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Effect of a Dual-Task Net-Step Exercise on Cognitive and Gait Function in Older Adults

Kitazawa, Kazutoshi PhD1,2; Showa, Satoko PhD1; Hiraoka, Akira MPEd2; Fushiki, Yasuhiro PhD1; Sakauchi, Humio MD, PhD1; Mori, Mitsuru MD, PhD1

Journal of Geriatric Physical Therapy: July/September 2015 - Volume 38 - Issue 3 - p 133–140
doi: 10.1519/JPT.0000000000000029
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Background and Purpose: Participation in generally recommended aerobics or strength exercises may be challenging for older adults. Therefore, it is necessary to consider the types and levels of physical activities suited for them to improve their cognitive and gait function and adherence to exercise programs. This has prompted efforts to identify exercises that require less physical strength and frequency of performance, while still offering cognitive and health benefits. Here, we aimed to assess the effect of a novel dual-task net-step exercise (NSE) performed once a week for 8 consecutive weeks on improvements in cognitive performance and gait function in an older population.

Methods: In this pretest/posttest experimental case control study, 60 healthy older adults (mean age 76.4 years) were recruited from community-dwelling people and separated randomly into 2 groups: a dual-task NSE group and a control group. The NSE group was asked to walk across a net without stepping on the ropes or being caught in the net. Two computer panel-type cognitive functional assessments, the Touch-M and Touch Panel-Type Dementia Assessment Scale, were administered at baseline and after 8 weeks of intervention to determine the effects of NSE. Improvements in gait function were also evaluated using Timed Up and Go test scores. Mixed-effect models with repeated measures (group × time) (analysis of variance, F test) were used to test the effects of NSE. Adjustments were made for covariates including age and sex (analysis of covariance).

Results: The NSE group showed significant improvement in cognitive performance (6.8% change; total Touch-M score 5.4 points; P = .04) and gait performance (11.5% change; Timed Up and Go time −0.98 second; P < .001) over the 8-week period. In the control group, there was no significant improvement.

Conclusions: This study shows that dual-task NSE is capable of improving cognitive and gait performance in healthy older adults. Our results indicate that NSE offers an option for a large segment of the older population who need an easier way to maintain their cognitive health and gait function.

Supplemental Digital Content is Available in the Text.

1Department of Public Health, School of Medicine, Sapporo Medical University, Sapporo, Japan.

2Hokkaido University of Education, Kushiro Campus, Hokkaido, Japan.

Address correspondence to: Kazutoshi Kitazawa, PhD, Department of Public Health, School of Medicine, Sapporo Medical University, Minami 1, Nishi 17, Chuo-ku, Sapporo, Hokkaido 060-8556, Japan (kkitazawa@sapmed.ac.jp).

This work was supported by a Grant-in-Aid for Scientific Research© from the Ministry of Education, Culture, Sports, Science and Technology (KAKENHI 22530598) and a grant from Hokkaido Kenko-zukuri Zaidan in 2009-2010.

The authors declare no conflicts of interest.

Supplemental digital contents are available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (www.jgpt.org).

Bernadette Williams-York was the Decision Editor.

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INTRODUCTION

Physical activity has a beneficial effect on cognitive and gait function and has been shown to reduce the risks of dementia and falls in older adults.1–3 Indeed, there are some physical activity guidelines for older adults, for example, to participate in moderate-intensity aerobic activity for at least 150 minutes over the week to promote their health benefits and prevent disease.4,5

However, for much of the older adult population, including many with deteriorating cognitive health, performing this amount of exercise is not easy.6 Indeed, Kruger et al7 found that among 160 randomized controlled trials conducted between 1980 and 2005, none of the frail, older adults completed the prescribed amount of physical activity.

There is a clear need to identify types and levels of physical activity that are suitable for the majority of older people to improve their cognitive and gait function.8 This demand has prompted efforts to identify exercises that require less physical strength and frequency while still offering cognitive health benefits.

One promising solution is to use dual-task exercises (ie, tasks that require the simultaneous use of cognitive and gait functions).9 Recent dual-task studies suggest that walking and other motor functions require higher-level cognitive function.10,11 Applying this principle, Verghese et al9 reported improvement in mobility among patients completing cognitive remediation processes. Li et al12 observed improvement in both cognitive and motor functions such as gait and body-sway balance in older adults who underwent nonmotor cognitive dual-task training.

Our goal was to devise a new type of physical exercise program that was easier than previously studied regimens and still offered the benefits of improved physical and cognitive function. To do so, we focused on the dual-task principle and developed a dual-task net-step exercise (NSE). The NSE uses a net and features slow and low-impact physical movement. The NSE requires approximately 200 steps per session and is completed only once per week. The present study aimed to assess the effect of a novel dual-task NSE performed once a week for 8 consecutive weeks on improvements primarily in cognitive performance and secondarily in gait function and quality of life (QOL) in an older population.

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METHODS

Study Design and Participants

A randomized single-blind controlled trial, pre-/posttest experimental case control study was used to evaluate the effect of the dual-task NSE on cognitive and gait function in older adults. Participants included volunteers from the Federation of Senior Citizen's Club in Kushiro city, Hokkaido Prefecture, Japan. These individuals were informed of the nature and purpose of the study. Individuals who met the inclusion criteria and consented to the terms of the study were invited to our research office and enrolled in the 8-week-long experiment.

The inclusion criteria were as follows: (1) at least 70 years of age; (2) be independent and healthy; (3) able (by self report) to walk at their own normal speed for more than 10 minutes without sitting or using an assistive device; (4) not experienced NSE in the past 6 months; and (5) free of severe heart failure. In addition, to exclude individuals with dementia or other cognitive and physical impairments, the participants had to possess a driver's license and drive more than once a week. In Japan, driver's license holders older than 70 years must pass an official government screening test for dementia, eyesight, and motor skills every 3 years.

A priori power analysis was not conducted in this study. The number of participants was determined to be the maximum under realistic conditions to safely complete the 8-week intervention protocol and assessments. In total, 74 volunteered for this study and 14 were excluded because they met the exclusion criterion, did not meet the age criteria, or did not have a driver's license. Thus, 60 participants between the ages of 71 and 89 years who met the inclusion criteria were enrolled in the study. The study participants did not receive any monetary compensation but were provided transportation to attend all sessions and assessments. The institutional review board of the medical ethics committee of Sapporo Medical University approved this study. To avoid selection bias, participants were divided into the NSE and control groups using a lottery. The control group participants were informed that they were on a wait-list for participation in future studies at our laboratory.

The control group participants were asked to retain their habits or lifestyle throughout the study period. Questionnaires regarding daily exercise, food, and medication schedules were administered to the control group to confirm that their individual habits did not change during the study period.

All participants in the NSE and control groups completed all sessions and assessments without any dropouts.

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Intervention Protocol

To avoid irregularity in exercise instruction and to ensure consistency in the level of NSE, the step designs for the entire 8-week NSE program were thoroughly described in code, as shown in the Appendix (see Supplemental Digital Content 1, http://links.lww.com/JGPT/A3). The written program was provided to all instructors. In addition, the 8-week NSE program was conducted at the same time and day of the week, and in the same room of the Hokkaido University of Education Kushiro Campus, for all members of the intervention group. To prepare for the program, 6-hour lectures were administered. The nonprofit community health organization in Hokkaido provided 6-hour lectures for safe and correct NSE instruction and NSE accreditation to the 10 volunteer instructors in this study. The instructors were required to follow the NSE program rigorously and conduct sessions once a week for 60 minutes without deviating from the protocol.

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Intervention Method: Dual-Task NSE

The newly developed dual-task NSE uses a net, Fumanet, the name of which is derived from “net” and “fumanai,” which in Japanese means “to avoid stepping on something.” The Fumanet is a 4 m × 1.5 m net that comprises 50 cm × 50 cm squares arranged in a 3 × 8 grid (Figure 1). The columns are labeled A, B, and C, and the rows are numbered 1 to 8 such that each of the 24 squares is assigned a unique coordinate (A1 through C8) (Figure 2). The dual-task NSE was conducted with groups of approximately 10 people each. One or 2 people at a time were required to walk carefully, but rhythmically from one end of the Fumanet to the other without stepping on the ropes or being caught in the net. Participants waiting for their turn remained seated in chairs around the Fumanet (Figure 1).

Figure 1

Figure 1

Figure 2

Figure 2

Many different net-step designs are possible and were employed during the study, each with specific instructions regarding the placement and use of the participants' feet (left vs right), number of steps, and grid order. Figure 2 shows a step design, One Two Three step, used on the third day of the 8-week NSE program. For this step design, participants had to perform 3 steps and 1 hand clap per square, as indicated by the feet and circles, respectively (see Video, Supplemental Digital Content 2, http://links.lww.com/JGPT/A4, which demonstrates the One Two Three step design). Illustrations of these step designs (Figure 2) were provided only to instructors, who demonstrated the step designs to the participants. All participants were required to repeat the step designs in exactly the same way as their instructors.

Every session of the 8-week NSE program consisted of 3 stages. The first was the warm-up step, conducted at the beginning of each session to assess the participants' physical condition. The second was the trial step, where participants learned the new step design to be performed during that session. The participants had to memorize each step design on the basis of the instructor's demonstration. After the demonstration, the participants practiced each step design twice. The instructors tried to encourage the participants, never mentioning their mistakes. Most participants showed improvement during the trial step, even if they made a mistake or tread on the net in the first trial. The third stage was the recreation step. The participants formed a line and step in the same rhythm while singing a children's song. They had to watch their steps and move in synchrony with the other participants while singing the song. The total time for actual walking by each participant was approximately 30 minutes in each session.

Throughout the 8-week NSE program, the difficulty of the step designs and the number of steps required in each session were gradually increased. Participants walked 216 steps per session during the first 4 weeks of the program and 240 steps per session from the fifth to eighth weeks (see Appendix, Supplemental Digital Content 1, http://links.lww.com/JGPT/A3, which shows the schedule of step designs used in the program).

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Measurements

Cognitive function, gait and balance function, and QOL assessments were performed at baseline (before the intervention period), and after the 8-week intervention period. To prevent potential bias and ensure that the study was single-blind, the staff responsible for data collection were blinded to the information about the groups to which the participants belonged.

Cognitive assessment was conducted using 2 touch panel computer screen devices: a Touch-M system and a Touch Panel-Type Dementia Assessment Scale (TDAS). The Timed Up and Go (TUG) test was used to measure gait function and balance (propensity to fall). The Medical Outcome Study Short Form-8 (SF-8) was used to assess changes in the participants' QOL.

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Assessment of Cognitive Function

To reduce error or dispersion of subjective judgments, cognitive function in this study was assessed using 2 computer-based assessments: Touch-M and TDAS.

The Touch-M system evaluates visuospatial function in the lateral prefrontal area to assess cognitive function and diagnose early stages of Alzheimer disease. Hatakeyama et al13 reported that this system has 100% specificity and 75.9% sensitivity in the diagnosis of Alzheimer disease. The Touch-M system also shows a significant correlation with the Mini Mental State Examination (r = 0.53; P < .001).13

The Touch-M system runs on the Microsoft Windows Operation system and a touch-panel-type desktop PC. It employs single-color stimulation in a visuospatial task. Blue color signals are presented in a random order within the cells on the touch panel display, which is divided into 2, 3, 4, 5, or 6 cells, either vertically or horizontally. Subjects are instructed to memorize the sequence and location of signals in a series and reproduce the sequence by touching the cells on the display. The participants were scored on a 100-point scale, with 100 being the best possible score.

The TDAS is a modification of the Alzheimer's Disease Assessment Scale14 and its subscale, the Alzheimer's Disease Assessment Scale-Cognitive subscale,15 which is widely used to measure decline in cognitive function. The TDAS also runs on the Microsoft Windows Operation system and touch-panel-type desktop PC and shows a high correlation with the Alzheimer's Disease Assessment Scale-Cognitive subscale (r = 0.69; P < .001).16 The TDAS measures the level of cognitive decline using questions that test word recognition, one's ability to follow commands, visuospatial perception, accuracy of the order of a process, naming fingers, money calculations, orientation, object recognition, and clock time recognition. The accuracy of the order of a process examines whether the subject can recognize the process of writing a letter through to posting it. Naming finger examines whether the subject can remember the name of the finger correctly. Orientation examines the subject's identification of the year, month, day, and day of the week. In the TDAS, decreasing scores indicate improvements in cognitive function, with zero as the best possible score.

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Balance and Propensity to Fall

The TUG test was used to assess the participants' gait and balance function at baseline and 8-week follow-up.17 The relative reliability of the TUG test between test sessions reached 0.92 (95% confidence interval, 0.85-0.95).18 The TUG test also shows a high correlation with the Berg Balance Scale (r = −0.81), gait speed (r = −0.61), and Barthel index of activities of daily living (r = −0.78)19.

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QOL Assessment

We assessed the participants' QOL using composite scores from the SF-8 health survey. This form has a population norm of 50 points, with lower scores indicating worsening QOL. In this study, physical component summary scores (PCS) and mental component summary scores (MCS) were used. The SF-8 evaluates changes in subjective health perception and is useful for estimating the effectiveness of medical intervention from the subject's viewpoint.20 We focused on only 2 scores from this survey, the PCS and MCS, to evaluate changes in participants' QOL during the experimental period. The relative reliability of the PCS and MCS is 0.77 and 0.73, respectively.20 The relative validity of the PCS and MCS is 0.82 (P < .001) and 0.03, respectively.20

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Statistical Analysis

The data were analyzed using SPSS 21.0 for Windows. For baseline comparison between the NSE and control groups, the Pearson method was used to analyze categorical data (sex). For normally distributed variables, t tests were used to analyze basic characteristics between the 2 groups.

The repeated-measures procedure was used in an analysis of covariance (ANCOVA). The 2 time points (baseline and 8-week) were treated as a within-participant factor (effect over time). The difference between the NSE and control groups was treated as a between-participant factor. Covariates, such as age and sex, were included in the multivariate model. All statistical tests were 2-sided, and P ≤ .05 was considered statistically significant.

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RESULTS

Participants' Characteristics at Baseline

Table 1 shows the participants' baseline characteristics. The mean age did not differ (t test, P = .22) between the NSE group (76.8 ± 4.4 years) and the control group (75.5 ± 3.7 years). The sex ratios of the 2 groups showed a difference. Thirteen (43.3%) participants in the NSE group and 20 (66.7%) participants in the control group were female, but this difference was not significant (P = .07).

Table 1

Table 1

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Effect of the NSE on Gait and Cognitive Performance

Table 2 shows the mean difference from the baseline in the TUG test, cognitive test scores, and QOL over 8 weeks by group. The results from the repeated-measures ANCOVA showed a significant effect for the within-participant interaction in the TUG test (P < .001). The time in the TUG test significantly improved (by 0.98 second, 11.5%; P < .001) in the NSE group relative to the baseline assessment. The TUG times of the control group significantly deteriorated (by 0.4 second, 0.05%; P < .02) relative to the baseline.

Table 2

Table 2

The mean difference from baseline in the Touch-M cognitive test score was 4.9 times higher in the NSE group than in the control group (ANCOVA, P = .04). The total score of the Touch-M significantly improved by 5.4 points (6.8%; P = .04) from the baseline in the NSE group.

Because the participants scored almost full marks at the baseline assessment on 7 of the 9 items of the TDAS, significant differences between participants and within participants were not observed in these items. Naming fingers improved significantly in the control group. Accuracy of the order of a process showed a significant difference between participants.

Neither group experienced a significant change in QOL, indicating that the participants' physical and mental health condition remained constant during the course of the program.

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DISCUSSION

The present study results demonstrate that NSE may have a positive influence on gait and cognitive performance in older adults. In our study, the cognitive performance of participants in the NSE group improved by more than 4.9-fold relative to that of the control group participants in terms of the mean difference from baseline in the total Touch-M score. The gait performance of participants in the NSE group showed a significant improvement from the baseline in the time required for the TUG test. Although this study has limitations, these results suggest that the NSE program has potential applications for maintaining or improving gait and cognitive function in the older population. In contrast, significant deterioration of gait performance was observed in the control group. Although the degree of this deterioration (0.05%) was not clinically significant, the decline seemed to result from the inactivity of the control group relative to the NSE group, and it reflected the natural transformation of gait and physical performance in older populations.21

Cognitive performance improved significantly after 8 weeks of NSE. This finding is consistent with previous research, which suggests that physical activity can improve cognitive function in older adults.2,3,22 The NSE group also showed improvement in gait and balance function. These results are consistent with research suggesting that cognitive function is an indicator of gait and balance function.12,23 Gait is no longer considered to be merely an automated motor activity; rather, it is understood to involve a higher level of cognitive function.24 Accordingly, studies that have reported improvements in gait in older adults after a dual-task intervention also observed improvements in cognitive function.9,12 Multifaceted neuropsychological influences on walking and interactions with mobility control are increasingly reported in studies of dual-task exercise25 and emphasize the link between cognitive and motor functions.26,27

A novel finding of this study is that by using dual-task NSE, it is possible to reduce the duration and frequency of physical activity required to particularly improve the cognitive and gait performance for older adults. To promote cardiovascular function and maintain health, older adults are recommended to participate in moderate-intensity aerobic activity for at least 30 minutes on 5 days of the week, or vigorous aerobic activity for at least 20 minutes on 3 days of the week.4,5 The dual-task NSE, which primarily focuses on the cognitive health, offers an easier type of physical activity that employs complex cognitive tasks requiring attention and concentration. For example, when participants try to avoid stepping on a net, they must keep their attention on both the net and their feet. They must also remember the step design correctly and reproduce it exactly. They have to simultaneously concentrate on clapping their hands and completing the step design. These cognitive tasks indicate NSE as a new type of physical exercise. In addition, because the step design is changed every time, NSE enables fresh cognitive tasks to be performed each time. Although many cognitive tasks have been attempted in dual-task studies previously, most of them, for example, subtracting 7s10 or talking while walking,28 seemed easier than NSE and monotonous. We believe that NSE requires a higher level of coordination, and because the step design is changed every time, participants are less likely to become bored with the exercise.

In addition to these components of cognitive tasks, NSE offers the benefits associated with other dual-task exercises. For example, Erickson et al29 observed a correlation between the activation of brain regions involved in dual-task performance and improved performance on the task. Bherer et al30 suggested that dual-task skills can be substantially improved in older adults and that cognitive plasticity in attention control is still possible in old age. The brain regions involved in attention control and task coordination during dual-task processing have been investigated using functional magnetic resonance imaging and positron emission tomography. These studies demonstrate the possible physiological basis underlying improvements in cognitive function by dual-task performance. In addition, Low et al31 proposed that the dorsolateral prefrontal cortex is important for executive function and dual-task performance. Specifically, they postulated that different task processing streams are represented in different processing units within this region, with attention control being implemented through the differential activation of the units associated with each processing stream. According to this view, they suggested that dual-task conditions involve the selective activation and inhibition of different units within the dorsolateral prefrontal cortex.31

Possible evidence for Low's hypothesis may be observed in the NSE participants. When the participants were practicing NSE, they would miss the hand clapping if they were concentrating on stepping over the net. However, if the participants were concentrating on hand clapping, their feet would stop involuntarily and they would step incorrectly. Consequently, the NSE participants had to simultaneously pay attention to hand clapping, stepping in the right square, and watching the net to perform the exercise correctly. Dux et al32 found that improvement in dual-task performance is achieved by increasing the speed of information processing in the brain region, thereby allowing multiple tasks to be processed in rapid succession. The improved cognitive function observed here is likely a result of these various dual-task influences on the brain.

Our results demonstrate that a dual-task NSE is able to improve gait and cognitive performance in a group of apparently healthy, community-dwelling, older adults. The frequency and intensity (ie, once in a week and <300 steps per session) of NSE may make physical activity easier for older adults. Accordingly, NSE offers an option for the older adults who may want to participate in physical activity to gain improvement of cognitive and gait function.

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Study Limitations

This study has some limitations. First, we focused on the effects of NSE on gait and cognitive function but did not evaluate carryover effects. It would be helpful to know whether the beneficial effects of NSE persist by conducting several follow-up assessments. In addition, a randomized control trial with a double-blind study design was not possible, as it was necessary for the participants to know whether they belonged to the intervention or control group. Further research is necessary to compare the dual-task NSE group and a single-task, walking group.

Another limitation of the study is that the physical activity/inactivity and social activity of the participants were not controlled or monitored. In addition, NSE is a group therapy during which the participants can talk to and encourage each other. This social interaction may have psychological influences on the participants. Thus, further research is needed to evaluate both the influence of physical activities in daily life outside of the intervention and psychological influences in participants who perform NSE.

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CONCLUSIONS

This study shows that dual-task NSE is capable of improving cognitive and gait performance in healthy older adults. Our results indicate that NSE offers an option for a large segment of the older population who need an easier way to maintain their cognitive health and gait function.

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ACKNOWLEDGMENTS

We thank the dedicated staff at the nonprofit organization for community health in Hokkaido and the volunteers who shared their lives and experiences with us.

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Keywords:

dementia prevention; executive function; older adults; physical exercise

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