Increased Visual Use in Chronic Ankle Instability: A Meta-analysis

Lateral ankle instability-induced neuroplasticity in brain grey matter: A voxel-based morphometry MRI study

OBJECTIVES

The deficits in sensory pathways caused by peripheral edema, pain, and inflammation of the damaged ligaments may induce maladaptive changes within the central nervous system. The purpose of this study was to determine whether patients with lateral ankle instability (LAI) exhibit morphological differences of brain grey matter when compared with healthy controls, and then assess the relationships between the observed differences and the characteristics of patients.

DESIGN

Cross-sectional.

METHODS

Thirty patients with LAI and 32 healthy controls without LAI underwent MRI scans using anatomical T1 sequences. A voxel-wise general linear model was used to compare the grey matter volume throughout the whole brain between patients and controls. Linear regression analyses were performed for the grey matter volume within the significant clusters to assess their relationship with age, sex, the existence of acute injury, pain level, sports activity level, and the duration of LAI within the patient group.

RESULTS

The grey matter volume of a cluster within the cerebellar vermis (Vermis_4_5 in automated anatomical labeling template) was significantly reduced in patients with LAI (Gaussian Random Field corrections with two-tailed p-cluster < 0.05 and p-voxel < 0.001). Multivariate linear regression analysis revealed that the duration of LAI tended to be passively associated with the grey matter volume of this LAI-related vermal cluster (p = 0.092).

CONCLUSIONS

Participants with LAI exhibited a reduced grey matter volume of a cluster within the cerebellar vermis compared with participants without LAI, and the degree of volume reduction tended to be positively associated with the duration of LAI.

Progressive Visual Occlusion and Postural Control Responses in Individuals With and Without Chronic Ankle Instability

CONTEXT

Prophylactic and rehabilitative balance training is needed to maximize postural control and develop appropriate sensory organization strategies. Partially occluding vision during functional exercise may promote appropriate sensory organization strategies, but little is known about the influence of partially occluded vision on postural control in those with and without a history of musculoskeletal injury.

OBJECTIVE

To determine the effect of increasing levels of visual occlusion on postural control in a heterogeneous sample of those with and without chronic ankle instability (CAI). The secondary objective was to explore postural control responses to increasing levels of visual occlusion among those with unilateral and bilateral CAI relative to uninjured controls.

DESIGN

Cross-sectional.

SETTING

Sports medicine research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twenty-five participants with unilateral CAI, 10 with bilateral CAI, and 16 participants with no history of lower extremity injury.

MAIN OUTCOME MEASURES

All participants completed four 3-minute postural control assessments in double-limb stance under the following 4 visual conditions: (1) eyes open, (2) low occlusion, (3) high occlusion, and (4) eyes closed. Low- and high-occlusion conditions were produced using stroboscopic eyewear. Postural control outcomes included time-to-boundary minima means in the anteroposterior (TTB-AP) and mediolateral directions (TTB-ML). Repeated-measures analysis of variances tested the effects of visual condition on TTB-AP and TTB-ML.

RESULTS

Postural control under the eyes-open condition was significantly better (ie, higher) than the limited visual occlusion and eyes-closed conditions (P < .001) for TTB-AP and TTB-ML. For TTB-AP only, partially occluded vision resulted in better postural control than the eyes-closed condition (P ≤ .003).

CONCLUSIONS

Partial and complete visual occlusion impaired postural control during dual-limb stance in a heterogeneous sample of those with and without CAI. Stroboscopic eyewear appears to induce postural control impairments to the same extent as complete visual occlusion in the mediolateral direction.

Short-Term Effects of Balance Training with Stroboscopic Vision for Patients with Chronic Ankle Instability: A Single-Blinded Randomized Controlled Trial

Chronic Ankle Instability (CAI) is one of the most common musculoskeletal dysfunctions. Stroboscopic vision (SV) training has been deemed to enhance somatosensorial pathways in this population group; nevertheless, until recently no studies have addressed the additional effects of this treatment option to the traditional therapeutic approach.

METHODS

To evaluate the effectiveness of a partial visual deprivation training protocol in patients with CAI, a randomized controlled trial was carried out. Patients with CAI (n = 73) were randomized into either a balance training, SV training, or a control (no training) group. For participants assigned into training groups, they received 18 training sessions over 6 weeks. The primary outcome was dynamic balance as measured by the Star Excursion Balance Test assessed at baseline and after 6 weeks of intervention. Secondary outcome measures included ankle dorsiflexion range of motion, self-reported instability feeling, and ankle functional status.

RESULTS

Better scores in stroboscopic training and balance training groups in all outcome measures were observed in comparison with the control group with moderate to large effect sizes. Stroboscopic training was more effective than neuromuscular training in self-reported instability feeling (cohen's d = 0.71; p = 0.042) and anterior reach distance of the star excursion balance test (cohen's d = 1.23; p = 0.001).

CONCLUSIONS

Preliminary findings from the effects of SV Stroboscopic training in patients with CAI, suggest that SV may be beneficial in CAI rehabilitation.

Submaximal Force Steadiness and Accuracy in Patients With Chronic Ankle Instability

CONTEXT

Patients with chronic ankle instability (CAI) have demonstrated sensorimotor impairments. Submaximal force steadiness and accuracy measure sensory, motor, and visual function via a feedback mechanism, which helps researchers and clinicians comprehend the sensorimotor deficits associated with CAI.

OBJECTIVE

To determine if participants with CAI experienced deficits in hip and ankle submaximal force steadiness and accuracy compared with healthy control participants.

DESIGN

Case-control study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twenty-one patients with CAI and 21 uninjured individuals.

MAIN OUTCOME MEASURE(S)

Maximal voluntary isometric contraction (MVIC) and force steadiness and accuracy (10% and 30% of MVIC) of the ankle evertors and invertors and hip abductors were assessed using the central 10 seconds (20%-87% of the total time) of the 3 trials.

RESULTS

Relative to the control group, the CAI group demonstrated less accuracy of the invertors (P < .001). Across all motions, the CAI group showed less steadiness (P < .001) and less accuracy (P < .01) than the control group at 10% of MVIC. For MVIC, the CAI group displayed less force output in hip abduction than the uninjured group (P < .0001).

CONCLUSIONS

Patients with CAI were unable to control ongoing fine force (10% and 30% of MVIC) through a feedback mechanism during an active test. These findings suggested that deficits in sensorimotor control predisposed patients with CAI to injury positions because they had difficulty integrating the peripheral information and correcting their movements in relation to visual information.

The effects of stroboscopic balance training on cortical activities in athletes with chronic ankle instability

OBJECTIVES

To investigate the effect of a 6-week stroboscopic balance training program on cortical activities in athletes with chronic ankle instability.

DESIGN

Randomized controlled trial.

SETTING

Single-center.

PARTICIPANTS

Thirty-nine participants were assigned to the strobe group (SG, n = 13), non-strobe group (NSG, n = 13), and control group (CG, n = 13).

MAIN OUTCOME MEASURES

Cortical activity and balance velocity were evaluated while the athletes were on the HUBER balance device. Electroencephalographic measurements of cortical activity were made at the transition from bipedal stance to single-leg stance.

RESULTS

The SG showed significant increases in Cz theta and alpha values and COP-v (center of pressure velocity) between pretest and posttest (p < 0.001, p = 0.003, p < 0.001). Posttest Cz theta was significantly higher in the SG compared to the CG (p = 0.009) and posttest Cz alpha was significantly higher in the SG compared to the NSG (p = 0.039) and CG (p = 0.001). Posttest COP-v was significantly higher in the SG than in the CG (p = 0.031) and NSG (p = 0.03).

CONCLUSIONS

Stroboscopic training may be clinically beneficial to improve balance parameters in athletes with CAI, and may have utility in sport-specific activity phases of rehabilitation to reduce visual input and increase motor control.

Eyes-Open Versus Eyes-Closed Somatosensory Motor Balance in Professional Soccer Players With Chronic Ankle Instability: A Case-Control Study

Background:

Chronic ankle instability (CAI) is a condition defined by certain structural and functional deficits in the ankle joint complex after acute ankle injury. These deficits include pathological joint laxity, impaired postural control, and decreased strength and neuromuscular control.

Purpose:

To compare an eyes-open versus an eyes-closed balance training protocol in professional soccer players with CAI.

Study Design:

Cohort study; Level of evidence, 2.

Methods:

For this study, we evaluated 19 players from 2 professional soccer teams in Madrid, Spain, all of whom had CAI. Participants from both teams were randomly assigned to an eyes-open group (n = 9) or eyes-closed group (n = 10). All participants completed 4 weeks of a supervised exercise protocol consisting of 3 sessions per week. Members of both the eyes-open and eyes-closed groups performed the same exercise protocol in the same order of execution. At the end of the protocol, the participants were assessed for pain (visual analog scale), ankle dorsiflexion range of motion (weightbearing lunge test), dynamic stability (Star Excursion Balance Test), and fear of movement and reinjury (Tampa Scale for Kinesiophobia). We compared results both before and after balance training and between the eyes-open and eyes-closed balance training groups.

Results:

Statistically significant differences were found for all of the assessed variables before and after balance training. No statistically significant differences were found between the eyes-closed and eyes-open groups on any variable.

Conclusion:

In the current study, eyes-closed balance training was not more effective than eyes-open balance training for CAI in professional soccer players.

Added body mass alters plantar shear stresses, postural control, and gait kinetics: Implications for obesity

Context

Obesity is a growing global health concern. The increased body mass and altered mass distribution associated with obesity may be related to increases in plantar shear that putatively leads to physical functional deficits. Therefore, measurement of plantar shear may provide unique insights on the effects of body mass and body distribution on physical function or performance.

Purpose

1) To investigate the effects of body mass and distribution on plantar shear. 2) To examine how altered plantar shear influences postural control and gait kinetics.

Hypothesis

1) a weighted vest forward distributed (FV) would shift the center of pressure (CoP) location forward during standing compared with a weighted vest evenly distributed (EV), 2) FV would increase plantar shear spreading forces more than EV during standing, 3) FV would increase postural sway during standing while EV would not, and 4) FV would elicit greater compensatory changes during walking than EV.

Methods

Twenty healthy young males participated in four different tests: 1) static test (for measuring plantar shear and CoP location without acceleration, 2) bilateral-foot standing postural control test, 3) single-foot standing postural test, and 4) walking test. All tests were executed in three different weight conditions: 1) unweighted (NV), 2) EV with 20% added body mass, and 3) FV, also with 20% added body mass. Plantar shear stresses were measured using a pressure/shear device, and several shear and postural control metrics were extracted. Repeated measures ANOVAs with Holms post hoc test were used to compare each metric among the three conditions (α = 0.05).

Results

FV and EV increased both AP and ML plantar shear forces compared to NV. FV shifted CoP forward in single-foot trials. FV and EV showed decreased CoP range and velocity and increased Time-to-Boundary (TTB) during postural control compared to NV. EV and FV showed increased breaking impulse and propulsive impulse compared to NV. In addition, EV showed even greater impulses than FV. While EV increased ML plantar shear spreading force, FV increased AP plantar shear spreading force during walking.

Conclusion

Added body mass increases plantar shear spreading forces. Body mass distribution had greater effects during dynamic tasks. In addition, healthy young individuals seem to quickly adapt to external stimuli to control postural stability. However, as this is a first step study, follow-up studies are necessary to further support the clinical role of plantar shear in other populations such as elderly and individuals with obesity or diabetes.

Effect of Dry Needling on Spinal Reflex Excitability and Postural Control in Individuals With Chronic Ankle Instability

OBJECTIVE

The purpose of this study was to compare postural control and neurophysiologic components of balance after dry needling of the fibularis longus between individuals with chronic ankle instability (CAI) and a healthy control group.

METHODS

This quasi-experimental university-laboratory study included 50 adult volunteers-25 with CAI (16 female, 9 male; age: 26 ± 9.42 years; height: 173.12 ± 9.85 cm; weight: 79.27 ± 18 kg) and 25 healthy controls (15 female, 10 male; age: 25.8 ± 5.45 years; height: 169.47 ± 9.43 cm; weight: 68.47 ± 13 kg). Participants completed the Star Excursion Balance Test (SEBT), single-leg balance, and assessment of spinal reflex excitability before and after a single treatment of dry needling to the fibularis longus. The anterior, posterolateral, and posteromedial directions of the SEBT were randomized, and reach distances were normalized to a percentage of leg length. A composite SEBT score was calculated by averaging the normalized scores. Postural control was assessed in single-limb stance on a force plate through time-to-boundary measurements in eyes-open and eyes-closed conditions. Fibularis longus and soleus spinal reflexes were obtained by providing electrical stimulation to the common fibular and tibial nerves with participants lying prone. A Group × Time analysis examined changes in performance, and effect sizes were calculated to assess significance.

RESULTS

Significant group × time interactions were identified for composite (P = .006) and posteromedial (P = .017) SEBT scores. Significant time effects for all directions of the SEBT, time to boundary with eyes open, and the mediolateral direction with eyes closed indicate improved postural control following treatment (P < .008). Within-group effect sizes for significant time effects ranged from small to large, indicating potential clinical utility.

CONCLUSION

Dry needling demonstrated immediate short-term improvement in measures of static and postural control in individuals with CAI as well as healthy controls.

Effects of Combining High-Definition Transcranial Direct Current Stimulation with Short-Foot Exercise on Chronic Ankle Instability: A Pilot Randomized and Double-Blinded Study

(1) Background: Balance decline is highly prevalent in people suffering from chronic ankle instability (CAI). The control of balance depends upon multiple neurophysiologic systems including the activation of cortical brain regions (e.g., the primary sensorimotor cortex). The excitability of this region, however, is diminished in people with CAI. In this pilot double-blinded randomized controlled trial, we tested the effects of high-definition transcranial direct current stimulation (HD-tDCS) designed to facilitate the excitability of M1 and S1 in combination with short-foot exercise (SFE) training on proprioception and dynamic balance performance in individuals with CAI. (2) Methods: Thirty young adults completed baseline assessments including the Active Movement Extent Discrimination Apparatus (AMEDA), Joint Position Reproduction (JPR) test, Y-balance test, and the Sensory Organization Test (SOT). They were then randomized to receive a four-week intervention of SFE in combination with tDCS (i.e., HD-tDCS+SFE) or sham (i.e., control) stimulation. Baseline assessments were repeated once-weekly throughout the intervention and during a two-week follow-up period. (3) Results: Twenty-eight participants completed this study. Blinding procedures were successful and no adverse events were reported. As compared to the control group, the HD-tDCS+SFE group exhibited significant improvements in the JPR test, the Y balance test, and the SOT at different time points. No group by time interaction was observed in AMEDA test performance. (4) Conclusions: HD-tDCS combined with SFE may improve dynamic balance and proprioception in CAI. Larger, more definitive trials with extended follow-up are warranted.

Walking Gait Mechanics and Gaze Fixation in Individuals With Chronic Ankle Instability

CONTEXT

Many individuals who suffer a lateral ankle sprain will develop chronic ankle instability (CAI). Individuals with CAI demonstrate kinematic differences in walking gait, as well as somatosensory alterations compared with healthy individuals. However, the role of vision during walking gait in this population remains unclear.

OBJECTIVE

To evaluate ankle kinematics, gaze deviations, and gaze velocity between participants with CAI and healthy controls while walking on a treadmill during 3 separate visual conditions (no target, fixed target, and moving target).

DESIGN

Case-control study.

SETTING

Laboratory. Patients (or Other Participants): Ten CAI participants and 10 healthy matched controls participated.

MAIN OUTCOME MEASURES

Ankle sagittal and frontal plane kinematics were analyzed for the entire gait cycle. Average and standard deviation (SD) for gaze deviation and gaze velocity were calculated in the horizontal (X) and vertical (Y) planes.

RESULTS

No significant differences were found between groups for either ankle kinematics or gaze variables; however, large effect sizes were found in the no target condition for average deviation of X (healthy 0.05 [0.02], CAI 0.12 [0.11]). Moderate effect sizes were identified in the no target condition for SD of Y (healthy 0.04 [0.03], CAI 0.11 [0.15]) and the moving target condition for average velocity of X (healthy 1.56 [0.73], CAI 2.27 [1.15]) and Y (healthy 1.07 [0.51], CAI 1.47 [0.52]).

CONCLUSIONS

Although no significant differences were found between groups, it is possible that the role of vision in individuals with CAI may be altered with a more difficult task.

Center of pressure excursion and muscle activation during gait initiation in individuals with and without chronic ankle instability

The aim of the current study was to determine differences in center of pressure (COP)excursion and muscle activation during gait initiation (GI) in those with and without chronic ankle instability (CAI). Thirty-four participants, 17 per group, volunteered to participate. Participants were asked to stand barefoot on a force plate before initiating gait upon hearing an auditory cue. Reaction time, anticipatory postural adjustment phase time, as well as normalized peak COP excursion during the anticipatory postural adjustment phase was calculated. Response time of Soleus and Tibialis Anterior muscles were concurrently recorded via electromyography. The results demonstrate a longer reaction time and shorter anticipatory postural adjustment phase time in the CAI group (p < 0.05). No significant between group differences in peak normalized COP excursion were noted (p > 0.05). Muscle onset patterns differed between groups as those with CAI demonstrated earlier Soleus activation compared to the control group (p < 0.05). The results suggest that those with CAI have an altered GI motor control strategy as evidenced by reduced or absent Soleus muscle inhibition during APA phase of GI relative to controls. The APA phase is controlled by the secondary motor area, therefore, the presence of motor control alterations in CAI patients may be due to a supra-spinal alterations.

THE EFFECTS OF MULTIPLE MODALITIES OF COGNITIVE LOADING ON DYNAMIC POSTURAL CONTROL IN INDIVIDUALS WITH CHRONIC ANKLE INSTABILITY

BACKGROUND

Evidence of neuroplasticity after joint injury has suggested that individuals with chronic ankle instability (CAI) may have degraded movement when facing cognitive demand. To date, research into these effects have been limited to static balance models, and typically only incorporate a single type of cognitive demands.

RESEARCH QUESTION

We aimed to determine the effects of multiple modalities of cognitive load (quantitative, verbal-memory, visuospatial) on dynamic postural control strategies in a sample of patients with CAI compared to uninjured controls.

METHODS

Thirty-two participants (16 CAI, 16 healthy) performed a series of 20 hops-to-stabilization while either under no cognitive load (CON), or while performing Benton's judgment of line orientation (JLO), the symbol digit modalities test (SDM), or a serial seven task (SVN). Dynamic postural stability indices and mean muscle activation from the lower leg muscles were extracted and assessed via analysis of variance.

RESULTS

Healthy subjects demonstrated better vertical and dynamic postural stability indices under JLO (P ≤ 0.017) and SVN (P ≤ 0.010) conditions compared to CON. Postural stability was unaffected in CAI (P > 0.050). Peroneus longus and lateral gastrocnemius activation was lowest in SVN across all subjects (P ≤ 0.033). Lateral gastrocnemius activation was greatest in SDM (P ≤ 0.033).

SIGNIFICANCE

These results suggest improvements in postural stability under cognitive demand in healthy individuals that did not occur in CAI, suggesting less movement optimization. Quantitative tasks appear to impede stabilizing muscle activation in the leg, while verbal-memory tasks result in a more protective landing strategy.

Attentional Demands of Postural Control in Chronic Ankle Instability, Copers and Healthy Controls: A Controlled Cross-sectional Study

BACKGROUND

It has been shown that cognitive loading affects postural control in different populations. However, there is limited and conflicting information about dual task challenges on postural control in chronic ankle instability (CAI).

RESEARCH QUESTION

Does cognitive task performance change standing postural control in individuals with CAI, copers and healthy subjects?

METHODS

A descriptive, analytic, and controlled cross-sectional study was conducted on 75 individuals. They were assigned into three matched groups, including CAI, copers, and healthy controls. Postural control variables were collected during single leg standing on a force plate with and without vision and cognition. Parameters of center of pressure (COP), including mean COP area, range, sway index and velocity, were measured. Additionally, cognitive task performance by auditory stroop was assessed by calculating the reaction time and error ratio. Mixed model ANOVAs were used to determine the effects of group and testing conditions.

RESULTS

The CAI group demonstrated greater COP sway parameters compared to other groups under all testing conditions. The main significant effect of vision was observed for all COP parameters with greater COP sway during eyes closed compared to eyes open (P < 0.05). The main effect of a cognitive task was significant with reduced COP sway while performing the secondary cognitive compared to a single task in all three groups (P < 0.05). The cognitive task results revealed significantly longer reaction times in the CAI group compared to copers and healthy individuals (p < 0.05).

SIGNIFICANCE

Considering postural control deficits in CAI, especially in eye-closed condition and effects of cognitive loading, may guide us to improve postural control in those with CAI with neurocognitive training. Furthermore, no difference between coper and healthy groups may imply a successful compensatory postural control mechanism in copers.

Stroboscopic Vision as a Dynamic Sensory Reweighting Alternative to the Sensory Organization Test

CONTEXT

The sensory organization test (SOT) is a standard for quantifying sensory dependence via sway-referenced conditions (sway-referenced support and sway-referenced vision [SRV]). However, the SOT is limited to expensive equipment. Thus, a practical version of the SOT is more commonly employed-the clinical test for sensory integration in balance; however, it fails to induce postural instability to the level of SRV.

OBJECTIVE

Determine if Stroboscopic vision (SV), characterized by intermittent visual blocking, may provide an alternative to the SRV for assessing postural stability.

DESIGN

Descriptive laboratory study.

SETTING

Research laboratory.

PARTICIPANTS

Eighteen participants (9 males, 9 females; age = 22.1 [2.1] y, height = 169.8 [8.5] cm, weight = 66.5 [10.6] kg).

INTERVENTION

Participants completed the SOT conditions, and then repeated SOT conditions 2 and 5 with SV created by specialized eyewear.

MAIN OUTCOME MEASURES

A repeated-measures analysis of variance was completed on the time-to-boundary metrics of center-of-pressure excursion in the anteroposterior and mediolateral directions in order to determine the difference between the full-vision, SV, and SRV conditions.

RESULTS

Postural stability with either SRV or SV was significantly worse than with full vision (P < .05), with no significant difference between SV and SRV (P > .05). Limits of agreement analysis revealed similar effects of SV and SRV except for unstable surface mediolateral time-to-boundary.

CONCLUSIONS

In general, SV was found to induce a degree of postural instability similar to that induced by SRV, indicating that SV could be a portable and relatively inexpensive alternative for the assessment of sensory dependence and reweighting.

Minimal detectable change and reliability of the star excursion balance test in patients with lateral ankle sprain

OBJECTIVE

Lateral ankle sprain (LAS) is one of the most prevalent musculoskeletal injuries in the general population and athletes. Dynamic postural control deficits and somatosensory alterations are common signs after an episode of LAS. It is important to detect these deficits to prevent a recurrent sprain and the development of chronic ankle instability. The Star Excursion Balance Test (SEBT) is a tool used to assess dynamic postural control in patients with LAS. SEBT test-retest reliability has been evaluated in several populations. However, no data on patients with LAS are available and we do not know the minimal detectable change (MDC). The primary objective of our study was to obtain the MDC for normalized reach distances of the eight SEBT directions in patients with LAS. The secondary objective was to determine test-retest reliability.

METHODS

Cross-sectional study. Thirty-one patients (between 18 and 40 years old) diagnosed with a Grade I or II LAS. Participants were evaluated by two raters at two time-points separated by an interval of 24-72 hrs. In each assessment, four practice trials were allowed, then three test trials were performed in a randomized order. Normalized reaching distances were analyzed.

RESULTS

From the initial 31 patients, two were eliminated, so 29 patients were considered for the final analysis. The MDC values obtained were 6.73-13.36%, and the medial and posteromedial directions showed the lowest and highest values, respectively. A statistically significant increase was found in lateral direction between T0 and T1. Intraclass correlation coefficients ranged from 0.72 to 0.93.

CONCLUSION

The SEBT is an accurate and reliable tool to assess dynamic postural control in patients with LAS.

The Effects of Cognitive Loading on Motor Behavior in Injured Individuals: A Systematic Review

BACKGROUND

Research suggests that individuals with musculoskeletal injury may have difficulty negotiating physical tasks when they are combined with cognitive loads.

OBJECTIVE

Our objective was to conduct a systematic review to understand the effects of increased cognitive demand on movement patterns among individuals with musculoskeletal injuries.

METHODS

A comprehensive search of PubMed, MEDLINE, the Cumulative Index for Nursing and Allied Health Literature (CINAHL), and SPORTDiscus was conducted to find research reports that included a population that had previously experienced an ankle, knee, or low back injury, included an uninjured control group, and assessed a dual-task paradigm.

RESULTS

Forty-five full-text research reports were assessed, of which 28 studies (six ankle injury, nine knee injury, and 13 low back pain studies) were included in the review. Included studies were assessed for methodological quality and the study design extracted for analysis including the participants, cognitive and physical tasks performed, as well as outcome measures (e.g., three-dimensional kinematics, center of pressure, etc.). All studies included were cross-sectional or case-control with methodological quality scores of 17.8 ± 2.2 out of a possible 22. Twenty-five of the 28 studies found changes in motor performance with dual-task conditions compared with single tasks. Furthermore, 54% of studies reported a significant group by task interaction effect, reporting at least one alteration in injured groups' motor performance under dual-task conditions when compared with an uninjured group.

CONCLUSION

The results of this systematic review indicate that motor performance is further impaired by placing a cognitive load on individuals in populations with musculoskeletal injury. More demanding tasks such as gait appear to be more affected in injured individuals than simple balance tasks. Future investigators may want to consider the difficulty of the tasks included as well as the impact of dual-task paradigms on rehabilitation programs.

Higher visual reliance during single-leg balance bilaterally occurring following acute lateral ankle sprain: A potential central mechanism of bilateral sensorimotor deficits

BACKGROUND

Single-leg balance (SLB) impairment from eyes-open to eyes-closed trials is significantly greater in patients with chronic ankle instability than in uninjured controls, indicating higher reliance on visual information. It is of clinical interest to see if the visual adaptation occurs immediately after injury.

RESEARCH QUESTION

We aimed to investigate visual reliance in patients with acute lateral ankle sprain (ALAS) during SLB with both injured and uninjured limbs and during double-leg balance (DLB).

METHODS

The study assessed visual reliance of 53 participants: 27 ALAS patients and 26 persons without a history of ALAS. All participants executed DLB with eyes open and closed, and then completed SLB with both the injured and uninjured limbs (side-matched limbs of the uninjured control group) in both visual conditions. Order of limb and visual condition for SLB was randomly selected. Visual reliance was quantified for each postural task with a percent change between the two visual conditions, with the greater change representing higher visual reliance. We performed separate group-by-limb analysis-of-variance with repeated measures for SLB percent scores and independent t-tests for DLB outcomes.

RESULTS

For all SLB measures there were no significant group-by-limb interactions (p > 0.05) but significant group main effects (p = 0.013-0.029). With no side-to-side differences, the ALAS group presented higher declines in SLB from the eyes-open to eyes-closed conditions than did the uninjured control group, indicating higher visual reliance. Similarly, for DLB there were significant group differences for almost all measures (p = <.001-0.037), with the ALAS group showing greater visual reliance.

SIGNIFICANCE

Moderately higher visual reliance occurs acutely and bilaterally during SLB in ALAS patients. Similar visual adaptions also occur during DLS. These findings will provide insight into a central mechanism underlying bilateral sensorimotor deficits following ALAS and allow clinicians to improve current rehabilitation strategies for acute patients.

An Updated Model of Chronic Ankle Instability

Lateral ankle sprains (LASs) are among the most common injuries incurred during participation in sport and physical activity, and it is estimated that up to 40% of individuals who experience a first-time LAS will develop chronic ankle instability (CAI). Chronic ankle instability is characterized by a patient's being more than 12 months removed from the initial LAS and exhibiting a propensity for recurrent ankle sprains, frequent episodes or perceptions of the ankle giving way, and persistent symptoms such as pain, swelling, limited motion, weakness, and diminished self-reported function. We present an updated model of CAI that aims to synthesize the current understanding of its causes and serves as a framework for the clinical assessment and rehabilitation of patients with LASs or CAI. Our goal was to describe how primary injury to the lateral ankle ligaments from an acute LAS may lead to a collection of interrelated pathomechanical, sensory-perceptual, and motor-behavioral impairments that influence a patient's clinical outcome. With an underpinning of the biopsychosocial model, the concepts of self-organization and perception-action cycles derived from dynamic systems theory and a patient-specific neurosignature, stemming from the Melzack neuromatrix of pain theory, are used to describe these interrelationships.

Alterations in Cortical Activation Among Individuals With Chronic Ankle Instability During Single-Limb Postural Control

CONTEXT

Chronic ankle instability (CAI) is characterized by repetitive ankle sprains and perceived instability. Whereas the underlying cause of CAI is disputed, alterations in cortical motor functioning may contribute to the perceived dysfunction.

OBJECTIVE

To assess differences in cortical activity during single-limb stance among control, coper, and CAI groups.

DESIGN

Cross-sectional study.

SETTING

Biomechanics laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 31 individuals (10 men, 21 women; age = 22.3 ± 2.4 years, height = 169.6 ± 9.7 cm, mass = 70.6 ± 11.6 kg), who were classified into control (n = 13), coper (n = 7), and CAI (n = 11) groups participated in this study.

INTERVENTION(S)

Participants performed single-limb stance on a force platform for 60 seconds while wearing a 24-channel functional near-infrared spectroscopy system. Oxyhemoglobin (HbO2) changes in the supplementary motor area (SMA), precentral gyrus, postcentral gyrus, and superior parietal lobe were measured.

MAIN OUTCOME MEASURE(S)

Differences in averages and standard deviations of HbO2 were assessed across groups. In the CAI group, correlations were analyzed between measures of cortical activation and Cumberland Ankle Instability Tool (CAIT) scores.

RESULTS

No differences in average HbO2 were present for any cortical areas. We observed differences in the standard deviation for the SMA across groups; specifically, the CAI group demonstrated greater variability than the control (r = 0.395, P = .02; 95% confidence interval = 0.34, 0.67) and coper (r = 0.38, P = .04; 95% confidence interval = -0.05, 0.69) groups. We demonstrated a strong correlation that was significant in the CAI group between the CAIT score and the average HbO2 of the precentral gyrus (ρ = 0.64, P = .02) and a strong correlation that was not significant between the CAIT score and the average HbO2 of the SMA (ρ = 0.52, P = .06).

CONCLUSIONS

The CAI group displayed large differences in SMA cortical-activation variability. Greater variations in cortical activation may be necessary for similar static postural-control outcomes among individuals with CAI. Consequently, variations in cortical activation for these areas provide evidence for an altered neural mechanism of postural control among populations with CAI.

External feedback during walking improves measures of plantar pressure in individuals with chronic ankle instability

BACKGROUND

Individuals with chronic ankle instability (CAI) commonly present with an altered walking gait which favors the lateral aspect of their foot. Current rehabilitative protocols are unable to address these gait modifications which are potentially hindering improvements in patient-reported outcomes. Protocols for gait retraining are scarce, thus there is a need to develop intervention strategies and instruments to specifically target foot motion to address gait deficits in individuals with CAI.

RESEARCH QUESTION

To determine the ability of a novel laser device providing external visual feedback (ExFB) during real-time to cause alterations in plantar pressure measures in individuals with CAI.

METHODS

Twenty-six participants with CAI walked on a treadmill while real-time plantar pressure measures were being recorded during a baseline and feedback condition. Baseline trials were compared with ExFB trials within each subject.

RESULTS

The ExFB condition was able to significantly reduce plantar pressures on the lateral midfoot and forefoot compared to baseline. A statistically significant medial shift in center of pressure trajectory was also observed in the ExFB condition compared to baseline.

SIGNIFICANCE

Real-time external feedback provided by a novel laser device has the ability to reduce lateral column plantar pressures during walking in individuals with CAI.

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

BACKGROUND

Acute 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 QUESTION

We aimed to examine postural stability during bipedal stance in patients with ALAS using TTB outcomes, and to determine bilateral deficits in unipedal balance.

METHODS

Twenty-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.

RESULTS

Independent 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.

SIGNIFICANCE

TTB 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.

Factors Contributing to Chronic Ankle Instability: A Systematic Review and Meta-Analysis of Systematic Reviews

BACKGROUND

Many factors are thought to contribute to chronic ankle instability (CAI). Multiple systematic reviews have synthesised the available evidence to identify the primary contributing factors. However, readers are now faced with several systematic reviews that present conflicting findings.

OBJECTIVE

The aim of this systematic review and meta-analysis was to establish the statistical significance and effect size of primary factors contributing to CAI and to identify likely reasons for inconsistencies in the literature.

METHODS

Relevant health databases were searched: CINAHL, MEDLINE, PubMed, Scopus and SPORTDiscus. Systematic reviews were included if they answered a focused research question, clearly defined the search strategy criteria and study selection/inclusion and completed a comprehensive search of the literature. Included reviews needed to be published in a peer-reviewed journal and needed to review observational studies of factors and/or characteristics of persons with CAI, with or without meta-analysis. There was no language restriction. Studies using a non-systematic review methodology (e.g. primary studies and narrative reviews) were excluded. Methodological quality of systematic reviews was assessed using the modified R-AMSTAR tool. Meta-analysis on included primary studies was performed.

RESULTS

Only 17% of primary studies measured a clearly defined CAI population. There is strong evidence to support the contribution of dynamic balance, peroneal reaction time and eversion strength deficits and moderate evidence for proprioception and static balance deficits to non-specific ankle instability.

CONCLUSIONS

Evidence from previous systematic reviews does not accurately reflect the CAI population. For treatment of non-specific ankle instability, clinicians should focus on dynamic balance, reaction time and strength deficits; however, these findings may not be translated to the CAI population. Research should be updated with an adequately controlled CAI population.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO 2016, CRD42016032592.

Nonlinear Dynamic Measures for Evaluating Postural Control in Individuals With and Without Chronic Ankle Instability

This study aimed to compare time-to-boundary and sample entropy during a single-leg balance task between individuals with chronic ankle instability (CAI), lateral ankle sprain copers, and healthy controls. Twenty-two participants with CAI, 20 lateral ankle sprain copers, and 24 healthy controls performed a single-leg balance task during an eyes-closed condition. Participants with CAI exhibited lower time-to-boundary values compared with lateral ankle sprain copers and healthy controls. However, we did not find differences in sample entropy variables between cohorts. A decrease in time-to-boundary values in participants with CAI indicated that CAI may constrain the ability of the sensorimotor system to maintain the center of pressure within the boundaries of the base of support. However, the regularity of the center of pressure velocity time series appears not to be altered in the CAI cohort in this study.

Altered postural control variability in older-aged individuals with a history of lateral ankle sprain

The current study aimed to examine postural control performance during a single-leg balance task in elderly individuals with and without a previous history of lateral ankle sprain (LAS). Eighteen adults with a previous history of LAS (mean age = 66 years old) and 12 healthy controls (mean age = 65 years old) were included in the study. Participants performed three trials of a single-leg balance task during an eyes-opened condition for 20-s. Center of pressure (COP) trajectories in the anteroposterior (AP) and mediolateral (ML) directions were collected with a force plate. The following postural control measures were calculated in the AP and ML directions: 1) Sample Entropy (SampEn); 2) Approximate Entropy (ApEn); 3) mean of Time-to-Boundary minima (mean TTB); and 4) COP velocity (COPV). Older-age participants with a history LAS exhibited lower ApEn-AP, SampEn-AP, and SampEn-ML values compared to healthy controls (p < 0.05). The information gained from this investigation indicates more rigid postural control patterns, less adaptability, and more difficulty maintaining COP during a single-leg balance task in adults with a previous history of LAS. Our data suggest that there is a need to consider history of musculoskeletal injury when evaluating factors for postural control and fall risk in the elderly. Future investigations are needed to assess the effect of LAS on age-related declines in postural control and discern associations between potential risk factors of fall-related injuries and LAS in an elderly population.

High lateral plantar pressure is related to an increased tibialis anterior/fibularis longus activity ratio in patients with recurrent lateral ankle sprain

Introduction

Center of pressure (COP) is a sudden displacement at the time of a lateral ankle sprain (LAS). It has been suggested that the distribution of plantar pressure and the quantity of COP displacement are important for assessing the risk of LAS. Therefore, we evaluated the plantar pressure during a single-leg balance test with eyes closed (SLB-C) to identify the factors and characteristics of plantar pressure in people with repeated cases of LAS.

Methods

We recruited 22 collegiate athletes and divided them into an instability group (IG; n=11) and a control group (CG; n=11). We measured the distribution of plantar pressure and lower extremity muscle activity during a SLB-C along with static alignment and isometric ankle strength.

Results

The fibularis longus (FL) activity was significantly lower in the IG than in the CG. The lateral plantar pressure (LPP)/medial plantar pressure (MPP) ratio was also higher in the IG than in the CG. In addition, the LPP/MPP ratio was correlated with the tibialis anterior (TA)/FL ratio.

Conclusion

These results suggest that increased lateral plantar pressure is related to decreased FL activity and increased TA/FL ratio.

Visual Utilization During Postural Control in Anterior Cruciate Ligament- Deficient and -Reconstructed Patients: Systematic Reviews and Meta-Analyses

OBJECTIVE

To determine whether anterior cruciate ligament-deficient (ACL-D) individuals and individuals with a reconstructed anterior cruciate ligament (ACL-R) rely more heavily on visual information to maintain postural control.

DATA SOURCES

PubMed, CINAHL, and SPORTDiscus databases were searched from their earliest available date to May 24, 2016, using a combination of keywords.

STUDY SELECTION

Articles were included if they reported any instrumented static single-leg balance outcome in both a patient and control sample. The means and SDs of these outcomes must have been reported with both eyes open and eyes closed.

DATA EXTRACTION

Sample sizes, means, and SDs of single-leg balance measures for each group's eyes open and eyes closed testing conditions were extracted. The methodological quality of included studies was independently evaluated by multiple authors using an adapted version of the Quality Index.

DATA SYNTHESIS

Effect sizes were calculated by dividing the differences in change between eyes closed and eyes open in the ACL-D and control group and the ACL-R and control group by the pooled SD from the eyes closed trials for each analysis. Significant differences between the ACL-D and control group (effect size, -1.66; 95% confidence interval [CI], -2.90 to -.41) were noted. The ACL-R and control group were not different (effect size, -.61; 95% CI, -2.17 to .95).

CONCLUSIONS

ACL-D individuals but not individuals with ACL-R demonstrate a greater reliance on visual information during single-leg stance compared with healthy individuals.