Abstract
Background Effective balance rehabilitation is critically important to the aging population. Optimal exercise prescription for balance rehabilitation has not been described, as there is no measure of balance exercise intensity. To rate the intensity of balance exercise, an item set is required.
Objectives The aim of this study was to explore verbal and nonverbal markers that differentiated tasks of high, medium, and low balance intensity to inform the development of an instrument to measure the intensity of balance challenge.
Design This was an observational study utilizing an interpretive description approach.
Methods Twenty older adults were observed performing 3 balance tasks that challenged balance at low to high intensity. Verbal and nonverbal responses were recorded. After each task, participants were asked to describe the test experience. Data were analyzed to identify potential markers of balance challenge intensity.
Results Markers of the intensity of balance challenge were grouped by time periods defined as pretask, in-task, and posttask. A key pretask finding was an increased delay to task commencement with increased task difficulty. Commencement delay was accompanied by talk in 19 of 21 instances. Physical markers of the intensity of balance challenge were grouped into 3 categories—bracing, postural reactions, and sway—and were increasingly observed as intensity of balance challenge increased. Participants described tasks as pushing them toward the limits of their balancing capacity as the intensity of balance challenge increased.
Conclusions Verbal and nonverbal markers of the intensity of balance challenge in older adults performing balance tasks that differentiated high-intensity tasks from medium- to low-intensity tasks were identified. The pretask phase of balance exercise performance is an important diagnostic space, rich in verbal and nonverbal markers.
Falls are a growing cause of accidental injury and death in older adults worldwide. The World Health Organization reports worldwide falls rates of 35% (65-year-olds) to 42% (70 years of age and older) each year and attributes 40% of injury-related mortality to injuries sustained from falls.1 Interventions that reduce the risk of falls and fall-related morbidity and mortality are urgently needed. Recent falls prevention research has focused on the use of exercise to improve balance and reduce falls in older adults, with varying results.2 The optimal exercise dosage for rehabilitation of balance, however, is yet to be fully described.3
The universally recognized approach to exercise prescription utilizes the FITT principle, combining exercise frequency, intensity, type, and time variables that are then manipulated in a standardized manner to elicit a dose response.4 A recent qualitative study of physical therapists specializing in falls and balance rehabilitation, however, concluded that exercise prescription practices were highly individualized and lacked a standardized approach.5 For example, the types of exercises prescribed by these expert falls and balance therapists were highly influenced by individual assessment findings and constrained by perceptions of safety and falls risk. This finding may have been due to the absence of an evidence-based method for standardized balance exercise prescription.4 This lack of a standardized approach is further illustrated by the fact that the practitioners interviewed were able to quantify the frequency, type, and duration of exercises prescribed but were unable to precisely define the intensity of their prescribed balance exercises.5 Similar conclusions were drawn from a systematic review of the reporting of intensity in randomized trials of balance exercise interventions.3 Frequency, type, and time variables were well reported, but, in 148 trials, no validated instrument or method was used to measure or quantify the intensity of exercises designed to challenge the balance control system.3 This review also did not identify any published instruments that assess balance exercise intensity.3
These findings point to a need to further develop the science of balance exercise prescription by quantifying the intensity variable. At the time of this study being conceptualized, no published definition of balance exercise intensity could be found, nor could expert clinicians readily recall any working definition, other than to say balance exercises needed to be “challenging.”5(p672) Balance exercise intensity for the purpose of this line of inquiry was conceptualized by the research team as “the degree of challenge to the balance control system relative to the capacity of the individual to maintain balance.” The most recent edition of the American College of Sports Medicine's Resource Manual of Guidelines for Exercise Testing and Prescription defines balance exercise intensity as “the highest level [of balance-enhancing exercises] that can be tolerated without inducing a fall or near fall.”4(p589) Given the putative method of exercise prescription is use of the FITT principle, where frequency, intensity, type, and time of exercise sessions are all independent variables, identification of optimal balance exercise prescription that will result in a favorable dose response theoretically requires an ability to control for the intensity variable.6 However, at this time, it is unknown whether a reliable and valid instrument can be created to measure the intensity of challenge to the balance control system during exercise.
Adhering to the principles of scale development theory, for a new instrument to be created, such as a measure of balance exercise intensity, an in-depth exploration of the construct is required to produce an item set that will potentially measure the construct of interest.7 If it can be demonstrated that there are common, observable verbal or nonverbal markers of the intensity of challenge to the balance control system that occur when people perform balance activities, these markers could be used to develop a scale to measure the intensity of balance challenge. This scale would then allow exercise prescribers to standardize balance exercise prescriptions for all 4 variables in balance exercise prescriptions and give researchers the opportunity to further study the dose-response relationship between balance exercise and balance performance.
The purposes of this observational study were: (1) to classify the verbal and nonverbal responses of older adults to balance challenges and (2) to identify categories of responses that are likely to be common in this population so that common responses are not omitted in subsequent scale development. This study is part of a larger program of research that aims to create a measurement of balance exercise intensity. The clinical measure that emerges can be evaluated in subsequent study phases in larger samples of older adult exercisers across hospital and community populations.
Method
Design and Sample Size Considerations
This observational study was conducted utilizing an interpretive description approach. Interpretive description, as described by Thorne,8 is a pragmatic applied research approach that draws most strongly on the tradition of naturalistic inquiry9 and is grounded in the description, exploration, and interpretation of clinical phenomena.8 Interpretive description results in a “thematic or integrative description of a phenomenon of clinical interest”8(p75) through an exploration of the phenomenon, seeking to understand its complexity from multiple angles and perspectives.
There are 2 clear problems that must be addressed in developing a list of items that could potentially feed into the development of a scale that measures balance challenge intensity: (1) classifying observed verbal and nonverbal responses to balance challenge into homogeneous categories that can then be used to construct potential items and (2) identifying categories that are likely to be commonly represented in the broader older adult population to which this scale may be applied. The first problem is one best addressed using a qualitative approach, whereas the second problem requires the application of a quantitative approach. Interpretive description studies can draw from both qualitative and quantitative traditions of inquiry to describe and explore clinical phenomena.8,10
Qualitative content analysis11,12 was used to address the first aim (ie, to classify observed verbal and nonverbal responses into homogeneous categories). A probabilistic sampling approach was used to address the second aim, despite the use of qualitative methods to address aim 1. Cross-sectional observational studies traditionally focus on identifying the prevalence of particular characteristics or diseases in a sample in order to extrapolate their likely prevalence in a population (ie, representative sampling). However, in this study, probabilistic sampling was used to try to identify response categories that “may be” common in the broader older adult population, rather than to try to estimate what “is” common. Whether the response categories identified in this study are common will be determined in later stages of inquiry.
For this study, we arbitrarily determined that for a response category to be considered “common,” and worth including in the resultant item set, it would be present in at least 20% of the broader older adult population. With an a priori plan for 20 participants, this study was designed to have only a 1.2% chance of not observing a “minimally common” response in the broader adult population at least once in our sample of older adults. To illustrate, if we recruited a sample of one participant, there would be an 80% [(100% − prevalence in broader older adult population)]n = (100% − 20%)1] probability that we would not observe a “minimally common“ response in our sample. For 2 participants, there would be a 64% probability (100% − 20%)2 and so on. A consecutive sampling approach was applied to recruit the required number of older adults from a rehabilitation hospital as they approached discharge back into the community. This study was conducted in a subacute inpatient rehabilitation facility in Australia over a 7-month period (August 2011–February 2012).
Participant Setting and Recruitment
The rehabilitation population in this study included older adults from a broad range of diagnostic categories and ability levels who were currently participating in some form of balance rehabilitation exercises. Participants were recruited from general, orthopedic, neurological, and cardiorespiratory rehabilitation units and geriatric evaluation and management units. Potential participants were informed of the study by their treating physical therapist. If they expressed interest, the lead investigator (M.K.F.) met with potential participants to confirm they met eligibility criteria and to obtain informed consent. To be eligible for inclusion, participants needed to be able to give informed written consent, perform at least 3 standing items on the de Morton Mobility Index (DEMMI)13 unaided, and be able to participate in an interview in English. All participants provided informed written consent at the time of recruitment.
Testing Session Balance Tasks
The balance tasks used in this study were drawn from the DEMMI, a functional mobility measure commonly used in the geriatric rehabilitation setting.13 The items of the DEMMI are hierarchically ranked, with “stand feet apart 10 seconds” being the easiest standing balance task and “tandem stand eyes closed for 10 seconds” the most challenging. The DEMMI scale ranges from 0 to 100 points, with a higher score indicating better performance. Rasch analysis indicates that DEMMI data have interval properties.13
All participants completed “stands feet apart” as the low balance intensity task. Medium and high balance intensity tasks were chosen relative to the most challenging DEMMI item the participants could successfully demonstrate to their treating physical therapist in the 24 hours prior to the testing session. Because DEMMI items were matched according to participant capability, the same DEMMI item (ie, “pick up a pen from the floor”) may have been the high balance intensity task for one participant (the most difficult DEMMI item that the participant could successfully complete without falling or nearly falling) or the medium balance intensity task for another participant who was able to complete a more challenging item (eg, “jump”) as his or her high balance intensity task.
Testing Session Procedure
The testing session for each participant involved his or her treating therapist and the lead investigator. Testing was conducted in a physical therapy gym where patients usually participated in rehabilitation. During the testing and interview period, the participant was supervised by his or her treating therapist and observed by the lead investigator. The therapists and lead investigator were physical therapists experienced in geriatric physical therapist practice and proficient in the use of the DEMMI to assess functional mobility and balance in the older adult rehabilitation population. During testing, participants wore a safety belt, and their therapist remained within reach, by their side, to augment participant safety and prevent the participants from falling during testing. This approach replicated usual practice in this facility for administration of the DEMMI.
Each testing and interview session included the participant completing the 3 standing balance tasks with a brief interview immediately after each balance task. The posttask interview questions sought to explore participant perceptions of the challenge associated with each task. Task performance and interviews were captured in an audiovisual recording for later transcription, review, and analysis.
Data Collection and Management
During testing sessions, the lead investigator made field notes of observations of verbal and nonverbal reactions to each balance task and key interview responses. Following each field testing session, the lead investigator typed up the field notes into a de-identified table and downloaded the audiovisual recordings using the corresponding de-identification code. The lead investigator reviewed the audiovisual footage to confirm content of field notes, further explore the performance of each participant on each task, and make additional observations as necessary. All verbal responses of participants made during the task performances, as well as during the formal interview following each task, were transcribed verbatim into an Excel (Microsoft Corporation, Redmond, Washington) spreadsheet.
Validation by Peer Review
After the lead investigator completed this process for 5 participants, a peer review process was undertaken to validate the lead investigator's observations and to confirm that the method was eliciting the data required to achieve the study goals. For this validation session, the research team and a panel of clinical experts (the “review team”) viewed the video footage of the first 5 testing sessions and made notes of their observations of the task performance (verbal and nonverbal responses to testing). The review team also read the transcribed verbal responses to make notes of emerging content and potential categories of responses. The observations of each individual in the review team were pooled, and consensus was reached on all verbal and nonverbal responses that could be identified from observing the video footage and reading the transcripts. This process confirmed that the study protocol was appropriate to enable experienced clinicians to identify verbal and nonverbal markers of balance task intensity, and it further focused the field note generation of the lead investigator for the remainder of the study. One adjustment in the testing protocol, following this review session, was to change the focus of the posttask interview question from how the participant would describe “the challenge” of that task to a broader query of “how he or she felt” completing the task to minimize the potential to lead the participant in his or her responses after the task.
Development of a Framework to Guide Analysis of Participant Performance
The review team determined the most useful and informative segments of the observed performances and designed an analytical framework that informed the in-field, audio, and video footage analysis for the remainder of the study. This approach is consistent with other studies that have validated visual observation of actual and videotaped performances analyzed by experienced physical therapists; use of predetermined criteria and dichotomous scoring of observations has been shown to result in excellent agreement and high correlation.14,15 The review team determined that the balance performance should be analyzed by prespecified time periods and body parts and by using standardized categories for verbal expressions. The analytical framework developed is presented in Figure 1.
Framework created to guide the analysis of verbal and nonverbal responses to testing. Analysis was concentrated on 3 time periods related to task completion and a head-to-toe analysis of verbal responses and nonverbal responses during testing. Each category was scored dichotomously.
Analysis was focused on 3 time periods: pretask—the time from when the participant was cued to start the task but before he or she physically commenced the task, in-task—the time the participant was performing the task, and posttask—the time when the participant had completed the task and returned to his or her pretask state (“at ease”). Categories of verbal responses during testing were related to “comprehension of task” and “any positive, neutral, or negative remarks about the task.” Any movement or physical reaction that indicated challenge to the postural control system was recorded, by body part, in a dichotomously coded “head-to-toe” analysis as either observed or not observed. The head-to-toe analysis, in turn, looked at global (whole body); cardiorespiratory; head, neck, and face; shoulder and upper limb; trunk; lower limb; and hand and feet movements and reactions.
Data Analysis
Participant verbal and nonverbal responses were independently analyzed by the principal investigator (M.K.F.) and associate investigator (E.M.), following the initial peer review, using content analysis.11,12 Spontaneous verbal responses were coded and mapped to time period and task intensity level, and posttesting interview responses were coded and mapped to intensity level. Nonverbal responses were treated as qualitative data by grouping similar physical responses into coded categories. The research group was consulted to resolve differences of opinion relating to the emergent categories.
Role of the Funding Source
Professor Haines was supported by a Career Development Fellowship from the Australian National Health and Medical Research Council. Ms Farlie was supported by a grant from the Lions John Cockayne Memorial Fellowship Trust Fund. The Lions John Cockayne Memorial Fellowship Trust is jointly funded by Oakleigh Lions Club Elderly People's Home Inc and Monash Health.
Results
Twenty inpatients meeting the study criteria were consecutively recruited during their inpatient stay. Demographic details are presented in Table 1. The mean age of the participants was 75 years (SD=9.1, range=63–91). Diversity in balance performance ability at the time of testing was evident in the range of baseline DEMMI scores.
Participant Characteristics (N=20)a
All participants completed the “stand unsupported” task as their low-intensity test (N=20). The medium-intensity tests used were “stand feet together” (n=3), “pick up pen” (n=12), and “four steps backwards” (n=5). The high-intensity tests were “pick up pen” (n=1), “four steps backwards” (n=7), “jump” (n=3), “stand on toes” (n=7), and “tandem stand eyes closed” (n=2).
Spontaneous Verbal Responses During Task Performance
Participants offered 2 types of verbal responses: (1) spontaneous responses, or information volunteered to the clinician without any questioning prompts from the clinician or lead investigator, and (2) interview responses, or comments made in response to questions posed by the lead investigator after completion of each task. As shown in Figure 2, the themes of spontaneous verbal responses evolved as intensity level increased.
Bubble plot of categories of spontaneous verbal responses to tasks by incidence, at low-, medium-, and high-challenge levels. Circles are proportional to number of responses in each category.
Pretask verbalization: comprehension, clarity, and perceptions of capacity to complete the task.
Prior to commencement of the low-intensity task, there was no incidence of spontaneous verbal response for any participant. Prior to commencing the medium-intensity task, 9 participants commented spontaneously. The content of these comments were grouped into 3 predominant categories: (1) task comprehension (eg, “Walk 4 steps backward, OK” [participant 15]), (2) instruction clarity (eg, “Bend over?” [participant 18]), and (3) task capacity (eg, “I need to step forward to be able to do it” [participant 7]). Eleven participants made a comment prior to commencing the high-intensity task. While comments relating to themes of task comprehension and capacity continued, new categories emerged at this level: (1) perceived threat (eg, “Now, this is a different story” [participant 18]), (2) prediction of failure (eg, “Ooh, that will be hard” [participant 9]), and (3) seeking reassurance (eg, “And there is nothing behind me?” [participant 8]).
All instances of spontaneous verbalization in the pretask phase, regardless of theme, were associated with time delay to task commencement (Tab. 2). There were only 2 occurrences of task commencement delay by a participant that were not accompanied by a spontaneous verbal response (participants 3 and 14, high-intensity task).
Comparative Table of Time to Commence Task, Talk After Cue, and Observed Category of Physical Reactions by Task Difficultya
In-task verbalization: perceptions of capacity to complete the task and perception of threat to balance.
During the in-task phase of the low-intensity task, 1 participant made positive comments regarding the capacity to complete the task. During the medium-intensity task, only 4 participants made comments, and these were only 1- to 3-word utterances (ie, “I can walk?,” “Oops,” “Hmm,” and “Right” [participants 9, 10, 13, and 19, respectively]). During completion of the high-intensity task, 8 participants made comments, with perceived threat to balance emerging again as the predominant category (eg, “That's very difficult” [participant 13]) along with prediction of failure (eg, “Not so secure with this one” [participant 9]) and confirmation of failure (eg, “Oh no, can't do it” [participant 9]).
Task completion verbalization: checking performance against expectations and declarations of failure.
During the posttask phase, no participants made any spontaneous verbal comment on completion of the low-intensity task. Three participants made single-word utterances following the medium-intensity task relating to task comprehension (eg, “Right” [participant 5], “OK?” [participant 15]). Seven participants made utterances or comments following the high-intensity tasks related to relief (eg, “[laughs]” [participant 1]), seeks reassurance (eg, “Is that right?” [participant 19]), or task failure (eg, “Sorry, I just lost my footing doing that one!” [participant 15]).
Nonverbal Responses During Task Performance
As intensity level increased, analysis of physical responses to task challenge indicated increasing incidence of nonverbal responses. Following the head-to-toe analysis of each participant's task performance, 3 primary nonverbal response categories were identified: (1) “postural reactions,” as evidenced by observed ankle or hip strategies and stepping or reach strategies, including any flaring of arms; (2) “bracing,” as evidenced by holding arms, legs, or trunk stiff in any position, making a fist, or pulling on clothing; and (3) “postural sway,” as evidenced by increased sway compared with baseline resting position (Tab. 2).
Secondary nonverbal responses that were either noted by the lead investigator during testing or reported by treating therapists on the day of testing, but could not be readily validated on video review, were increased depth of breathing and increased respiratory rate. In addition, the provision or withholding of support and the need for multiple attempts to get into the initial starting position were not standardized in the testing protocol. However, it was noted when participants received support to get into the starting position for some tasks or took several attempts to assume the starting position.
Interview Responses After Task Performance
Interview responses after task performance: a hierarchy from within capability, to testing capability, to the limits of capability.
At the conclusion of each test, the participants were asked to describe in their own words how challenging they found the task. The statements were participant descriptions of the challenge or intensity level of each task. Sixty-eight statements from 60 posttask interviews were entered into 2 content analysis matrices based on the root statement used by participants (Tabs. 3 and 4). Root statements were predominantly task centered (“It was…”/“It was not…”), with a lesser number of person-centered statements (“I felt…”/“I did not feel…”). The responses were further broken down into qualifiers and were mapped to the challenge level of the task. Categories that emerged from the content analysis were: (1) “within capability”—responses that reflected that the participant identified that the task did not challenge his or her balance capability, (2) “testing capability”—responses that reflected that the participant identified the task to be nearing the limits of his or her physical capability to maintain balance, and (3) “limit of capability”—responses that reflected the participant's perception that the task was near to the maximum limit of his or her ability to maintain balance, approaching the threshold of losing balance. A small number of responses were categorized as “discordant”: verbal responses reflected remarks by the participant that his or her balance was not challenged by the task despite physical responses consistent with high balance intensity (ie, postural reactions, bracing or sway provoked) or that balance was challenged when performing low-intensity tasks in the absence of physical markers of challenge (ie, no postural reaction, bracing or sway provoked).
Content Analysis of Interview Responses That Were Task Focused Following Low-, Medium-, and High-Challenge Tasksa
Content Analysis of Interview Responses That Were Person Focused Following Low-, Medium-, and High-Challenge Tasksa
The content of the task-centered responses (Tab. 3) and the person-centered responses (Tab. 4) as tabulated showed a match between participant responses and task intensity as comments transitioned from “within capability” responses to “limit of capability” responses with increasing task intensity. Four instances of discordant response were identified where the task performance (eg, losing balance during testing) was not consistent with the verbal response (ie, “It was quite easy” [participant 4], high-intensity task performance including bracing, increased sway, and stepping reaction).
Emergent Analysis: Relationship Between Time Delay and Balance Challenge
In the global assessment of performance, hesitation to commence a task was noted for a large number of participants as balance intensity increased. Hesitation to commence tasks was associated with the participant talking in all but 2 instances, as described earlier. To further explore this hesitation in the “action preparation” phase, additional data analysis was conducted to quantify the time from when a participant was asked to perform the balance task to the time he or she commenced the task, measured using a stopwatch on video playback (Tab. 2). No participant delayed the start of the low-intensity task, whereas increasing numbers of participants delayed the start of the medium-intensity (n=9, average delay 2.7 seconds, range=0–5) and high-intensity (n=14, average delay 5.6 seconds, range=0–13.4) tasks.
Discussion
This study identified a number of verbal and nonverbal markers of the intensity of balance challenge in older adults when tested on tasks of varying difficulty. We found that the pretask and in-task phases of balance task performance are rich in both verbal and nonverbal markers. The presence of time delay to commence tasks and participant talking in the pretask phase were both indicative of increasing balance intensity. The ability of the clinician to pick up on verbal cues that reflect the individual's perception of the degree of challenge of the task relative to his or her capacity even before movement begins may be an important finding. As the intensity of balance challenge increased, the themes identified in participant talk changed from comments regarding the task and the participant's capacity to perform the task to comments reflecting a perceived threat to balance. Similarly, the longer time that elapses between cues to start and commence a task is instructive. Talking and delay in task commencement with increasing difficulty appear to be consistent with the action preparation phase described in motor control theory. Magill16 posited that reaction time increases with task complexity and with task elements that reduce predictability in task execution (ie, loss of visual input, movement of supporting surface). This time delay range could be used for the purpose of creation of an item category (ie, hesitation less than x seconds/hesitation more than x seconds) to contribute to the emergent item set.
We found progression of nonverbal markers of the intensity of balance challenge in the form of increasing incidence of bracing, postural reactions, and sway as the intensity increased. The change in nonverbal indicators of challenge could be interpreted as signs of “overflow,” or neuromuscular activity in excess of the task requirements.17 This increase in “all of body” activity with increasing effort has been demonstrated in electromyographic studies of facial muscle activation in effortful lower limb exercise18 and testing of contralateral muscle activity during submaximal and maximal exercise efforts,17 and excess neuromuscular activity has been shown to decrease with neuromuscular exercise training such as tai chi practice19 and after balance and multitask training in older adults.20 The increase in bracing or “stiffness” increasing with increasing balance challenge has been noted in other studies.21,22
Initially, researchers investigating compensatory postural reactions following balance perturbation proposed a reaction hierarchy from ankle strategy to hip strategy and then to a step or reach strategy.23 It has subsequently been established that the central nervous system is less predictable when responding to balance challenges.24 Although a step or reach strategy may be the only option for maintaining balance in response to a large perturbation, these reactions also may be the reaction of first choice for small perturbations.25 This possibility has implications for the interpretation of the observed nonverbal reactions in this study in that the presence of any postural reaction may be the important signal. Although the observation of a step or reach/grab strategy may indicate a high degree of perturbation, this is not necessarily so. Conversely, however, as ankle or hip strategies are only effective in controlling small-scale perturbations, observations of these reactions correlate with lower intensity of balance challenge. Increased sway in older adults has been linked to increased balance task challenge26,27 and has been shown to be greater when perturbations are unexpected.21
When participants were asked to describe the challenges they experienced in their own words, responses changed from statements of perception of the tasks being well within the balance capability of the individual to perception of the challenges as being at the limits of balance capabilities. These responses are consistent with the conceptualization of balance exercise intensity as the degree of challenge to the balance control system relative to the capacity of the individual to maintain balance. This finding indicates that inclusion of self-report of perceived balance challenge may be a useful indicator of balance exercise intensity to incorporate into a future intensity measure. Such inclusion would be consistent with other instruments that measure exercise intensity from the patient's perspective, such as the Rating of Perceived Exertion (RPE) Scale for aerobic28 and strength training29 exercise. Further testing will be needed to determine if posttask verbal responses to the clinician's questions reinforce the spontaneous verbal responses observed.
There were study limitations. This study investigated a sample of 20 older adults nearing discharge from rehabilitation; their responses may not be indicative of the entire population of older adults. There is a possibility that minimally common responses in the broader adult population may not have been observed in this sample. However, older adults at the time of discharge from hospital are a group at high risk of falls and injury resulting from falls30 and as such would be a key population for application of a balance intensity rating instrument in the prescription of balance rehabilitation exercise. In addition, this study used balance challenge tasks known to the participant, as they had completed the DEMMI assessment in the 24 hours prior to the testing session, and the balance task was completed only once at each challenge level. Differences have been demonstrated in older adults' responses to a predicted rather than unpredicted balance challenge with the presence of anticipatory postural adjustments (APAs) as well as compensatory postural adjustments (CPAs) when the perturbation is predicted, as they were in this study. This finding may be an issue because APAs have been shown to modulate CPAs21,31 and, therefore, may reduce the sensitivity of our observations, as these nonverbal responses may not be as prominent if the balance challenges are novel and unpredictable.
In considering that, it also has been reported that the APA response in older adults may only be seen after multiple attempts at a balance challenge task.32 In relation to the single trial of a balance challenge task at each level in this study, this finding will need to be considered in the testing phase of any items derived from these observations with regard to sensitivity. Previous research has demonstrated that the magnitude of CPAs in response to balance challenges decreases with repeated trials.22 This finding suggests that a single trial of exercises to determine dosage may lead to underrating of balance exercise intensity; however, as a starting point, a single trial does give an indication of the intensity of balance challenge, particularly differentiating challenges that are only low in intensity. Multiple sequential trials may be needed to find the level of intensity that is intractable to within-session improvements and is an area for examination in future studies.
We did not standardize the provision or withholding of physical support for participants by testing therapists; however, we observed in the performance analysis that the need for support to assume starting positions varied. One recent study investigating the impact of providing initial support to older adults trying to assume a tandem stand test starting position showed the provision of support inflated balance estimates.33 Like our study, this study also showed that what happened before participants commenced the balance task should be taken into consideration along with the task performance when interpreting the degree of balance challenge.33 By extension, requiring support to assume a balance exercise starting position may be a marker of the intensity of balance challenge that is appropriate to consider in the item set for the potential rating of balance challenge.
We identified a small number of discordant responses in our data. For 2 participants, physical responses were discordant with verbal responses. Even though a participant was demonstrating increasing physical evidence of challenge to balance control (increased sway, postural reactions, bracing), he or she reported not feeling challenged or that everything was “alright.” This phenomenon of discordant signals was described in another study of 500 community-dwelling older adults where 20% were found to be “stoic” (low fear of falling in the presence of impaired physiological balance) and 10% were found to be “anxious” (high fear of falling in the presence of high levels of physiological balance performance).34 These findings underscore the importance of considering both verbal and nonverbal markers when rating the intensity of balance challenge of a task for an individual.
To date, studies investigating the responses of older adults to balance perturbations have focused on the electromyographic, biomechanical, and physiological responses to induced perturbations.21,23,35–37 These studies did not systematically explore the verbal and nonverbal markers of intensity of challenge to the balance control system. The purpose of this study was to search for observable markers that differentiate high balance intensity tasks from low balance intensity tasks. This study is unique in its approach to this long-standing deficit in therapeutic exercise prescription.3
This study has provided direction and has given rise to a number of potential verbal and nonverbal items that could be incorporated into a measure of intensity of balance challenge. Based on the data analysis, the potential balance intensity assessment items have been grouped by time periods (ie, pretask, in-task, and posttask) and draw on the well-developed systematic (head-to-toe) visual observation skills of therapists who would already routinely look for the presence of commonly recognized physiological signs of balance challenge in bracing, postural reactions, and sway. The integration of time to commence task and verbal response analysis (both spontaneous and therapist elicited) is a novel approach for this type of balance task analysis. The presence of any talk in the pretask phase appears to be important. This is a key finding because therapists are typically trained to hone their “diagnostic” eye on movement during a task rather than focus a diagnostic eye and ear to the pretask phase. The results suggest that the pretask phase may hold information that is key to predicting the intensity of balance challenge. Inclusion of other general markers of task challenge, such as increasing heart rate or respiratory rate, may provide additional information easily measured in a clinical setting, particularly if psychological factors such as anxiety, stoicism, or fear of falling emerge as important factors that need to be differentiated in interpreting patient self-report of the intensity of balance challenge.
The potential patient rating items now need to be presented to therapists, patients, and falls and balance experts for user acceptance testing and refinement before an instrument prototype can be tested in a large cohort study. The development of this instrument is a key step in the systematic investigation of optimal balance exercise dosage. The aim is to enable researchers to determine the optimal exercise prescription required to improve balance and consequently maximize falls prevention interventions for older adults.
Footnotes
All authors provided concept/idea/research design and writing. Ms Farlie and Associate Professor Molloy provided data collection. Ms Farlie, Associate Professor Molloy, and Professor Haines provided data analysis. Ms Farlie provided project management. Professor Haines and Associate Professor Molloy provided facilities/equipment. Associate Professor Molloy, Professor Keating, and Professor Haines provided consultation (including review of manuscript before submission).
Prior approval to conduct this study was obtained from the Monash Health and Monash University human research and ethics committees (reference number 11030B).
Professor Haines was supported by a Career Development Fellowship from the Australian National Health and Medical Research Council. Ms Farlie was supported by a grant from the Lions John Cockayne Memorial Fellowship Trust Fund. The Lions John Cockayne Memorial Fellowship Trust is jointly funded by Oakleigh Lions Club Elderly People's Home Inc and Monash Health.
- Received November 27, 2014.
- Accepted July 5, 2015.
- © 2016 American Physical Therapy Association
References
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