For data analysis, participants were divided into 3 age groups. Data for each reaching context were screened for homogeneity of variance and for normality using the Kolmogoroz-Smirnov Z test. Intertrial reliability of distance reached in the TFR context was determined using an interclass correlation (2,1) 2-way random-effects model. The association between reach distance for each context and age was tested using Pearson correlation coefficients. Separate Pearson correlation coefficients for each age group were calculated to determine the association between TFR and each object-present context.
A 2-way repeated-measures analysis of variance (3 × 3) with 1 between-subject factor (age) and 1 within-subject factor (reaching context) was conducted to determine the effect of age and context on reach ability.7 Post hoc analysis was conducted using Bonferroni tests for pairwise comparisons between age groups and within-reach contexts. An α level of .05 was used to determine statistical significance. Statistical Package for the Social Sciences, version 12.0 (SPSS Inc, Chicago, Illinois) was used for all statistical analyses.
Error variances for each context-oriented reach score was the same across all groups, satisfying the homogeneity of variance assumption. Normality assumptions were also met for the reach score of each context. Meeting the assumptions for homogeneity of variance and normality negated any potential impact of unequal sample sizes. Intertrial reliability of reach distance between 3 trials for TFR was excellent (interclass correlation ≥0.96).7 The correlation between reach distance and age was high for all contexts (r = −0.72, P ≤ .05). The correlation between TFR and OPFR and between TFR and FRG was moderate for the young age group (r > 0.69) and high for the middle and older age groups (r > 0.78 and 0.73, respectively; P ≤ .001).
The repeated-measures analysis of variance revealed a significant interaction (P = .001) between age and reaching context and significant main effects of both age (P = .001) and context (P = .001).
Pairwise comparisons for the simple effects of age revealed that, for all reach contexts, participants in the youngest group reached further (P ≤ .001) than both of the older age groups, and participants in the middle age group reached further (P ≤ .001) than participants in the oldest age group. Table 3 summarizes the results of the multiple comparisons for the simple effects of age group.
Pairwise comparisons of the simple effects of reach context revealed that, for the youngest age group, TFR was less than OPFR (P = .005) and marginally less than FRG (P = .053). There was no difference between FRG and OPFR. For the middle age group, TFR was less than OPFR (P = .001) and FRG (P = .001), and FRG was less than OPFR (P = .006). For the oldest age group, TFR was less than OPFR (P = .001) and less than FRG (P = .001). Similar to the young age group, there was no difference between FRG and OPFR for the oldest age group. Figure 2 illustrates the results of the simple effects of age and context on reach ability. Table 3 summarizes the results of the multiple comparisons for the simple effects of reach context.
The results of this study support the hypothesis that dynamic standing balance, as measured by FR ability, would be affected by the context in which it is performed. These findings are in agreement with research by Chen et al4 and Chevan et al,6 both of whom reported increased reach distance when reaching was performed in the presence of an object. Chen et al4 found that healthy adults (aged 60.1 years) and adults with right cerebral vascular accidents reached further when moving coins forward on a table as compared with reaching forward, while moving the hand along a table. Likewise, Chevan et al6 reported increased reach distance for older adults at risk for falls when reaching to grasp an object. In each of these studies, only one object context was examined, whereas, in the present study, we compared FR without an object present with FR performed in 2 object-present contexts. Thus, the results of the current study expand the benefit of context-oriented FR to include tasks that involve touching an object and grasping an object. Furthermore, we found the benefit of context-oriented FR to apply to young, middle-aged, and older adults, providing a basis for establishing performance data across the lifespan.
The negative correlation between FR ability and age for each reaching context suggests that FR ability declines with age regardless of the context in which FR is performed. Post hoc analysis of the simple effects of age confirmed this age-related decline. For all reaching contexts, younger participants reached further than middle aged and older participants, and middle age participants reached further than older participants. Furthermore, the high correlation between object context and TFR indicate that the reaching tasks are measuring a similar construct of dynamic balance.
As previously mentioned, Chevan et al6 reported increased reach distance in a group of older adults (mean age 80.6 years, SD 7.6 years) at risk for falls (FR < 7 in) who grasped a can. The authors selected a cutoff of less than 7 in to investigate subjects with high fall risk. In our study, we did not use FR scores as inclusion criteria; however, retrospectively, we were able to divide the older participants into groups on the basis of fall risk. According to Duncan et al,2 FR scores of 10 or more indicate no risk for falls, FR scores of 6 or more but less than 10 indicate minimal risk, and FR scores of less than 6 inches indicate high fall risk. In our study, 48 (62%) of the older participants had FR scores of greater than or equal to 10 in (no fall risk) and 30 participants (38%) in the older age group had FR scores greater than or equal to 6 in but less than 10 (minimal fall risk). To determine whether there was a difference between context-oriented FR scores between the older participants without fall risk and those with minimal fall risk, we conducted a secondary analysis using a 2 (fall risk group) by 3 (reach context) repeated-measures analysis of variance. The interaction between fall risk group and reach context was significant (P = .000) warranting post hoc analysis of simple effects. For each reach context, the older adults without fall risk had higher reach scores than the older adults with fall risk (Figure 2). For both groups of older participants, TFR was less than OPFR and FRG, with no difference between OPFR and FRG. Thus, results of the present study extend the findings of Chevan et al6 to a broader age range of adults (8 decades) who had minimal or no fall risk as demonstrated by TFR scores.
Analysis of the simple effect of context allowed us to compare reach ability in each contextual variation. Our results suggest that reach ability differs depending on the context in which reaching was performed. For example, for all age groups, reach distance increased significantly when participants were reaching toward an object (OPFR) as compared with reaching without an object present. This increase was 6.43%, 15.51%, and 27.90% in the young, middle, and older age groups, respectively. When considering the increase in context-oriented reach scores for older participants with and without fall risk, the increase was 16.55% for older participants without fall risk (FR scores ≥10 in) and 45.40% for older adults with fall risk (FR scores ≥6, <10 in). Likewise, the increase in reach ability when reaching to grasp an object was 4.7%, 11.6%, and 26.7% for the young, middle, and older age groups, respectively, and 15.9% and 42.9% for older participants without fall risk and with fall risk, respectively. The increase in reach ability when an object is present suggests that individuals are not attaining their true stability limits in the anterior direction when performing the FR test according to the methodology of Duncan.1 Furthermore, this increase in context-oriented reach beyond traditional FR was more pronounced for older adults with fall risk.
One explanation for the increase in FR ability in the presence of an object may be the motivational factor inherent in having a target to reach toward. Clark et al8 compared COG excursion during FR to COG excursion during the limits of stability (LOS) test on the Balance Master (Neurocom International, Inc, Clackamas, Oregon). The LOS utilizes a target on a computer screen to direct the leaning movement of the individual, whereas FR requires no target. They found that individuals exhibited greater COG excursion during the LOS tests than during the FR. The authors argue that individuals may consider the goals of the LOS tests and FR to be different and may tolerate greater potential for instability when a target is present. Although we did not measure COG excursion, we did find that reaching distance increased in the presence of an object, suggesting that the presence of an object may motivate individuals to reach beyond their self-imposed stability limits when a goal or target is absent. This disregard of innate caution when an object is present may increase fall risk. Further research is needed to determine the ability of OPFR or FRG tests to predict fall risk. Therefore, we concur with Chevan et al6 that clinicians should be cautioned not to substitute the OPFR or FRG for TFR at this point.
The increase in FR ability when an object is present may also be a result of external focus of attention provided by the instructions given to the participants during the context-oriented reach tasks. Research has found that the performance and learning of motor skills is enhanced by instructions that emphasize an external focus of attention in which the learner is directed to focus on the effect of his or her movements as opposed to instructions that provide an internal focus of attention in which the learner is directed to focus on body movements or how movement is performed.9,10 These findings have been reported for a range of motor skills that include sport skills,11,12 dynamic balance,10,13–15 and reaching performance.16 In addition, enhanced motor skill learning with external focus of attention instructions has occurred for healthy participants and participants with impairments.13,16
In our study, instructions for performing the traditional FR task were “Reach as far forward as you can without losing your balance. Keep your feet on the floor. You are not allowed to touch the platform as you reach.” These instructions could be viewed as providing an internal focus of attention in that participants were directed to focus on body movements during the reaching task. That is, they were to maintain their balance, keep their feet on the floor, and not to touch the platform. In contrast, instructions for performing the object-present context-oriented reaching task were “Reach toward the bottle to touch your fist to the bottle without tipping the bottle over. Hold this position, keeping your feet on the floor, until I tell you to relax. You are not allowed to touch the platform as you reach.” Although the instructions for both reaching conditions were similar in the provisions of keeping feet on the floor and not touching the platform, instructions for the context-oriented condition directed the participants to reach toward and touch the object without tipping it over. The inclusion of reaching to touch an object without tipping it over may have provided an external focus of attention in which the participants focused on the effects of their movements, that is, reaching to the water bottle and keeping the bottle upright. Focusing the effect of their movements, touching the water bottle, may have contributed to the ability of participants in all age groups to maintain their balance over a greater reaching distance.
A limitation in the present study is that we did not examine kinematic factors, such as the control of COP movement that may have also contributed to the increased reach ability in the target-oriented contexts. Lin and colleagues5 found that the average velocity of COP movement decreased when reaching was performed in the presence of an object, both in individuals with unilateral stroke and in healthy adults. Although there was no difference in reach distance when an object was present or absent, the authors concluded that the findings of decreased COP velocity when reaching in the presence of an object might facilitate greater balance control through a decrease in postural sway. Based on the findings of Lin et al5 regarding COP velocity, the greater reach ability during the context oriented tasks in the current study may be due to better control of COP velocity when an object is present. Further research regarding COP excursions and velocity during context-oriented FR tasks is warranted to explore underlying balance control mechanisms.
Although the benefits of object presence on reaching distance attained during FR were found in one testing session, the implication of these findings may be considered for(in the assessment and rehabilitation of dynamic balance dysfunction. Testing dynamic balance using traditional FR does not allow an assessment of performance under conditions similar to balance requirements during real-life tasks. All of our participants reached further in the presence of an object than during TFR. Therefore, assessing reach ability under differing contexts might provide more information about real-life balance performance.
In addition to including context-oriented tasks in the assessment of dynamic standing balance, therapists may want to incorporate the use of context-oriented tasks during balance training. Specifically, therapists might include an object to reach toward during practice sessions.
Previous research shows that the interaction of the individual with an object may provide visual and spatial feedback that assists in the organization of postural control.4,16 Furthermore, clinicians might structure the goals of the object-present reaching task according to the abilities of the individual. Our findings indicate that balance was maintained over a greater reach distance when reaching both to touch the object and to grasp the object. Having flexibility in the object-present task goals may be important for the individual with impairments that limit their ability to grasp objects. Likewise, the therapist may elect to implement variability in practice by utilizing tasks that involve both touching and grasping objects.
In addition to organizing balance training to include reaching to an object, therapists may also consider the instructions that accompany the reaching tasks. Following the line of research regarding attentional focus effects on motor skill performance and learning,9,10,13,15–17 a greater reaching distance, thus improved postural control, may be attained with instructions that focus the attention of the individual on the effects of their movements. Although our study did not specifically examine the effectiveness of instructions that provide external verses internal focus of attention, participants were instructed to “reach forward as far as possible to touch the object without tipping it over” during the object-present contexts. These instructions may have focused the participant's attention externally, thereby increasing reach distance. Using instructions that direct attention externally may increase the effectiveness of the task-related balance training.
It should be noted that the object-present reaching tasks in our study utilized equipment that was of low cost and could be easily replicated in any clinical setting. Previous research has found that dynamic balance is improved when subjects' weight shift toward visual targets displayed on a computer screen.18,19 Computerized balance training of this nature is similar to the context-oriented tasks that we utilized in that both incorporated targets to move toward. Clinicians, however, may have limited access to computerized balance training equipment. Furthermore, weight shifting toward targets on a computer screen differs from functional reaching tasks. The context-oriented tasks that we investigated, however, offer a practical alternative for dynamic balance training and closely simulate balance requirements during real-life situations.
In addition to investigating fall risk and kinematic measures of posture control, future studies should examine the effects of fear of falling on context-oriented FR performance. Individuals with low balance confidence often restrict their movements or activity level and often have lower balance performance scores than individuals with high balance confidence.20,21 Newton22 found decreased amount of backward reach distance in a sample of older adults with a fear of falling. It is unknown how fear of falling might impact reach performance under object contexts. Lastly, to expand the usefulness of context-oriented FR as a clinical measure of balance performance, measures of reliability, validity, and minimal detectable change need to be established.
The results of the present study indicate that the presence of an object to reach toward or to grasp may increase maximum forward reach distance in participants of all ages, regardless of fall risk. These findings suggest that dynamic standing balance may be enhanced by the use of context-oriented reaching tasks. Further research is needed, however, to determine the mechanisms underlying balance control during context-oriented FR tasks and the ability of context-oriented FR to predict fall risk.
A portion of this work was presented at work was presented at the American Physical Therapy Association Combined Sections Meeting, Nashville, Tennessee, in 2008 and at Las Vegas, in 2009. These works were abstracted in the Journal of Neurological Physical Therapy in 2007 and in the Journal of Geriatric Physical Therapy in 2009.
The authors thank their graduate students who assisted with this work.
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Keywords:Copyright © 2011 the Section on Geriatrics of the American Physical Therapy Association
balance; fall risk; functional reach test; geriatrics; posture