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  • 1. Research Report Sensory-Specific Balance Training in Older Adults: Effect on Proprioceptive Reintegration and Cognitive Demands Kelly P Westlake, Elsie G CulhamKP Westlake, PT, PhD, MSc, isPost-Doctoral Fellow, Rehabilita-tion Research and Development Background and PurposeCenter, VA Palo Alto HCC, 3801 Age-related changes in the ability to adjust to alterations in sensory informationMiranda Ave, Palo Alto, CA 94304 contribute to impaired postural stability. The purpose of this randomized controlled(USA). Address all correspondence trial was to investigate the effect of sensory-specific balance training on propriocep-to Dr Westlake at: westlake@rrd.stanford.edu. tive reintegration.EG Culham, PT, PhD, is Professor Subjectsand Director, School of Rehabilita-tion Therapy, Queen’s University, The subjects of this study were 36 older participants who were healthy.Kingston, Ontario, Canada.[Westlake KP, Culham EG. MethodsSensory-specific balance training Participants were randomly assigned to a balance exercise group (n 17) or a fallsin older adults: effect on proprio- prevention education group (n 19). The primary outcome measure was the center-ceptive reintegration and cogni- of-pressure (COP) velocity change score. This score represented the differencetive demands. Phys Ther.2007;87:1274 –1283.] between COP velocity over 45 seconds of quiet standing and each of six 5-second intervals following proprioceptive perturbation through vibration with or without a© 2007 American Physical Therapy secondary cognitive task. Clinical outcome measures included the Fullerton Ad-Association vanced Balance (FAB) Scale and the Activities-specific Balance Confidence (ABC) Scale. Assessments were conducted at baseline, postintervention, and at an 8-week follow-up. Results Following the exercise intervention, there was less destabilization within the first 5 seconds following vibration with or without a secondary task than there was at baseline or in the falls prevention education group. These training effects were not maintained at the 8-week follow-up. Postintervention improvements also were seen on the FAB Scale and were maintained at follow-up. No changes in ABC Scale scores were identified in the balance exercise group, but ABC Scale scores indicated reduced balance confidence in the falls prevention education group postintervention. Discussion and Conclusion The results of this study support short-term enhanced postural responses to propri- oceptive reintegration following a sensory-specific balance exercise program. Post a Rapid Response or find The Bottom Line: www.ptjournal.org1274 f Physical Therapy Volume 87 Number 10 October 2007
  • 2. Balance Training in Older AdultsP ostural control depends on the sensory environments, result in in- strate reduced postural destabiliza- ability to extract peripheral sen- creased postural stability compared tion and earlier restabilization imme- sory inputs, integrate this infor- with the effects of nonspecific activ- diately following the termination ofmation within the central nervous ity interventions, such as running or proprioceptive perturbation throughsystem (CNS), and coordinate and strength training, lend support to vibration in comparison with pre-execute an appropriate motor re- this theory.11–13 exercise outcomes or with the out-sponse. Proprioception is an essen- comes in a falls prevention educa-tial component of this sequence of One method used to evaluate the tion group. These effects wereevents, providing orientation infor- contribution of proprioceptive in- postulated to improve during a con-mation about passive and active puts to postural control and the in- comitant cognitive task. The second-movements and positions of the tegrity of the integrative mechanisms ary hypothesis was that the en-joints as well as the force resulting within the CNS is to measure hanced postural stability would befrom muscular contractions. Age- changes in postural sway during or reflected in superior scores on a bal-related changes in the ability to as- following vibration applied over the ance performance scale and asess the contribution of propriocep- muscle belly or tendon.14 This tech- balance confidence questionnaire.tive inputs relative to those of other nique directly targets the primarysensory inputs become evident un- muscle afferents contributing to pro- Methodder conditions in which the propri- prioception and may effectively re- Study Participants andoceptive inputs are distorted or dis- flect a perturbation of this system. Study Designtorted and then suddenly restored.1 Participants were volunteers over 65Whereas young adults who are Muscle vibration evokes a sensation years of age who were healthy andhealthy are able to restore balance of movement in a direction that nor- recruited through advertisementsquickly by taking advantage of sen- mally would cause elongation of the and flyers in the community. Exclu-sory redundancy and centrally re- vibrated muscle. Accordingly, vibra- sion criteria were pre-existing majorweighing available information,2– 4 tion of antagonistic muscle groups lower-extremity pathology (eg,older adults do not as readily inter- results in immediate disruption of chronic ankle instability or severepret misleading cues or recognize the proprioceptive system.3 Postural osteoarthritis), neurological disor-and reintegrate accurate propriocep- responses to such a perturbation ders or balance difficulties (eg, ver-tive information and therefore can then can be assessed in a quiet stand- tigo, poor vision, dizziness, stroke,experience postural instability.3,5 ing position by recording center-of- or epilepsy) that would preventThese effects are particularly evident pressure (COP) outcomes on a force standing for the duration of the test-when attentional resources are platform.3,15 This position effectively ing procedures without the aid of andivided.3,6 – 8 reduces confounding variables, such assistive device, and health condi- as muscle activation, torque genera- tions (eg, heart disease, uncontrolledGiven that the sensory inputs related tion, and biomechanical changes, hypertension, chronic obstructiveto various environmental conditions that are present during more dy- pulmonary disease, or osteoporosis)are constantly changing,9 the ability namic tasks. Such variables inevita- that would preclude participation into adjust instantly to a change in sen- bly would become a source of accu- a balance exercise program.sory information is central to the re- rate proprioceptive information thatduction of fall risk in older adults.10 could override the controlled effect A brief clinical examination was usedTo date, there have been no reports of proprioceptive perturbation at the to screen for symptoms of peripheralof training interventions designed to ankle joints. Because the present neuropathy, which are considered aenhance the ability of older adults to study represents one of the earliest risk factor for falls.16 This examina-use proprioceptive information in reports on the ability to train sensory tion identified the presence, diminu-balance control. The successful iden- integration immediately following vi- tion, or absence of sensation to lighttification of training effects necessar- bration perturbation, the quiet stand- touch on the dorsal and plantar as-ily involves a randomized controlled ing protocol was considered advan- pects of the foot, the Achilles tendontrial with an exercise intervention tageous as a means to isolate changes reflex, and position sensation of thedesigned to induce specific changes in this ability. big toe. Subjects demonstrating thein the recognition and effective use absence or diminution of one orof sensory information. Findings that Thus, the primary hypothesis of the more of these characteristics weresensory-specific balance exercises, present study was that older adults, excluded from participation. Physi-such as training on unsteady support having completed a sensory-specific cian approval was required beforesurfaces with transitions between exercise program, would demon- the subjects were allowed to partic-October 2007 Volume 87 Number 10 Physical Therapy f 1275
  • 3. Balance Training in Older Adults together position. Progressions to these tasks included simultaneous alterations of visual and vestibular inputs. To alter visual cues, partici- pants were instructed to close their eyes, to engage vision with a reading or tracking secondary task, or to per- form balance tasks with a distracting background, such as a checked pat- tern or moving people. To modify vestibular cues, participants were in- structed to tilt their head backward or to quickly move their head side to side and up and down. Measurement of Central Integration and Attentional Capacity The mean COP velocity for the total COP path length was measured on a force platform* as an estimate of theFigure 1. frequency of postural corrections.Experimental setup of the vibrators at the Achilles and tibialis anterior tendons. Par- Of the COP stability parameters,ticipants stood as steadily as possible with arms alongside the body, heels positioned COP velocity generally is consideredaccording to height, and forefeet splayed to a comfortable stance. to be most useful in identifying age- related changes and fall risk.18 –20 The mean velocity also demon-ipate in the exercise program. All by participants in the exercise group strated the highest sensitivity to thesubjects gave written informed con- and the education group were 21.5 effects of vibration on posturo-sent prior to data collection. (89.9%) and 5.4 (66.3%), respec- graphic measurements21 and had the tively. The 36 participants who com- smallest reproducibility error (intra-In this single-blind, randomized con- pleted the exercise (n 17) and individual standardized coefficient oftrolled trial, participants were as- education (n 19) interventions re- variation of 14) over a 1-weeksigned to an exercise group or a falls turned for postintervention testing. period.20prevention education group. Both By the 8-week follow-up, conductedgroups were assessed at baseline only with the exercise group, 15 par- Data were sampled at 200 Hz andand within 1 week postintervention. ticipants returned for testing. smoothed with a fourth-orderFollow-up testing was done for the double-pass Butterworth filter with aexercise group only at 8 weeks Sensory-specific balance classes cutoff frequency of 10 Hz. Proprio-postintervention. were held 3 times per week, for 1 ceptive input was perturbed by use hour each session, over an 8-week of 4 vibrators oscillating at 80 Hz, 1Of the 64 older adults who re- period. The exercise protocol fol- mm in amplitude,2,22 and secured atsponded to study advertisements, 44 lowed the FallProof Program,17 both ankles with 3-cm-wide elasticmet study criteria and were random- which emphasizes static and dy- bands (Fig. 1).ized into the exercise or education namic balance exercises with transi-group. Eight participants dropped tions between different sensory con- The COP velocity was measured forout of the study for reasons such as ditions. Activities were designed to each of the 45-second postural con-time commitment issues, lack of optimize and force use of the so- ditions shown in Table 1, completedtransportation, language barrier, and matosensory system. Tasks included as one set in a random order, fol-disinterest. By the end of the 8-week standing or walking on various sup- lowed by 3 minutes of seated rest.interventions, 17 and 19 participants port surfaces, such as a rocker board,remained in the exercise and educa- foam, or narrow beam, and standingtion programs, respectively. The in a tandem position, a semitandem * Biodex Medical Systems Inc, 20 Ramsay Rd,mean numbers of all visits attended position, on one leg, or in a feet- Shirley, NY 11967.1276 f Physical Therapy Volume 87 Number 10 October 2007
  • 4. Balance Training in Older AdultsThree sets were performed, and the Table 1.average of 3 trials was recorded for Postural Conditions Used to Evaluate Proprioceptive Reintegration With or Without aeach condition. Conditions 3 and 4 Secondary Taskincluded 5 seconds of stable stand- Testing Descriptioning followed by 10 seconds of vibra- Conditionation activation3,21 and then 30 sec- 1 Quiet standing, eyes closedonds of deactivation. The initial 5 2 Quiet standing, eyes closed, secondary taskseconds was used so that partici-pants could become acclimated to 3 Quiet standing, eyes closed, vibrationstanding on the force platform prior 4 Quiet standing, eyes closed, vibration, secondary taskto the onset of vibration. The third, a The duration of each condition was 45 seconds.30-second interval was used becauseprevious work had indicated that 10seconds was insufficient for com- responsiveness of the FAB Scale fol- ence of strength (force-generatingplete recovery of postural stability in lowing an exercise intervention had capacity) between and withinthe absence of vision in either a not yet been established. groups. Following one practice trial,young or an older population.3 The an average of the best 3 of 5 peakCOP velocity was analyzed over The Activities-specific Balance Confi- torque values normalized to body5-second intervals from the moment dence (ABC) Scale was used to assess weight was recorded.the vibration was turned off, at 15.05 participants’ level of balance confi-to 20 seconds (time 1), 20.05 to 25 dence in performing particular Data Analysisseconds (time 2), 25.05 to 30 sec- tasks.24 Confidence in performing The effects of the interventions ononds (time 3), 30.05 to 35 seconds each task was rated on a scale of 0 the ability of older adults to regain(time 4), 35.05 to 40 seconds (time (no confidence) to 10. The ABC postural stability with or without a5), and 40.05 to 45 seconds (time 6). Scale showed excellent internal con- secondary task were assessed by useFor the secondary task in conditions sistency (Cronbach alpha .96), test- of a group time interval visit2 and 4, participants counted back- retest reliability (r .92), and validity (2 6 2) analysis of varianceward by 3 from a random 3-digit for community-dwelling older (ANOVA) for repeated measures onnumber as quickly and accurately as people.24,25 the last 2 factors. The dependentpossible throughout the 45-second variable was COP change scores, ob-trials.7 The Physical Activity Scale for the tained by subtracting COP velocity Elderly (PASE) was used to deter- averaged over 3 trials for each timeClinical Measures mine group equivalences in activity interval of conditions 3 and 4 fromThe Fullerton Advanced Balance levels outside of the treatment inter- the average COP velocity in the three(FAB) Scale was used to measure vention. Scores ranged from 0 to 45-second trials in conditions 1 andfunctional limitations associated greater than 400, depending on sub- 2, respectively. The equivalences ofwith 10 high-level balance tasks in- jects’ reported activity intensities COP velocity across the six 5-secondcorporating tests that challenge sen- and frequencies over 7 days. The intervals and over the entire 45-sory integration.23 The FAB Scale PASE showed good test-retest reli- second time interval during condi-included modified clinical tests for ability (r .75) and validity for older tion 1 were verified by use of datasensory integration in balance: walk- subjects who were healthy.26,27 from 10 randomly selected partici-ing with head turns, Functional pants (F 0.37; df 6,54; P .76).Reach Test, 360-degree turn, tandem The concentric isokinetic strength of Changes in strength and clinical mea-walking, one-leg stance, 2-foot jump, the hip, knee, and ankle flexor and sures were determined by use of astep up and over, and reactive pos- extensor muscles of the dominant group visit (2 2) repeated-tural control. Scores ranged from 0 leg was assessed by use of an isoki- measures ANOVA for continuous(unable) to 4, with a maximum score netic dynamometer (AMTI Multiaxis variables or a Friedman test for cate-of 40. Psychometric testing of this Force Platforms, model OR 6-7)† set gorical variables.scale indicated good convergent va- at a velocity of 60°/s. These measure-lidity compared with the Berg Bal- ments were taken in consideration of The outcomes for the exercise groupance Scale ( .75) and demon- the potentially confounding influ- at the 8-week follow-up were com-strated high test-retest ( .96), pared with the outcomes at baselineintrarater ( .97–1.00), and inter- † Advanced Medical Technologies Inc, 176 and postintervention by use of arater ( .94 –.97) reliability.23 The Waltham St, Watertown, MA 02172.October 2007 Volume 87 Number 10 Physical Therapy f 1277
  • 5. Balance Training in Older Adults A less destabilization occurring in the COP Velocity Change (cm/s) 4.0 exercise group (change score 3.5 Exercise Group [X SD], 1.31 0.91 cm/s) than in * Education Group the education group (2.00 1.05 3.0 cm/s) postintervention (Fig. 2A). 2.5 Separate analysis of the exercise 2.0 group revealed a visit time inter- 1.5 action (F 8.62; df 5,80; P .001), 1.0 indicating training effects on both 0.5 the time to restabilize and the * amount of destabilization (Fig. 3A). 0.0 -0.5 Change scores began to stabilize dur- -1.0 ing time interval 4 at baseline and 1 2 3 4 5 6 during earlier time interval 3 postin- Time Interval tervention. A reduction in the extent of destabilization was indicated by a B significant decrease in change scores 4.0 from baseline to postintervention COP Velocity Change (cm/s) 3.5 Exercise Group during time interval 1 (2.23 1.18 Education Group versus 1.31 0.91 cm/s) (P .002), 3.0 * with a trend toward significance dur- 2.5 ing time interval 2 (0.72 0.76 versus 2.0 0.43 0.52 cm/s) (P .081). Analysis 1.5 of the education group revealed a 1.0 nonsignificant visit time interac- tion (F 0.42; df 5,90; P .70), indi- 0.5 * cating no change in the ability to 0.0 stabilize following vibration. -0.5 -1.0 The COP change scores for the ex- 1 2 3 4 5 6 ercise group were different postin- Time Interval tervention (1.31 0.91 cm/s) and atFigure 2. the 8-week follow-up (2.11 1.50Change in center-of-pressure (COP) outcomes following vibration in exercise and cm/s) during time interval 1education groups postintervention (X SD). (A) COP sway velocity change score fol- (P .029), suggesting that postinter-lowing vibration perturbation. (B) COP sway velocity change score following vibration vention improvements were notperturbation and while performing a secondary task. *Significant difference between maintained. No differences weregroups (P .044). identified between baseline (2.29 1.19 cm/s) and the 8-week follow-up (P 1.00).repeated-measures ANOVA or a ResultsFriedman test with visit as the Proprioceptive Reintegration Quiet standing with vibrationwithin-subject factor. Significant in- Quiet standing with vibration and secondary task (condition 4).teraction effects (P .05) were ana- (condition 3). The first objective The second objective of this studylyzed with Bonferroni-adjusted post of this study was to examine postural was to examine postural stability fol-hoc tests. Statistical procedures were recovery following vibratory pertur- lowing vibratory perturbation duringperformed with SPSS, version 11.5.‡ bation without a secondary task. A secondary task performance. One visit time group interaction was outlier in the education group was identified (F 3.82; df 5,170; identified as having a mean change P .019). Group differences were score greater than 3 standard devia- found only during time interval 1 tions above the group mean and was‡ SPSS Inc, 233 S Wacker Dr, Chicago, IL (F 4.36; df 1,35; P .044), with excluded from subsequent analysis.60606. A visit time group interaction1278 f Physical Therapy Volume 87 Number 10 October 2007
  • 6. Balance Training in Older Adultswas revealed (F 3.13; df 5,165; AP .018). 4.0 COP Velocity Change (cm/s) 3.5 *† BaselineAnalysis of group differences foreach time interval across baseline 3.0 Postinterventionand postintervention visits indicated 2.5a difference in the extent of desta- 2.0bilization during time interval 1 † 1.5(F 4.90; df 1,34; P .034) post- 1.0intervention, with lower mean † †change scores in the exercise group 0.5 *‡(1.12 0.58 cm/s) than in the educa- 0.0tion group (1.71 0.85 cm/s) -0.5 ‡(Fig. 2B). Separate analysis of the ex- ‡ -1.0ercise group revealed a visit time 1 2 3 4 5 6interaction (F 5.76; df 5,80; Time IntervalP .001) (Fig. 3B). No improvementsin the time to stabilize were noted.Further analysis of change scores be- B 4.0 COP Velocity Change (cm/s)tween baseline and postintervention 3.5 Baselineas a function of each time interval 3.0 *† Postinterventionrevealed a difference during time in-terval 1 (P .002). This finding con- 2.5firmed that there was less destabili- 2.0zation during the 5 seconds 1.5 †immediately following vibration as a 1.0 †result of the exercise intervention. 0.5Analysis of the education group re- *‡vealed a nonsignificant visit time 0.0interaction (F 1.27; df 5,85; -0.5 ‡ ‡P .30). -1.0 1 2 3 4 5 6The inclusion of the 8-week Time Intervalfollow-up change scores for the ex- Figure 3.ercise group revealed a visit time Change in center-of-pressure (COP) outcomes following vibration at baseline andinteraction (F 2.93; df 10,140; postintervention in exercise group (X SD). (A) COP velocity change scores followingP .012), with higher change scores vibration perturbation. (B) COP velocity change scores following vibration perturbation and while performing a secondary task. *Significant difference between baseline andat the 8-week follow-up (2.05 postintervention (P .006). †Significant difference between baseline time intervals1.47 cm/s) than postintervention (P .025). ‡Significant difference between postintervention time intervals (P .001).(1.14 0.61 cm/s) during time inter-val 1 (P .023). These results furthersupport the fact that improvements Clinical Measures postintervention and at follow-upin the ability to stabilize after the Means and standard deviations for were maintained. Specific details re-exercise intervention were not clinical measures are shown in Table garding changes in the mean andmaintained. 3. In terms of the FAB Scale, the standard deviation of each FAB Scale Friedman test revealed differences item are shown in Table 4. Post hocThe response accuracy and speed of between visits in the exercise group analysis revealed differences be-performance of the secondary task ( 2 16, P .001). Post hoc analysis tween baseline and postinterventionare shown in Table 2. No differences revealed differences between base- for items 6 (one-leg stance), 7 (stand-were identified between groups, nor line and postintervention total ing on foam), and 9 (walking withwas there a group visit interaction. scores (P .001) and between base- head turns) and differences between line and 8-week follow-up total baseline and the 8-week follow-up scores (P .001), suggesting that the for item 9 (Bonferroni-adjusted P improvements in functional balance value of .025).October 2007 Volume 87 Number 10 Physical Therapy f 1279
  • 7. Balance Training in Older AdultsTable 2.Accuracy and Speed of Backward Counting by 3 During Condition 4a Parameter X SD for the Following Group: Baseline Postintervention 8-wk Follow-up Exercise Education Exercise Education Exercise Accuracy (no. of correct responses/total no. of 0.94 0.093 0.96 0.035 0.95 0.06 0.97 0.05 0.94 0.06 responses) Speed (no. of responses/s) 0.41 0.13 0.44 0.16 0.47 0.16 0.47 0.15 0.43 0.19a Condition 4 quiet standing, eyes closed, vibration, secondary task.Regarding the PASE scores, no differ- group visit interaction (P .44) Although it may be argued that en-ences were identified between were identified, thereby supporting hanced signals arising at the level ofgroups or visits at baseline or postint- group equivalences at baseline and the proprioceptive receptors mayervention; significantly lower scores postintervention. account for the postural improve-were found in the exercise group at ments, we recently demonstratedthe 8-week follow-up than postinter- Discussion that this mechanism is not likely tovention (P .003). Interestingly, a The results of the present study ap- be the substrate for change.30 WithPearson correlation analysis between pear to support the original hypoth- only 1 of 3 proprioceptive measuresPASE scores and time interval 1 for esis that the ability of older adults indicating improvements with train-conditions 3 and 4 revealed no rela- to reintegrate proprioceptive inputs ing in our previous work, it was dif-tionships (r .16, P .13, and r is augmented following sensory- ficult to ascribe a training effect at .06, P .57). specific training, and this effect is the peripheral level. However, with- not likely to be attributable to an out sufficient physiological evidenceFor the ABC Scale questionnaire, a increase in lower-extremity strength from receptor isolation techniques,group visit interaction was identi- or activity level. Although a few stud- such as microneurography,14 thefied (F 4.27; df 1,34; P .047), ies reported training effects on pos- possibility of an increase in the dis-with a lower balance confidence tural stability when proprioceptive charge of these receptors cannot bescore postintervention than at base- input was reduced,28,29 an improved discounted.line only for the education group ability of older adults to recognize(F 4.56; df 1,18; P .047). and use the restoration of accurate A more probable explanation for proprioceptive information had not these results is an increase duringIn terms of strength at the hip, knee, previously been documented. the training intervention in the atten-and ankle, no main effect of group tion allocated to proprioceptive cues(P .66) or visit (P .072) and no (explicit learning), which eventuallyTable 3.Clinical Measures for Exercise and Education Groups at Baseline, Postintervention, and 8-Week Follow-up Clinical Measurea X SD Score for the Following Group: Baseline Postintervention 8-wk Follow-up Exercise Education Exercise Education Exercise b,c b FAB Scale 31 5 32 8 35 4 33 8 35 5c PASE 102.4 45.0 99.1 44.0 127.3 57.6d 101.6 51.4 79.5 24.9d ABC Scale 84.8 9.3 87.5 10.7e 85.7 9.5 79.1 24.2e 85.0 9.7a ABC Activities-specific Balance Confidence, FAB Fullerton Advanced Balance, PASE Physical Activity Scale for the Elderly.b Significant difference between baseline and postintervention FAB Scale scores (P .001).c Significant difference between baseline and 8-week follow-up FAB Scale scores (P .02).d Significant difference between postintervention and 8-week follow-up PASE scores for exercise group (P .003).e Significant difference between baseline and postintervention ABC Scale scores for education group (P .047).1280 f Physical Therapy Volume 87 Number 10 October 2007
  • 8. Balance Training in Older AdultsTable 4.Mean ( SD) and Friedman Mean Rank for Scores on the Fullerton Advanced Balance (FAB) Scale for the Exercise Group FAB Scale Item Baseline Group Postintervention 8-Week Follow- P Group up Group X SD Mean X SD Mean X SD Mean Rank Rank Rank 1. Stand with feet together, eyes closed 4 0 1.9 4 0 2.0 4 0 2.0 .39 2. Forward reach 4 1 1.9 4 0 2.1 4 1 1.9 .26 3. 360° turn 3 1 1.8 3 1 1.9 4 1 2.3 .05 4. Step up and over 4 0 1.9 4 0 2.0 4 0 2.0 .37 5. Tandem walk 3 1 1.8 4 1 2.3 3 1 1.9 .14 a a 6. One-leg stance 3 1 1.6 3 1 2.2 3 1 2.2 .02b 7. Stand on foam, eyes closed 3 1 1.7a 4 0 2.2a 4 0 2.0 .02b 8. 2-foot jump 3 1 1.8 3 1 2.1 3 1 2.1 .35 a,c a c 9. Walk with head turns 2 1 1.5 3 1 2.3 3 1 2.2 .01b 10. Reactive postural control 2 1 1.6 3 1 2.2 3 1 2.2 .12 Total score 31 5 1.2a,c 35 4 2.5a 35 5 2.3c .001ba Significant difference between baseline and postintervention scores (P .025).b Significant difference between testing sessions (P .05).c Significant difference between baseline and 8-week follow-up scores (P .025).led to a less attentionally demanding identified correctly. Thus, a greater postural stability improved or de-recovery of postural stability (im- extent of cognitive resources was clined relative to baseline perfor-plicit learning).31 Improvements in necessary for this test than for other mance depending on the cognitivepostural control in the exercise proprioceptive measures, meaning demands of the secondary task.32group without evidence of reduc- that the possibility of improved at- Perhaps the task of counting back-tions in the accuracy or speed of the tention cannot be ruled out. Besides ward by 3, used in the present study,counting task support this theory. As the possible influence of attention in did not represent a sufficiently chal-the accuracy of peripheral input de- recognizing and selecting proprio- lenging cognitive task to tax atten-clines with age, attentional resources ceptive information, it also has been tional resources effectively. Never-become more focused on the control suggested that attention is involved theless, the finding that the extent ofof posture.1 Thus, the introduction in sensory integration under condi- destabilization was reduced postin-of a sufficiently challenging second- tions of sensory conflict.33 tervention with or without a second-ary task or postural condition often ary task suggests that either a shift inresults in reduced task performance One surprising outcome was the de- attention or increased attentional ca-or instability.6,32 Because the specific crease in COP velocity change scores pacity is possible. A follow-up train-instructions provided to participants (ie, reduced destabilization) during ing study involving a more cogni-in the present study were to main- secondary task performance relative tively demanding secondary tasktain focus on the secondary task, ev- to the results obtained in the no- under conditions of sensory conflictidence that stability was increased secondary-task condition (Fig. 2). Al- may bring further clarity to thissuggests an implicit learning effect. though the difference was not signif- discussion. icant, it was evident in both theOur previous finding that a velocity exercise and the education groups. Several authors3,4,35 have proposeddiscrimination test was the only pro- that the explanation for impairedprioceptive outcome to improve In contrast, previous studies6,33,34 postural responses in older adultswith exercise also suggests en- demonstrated a destabilizing rather lies in age-related changes in centralhanced central mechanisms.30 This than a stabilizing effect with the ad- integration mechanisms. During thetest required subjects to identify the dition of a secondary task. These exercise intervention in the presentfaster of 2 presented velocities until conflicting results may be reconciled study, sensory inputs were manipu-the smallest velocity difference was by a recent study demonstrating that lated by altering the support surfaceOctober 2007 Volume 87 Number 10 Physical Therapy f 1281
  • 9. Balance Training in Older Adultsor by reducing the sensory redun- bation. This lack of an effect suggests improvements in the FAB Scaledancy of the visual and vestibular that there are context-dependent dif- scores were maintained in the exer-systems; these manipulations forced ferences following a targeted train- cise group, it remains unclearparticipants to effectively reweigh ing intervention and thereby sup- whether the control group also ex-remaining inputs within the CNS.17 ports the need for ongoing sensory perienced changes over the 8-weekThe direct beneficial consequences training. In turn, compensatory sen- time period. The second limitation isof these tasks were reflected in the sory mechanisms may be selected that the participants were olderability of the participants to regain more efficiently under conditions of adults who were healthy rather thanstability, likely by taking advantage sensory deprivation38 or restoration. older adults with balance impair-of the restored proprioceptive infor- ments, who may have benefited to amation and integrating it with vestib- The decrease in balance confidence greater extent. Future research mayular inputs and other sensorimotor in the education group postinterven- include a group of older adults withcues. Evidence of similarly enhanced tion may be explained by discussions declining balance to assess the effectcentral integration following sensory centered on effective means of of training on central sensory reinte-training has been found in studies reducing fall risk. An increased gration. Such an investigation alsodemonstrating improved stability awareness of these topics may have may include a kinematic and kineticduring the manipulation of proprio- underscored the apprehension expe- analysis of the effect of vibration onceptive, vestibular, or visual systems rienced during functional balance dynamic stability tasks. A combina-or all of these by use of the Sensory tasks until changes could be imple- tion of findings from these studiesOrganization Test (SOT).28,36 Al- mented. Two recent studies examin- and those from the present studythough the use of a sway reference ing the effectiveness of falls preven- may lead to more efficient balancestanding surface during the SOT is tion education reported similar exercise interventions and, ulti-considered to be a proprioceptive findings, with almost half of the par- mately, to a reduction in fall risk inperturbation, the muscle spindles ticipants demonstrating increased older adults.serving this system cannot be tar- fear of falling39 and a 28% increase ingeted as precisely as with vibration. 1 or more falls40 at follow-up. Both authors provided concept/idea/re-These studies also were limited be- search design, writing, and data analysis. Drcause of the use of a cross-sectional Seasonal variations in PASE scores Westlake provided data collection, projectdesign including seasoned tai chi may account for the reduction in management, fund procurement, and sub-practitioners36 and the use of the scores at the 8-week follow-up in the jects. Dr Culham provided facilities/equip- ment and consultation (including review ofSOT for both training and testing exercise group.26 Follow-up testing manuscript before submission).procedures,28 which may have re- occurred during both the winter andsulted in a learning effect.37 the summer months, when either This study was approved by Queen’s Univer- sity Health Science and Affiliated Teaching snow and ice or high heat and hu- Hospitals Research Ethics Board.The functional significance of the re- midity may have forced participantssults of the present research was ev- indoors. Arguably, the reduction in Data from this study were presented at the International Congress of the World Confed-ident because of improvements in activity level may explain the lack of eration for Physical Therapy; June 2– 6, 2007;the FAB Scale scores in the exercise retention in the ability to reintegrate Vancouver, British Columbia, Canada.group. These results, demonstrating proprioceptive information effec- Dr Westlake was supported by a Canadianresponsiveness to training, further tively. However, without a signifi- Institutes of Health Research Fellowship.support the validity of FAB Scale cant correlation between PASEscores. Interestingly, the items dem- scores and COP velocity in the first 5 This article was received September 7, 2006, and was accepted May 8, 2007.onstrating improvements across vis- seconds following vibration, this the-its were items 6 (one-leg stance), 7 ory is not substantiated. DOI: 10.2522/ptj.20060263(standing on foam), and 9 (walkingwith head turns), each of which Conclusioncomprises an element of sensory in- The results of the present study sug- Referencestegration. However, even though gested that sensory-specific exercise 1 Kristinsdottir EK, Fransson PA, Magnusson M. Changes in postural control in healthysubjects showed improvements in had a training effect on propriocep- elderly subjects are related to vibrationand maintenance of FAB Scale scores tive reintegration. However, 2 limita- sensation, vision and vestibular asymme- try. Acta Otolaryngol. 2001;121:700 –706.at the 8-week follow-up, the im- tions should be mentioned. The first 2 Hay L, Bard C, Fleury M, Teasdale N. Avail-provements did not translate to the limitation is that 8-week follow-up ability of visual and proprioceptive affer-maintenance of enhanced postural scores were not obtained for the ed- ent messages and postural control in el- derly adults. Exp Brain Res. 1996;stability following vibratory pertur- ucation group. Therefore, although 108:129 –139.1282 f Physical Therapy Volume 87 Number 10 October 2007
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