.014) at POST were also observed during ECF. No differences were found in the EO condition (p > 0.05).SignificanceIncreases in postural sway excursion and variability were observed in individuals with minimal offshore experience after disembarking. Our findings suggest sensory re-organization difficulties in order to maintain an upright posture in challenging sensory conditions are dependent on vestibular and somatosensory inputs following exposure to boat motion at sea.     

Impaired static postural control correlates to the contraction ability of trunk muscle in young adults with chronic non-specific low back pain: A cross-sectional study

IntroductionPatients with chronic non-specific low back pain (CNSLBP) were found with impaired postural control in previous studies. Since the trunk muscle take important efforts on core stability, the study aimed to examine the relationships of postural control during stance tasks and the contractility of trunk muscle in young adults with CNSLBP and without.MethodsHealthy individuals (n = 25) and individuals with CNSLBP (n = 30) were included. The thickness of the bilateral transversus abdominis (TrA) and lumbar multifidus (MF) was measured during rest and maximal voluntary contraction, and the change percentages (TrA%, MF%) were calculated. Regarding postural control, COP path length and sway area during the stance tasks were measured thrice in each group.ResultsThe bilateral TrA% of the CNSLBP group was less than that of the HC group (p < 0.05). The bilateral TrA% of the CNSLBP group was less than that of the HC group (p < 0.05). The bilateral MF% showed no significantly different(p > 0.05) between the two groups. Compared with healthy controls, CNSLBP patients resulted larger path length and sway area of COP during most of static stance tasks. During the EO task in the CNSLBP group, TrA% was found correlate to COP path length (p < 0.05); the right MF% was correlated with COP sway area (p < 0.05). No significant correlations appeared in the healthy controls (p > 0.05).ConclusionsCompared with healthy individuals, impaired postural control during static stance with eyes open in patients with CNSLBP was likely to be related to the poor contraction ability of bilateral transversus abdominis and correlated to the normal contraction ability of right lumbar multifidus.     

Comparison of the reliance of the postural control system on the visual,vestibular and proprioceptive inputs in chronic low back pain patients and asymptomatic participants

BackgroundAlthough proprioception deficits have been documented in chronic low back pain (CLBP) patients, little is known about adaptive strategies to provide postural control in these patients. Substitution of unreliable proprioceptive information with other afferents might be considered plausible.Research questionIs the response of the postural control system dependent on the source of sensory afferents being manipulated in persons with and without CLBP?MethodsSixty persons with and without CLBP participated in this cross-sectional study. Center of pressure (COP) displacement range, velocity, path length and area were calculated under four sensory conditions: 1) normal upright standing; 2) upright standing on a foam with eyes open and head in neutral position; 3) upright standing with eyes open and 60° cervical extension and 4) upright standing with eyes closed and 60° cervical extension. A two-way repeated measures analysis of variance was used to compare COP masseurs under different conditions and between the groups.ResultsCLBP patients demonstrated fewer alterations to manipulation of both visual and vestibular afferents in terms of number of COP variables significantly altered. ML range and velocity in both groups and path length in the CLBP group were significantly different between conditions 2 and 4. In both groups, all COP variables except AP range increased significantly in condition 2 compared to conditions 1and 3 (p < 0.001). AP velocity was the only variable to be different between conditions 1 and 3 in both CLBP (p = 0.025) and control (p < 0.001) groups. Between group differences were significant on AP velocity (p = 0.019).SignificanceNo overweighting was observed in the vestibular or visual afferents in CLBP patients. Compensatory strategies seem to lie within proprioceptive system by reweighting afferents from different body segments. The postural control system behaved more robustly in CLBP patients while AP COP velocity was found as the most sensitive and discriminating parameter.     

The use of inertial measurement units to assess gait and postural control following concussion

BackgroundImpairments in gait and balance function are typical after concussion. There is evidence that these neuromuscular deficits persist past the typical time of symptom resolution. The ability to quantify these changes in gait and balance may provide useful information when making return to play decisions in clinical settings.Research QuestionAre changes in gait function and postural control evident across the course of a concussion management program?MethodsA retrospective analysis of a convenience sample of 38 patients who were seen for concussion between October 2017 and May 2019 was performed. Gait and balance measures were assessed at their initial clinic visit post-injury and at their clearance visit using inertial measurement units. During dual-task walking trials, the medial-lateral motion of the center of mass and gait velocity were measured. Postural sway complexity and jerk index were measured during both eyes-open and eyes-closed balance trials.ResultsPaired samples t-tests and Wilcoxon signed rank tests were used to determine whether statistically significant changes occurred for the gait and balance variables, respectively. Medial-lateral sway decreased (4.4 ± 1.3 cm to 4.0 ± 1.2 cm, p = 0.018) and gait velocity increased (0.78 ± 0.23 m/s to 0.91 ± 0.18 m/s, p < 0.001) from initial to clearance testing. Jerk index decreased (6.41 ± 11.06 m²/s⁵ to 5.73 ± 4.28 m²/s⁵, p = 0.031) and (11.87 ± 26.42 m²/s⁵ to 7.87 ± 8.38 m²/s⁵, p = 0.003) from initial to clearance testing for the eyes-open and eyes-closed conditions, respectively. Complexity index increased (2.38 ± 1.08–2.86 ± 0.72, p = 0.010) from initial to clearance testing for the eyes-closed condition. There was no change in complexity index for the eyes-open condition.SignificanceThese preliminary results support the potential use of measures of gait and postural control to assess recovery following a concussion in a clinical setting.     

Motor dual task with eyes closed improves postural control in patients with functional motor disorders: A posturographic study

BackgroundFunctional motor disorders (FMD) are highly disabling neurological conditions in which postural control deficits increase the risk of falls and disability in performing daily living activities. Scattered evidence suggests that such disturbances may depend on abnormal attentional focus and might improve with distraction.Research questionHow do motor and cognitive dual tasks performed under two different sensory conditions shape postural control in patients with FMD.MethodsThis posturographic study involved 30 patients with FMD (age, 45.20 ± 14.57 years) and 30 healthy controls (age, 41.20 ± 16.50 years). Postural parameters were measured with eyes open, and eyes closed in quiet stance (single task) and on a motor dual task (m-DT) and a calculation (cognitive) dual task (c-DT). The dual task effect (DTE, expressed in percentage) on motor and cognitive performance was calculated for sway area, length of Center of Pressure (CoP), and velocity of CoP displacement.ResultsThere was a statistically significant three-way interaction between task, condition, and group for the DTE on sway area (p = 0.03). The mean sway area DTE on the motor task in the eyes-closed condition was increased by 70.4 % in the healthy controls, while it was decreased by 1% in the patient group (p = 0.003). No significant three-way interaction was observed for the DTE on length of CoP and velocity of CoP displacement.SignificanceThis study provides novel preliminary evidence for the benefit of a simple motor dual task in the eyes closed condition as a way to improve postural control in patients with FMD. These findings are relevant for the management of postural control disorders in patients with FMD.     

Performance of postural balance in children and adolescents living with and without HIV

Research questionThe present study aimed to compare the postural control of children and adolescents with and without Human Immunodeficiency Virus (HIV).MethodsA total of 32 children and adolescents (18 with HIV and 14 without) of both sexes, aged 6–18 years, were included in the present study. Participants in the HIV + group were infected through vertical transmission and received antiretroviral therapy. Participants maintained an erect, bipedal posture in the following conditions: with vision, without vision, and on a foam base.ResultsConcerning the evaluation of time variables, higher values ​​were observed in the HIV + group for mean anterior-posterior (AP) velocity, mean medial-lateral (ML) velocity, AP perimeter (p = 0.001), and ML perimeter (p = 0.001). Concerning the evaluation of conditions, a difference was observed in the mean AP mean sway amplitude (MSA) (p = 0.039), as the AP MSA was lower with vision than without vision or with foam. Concerning the evaluation of spectral domain variables, higher values ​​were observed in the HIV+ group for the predominant ML frequency (p = 0.04) and mean AP (p = 0.001) and ML frequencies (p = 0.001). Regarding the evaluation of conditions, a difference was found only in the predominant AP frequency (p = 0.001). Higher values ​​were found in the closed eye condition than in with foam (Δ = +103 %).ConclusionThe results of the present study indicated that children and adolescents living with HIV have poorer postural control performance than those without HIV.