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Original Research

Wobble Board Rehabilitation for Improving Balance in Ankles With Chronic Instability

Linens, Shelley W. PhD, ATC*; Ross, Scott E. PhD, ATC; Arnold, Brent L. PhD, ATC

Author Information
Clinical Journal of Sport Medicine: January 2016 - Volume 26 - Issue 1 - p 76-82
doi: 10.1097/JSM.0000000000000191
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Abstract

INTRODUCTION

Individuals participating in physical activity are at particular risk for sustaining an ankle injury.1 Chronic ankle instability (CAI) is a residual symptom of ankle sprains, and this instability is characterized by feelings of “giving way” at the ankle and recurrent ankle sprains.2 Residual symptoms are reported by 20% to 50% of those sustaining an ankle sprain.3–5 Some deficits associated with CAI are nonmodifiable such as ligament laxity; however, some deficits are modifiable such as poor balance, delayed muscle activation, decreased muscle strength, and impaired sensorimotor function. To correct CAI, clinicians rehabilitate CAI to return individuals to physical activity without functional instability targeting modifiable factors previously mentioned. Evidence indicates that performing multiple rehabilitation exercises improves balance or decreased ankle sprain incidence.6–11 In particular, adolescent soccer players participating in prevention programs with multiple components have a lower incidence of ankle injuries.12–14 Although clinical outcomes are desired, evidence is lacking on how each specific exercise in rehabilitation programs contribute to improving clinical impairments and outcomes. More specifically, more evidence is needed to quantify how a single rehabilitation exercise affects clinical balance measures.

Clinical tests focus on noninstrumented measures that quantify balance. Tests such as foot lift test and Time-in-Balance Test (TBT) have been developed as clinical measures of static balance. Researchers indicate that dynamic tests may provide better means of identifying subjects with CAI than static single leg balance tests because functional movements may magnify the degree to which sensorimotor deficits impact balance performance.15,16 Furthermore, researchers have proposed that dynamic balance tests provide an overall assessment of joint stability, strength, and sensorimotor function, which may help clinicians identify balance deficits that may otherwise go undetected with static tests.17 Clinically, dynamic balance tests are used to determine functional readiness for returning to physical activity. Tests such as Star Excursion Balance Test (SEBT), figure-of-eight hop test (FET), and side hop test (SHT) have either been used as clinical measures of dynamic balance17–20 and/or an outcome assessment of clinical balance impairment.21 The ease and efficiency of these clinical tests makes them ideal outcome assessments for rehabilitation.

Balance impairments are important to rehabilitate because these deficits have been identified as a causal factor of ankle sprains and associated factors with ankle instability and recurrent ankle sprains.10,22–26 Wobble board rehabilitation may be a useful intervention for ankle instability because it has improved static balance measured by instrumented equipment9,10 and decreased ankle sprain incidence.6–8 This type of rehabilitation is thought to assist with reeducation of sensorimotor system by improving mechanoreceptor function and restoring the normal neuromuscular feedback loop.27

We know rehabilitation protocols that use multiple therapeutic interventions improve balance deficits associated with CAI that are assessed with instrumented and noninstrumented measures. However, the extent that each exercise improves balance assessed with clinical tests is currently unknown. Thus, our first step was to identify the contributions of a wobble board protocol on improving clinical measures of balance after 4 weeks. We hypothesized that static and dynamic clinical outcome measures would improve following the rehabilitation protocol.

METHODS

Participants

Thirty-four recreationally active participants volunteered for our study. Seventeen participants were randomly assigned to a rehabilitation group (REH) and 17 participants were randomly assigned to a control group (CON). Participant characteristics are presented in Table 1. Inclusion criteria for all participants were as follows: (1) age ranging from 18 to 40 years, (2) perform cardiovascular or resistance training for at least 1.5 hours per week, (3) history of at least 1 significant ankle sprain, (4) self-report sensations of “giving way” at least twice a year, and (5) Cumberland Ankle Instability Tool (CAIT) score of less than 27. Exclusion criteria for all participants included the following: (1) any known vision deficits (other than myopia, hyperopia, or astigmatism), (2) any known vestibular deficits, (3) any current knee or hip injuries that limit function, (4) any signs or symptoms of acute injury, and (5) any known somatosensory deficits (other than those present in affected ankle). Participant matching was according to sex, height (±10 cm), mass (±15 kg), and age of participant that completed rehabilitation. Each group consisted of 14 females and 3 males, all were right foot dominant, and 14 had right ankle identified as test limb and 3 were left. Limb dominance was determined as the foot chosen to kick a ball. Some participants presented with CAI bilaterally, in these cases, the more symptomatic ankle was chosen for study. All participants provided written informed consent and study was approved by university's institutional review board.

T1-11
TABLE 1:
Participants' Characteristics

Procedures

Data were collected during 2 sessions separated by 4 weeks. First session started with recording participant's height, weight, age, and leg length. Leg length was measured from anterior superior iliac spine to distal tip of medial malleolus of test leg. Participants then underwent an ankle evaluation for joint laxity using the anterior drawer and talar tilt tests, which was conducted by a single investigator who is a board certified athletic trainer. Examination for joint laxity was neither used as an inclusion or exclusion criteria. Then, before clinical balance assessments were conducted, participants completed a self-report questionnaire on their feelings of ankle stability and function, the CAIT.

Next, participants completed either static or dynamic balance tests. Testing type order (static or dynamic) was counterbalanced using a Latin square. Participants stood on leg with CAI for all tests. Order of testing for static balance tests was counterbalanced using a Latin square. Dynamic testing session began with SEBT due to potential fatigue from performing both side hop and FETs. Order of reach directions (anteromedial, medial, and posteromedial) of SEBT was counterbalanced using a Latin square. Both hop tests were then performed with the order of testing counterbalanced. Posttesting was completed 4 weeks later and in same order as pretesting for each participant. All balance testing was conducted by a single investigator who is a board certified athletic trainer. Participants were given 1 practice trial for each balance test before testing, except for the SEBT, in which 4 trials in each direction are recommended.28 All participants were instructed to avoid any other balance training not assigned to them during the study.

Time-in-Balance Test

Positioning for test was a single leg stance on a firm surface with weight-bearing leg in approximately 5 degrees of knee flexion and non–weight-bearing leg slightly flexed at hip and knee. Test determined how long participants could remain motionless before losing stability. Three trials with eyes closed were collected and longest time trial was used for analysis.29 Maximum length of each trial was 60 seconds.29

Foot Lift Test

Positioning was a single leg stance on a firm surface as previously described with TBT. Foot lift test assessed the number of times the stance foot was lifted during a 30-second trial.30 Frequency of foot lifts were counted as an error (1 error was equal to 1 foot lift).30 Foot lifts were documented as any part of foot that lost contact with ground (eg, lift toes from floor).30 Also included in this assessment were frequencies of foot touches of contralateral leg to floor. Foot touches to floor counted as an additional error for every “touch” and 1 more error was added for each second foot remained on floor.30 Average of 3 trials was used for analysis.30

Star Excursion Balance Test

Star Excursion Balance Test was performed according to methods described by Hertel et al.19 We followed the recommendation by Hertel et al.19 and isolated testing to anteromedial, medial, and posteromedial reach directions. Participants performed reach tasks while standing barefoot on test leg at center of grid laid on floor with 3 cloth tape measures extending at 45-degree angle from center. Participants maintained single leg stance with eyes open and hands on hips while reaching with contralateral leg to touch as far as possible along tape measure and then returned to bilateral stance. Point touched during each attempt was recorded and reach distance was normalized to participants' leg length. Each participant performed 4 practice trials in each of 3 directions followed by 5 minutes of rest before recording began. Participants then performed 3 trials in each direction. Ten seconds of rest were provided between individual reach trials. Average of 3 trials normalized to leg length was used for analysis.

Figure-of-Eight Hop Test

Methods described by Docherty et al17 were used for this test. Participants performed test barefoot on 5-m course outlined by cones in figure-of-eight pattern. Participants were instructed to hop on their test leg in figure-of-eight pattern 2 times as quickly as possible. Total time was recorded with a hand-held stopwatch to nearest 0.01 seconds. Participants completed test 2 times and best (shortest) time was used for analysis.17

Side Hop Test

Methods described by Docherty et al17 were also used for this test. Participants performed test barefoot on test leg. Participants were instructed to hop laterally 30 cm and back medially 30 cm for total of 10 repetitions.17 Total time taken to complete 10 repetitions was recorded with a handheld stopwatch to nearest 0.01 seconds. Participants completed test 2 times and best (shortest) time was used for analysis.17

Wobble Board Rehabilitation

The wobble board (CANDO MVP Balance System; USA) is a circular platform (30 inches) with different sized domes that screw into bottom of board to make balance exercises more or less challenging. Participants were placed near a wall and only allowed to touch fingertips to wall for any means of stability. A 1-legged stance was performed on the board, and then clockwise and counterclockwise rotations of the rim of the board were completed. Dome with shortest diameter was considered lowest level (ie, level 1) and all participants began rehabilitation on this level. Five levels were available for training and height of each level increased by half inches; thus, heights ranged between 1 and 3 inches. Initial direction of rotation was selected by participant and changed every 10 seconds of 40-second trial. Five 40-second trials were completed with 1 minute of rest in between trials. Difficulty of training progressed according to participant ability determined by smooth transitions between and within rotation directions as well as self-reported feelings of “easiness.” Participants reported for training 3 days per week for 4 weeks.

Statistical Analysis

SPSS version 18.0 (SPSS Inc., Chicago, Illinois) was used for statistical analyses. The independent variables were group (REH and CON) and time (pretest and posttest). Separate 2 × 2 repeated-measures analysis of variance analyzed changes in dependent measures from rehabilitation. For SEBT measures, the 3 reach distances were analyzed separately. Tukey Honest Significant Difference was used for post hoc pairwise comparisons to explain any significant interactions. Alpha level was set a priori (α = 0.05).

RESULTS

Mean ± SDs, 95% confidence intervals, main effects, and interaction results for each dependent measure are presented in Tables 2–6. In summary, significant main effects for time were found for all dependent measures. A significant main effect for group was only found for anteromedial reach direction of the SEBT. Significant time by group interactions were found for all dependent measures except for the TBT. Post hoc testing of significant interactions showed the REH group improved performance at posttest when compared with pretest, whereas CON group did not.

T2-11
TABLE 2:
Time-in-Balance Test
T3-11
TABLE 3:
Foot Lift Test
T4-11
TABLE 4:
Star Excursion Balance Test
T5-11
TABLE 5:
Figure-of-Eight Hop Test
T6-11
TABLE 6:
Side Hop Test

DISCUSSION

We found 4 weeks of wobble board training significantly improved static balance as detected by the foot lift measure, and dynamic postural control as assessed with SEBT, side hop, and figure-of-eight hop. We believe that balance improved because of a focus of using only 1 exercise that has been shown to enhance proprioception31 and strength.32 Clinicians can use our 4-week wobble board protocol to improve balance in physically active patients with CAI.

Static Balance Measures

Foot lift measure of static postural control significantly improved in REH compared with CON. Those with ankle instability have been shown to shift to a hip strategy after injury to compensate for their inability to balance.33,34 This strategy most likely occurs because they feel more confident in their ability to maintain their balance with shifts at their hip rather than their ankle. In other words, they try to “lock down” their ankle to maintain joint stability.30 After rehabilitation, participants lifted their foot fewer times than at pretest because corrections were likely made at their ankle as opposed to the hip. Our rehabilitation may have assisted those with CAI to return to an ankle strategy more commonly seen in stable ankles because patients are able to maintain more foot to ground contact while testing their limits of stability without fear of rolling their ankle. Our protocol forced patients to touch the edges of the board to the ground; therefore, they would reach progressively increased ankle range of motion without allowing a sprain or “roll over” event to occur. The protocol also may have strengthened the ankle musculature such as the tibialis anterior, peroneus longus, and gastrocnemius.32 Furthermore, the protocol may have improved muscle onset latency, which suggests improvement in mechanoreceptor function.35 Improved mechanoreceptor function may be leading to more effective usage of ankle musculature and possibly musculature further up the kinetic chain. Because of the combination of these aspects, it is likely that patients returned to an ankle strategy because they now present more like healthy individuals.

Our rehabilitation program was unsuccessful at improving the time-in-balance measure. It is noticeable that there is a lot of variability in this measure when simply looking at SDs of both groups. Large SDs in this measure can make it more difficult to detect statistically significant differences. However, there is not much overlap in the 95% confidence intervals, which indicates that there is improvement after rehabilitation, but we are underpowered to detect change at a statistical level.

Dynamic Balance

The figure-of-eight hop and SHTs were also significantly improved after rehabilitation. These tests each stress the dynamic stabilizers of the ankle joint and previous research has shown reduced muscle onset latency of the tibialis anterior and peroneus longus muscles after completing a wobble board program thereby improving mechanoreceptor function.36 We hypothesize that the dynamic stabilizers of the ankle are retrained during the wobble board rehabilitation program, which also allows for more effective usage of musculature further up the kinetic chain and therefore resulted in improved dynamic balance.

We also found significant improvements in the SEBT of REH compared with CON. According to the dynamical systems theory, after the completion of rehabilitation protocol, patients may have had less constraints on their sensorimotor system and as a result been afforded more range of motion in their lower extremity.21 In particular, patients may have more confidence in their ability to control their subtalar joint and ability to travel through a greater range of motion at the knee and hip while balancing on a firm surface without subsequent injury. Furthermore, both the SEBT and the wobble board are considered semidynamic balance tasks. The difference is that the wobble board has a moveable base of support and participants maintained their center of mass (COM) within their limits of stability to complete this task. The SEBT has a fixed base of support with a moveable COM. Participants again maintained their COM within their limits of stability to complete their task. So, it seems that the movable base of support (wobble board) task transferred to improving a fixed base of support task.

Our percent change scores pretest to posttest score ranged from approximately 9% to 14% (anteromedial, 9.0%; medial, 14%; posteromedial, 13%), which is greater than previous improvements reported in the literature (4%-9%).21,37,38 We believe that our percent change scores are higher because we used a single exercise as opposed to a multistation program. The multistation types of programs incorporate numerous ankle therapeutic exercises that are commonly used in clinical practice. The benefit of each exercise in a multistation program is not known; nor do we know if 1 exercise can counteract the benefits of another in a multistation exercise regimen. Thus, future research is needed to confirm our speculation that a single exercise could lead to greater improvements in the SEBT than a multistation program.

Multistation Programs

As briefly mentioned above, CAI rehabilitation commonly involves multistation programs consisting of several different exercises. Significant improvements in static instrumented force plate measures have been reported with effect sizes ranging from small to large (−0.20 to 0.80).25 Effect sizes were calculated for precomparisons to postcomparisons of REH. Although instrumented force plate measures are helpful for detecting improvement after rehabilitation, the clinical measures included here seem to outperform them with equal or much larger effect sizes (0.76-1.40) and are much easier to conduct in a clinic setting. Dynamic balance improvements have been reported for the posteromedial direction of SEBT with a medium effect size of 0.6421; however, our effect size was large and exceeded 1.0.

It is important to note that research using only 1 piece of equipment is demonstrating equal or larger effect sizes as compared with multistation programs. Multistation program research cannot determine whether each exercise is beneficial and therefore leading to results, only improvement as a whole is known. Multistation programs have shown to prevent subsequent ankle sprains,25,39 this remains to be determined with our protocol. However, a common component of multistation programs is a wobble board and a significantly reduced risk of ankle sprains has been found.39 We therefore propose we would find a reduced risk of ankle sprains as well. Multistation programs have been argued to prevent boredom of patients; however, we argue that our protocol takes such little time and the progressions of levels increases the difficulty of the task that boredom is prevented. A multistation program requires more equipment and more time to implement; therefore, determining that clinical measures of balance are improved with a simplified program is advantageous both to the clinician and patient.

Limitations

Limitations of this study include a relatively liberal definition of physically active. Our liberal definition of physical activity (at least 1.5 hours per week) was to include a more heterogeneous population to better generalize our results. However, participants drastically varied from those that completed moderate exercise to those that completed strenuous and competitive exercise. Furthermore, this protocol needs to be examined in more homogenous populations ranging from recreationally active to highly competitive populations to determine any differences. The researcher administering pretest and posttest measurements was not blinded to participants' group membership and therefore could have unintentionally inflated posttest results of the REH group. Future rehabilitation research could benefit from blinding the posttest evaluator to group membership.

Future Research

Future research needs to compare various wobble board protocols to determine the most effective regimen. It seems that a 4-week wobble board protocol is advantageous, but future research needs to determine the most beneficial time frame in which to conduct the rehabilitation protocol, whether it is 4 weeks or 6 weeks; 3 or 5 visits per week. Furthermore, it remains to be determined how long the improvements in clinical balance measures can be maintained. Finally, a wobble board protocol needs to be compared with another traditional rehabilitation tool for the treatment of CAI, such as Theraband exercises.

CONCLUSIONS

Our results show significant improvements in clinical outcome measures using a one-exercise intervention. We believe that our findings are advantageous for clinicians since our protocol involves minimal equipment, time, and space to conduct compared with more traditional multistation programs. In addition, we believe that patients will have improved compliance and decreased boredom since our protocol is simple yet progresses in difficulty. Therefore, we recommend that clinicians use our 4-week wobble board protocol to improve both static and dynamic balance in physically active individuals with CAI.

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Keywords:

static balance; dynamic balance; Star Excursion Balance Test

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