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a Department of Consumer Affairs, Auburn University, AL
b Merchandising, Environmental Design, and Consumer Economics, Texas Tech University, Lubbock
c Behavioral and Biobehavioral Processes—5, Center for Scientific Review, Bethesda, MD
Correspondence: Joan I. Dickinson, PhD,IIDA, IIDA, Department of Consumer Affairs, 308 Spidle Hall, Auburn University, Auburn, AL 36849-5603. E-mail: dickiji{at}auburn.edu.
Decision Editor: Laurence G. Branch, PhD
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Abstract |
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Key Words: Balance • Posturography • Flooring • Fall • Sensory Organization Test (SOT)
Accidental falls are a leading cause of injury-related morbidity and mortality in people aged older than 65 years (Rawsky 1998
; Wells and Evans 1996). Although the incidence rate for falling varies in the literature, most researchers estimate that 25% to 50% of older adults experience one or more falls per year (Donald and Bulpitt 1999; Rawsky 1998; Shroyer, Elias, Hutton, and Curry 1997). Because the majority of older adults do not report falling episodes, the numbers cited above are likely to be low estimates of the problem (Josephson, Fabacher, and Rubenstein 1991).
When a fall does occur, the older adult is much more likely to suffer from injury (Gregg, Pereira, and Caspersen 2000; Wells and Evans 1996). Consequently, falls by older adults have become an expensive cost to society. Approximately 10 billion dollars is spent per year on hip fractures in the United States, and the total indirect and direct costs from fall-related injuries are estimated to be 75 to 100 billion dollars each year (Cali and Kiel 1995). Yet, the physical injury and monetary impact of falling are only part of the problem. The psychological and social factors can be devastating (Donald and Bulpitt 1999; Rawsky 1998). Many older adults who have experienced a fall develop a fear of falling, which may limit their physical activity (Gray-Miceli 1997; Howland et al. 1998; Lachman et al. 1998). This limitation in activity often causes increased frailty, dependency, and isolation (Donald and Bulpitt 1999; Rawsky 1998). Furthermore, repeated falls can also lead to hospitalization and long-term care admittance (Donald and Bulpitt 1999; Mahoney 1999; Tinetti and Williams 1998).
These demographic trends illustrate the need to develop a preventative approach to reduce falling among elders. Although many risk factors (e.g., medications, gender, environmental design hazards, and normal age-related changes) have been identified as causes of falling (Connell and Wolf 1997; Rawsky 1998; Sattin, Rodriguez, DeVito, Wingo, & The SAFE Group, 1998; Schoenfelder and Why 1997; Shroyer et al. 1997), problems associated with balance or declines in postural control are frequently cited in the literature as important contributors to instability (Mahoney 1999; Rawsky 1998). To illustrate, a number of researchers have found that older adults sway significantly more than younger adults (Hageman, Leibowitz, and Blanke 1995; Hasselkus and Shambes 1975), and increases in postural sway are positively correlated with falling (Fernie, Gryfe, Holliday, and Llewellyn 1982; Maki, Holliday, and Topper 1994).
Postural control involves a complex interaction between central processing, sensory input (i.e., the visual, somatosensory, and vestibular systems), and motor output (Mahoney 1999; Shumway-Cook and Woollacott 1995). The sensory systems play an important role in maintaining balance by providing the central nervous system with information on the body's position in space (Maki and McIlroy 1996; Shumway-Cook and Woollacott 1995).
In response to the problems associated with falls among older adults, many researchers have studied the effect of the aging process on the sensory systems' contributions to standing balance (Anacker and DiFabio 1992; Camicioli, Panzer, and Kaye 1997; Ring, Nayak, and Isaacs 1989; Teasdale, Stelmach, and Breuing 1991; Whipple, Wolfson, Derby, Singh, and Tobin 1983). Many of these researchers have discovered that sensory conflict has a greater influence on postural sway among elders compared with younger adults (Camicioli et al. 1997; Teasdale et al. 1991; Wolfson et al. 1992).
To illustrate, the Sensory Organization Test (SOT) is a clinical instrument used to determine how individuals maintain balance under altered sensory conditions (e.g., eyes closed, confusing visual input, and confusing somatosensory input; Berg and Norman 1996; Tang, Moore, and Woollacott 1998). Research conducted by Colledge and colleagues 1994, Teasdale and colleagues 1991, Whipple and colleagues 1983, and Wolfson and colleagues 1992 found that postural sway increased linearly with age under each SOT condition. The older adults in all of these research studies swayed more than did young controls when (a) visual input was absent, (b) somatosensory input was altered, and (c) both visual and somatosensory inputs were inaccurate. Specifically, the older adults had more problems with balance control when inaccurate or absent visual cues were coupled with incorrect somatosensory inputs (Colledge et al. 1994; Teasdale et al. 1991; Whipple et al. 1983; Wolfson et al. 1992).
Colledge and colleagues 1994 found that when older adults encountered confusing sensory input, their postural sway increased. In particular, inaccurate somatosensory cues seemed to cause instability (Colledge et al. 1994; Teasdale et al. 1991; Whipple et al. 1983; Wolfson et al. 1992). Because the somatosensory system provides the brain with information about where the body is in relationship to a support surface (e.g., the floor), more compliant floor surfaces could provide sensory input that is different from less compliant surfaces (Redfern, Moore, and Yarsky 1997). Hard, noncompliant floors, for example, may provide a more stable, fixed support surface, while soft, compliant floors may provide an unstable surface (Redfern et al. 1997; Shroyer et al. 1997). The compliance of a softer floor covering such as carpet might influence the accuracy of the information received by the somatosensory system, subjecting elders to a greater risk of falling (Baloh, Spain, Socotch, Jacobson, and Bell 1995; Redfern et al. 1997; Shroyer et al. 1997).
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Purpose of the Study |
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Definition of Terms |
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).
Balance strategy is defined as the strategy the body uses to maintain stability when a disturbance in balance occurs. An ankle strategy restores the COM to the limits of stability through body movements centered on the ankle joints (Shumway-Cook and Woollacott 1995; Wolfson et al. 1992). An ankle strategy is primarily used for smaller disturbances in balance and on firm support surfaces (Shumway-Cook and Woollacott 1995). When body sway does not approach the limits of stability, an ankle strategy is employed (Wolfson et al. 1992).
Another strategy used to maintain balance during postural instability is the hip strategy. The hip strategy involves body movements at the hip joints (Shumway-Cook and Woollacott 1995). This strategy is used for larger disturbances in balance or when the support surface is small (e.g., a balance beam) or compliant (e.g., foam; Shumway-Cook and Woollacott 1995; Wolfson et al. 1992). A hip strategy is also used during an impending loss of balance or when body sway approaches the limits of stability; thus, more energy is required to maintain balance when a hip strategy is used (Wolfson et al. 1992). Balance strategy is an important measure, because if older adults rely more heavily on a hip strategy while standing on carpet, this would suggest that carpet makes balance control more difficult (Dickinson, Shroyer, Elias, Hutton, and Gentry 2001).
Compliance refers to the give or compressibility of the floor material (Hall 1993; Yeager and Teter-Justice 2000). To illustrate, wood flooring would be considered to have no compliance or give. On the other hand, carpet has varying degrees of compliancy depending on the density and pile height (i.e., the actual height of the carpet; Yeager and Teter-Justice 2000). A densely constructed carpet with a low pile height would have less compressibility than a carpet with a higher pile height. A deeper pile height, while providing a more luxurious feel, also has a greater tendency to compress (Hall 1993).
Postural sway is defined as the body's ability to shift during an upright stance (Hasselkus and Shambes 1975). Individuals do not stand absolutely still; instead the body moves in small amounts in a forward and backward motion, which is termed postural sway (Shumway-Cook and Woollacott 1995). The extent of this movement is one measure of the body's ability to balance (Hasselkus and Shambes 1975). Postural sway is an important measure because increases in postural sway have been correlated with falling (Fernie et al. 1982).
The somatosensory system provides the central nervous system with information about the body's position in space with reference to a support surface (Shumway-Cook and Woollacott 1995). Under normal conditions when an individual is standing on a horizontal, firm surface, the somatosensory system provides information about the position of the body in respect to the surface; however, if the support surface is moving (e.g., a boat) or vertical (e.g., a ramp) or if the support surface is compliant (e.g., foam or plush carpet), the somatosensory system becomes a less reliable sensory input for balance control (Baloh et al. 1995; Shumway-Cook and Woollacott 1995). In these situations, the older adult must rely on the visual and/or vestibular systems for postural stability (Shumway-Cook and Woollacott 1995). Anacker and DiFabio 1992, Ring and colleagues 1989, and Camicioli and colleagues 1997 suggested that older adults rely more heavily on the somatosensory system for balance control. This is an important research finding and suggests that elements such as ramps and/or compliant flooring such as carpet or foam that alter somatosensory input may become increasingly difficult to negotiate with age (Baloh et al. 1995; Redfern et al. 1997; Shumway-Cook and Woollacott 1995).
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Methods |
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; Ring et al. 1989; Teasdale et al. 1991; Whipple et al. 1983; Wolfson et al. 1992). The principal investigator contacted the remaining 49 respondents by phone to schedule a date and time for data collection. Of the 49 respondents, 47 agreed to be tested. Two respondents did not show up for their scheduled time; thus, the total sample size was 45 participants.
The mean age of the group was 72.84 (SD ± 5.35). The mean number of medical conditions (M = .689; Mdn = 0; Range = 0 to 2) and mean number of medications (M = 1.73; Mdn = 2; Range = 0 to 6) were low. Many of the participants (n = 21) had no history of medical problems, whereas other participants had minor symptoms of arthritis or cataracts that were corrected through contact lens or surgery. The majority of participants (n = 42) had not fallen in the last 6 months (see Table 1 ).
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; NeuroCom International 2001; Ring et al. 1989; Teasdale et al. 1991; Whipple et al. 1983; Wolfson et al. 1992). Because the goal of the current investigation was to examine the effect that a selected commercial carpet had on static balance, we controlled extraneous variables such as history of falling in this first round of data collection.
Measures
We measured balance by using the NeuroCom Computerized Equitest balance machine (NeuroCom International 1995; see Fig. 1). The balance machine consisted of a computerized forceplate and visual surround that moved during test conditions. The visual surround, provided by the manufacturer, displayed a mural of a mountain view with clouds and a horizon line. The forceplate measured postural sway and balance strategy. The possible range of postural sway scores was 0 to 100. A score of 100 indicated no sway, whereas a score of 0 indicated a loss of balance or sway that exceeded the limits of stability (i.e., a fall; NeuroCom International 1995; Wolfson et al. 1992). The possible range of balance strategy scores was also 0 to 100. A score of 0 indicated the use of a hip strategy, whereas a score of 100 indicated the use of an ankle strategy (NeuroCom International 1995).
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; NeuroCom International 2001; Whipple et al. 1983; Wolfson et al. 1992). The equipment has good to excellent retest reliability (NeuroCom International 2001). SOT scores obtained from the NeuroCom balance machine were also significantly correlated (p < .001 to .007) with the Tinetti Balance Scale and other clinical measures of balance (Camicioli et al. 1997; NeuroCom International 2001). Significant correlations between SOT scores and clinical measures of balance illustrate the validity or accuracy in the measuring capabilities of the balance machine (NeuroCom International 2001).
A commercial-grade carpet (i.e., a 28-oz, 1/10 in. gauge, 100% nylon, solid gray, 3/16 in. pile height, level loop carpet) was applied directly to the forceplate of the balance machine. According to Reg Burnett Incorporated (RBI) Carpet Consultants 1999, this carpet specification represented the most commonly installed carpet for nonresidential and/or commercial use. RBI was founded in 1967 and is the largest carpet-consulting firm in the world. RBI provides the carpet industry with research pertaining to carpet styles, markets, and specifications (RBI Carpet Consultants, 1999).
Participants completed the SOT while standing on the carpeted and noncarpeted forceplate of the balance machine. The SOT consisted of six conditions that altered sensory input for balance control (see Table 2 ). To illustrate, the visual surround and forceplate remained stationary during some SOT conditions, but were sway referenced (i.e., moved) during others (see Table 2 ). The purpose of the sway-referenced conditions was to determine how the older adults reacted to the loss of one or more sensory conditions under a carpeted and noncarpeted condition. For each SOT, we measured balance (i.e., postural sway and balance strategy) for three trials that lasted 20-s each. Measuring balance across trials allowed the researchers to examine adaptation to sensory limitations.
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). We instructed participants to stand upright on the forceplate and gaze straight ahead. Each participant completed all six SOT conditions on the balance machine with and without carpet. We randomly assigned approximately half of the participants to the carpeted condition first (n = 23) and assigned the other half to the noncarpeted condition first (n = 22). We used this procedure to control for any learned effects that might occur when using the balance machine. Participants wore comfortable, low-heeled shoes. Testing for each participant took place during one visit that lasted approximately 20 to 30 min. Participants were given breaks between conditions and/or trials when needed in order to help eliminate a fatigue factor.
Data Analysis
We entered, verified, and analyzed the data by using the SPSS for Windows 10.0 statistical software package. The data analyses for postural sway and balance strategy took the form of a mixed between–within design, with floor surface (2) as a between-subjects measure, and sensory condition (SOT; 6) and trials (3) as within-subjects measures. We considered probability levels of .05 as statistically significant.
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Results |
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For the floor surface main effect, the mean postural sway for the carpeted conditions was 81.23 (SD ± .707), and the mean postural sway for the noncarpeted conditions was 81.61 (SD ± .612). The possible range of postural sway scores was 0 to 100 with 0 indicating a fall and 100 indicating no postural sway. There was no significant difference between these means F(1,44) = .660, p = .421, suggesting that the commercial-grade carpet used in this study did not affect postural sway among this group of participants.
The analysis for balance strategy found significant main effects for floor surface, F(1,44) = 11.08, p < .01, sensory condition (SOT), F(5,40) = 136.70, p < .001, and trials, F(2,43) = 17.96, p < .001. The sensory condition (SOT) by trial interaction was significant, F(10,35) = 4.96, p < .001. There was no significant interaction with floor surface.
The mean balance strategy score was 91.89 (SD ± .338) for the carpeted conditions, and 92.64 (SD ± .281) for the noncarpeted conditions. Recall that scores for balance strategy ranged from 0 to 100, with 0 indicating the use of a hip strategy and 100 indicating the use of an ankle strategy. The scores for the carpet conditions were significantly lower, F(1,44) = 11.08, p < .01.
The floor surface by sensory condition interaction for balance strategy showed a trend toward significance, F(5,40) = 2.00, p = .099. Although interactions are not further examined when there is no statistical significance, due to the exploratory nature of this research study (i.e., only two other research studies have applied carpet to the forceplate of the balance machine), the interaction means were examined (see Table 3 ). First, the mean balance strategy scores during the easier SOT conditions (SOT 1, 2, and 3) did not differ substantially. The mean balance strategy scores obtained under the more difficult SOT conditions (SOT 4, 5, and 6), however, seemed to require greater hip strategy when the participants were standing on the carpet.
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Discussion |
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; Dickinson et al. 2001; Redfern et al. 1997). Although the carpeted condition is certainly more compliant than the noncarpet condition, the dense construction and low pile height of this carpet may contribute to the lack of difference found in postural sway. More important, the results are promising particularly since increases in postural sway have been positively correlated with falling in a number of research studies (Hageman et al. 1995). Although the carpet selected for this research study may be a safe floor-covering option for healthy, older adults in terms of postural sway and static balance, it should be noted that individuals with a history of falling might perform differently on this floor-covering surface. The clinical or practical significance of the floor surface main effect for balance strategy is questionable. Although there is a statistical difference between the mean scores of 91.89 (carpeted conditions) and 92.64 (noncarpeted conditions), the difference between these means is small for practical purposes as an overall main effect. Moreover, both scores are close to 100 suggesting that regardless of whether the older adults were standing on the carpeted or noncarpeted surface, an ankle strategy was employed. These main effect differences do show a trend toward magnification as the sensory conditions become more challenging. As sensory or sensory feedback conditions deteriorate as they might during different lighting conditions (e.g., low lighting levels, glare, or sudden changes in lighting levels) and perceptual or floor-slope conditions, the carpeted floor surface seems to require more active energy among this group of individuals. However, because the floor surface by sensory condition interaction is not significant, it is difficult to draw conclusions regarding balance strategy.
This study is unique because to this point few researchers have attempted to measure balance on differing floor surfaces by use of computerized balance machines. Redfern and colleagues 1997 examined the effects of seven floor coverings of varying levels of compliance with a group of younger controls (n = 8) and older adults (n = 8), whereas Dickinson and associates 2001(n = 25 healthy, older adults) applied a residential carpet and pad to the forceplate of the NeuroCom Computerized Equitest balance machine. Greater floor compliance increased postural sway among the older participants during the moving visual surround condition (SOT 3; Redfern et al. 1997) and when participants had their eyes closed and the forceplate of the balance machine moved (SOT 5; Dickinson et al. 2001). These two studies seem to support the thesis that carpet influenced balance control only during sensory conflict. The carpet used in the Dickinson and colleagues 2001 study was a residential carpet (i.e., 36 oz, 1/8 in. gauge, 100% nylon, solid, 1/2 in. cut pile carpet) with pad that was more compliant than the commercial-grade carpet used in the current investigation. Thus, it appears that the compliancy influenced sway. This was further supported by the Redfern and colleagues 1997 study, which found that the inclusion of the pad with the carpet significantly increased sway among older participants. Together, all three of these investigations illustrate the importance of the compliancy of the carpet.
Although balance strategy was not measured in the Redfern and colleagues 1997 study, in the current study, and in the Dickinson and colleagues 2001 study, balance strategy was observed. In the Dickinson and associates study (i.e., residential carpet and pad were investigated), there was a significant floor surface by sensory condition interaction for balance strategy suggesting that when older adults encountered conflicting sensory information, they were more likely to employ a hip strategy. In the current study, however, whether the commercial-grade carpet affects balance strategy is unclear. Clarification on balance strategy is needed because carpet is often marketed as protecting the older adult from injury if a fall should occur (Yeager and Teter-Justice 2000). Whether the benefits of carpet outweigh the risks is not known at this time.
Certainly more research is needed, and there are limitations to the current study. First, the participants in this investigation and in the other studies cited (Dickinson et al. 2001; Redfern et al. 1997) are healthy, and the results could be different if individuals with balance impairments had been included. This research study does not include older adults who had fallen more than two times in the last 6 months. Thus, all three studies that have examined the effects of floor coverings on static balance provide baseline information that serves as comparison data for future research. An important follow-up study would be to examine the effect of carpet on individuals who have a history of falling. Fallers would be expected to perform quite differently on the commercial-grade carpet used in this investigation and on the carpets used in the previous research studies. At this time, it is not known how fallers are affected by various floor-covering surfaces.
Second, although postural sway and balance strategy are important in measuring balance over a short length of time, a fatigue factor is not considered in this research study. More time spent on these surfaces over several hours may find even greater effects for floor surface particularly since balance strategy determines the amount of energy expended in order to maintain an erect position (Shumway-Cook and Woollacott 1995). Yet, there are limitations in measuring static balance (i.e., postural sway and balance strategy). Falls among healthy, older adults typically do not occur during standing balance control and are more likely to happen during a tripping or stumbling incident. Swaying more on a particular surface does not necessarily mean that individuals will fall on that surface. Rather, the findings thus far relating postural sway and falling reflect a correlation, not a causal relationship (Fernie et al. 1982).
Accidental falls are a serious problem among aged adults, and as the population of older adults continues to grow, the consequences of falling will have a greatly increased impact on society (Rawsky 1998). In particular, factors within the built environment have been frequently cited in the literature as a cause of falling (Connell and Wolf 1997; Sattin et al. 1998; Shroyer et al. 1997). This research study examines one of those factors: carpet. On the basis of the results from this study, we conclude that healthy, older adults do not seem to have great difficulty maintaining static balance while standing on the commercial-grade carpet. The results are promising and suggest that with additional testing, this carpet may be a safe floor-covering option in terms of static balance control for healthy, older adults.
The Forum
Book Reviews
Practice Concepts
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Acknowledgments |
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Received for publication August 7, 2001. Accepted for publication December 17, 2001.
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