Use of a Combination of Ankle Pressure and SENSERite System to Treat Older Adults With Impaired Ankle Proprioception: A Single-Blind Experimental Study

Article Outline

• Abstract
• Methods
  • Subjects
  • Instrumentation
    • The SENSERite system
    • Aneroid sphygmomanometer
  • Procedures
    • Ankle joint position sense test using the SENSERite system
    • Data acquisition and computation
    • Intervention
    • Ankle joint position sense visual feedback training
    • A combination of position feedback training and circumferential ankle pressure
  • Statistical Design and Analysis
• Results
  • Clinical Characteristics
  • Intervention Effects on Absolute Constant Error and Variable Error in Normative Subjects at the Pretest, Posttest, and Follow-Up Test
  • Intervention Effects on Absolute Constant Error and Variable Error in Subjects With Ankle JPS Impairment at the Pretest, Posttest, and Follow-Up Test
  • Posttest Questionnaire
• Discussion
  • Study Limitations
• Conclusions
• Acknowledgments
• References
• Copyright

Abstract 

You JH, Saliba S, Saliba E. Use of a combination of ankle pressure and SENSERite system to treat older adults with impaired ankle proprioception: a single-blind experimental study.

Objective

To investigate the effects of a combination of visual biofeedback and ankle pressure on ankle position sense in elderly adults with and without impaired ankle joint position sense (JPS).

Design

Independent 2 × 3 factorial design with an experimenter-blind study.

Setting

University motion laboratory.

Participants

Older adults (N=40) were recruited from local community centers. Among them, 21 elderly subjects had relatively normative score, whereas 19 subjects had impaired ankle position sense.

Intervention

Both the normative and impaired elderly subjects underwent either ankle JPS visual feedback training alone or a combination of ankle JPS visual feedback training and circumferential ankle pressure for one 30-minute training session.

Main Outcome Measures

The outcome measures included ankle JPS errors measured in absolute constant error (ACE) and variable error (VE) during standing at pretest, posttest, and 1-week follow-up test. A separate repeated measures analyses of variance was performed to evaluate the differential training effects on ACE and VE, respectively. The Pearson chi-square test and Bonferroni test were performed. Significance was assigned at P less than .05 for all analyses.

Results

Regardless of intervention conditions, older adults with and without ankle position sense impairment showed immediate treatment benefits, which relatively remained stable even at the follow-up test. These effects were reflected in significant improvements of JPS accuracy and consistency (P<.05).

Conclusions

Our findings may suggest that both interventions were equally effective in increasing ankle JPS accuracy and consistency in older adults with and without impairments, and therapeutic effects lasted for a week, reflecting long-term effect.

Key Words: Feedback, Pressure, Proprioception, Rehabilitation

List of Abbreviations: ACE, absolute constant error, ANOVA, analysis of variance, CAP, circumferential ankle pressure, JPS, joint position sense, ROM, range of motion, VE, variable error

ANKLE JOINT POSITION SENSE is essential information for the regulation of postural stability.¹, ² Postural instability may become accentuated for elderly adults in a dark or irregular surface environment unless they can compensate for impaired position sense with other intact sensory apparatus. Empirical evidence suggests that in the absence of visual and vestibular inputs, ankle position sense error as small as 0.1° can lead to approximately a 1.8-mm lateral postural deviation of the whole body center of mass.³ This may explain why older adults with visual or vestibular impairments who are reliant on ankle position sense are prone to falls. Amplitude scaling process during postural control was delayed in individuals with impaired proprioception,⁴, ⁵ but not in individuals with profound loss of vestibular function,⁶ signifying the importance of proprioceptive inputs.⁷

Current clinical managements for individuals with impaired ankle position sense have included proprioceptive retraining exercise using a balance board,⁸ Tai Chi exercise,⁹ taping,¹⁰ ankle pressure,¹¹ high-top shoes,¹² and feedback training.³, ¹³ There is some positive evidence supporting efficacy for these treatments, predominantly for young adults or athletes with chronic ankle sprain, but limited for older adults with or without impaired ankle position sense. To our knowledge, only 1 study examined the effect of ankle pressure support through high-top shoes and found them to be effective in enhancing ankle proprioception and balance function in healthy older adults.¹² Other studies³, ¹³ have reported that ankle reposition training with a visual feedback system can help increase the accuracy of ankle joint positions in healthy older adults. At present, evidence of the therapeutic effects of both ankle pressure and visual feedback training on ankle position sense in individuals with impaired ankle proprioception is scarce.

Recently we developed a portable computerized visual feedback system (the SENSERite system) to measure ankle proprioception accurately and to provide visual feedback of ankle position while concurrently applying ankle pressure. The portable SENSERite system was developed to measure and retrain the multifaceted ankle JPSs for the neutral, inversion, eversion, plantarflexion, and dorsiflexion positions in individuals with impaired ankle proprioception.¹¹ During the visual feedback training, the subject can see the target position in the monitor and practice the matching task using the visually guided ankle position feedback.¹¹

The effect of the SENSERite system training on ankle proprioception in older adults with impaired ankle proprioception has never been explored. The extent to which older adults with impaired ankle proprioception can benefit from augmented proprioceptive feedback from a combined application of ankle pressure and computerized feedback to improve JPS is yet to be determined. Hence, the specific aim of this study was to determine the differential effects of a combination of SENSERite and ankle pressure (position feedback training—CAP) versus the SENSERite training (position feedback training) alone on ankle JPS accuracy and consistency of the individuals with and without impaired ankle proprioception. Our basic assumption was that position feedback training and CAP may produce greater improvement in ankle JPS than position feedback training alone. If this assumption holds true, clinically the addition of ankle pressure may be a useful method to enhance ankle position sense in older adults with impaired ankle position sense. In particular, it is plausible that the older adults with normative ankle position sense who were already operating at close to normative levels to begin with may show no or little improvement from the interventions. On the other hand, the older adults with impaired ankle position sense may gain significant benefit from both interventions. This enhanced ankle sense may increase awareness or sensitivity of the ankle, which in turn helps reduce the risk of ankle sprain or fatal falls in older adults with a history of falls secondary to impaired ankle position sense.

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Methods 

Subjects 

A convenience sample of 40 subjects with and without ankle JPS impairments between the ages of 62 and 88 years (5 men, 35 women; mean age, 73.2±7.7y) was recruited from local community centers (table 1). The number of participants was determined by estimating the effect size and calculating the degree of freedom (μ=κ–1) and then setting the acceptable power. Our previous study revealed a medium effect size (F=.25); thus, we computed μ and located an acceptable power of .80, which yielded a target sample size of 40.¹⁴ The Human Investigations Committees approved this study. All subjects provided signed informed consent before participation. Selection criteria included (1) participants with no currently known cognitive, cardiopulmonary, or neuromusculoskeletal diagnosis; and (2) participants with independent ambulation. Exclusion criteria were (1) participants who were taking medications influencing neuromuscular performance and/or who exhibited signs and symptoms including the Homans sign, drowsiness, tremor, numbness, nausea, blurred vision, and hearing loss; these symptoms and signs were carefully screened with the demographic and health questionnaire and a posttest questionnaire and in part evaluated with the modified physical therapy checklist¹⁵; (2) participants who scored more than 9 on the Orientation-Memory-Concentration Test¹⁶; (3) participants who scored more than 7 on the modified physical therapy checklist; these criteria were used to ensure that all participants were capable of performing the testing and training; and (4) individuals diagnosed with diabetic and peripheral neuropathy. If not known, the sensation test in the physical therapy checklist was performed to determine this impairment. The modified physical therapy checklist included standard tests of routine sensation, ROM, muscle strength, balance, and gait. All subjects' physical and mental performances were within functional or normative limits.

Table 1. Clinical and Demographic Characteristics (N=40)

NOTE.

Abbreviations: NA, not applicable; OMCT, Orientation-Memory-Concentration Test; PTC, physical therapy checklist.

⁎Significance level was set at P<.01. Independent sample t tests were performed to determine group differences. There were no statistically significant group differences on age, sex, PTC, and OMCT scores. These findings indicate that all subjects had similar group characteristics. Independent sample t tests revealed that baseline proprioceptive acuity scores as measured in ACE were significantly different between the groups.

Baseline ankle JPS of all subjects was accurately determined by measuring ACE using the SENSERite system measurement. The subjects who had less than 2.3° ankle position sense error were categorized as normative (n=21), whereas any subjects who had greater than 2.3° error were classified as impaired (n=19). This critical value was adopted from our previous experiment.¹⁷ Our previous data showed ankle position sense error values in the older adults with a history of falls and stroke were 2.32°±0.70° and 2.61°±0.80°, respectively.¹⁷ Hence, we believe that the critical value (mean score: 2.30°) used was appropriate. Subjects with or without ankle JPS impairment were also stratified based on age and sex and were administered either position feedback training alone or a combination of position feedback training and CAP intervention. Subjects' clinical characteristics are summarized in table 2.

Table 2. Summary of Subjective Responses of Participants to the Posttest Health Questionnaire and Chi-Square Test (N=40)

NOTE. All subjects were asked to respond to the survey questions in the posttest health questionnaire by saying yes or no. Selective variables are included the following:

†Performance perceived to be accurate under any certain position.

‡Perceived effect of intervention on ankle reposition accuracy performance.

§Perceived fatigue experienced after performance. Pearson chi-square analysis revealed that there were significant associations between the subjects with and without impairment and the report category Intervention on proprioception as well as between the subjects with and without impairment and the report category Fatigue.

⁎P<.05.

Instrumentation 

The SENSERite system 

This electromechanical device was designed to measure the degree of ankle position sense error and also to provide accurate visual biofeedback about ankle joint position during the intervention. It is composed of a single axis potentiometer connected to a laptop computer through a 12-bit analog-to-digital converter of the LabVIEW 6.1 data acquisition system^a (fig 1). In essence, the SENSERite system features an electrogoniometer, which includes 1 potentiometer mounted on the endpoint of the longitudinal axis of this system. This potentiometer has the capability to measure .001°. The validity and test-retest reliability of SENSERite measure were well established in healthy and older adults with a history of falls.¹⁷

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• Fig 1. 

  Experimental setup for intervention.

Aneroid sphygmomanometer 

A 60-mmHg CAP was consistently provided to enhance cutaneous ankle sensation using a pediatric aneroid sphygmomanometer.^11,b

Procedures 

This study had a single-blind design in which subjects were blinded for the test results to reduce experimental bias. An experimental procedural checklist was followed to ensure a consistent protocol. In short, the experimental procedure included the pretest (baseline), intervention, posttest, and follow-up test. The follow-up test was performed 6 to 8 days after the posttest. All subjects reported to the laboratory at a similar time of day throughout the tests and completed the posttest health questionnaire.

Ankle joint position sense test using the SENSERite system 

The SENSERite system was calibrated before data acquisition. The subjects were asked to stand with 1 foot on a solid footstool and the test foot on a hinged platform of the SENSERite system as symmetrically and upright as possible (see fig 1). The subjects were not allowed to see their foot and were asked to fix their eyes at a certain point on the wall in front to eliminate visual feedback. The subjects started in a neutral ankle position and were then asked to move their test feet to select a specific target ankle joint position within the comfortable functional ranges and maintain this position for 3 seconds. The subjects were instructed to move their ankles to the initial neutral position.¹¹, ¹⁷ For example, for the neutral ankle joint position test, the subjects began in a fully inverted position and actively moved the ankle through the functional range and actively selected a specific target neutral position (ie, usually somewhere between 0° to ±3°), stopped at this target position, and maintained this position for 3 seconds, and returned to the start position. Each subject's selected joint position angle was recorded by the computer program and was verbally informed of the degree of this joint position. The subjects were then instructed actively to reproduce or match the target position as accurately as possible.

As with the neutral joint position test, other inversion, eversion, plantar flexion, and dorsiflexion joint position tests were performed in a similar fashion, but the sequence was randomized. The approximate target joint positions for each joint motion included 0° neutral, 15° inversion, 10° eversion, 25° plantar flexion, and 20° dorsiflexion. The sequence of the ankle JPS tests for the 5 different positions was randomized by a balanced 5 × 5 Latin square design to eliminate potential biasing effect in the repeated measure.¹⁸

Data acquisition and computation 

Ankle JPS data were collected through continuous electromechanical measurement using a potentiometer built into the SENSERite system. Conventional computation of ankle position sense error was obtained by 2 independent computation methods: ACE and VE.³, ¹¹, ¹³, ¹⁷ ACE was selected to measure performance accuracy, whereas VE was chosen to determine performance consistency.¹⁹ ACE represents absolute value of average magnitude of the movement deviations between the subject's target and actual repositions. This has been mathematically expressed as

where x_i is the actual reproduction error score on the trial, T is the target, and n is the number of the trials that a subject performed. Therefore, lower ACE scores indicate better accuracy in the performance. In contrast, VE is the variability of the mean matching performance and is the SD of the constant error scores.¹⁹ This has been expressed as where x_i is the actual reproduction error scores on the trial, M is the subject's average movement, and n is the number of the trials. Therefore, the lower VE scores mean more stable or consistent performance across the period.¹⁹ The 3 repeated trials for all the dependent variable measures were recorded and averaged for further analysis.

Intervention 

Both normative and impaired subjects were administered with 2 different ankle joint position feedback interventions: ankle position visual feedback training, and a combination of position feedback training and CAP.

Ankle joint position sense visual feedback training 

Position feedback training was provided by using the SENSERite system, which was designed to provide real-time visual feedback displayed on the computer monitor. Visual feedback is a form of proprioceptive feedback that conveyed information about ankle joint position as the subjects move their ankles (see fig 1). During the practice sessions, the subjects were allowed to see the real-time target joint position and error values that were graphically and numerically presented on the computer screen. The real-time visual feedback that was concurrently provided during the initial stages of the training was gradually decreased as accuracy and consistency in their JPS increased, which usually occurred after the first 10 practice trials. For example, ankle joint position visual feedback training started in the neutral ankle joint position. The subjects began in a fully inverted position and actively moved the ankle through the functional range and actively selected a specific target neutral position. The subjects were instructed to stop at this target position, maintain this position for 3 seconds, and then return to the start position. As with visual feedback training starting in the neutral ankle position, as per other position feedback training starting in other joint positions, the subjects always started in a neutral position, actively moved the ankle to a target joint position, returned to the start position, and then actively moved back to the target position to reproduce the target ankle position angle as accurately as possible. One 45-minute treatment session was provided, and this consisted of a total of 200 practice trials distributed over 5 blocks. A rest interval of 3 to 5 minutes was provided as requested by the subjects to avoid any fatigue.

A combination of position feedback training and circumferential ankle pressure 

In addition to the position feedback training, 60mmHg pressure was consistently applied just above the talocrural joint by a pediatric aneroid sphygmomanometer cuff so that it freely allowed ankle motion during the intervention session. CAP was provided to augment cutaneous ankle proprioception further.

Statistical Design and Analysis 

An independent variable included intervention (position feedback training, position feedback training and CAP). Dependent variables included the ACE and VE. Two independent 2 × 3 repeated-measures ANOVAs were used, where a separate ANOVA was performed to differentiate the ankle position sense intervention effects for subjects with normative and impaired ankle position sense, respectively. The intervention-related effects were determined on ACE and VE at pretest, posttest, and follow-up test. In addition, a 2-way contingency table analysis using the Pearson chi-square test was conducted to evaluate the subjectively perceived training effects on proprioception between groups reported in the posttest health questionnaire. Significance was assigned at P less than .05 for all analyses. The Bonferroni test was used for all 3 pairwise comparisons across the 3 repeated tests and adjusted at P less than .001.

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Results 

Clinical Characteristics 

Table 1 presents a summary of demographic and health information of all subjects. All subjects underwent the physical therapy checklist and the Orientation-Memory-Concentration Test prior to the participation of the experiment. The physical therapy checklist and Orientation-Memory-Concentration Test scores were 1.13±1.3 and 1.26±2.43, respectively, and indicate that all subjects were able to understand instruction and perform the required tests. All subjects were independent community ambulators. Independent sample t tests showed no statistically significant differences on age, sex, the physical therapy checklist, and Orientation-Memory-Concentration Test scores between the normative and impaired subjects. This finding indicates that all subjects presumably had similar characteristics. However, both baseline ACE and VE were significantly greater in the subjects with impaired ankle position sense than the normative subjects (P<.001). Table 2 presents a summary of clinical characteristics on ankle strength, ROM, cutaneous, and proprioception sensations for the normative and impaired subjects.

Intervention Effects on Absolute Constant Error and Variable Error in Normative Subjects at the Pretest, Posttest, and Follow-Up Test 

One-way repeated ANOVA for the mean ACE (fig 2) and VE scores (fig 3) across the 3 repeated tests revealed a significant within-subject time main effect (F_2,34=60.78 and F_2,34=36.13, at P=.001, respectively). These findings suggest that the normative subjects showed increased ankle JPS accuracy and consistency over time. The Bonferroni test showed that the ankle JPS accuracy and consistency scores at both the posttest and follow-up test were significantly greater than those at the pretest (P<.01). The ankle JPS accuracy and consistency scores at the follow-up test were significantly greater than those at the posttest (P<.01). Independent sample t tests (2-tailed) revealed that both ankle JPS accuracy and consistency scores between the position feedback training and position feedback training with CAP groups at the pretest were not significant (P>.05), indicating that both groups had similar baseline ankle JPS scores to begin with. No within-subject interaction effect or between-group main and interaction effects were seen in ACE and VE scores.

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• Fig 2. 

  ACE in normativee subjects. Abbreviations: deg, degrees; PFT, positive feedback training.

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• Fig 3. 

  VE in normative subjects. *Statistical significance at P<.05. Abbreviations: deg, degrees; PFT, positive feedback training.

Intervention Effects on Absolute Constant Error and Variable Error in Subjects With Ankle JPS Impairment at the Pretest, Posttest, and Follow-Up Test 

Significant within-subject time main effects (F_1.39,26.4=210.03 and F_1.19,22.71=59.01 at P=.001) were observed were respectively observed for the mean ACE (fig 4) and VE scores (fig 5) across the 3 repeated tests. These results suggest that the impaired subjects showed improved ankle JPS performance in accuracy and consistency measures over time. The Bonferroni test showed that the ankle JPS accuracy and consistency scores at both posttest and follow-up tests were significantly greater than those at the pretest (P<.01). The ankle JPS accuracy and consistency scores at the posttest were not significantly different from those at the follow-up test (P>.01). An independent sample t test demonstrated that both ankle JPS accuracy (P=.11) and consistency (P=.49) scores between the position feedback training and position feedback training with CAP groups at the pretest were not significant, suggesting that baseline ankle JPS scores were similar. Although there were neither within-subject nor between-subject interaction effects at P equal to .05, the tests of within-subjects contrasts in quadratic component showed a significant within-subject interaction of time × intervention for the ACE measure at a more liberal significance level of P equal to .08 (but not in linear component, P=.43). Moreover, there was a significant between-group main effect for the ACE measure at a more liberal significance level of P equal to .08, but this was not the case in the VE measure. These findings seem to suggest that there is a tendency for a possible differential intervention effect in the ankle JPS accuracy.

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• Fig 4. 

  ACE in subjects with impaired position sense. *Statistical significance at P<.05. Abbreviations: deg, degrees; PFT, positive feedback training.

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• Fig 5. 

  VE in subjects with impaired position sense. *Statistical significance at P<.05. Abbreviations: deg, degrees; PFT, positive feedback training.

Posttest Questionnaire 

Table 2 shows a summary of a 2-way contingency table analysis of the posttest health questionnaire data using the Pearson chi-square test to evaluate the associations between reports of performance perceived to be accurate under any certain position, perceived effect of intervention on ankle reposition accuracy performance, and perceived fatigue experienced after performance in subjects with and without ankle JPS impairments, respectively. Pearson chi-square analysis revealed that there were significant associations (χ²=4.27, P<.05) between subjects with and without impairments and the report category of perceived effect of intervention on ankle reposition accuracy performance as well as (χ²=4.95, P<.05) between subjects with and without impairments and the report category of perceived fatigue experienced after performance in subjects with and without ankle JPS impairments (see table 2). This finding suggests that subjects with impairments reported more benefit from the position feedback training with CAP than position feedback training alone on ankle proprioception, whereas normative subjects did not perceive such a difference.

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Discussion 

As anticipated, our findings suggest that subjects with position sense impairment benefited from both interventions. Interestingly, normative subjects who were supposed to operate at close to normal levels to begin with also showed improvement from the interventions. The joint position accuracy and variable performances in both subjects with and without position sense impairment were enhanced after either position feedback training or position feedback training with CAP intervention, and the intervention effects continued to exist at the follow-up test, indicating a relative long-term effect.

Most importantly, the clinical ramification of our results is that position sense impairment was reversible by exploiting augmented feedback effects from both interventions. Our results were in support of the previous study investigating the effect of feedback and ankle pressure on subjects with chronic ankle sprain.¹¹ Impaired ankle joint position in subjects with chronic ankle sprain was restored with ankle feedback training and pressure.¹¹ Taken together, these findings seem to support the concept of schema theory that motor memory for a simple motor pattern can be topographically organized in the motor control system by means of the presentation and recall of movement within a short period. This motor memory may be engrained in the system through repetitive practice of the same motor pattern and eventually become a part of the generalized motor program, thereby producing relative permanence in the skill acquisition.¹⁹ In the present study, the repetitive practice paradigm using augmented position feedback training and cutaneous pressure feedback may have helped in establishing recall and recognition schema. Specifically, not only did elderly adults with impaired position sense retain performance accuracy and consistency but also most subjects (78%) reported that both visual (position feedback training) and cutaneous (CAP) feedback invoked both mental (cognitive recall) and ankle sense (sensory) awareness during the interventions. Apparently, augmented feedback may have stimulated them cognitively to recall and increase recognition of expected sensory consequences for a desired ankle movement in the impaired subjects who received a combination of position feedback training and CAP.¹³, ¹⁹

We initially hypothesized that the training effect would be limited to those subjects with impaired JPS. This assumption was inferred based on previous research suggesting that additional (or augmented) sensory feedback from therapeutic pressure would not contribute to performance accuracy in normative subjects because they may rely on an intact central control mechanism.²⁰ Augmented feedback was documented to bombard subjects with inherently sound proprioception to begin with, but increase proprioceptive acuity for those subjects with inherently poor proprioception.¹¹, ²⁰ However, in the present experiment, this assumption was not supported by the fact that both normative subjects and subjects with impaired position sense showed improvement after interventions. Such discrepancy between our results and previous findings¹¹, ²⁰ may be a result of different critical values and subject characteristics (ie, young vs older adults; ankle sprain vs stroke or fallers; different joints). For example, we have used the critical value of 2.3° based on our 2 previous studies.¹¹, ¹⁷ One study examined the effect of ankle pressure on position sense in young adults with impaired position sense associated with chronic ankle sprain.¹¹ Initially, position sense error was 2.31°±0.27°, but it reduced significantly to 0.90°±0.31° when ankle pressure was applied.¹¹ This value was comparable to that of healthy young adults, which was 0.80°±0.20°. Similarly, the other study showed that the mean ankle position sense errors of the older adults with a history of falls and stroke patients were 2.32°±0.70° and 2.61°±0.80°, respectively. On the other hand, Batavia et al²⁰ used a somewhat larger critical value (5°) for the wrist joint to classify participants into either a high or a low position sense group.

Stelmach and Sirica²¹ suggested that central control mechanisms operating in a predictive mode could allow older adults to compensate for altered proprioception by means of enhancing sensitivity of sensory consequences of the intended motor action; subsequently, it reduces potential JPS error. Initially, the subjects may have learned the matching task using extrinsic proprioceptive feedback, which is primarily involved in a conscious, explicit learning process. Because the subjects use the self-selected reference positions and repetitively practice the task, corollary discharge is likely to activate the sensory systems for the intended sensory consequences of the motor action in predictive mode, which involves an automatic, implicit learning process. This seems to indicate that intrinsic feedback, reportedly deteriorated in older adults, did not affect performance accuracy.¹⁰, ²², ²³

Our assumption that position feedback training with CAP might produce greater improvement in ankle JPS than position feedback training alone was partially supported by our results. Participants with impaired position sense showed substantial improvement in the ACE measure at a more liberal significance level (P=.08), although it did not reach a statistical significance at P less than .05. Additionally, a significant between group main effect for ACE measure was observed at P equal to .08. These findings imply a trend of differential intervention effect in accuracy performance.

Joint receptors are believed to sense joint position signals throughout all ROM and mainly act as limit detectors in response to the extremes of joint motion.²³, ²⁴ A 60-mmHg ankle pressure was applied to provide tactile inputs in the present study. This amount of pressure may have primarily stimulated cutaneous receptors. In addition, the selected joint ranges for the JPS test were within functional limits, and thus it may have not stimulated joint receptors.²⁰ Further studies are needed to examine potential effects of different amounts of ankle pressure on ankle mechanoreceptors during a certain ankle motor task or movement.

Repeated testing procedure can influence results. It may change performance on subsequent trials because of a practice or motor learning effect.¹⁸ To control this potential confounding effect, all subjects in this study were given a series of practice trials, and data were collected when performance was stabilized. It is possible that subjects may experience fatigue or associated ankle pain, but only 1 subject complained of ankle muscle fatigue after intervention according to the postintervention questionnaire.

Study Limitations 

This was a preliminary experiment to investigate the effects of ankle feedback and a combination of ankle feedback and pressure for improving ankle position sense in older adults with and without ankle position sense impairment. Several shortcomings were identified in this research, which could be considered to enhance the design of a more robust and large-scale clinical study in future. First, the critical value was operationally defined such that those who were classified as normative subjects and whose scores fell between 1° and 2.3° may still have benefited from the interventions. Hence, future research may require further stratification of subjects according to severity of position sense impairment. One possibility is to categorize the participants into subgroups according to the level of joint position impairments. In fact, the JPS measurement using the SENSERite system may help classify the participants into 3 possible subgroups: normative (<1°), mild (1.00°–2.30°), and moderate (2.31°–5.00°). Second, in subjects with impaired position sense, the tests of within-subjects contrasts in quadratic component showed a significant interaction effect of time by intervention for the ACE measure at a liberal significance level (P=.08), indicating trends of greater improvement in position feedback training with CAP than position feedback training alone. However, the difference failed to reach statistical significance at a conventional significance level. This experiment might be underpowered to discriminate a significant difference between 2 interventions. The current study thus invites future research with a larger sample size. Last, only 1 method of active-active JPS measure was examined in this study. Other intervention approaches using different feedback paradigms including passive-passive, passive-active, active-passive, active or passive matching, or different velocities and torques should be further investigated to explore dynamic natures of proprioception. It would be of great interest to examine the efficacy of this intervention in various patient populations and in young children with impaired proprioception.

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Conclusions 

Clinically, the proprioceptive feedback training using the SENSERite system and ankle pressure is a new approach, and the potential efficacy of the system for rehabilitation is only just beginning to be explored. The system's ankle proprioception measure may be useful for examination, prevention, and training of older adults with impaired proprioception. Objective quantification of proprioception may help early detection in evaluation and monitor even minute progress after rehabilitation. From a prevention standpoint, the proprioceptive interventions used in this study could help slow down or prevent age-related deterioration of proprioception even in healthy older adults with relatively mild to moderate JPS error. However, this assumption warrants further investigations.

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Acknowledgments 

This study was completed in partial fulfillment of the requirements for Dr. You's Doctor of Philosophy degree in the School of Education, Motor Learning and Development Program, University of Virginia.

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• a National Instruments Corp, 11500 N Mopac Expy, Austin, TX 78759.
• b Model 5098-26; Welch Allyn Tycos Instruments, 950 Old Shoals Rd, Arden, NC 28704-9459.