Residual attentional capacity amongst young and elderly during dual and triple task walking

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Abstract

Walking is considered an automatic function which demands little attentional resources. Thus a residual attentional capacity is available for a concurrent task (dual task). Minor age-related deficits in postural control may minimize the residual attentional capacity, however this may not be detected by a simple examination of the individuals gait performance. This study investigated the use of challenging dual task combinations to detect age related changes in gait performance. Eleven community-dwelling elderly (mean age 76 years) and 13 young subjects (mean age 26 years) participated in the study. The participants walked along a figure-of-eight track at a self-selected speed. The effect of introducing a concurrent cognitive task and a concurrent functional motor task was evaluated. Stride-to-stride variability was measured by heel contacts and by trunk accelerometry. In response to the cognitive task the elderly increased their temporal stride-to-stride variability by 39% in the walking task and by 57% in the combined motor task. These increases were significantly larger than observed for the young. Equivalent decreases in trunk acceleration autocorrelation coefficients and gait speed were found. A combination of sufficiently challenging motor tasks and concurrent cognitive tasks can reveal signs of limited residual attentional capacity during walking amongst the elderly.

Introduction

Recently, there has been a focus on the interaction between cognitive factors and motor performance when assessing the functional capacity of a patient (Huang & Mercer, 2001). Mulder and colleagues have argued that most tests which are used to assess physical performance allow the participants to compensate for their deficits by utilizing other control strategies (e.g., visual and/or cognitive regulation of task performance). To better detect deficits a dual task assessment can be used (Mulder, Zijlstra, & Geurts, 2002). Dual task paradigms are typically used to investigate the attentional demands of a motor task and to examine the effects of concurrent cognitive or motor tasks on motor performance (Fraizer and Mitra, in press, Schmidt and Lee, 2005). The latter approach is sometimes referred to as a divided attention or “time-sharing” paradigm (Huang & Mercer, 2001). When one task is more demanding a greater proportion of the performer’s limited processing capacity must be allocated to this task in order to maintain an acceptable level of performance (Huang & Mercer, 2001). As the central processing capacity is limited, a primary task with higher attention demands will leave less residual processing capacity for a concurrent secondary task. An additional concurrent attention-demanding cognitive task or motor task may therefore exceed the available resource capacity. Dual task interference will only occur if the available central resource capacity is exceeded, resulting in impaired performance in one or both tasks (Abernethy, 1988). Dual task paradigms can be used to investigate the attentional demands on walking and to examine the effects of a concurrent cognitive or motor task on walking. The competition between the attention demands of walking and a concurrent attention-demanding task may result in gait alterations (Dubost et al., 2006).

Postural control is defined as the control of the body’s position in space to maintain balance and orientation (Shumway-Cook & Woollacott, 2001). Traditionally, maintenance of postural control has been considered automatic or reflex controlled, suggesting that control of posture requires minimal attention. However, recent research has shown that there are significant attention requirements for postural control which vary depending on the postural task, the age of the individual and his or her balance abilities (Woollacott & Shumway-Cook, 2002).

The organization of movement and postural control is developed through motor learning. Fitts and Posner articulated three stages of motor learning consisting of: a cognitive (verbal) stage, an associative stage (gradual decrease in errors; development of internal (sensory) reference of correctness), and an autonomous (automatic) stage (Shumway-Cook & Woollacott, 2001). The first stage requires conscious attention to each part of the movement whereas the third stage leaves attentional resources for other tasks. The movements related to the first stage become slow, cautious and uncertain compared to the more competent practice of the next stages.

Motor tasks which are well trained and not very demanding can be performed with little conscious attention which leaves a relatively large residual processing capacity. Maintenance of postural control during activities of daily living (e.g., walking) does not usually place high demands on attentional resources. In contrast, when sensory or motor deficits occur, the complex generation of movement may have to be restructured, and movements may then be controlled and performed at an associative or a cognitive stage. When the benefits from the movement automation are lost the postural control of the participant can be expected to be more vulnerable to cognitive distractions and additional tasks.

It may be expected that postural control changes with age due to age-related alterations in the brain, loss of muscle mass, and decreased perception of high frequency vibrations, touch, proprioception, and pressure stimuli (Kandel et al., 2000, Prince et al., 1997). Thus it is possible that the elderly require increased conscious attention to maintain postural control. However, impaired postural control may not be revealed in a standard examination in which the residual attentional capacity is not sufficiently challenged.

Walking is a very familiar and automated motor task to most people and the control of posture during this task will be expected to require little conscious attention. The quality of the gait performance is reflected in the stride-to-stride variability (Hausdorff, 2005, Hausdorff, 2007). When the walking pattern is planned and executed in a way so that no major corrections are needed the stride variability is low. Deficits in the postural control may disturb the planning and execution of the gait and this can lead to a walking pattern that needs postural adjustments revealed as increased stride-to-stride variability (Hausdorff, 2005). This approach to the assessment of gait performance has been investigated through many studies and good support has been found for its relevance (Hausdorff et al., 1999, Hausdorff et al., 2001).

An increase in gait variability, in response to a dual task, may be expected amongst elderly people. A study evaluating this hypothesis showed a significant effect for elderly fallers whereas elderly non-fallers were unaffected (Springer et al., 2006). This finding conflicts with other studies which do report increased stride variability amongst elderly in response to a dual task (Beauchet et al., 2003, Hollman et al., 2007). It is possible that the dual task combination in the first case may not have been sufficiently challenging to reveal deterioration in the postural control capacity of the elderly non-fallers.

Walking in a figure-of-eight has been shown to be a more challenging motor task than just walking in a straight path (Shkuratova, Morris, & Huxham, 2004). In the present study this task was used as the basic motor task in combination with either a cognitive task or a motor task in a dual task tests or in combination with both tasks in a triple task test.

The purpose of this study was to evaluate differences in the residual attentional capacity between healthy young and elderly persons. We hypothesized that the postural control of both young and elderly would be affected when a concurrent cognitive or motor task was added to the motor task of walking in a figure-of-eight. We expected that the motor planning and gait performance would be less successful and result in increased gait variability. In addition, we hypothesized that dual and triple task performance among elderly would be characterized by an increased relative change in gait variability (i.e., the postural control of the elderly would be more vulnerable to additional tasks). This finding would be consistent with the idea that the residual processing capacity is relatively smaller in elderly compared to young.

Section snippets

Participants

Eleven healthy community-dwelling elderly (mean age 76.4 years, SD: 5.0) and 13 young participants (mean age 25.6 years, SD: 2.0) were included in this study. There were four men in the group of young and one in the elderly group. Body mass index (BMI) was 22.5 (SD: 2.0) and 25.2 (SD: 4.4), respectively. Young adults were included if they were between the ages of 20 and 31 years and had no known disease or need for medication. Elderly adults older than 70 years were recruited from community

Participants’ characteristics

On the scales of physical activity (PASE), balance confidence (ABC), and self-estimated health the young had median (range) scores of 223 (183–341), 99 (97–100), and 10 (8–10), respectively, and the elderly had corresponding scores of 173 (140–271), 93 (56–99), and 8 (5–10). The elderly had a mean score of 7.6 (SD: 1.1) on the “Timed Up and Go test” (TUG).

Stride variance coefficient (Table 1 and Fig. 2)

A significant age effect, F(1, 22) = 7.3, p < .05, task effect, F(3, 22) = 10.9, p < .001, and Age × Task effect, F(3, 22) = 6.1, p < .01, were observed

Discussion

This study showed a higher relative increase in gait variability in response to increased attentional demands in the elderly compared to younger individuals. An age dependency of gait variability with concurrent tasks suggests that the elderly have a lower residual attentional capacity compared to the younger participants. This finding is in agreement with the initial hypothesis of this study. The observation that the elderly were more disturbed by the cognitive task compared to the young

Conclusion

The gait of both young participants and community-dwelling elderly participants between 70 and 80 years of age became slower and more variable when a concurrent cognitive task was performed while walking in a figure-of-eight. However, the gait characteristics of the elderly were more affected by a concurrent attention-demanding task. This suggests that the maintenance of postural control is more attention-demanding for the elderly. A combination of sufficiently challenging motor tasks and

Acknowledgements

The study was financially supported by Center for Clinical and Basic Research A/S (CCBR), The National Danish Research Foundation, Department of Health Science and Technology, Aalborg University and University College of Health, Aalborg.

Statistical assistance was provided by M. Hoejbjerre, Center for Health Statistics, Aalborg University.

References (35)

  • R. Moe-Nilssen et al.

    Interstride trunk acceleration variability but not step width variability can differentiate between fit and frail older adults

    Gait & Posture

    (2005)
  • T. Mulder et al.

    Assessment of motor recovery and decline

    Gait & Posture

    (2002)
  • F. Prince et al.

    Gait in the elderly

    Gait & Posture

    (1997)
  • N. Shkuratova et al.

    Effects of age on balance control during walking

    Archives of Physical Medicine and Rehabilitation

    (2004)
  • R.A. Washburn et al.

    The Physical Activity Scale for the Elderly (PASE): Development and evaluation

    Journal of Clinical Epidemiology

    (1993)
  • M. Woollacott et al.

    Attention and the control of posture and gait: A review of an emerging area of research

    Gait & Posture

    (2002)
  • B. Abernethy

    Dual-task methodology and motor skills research: Some applications and methodological constraints

    Journal of Human Movement Study

    (1988)
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