The interacting effect of cognitive and motor task demands on performance of gait, balance and cognition in young adults

doi:10.1016/j.gaitpost.2013.02.004

Gait & Posture

Volume 38, Issue 4, September 2013, Pages 596-602

https://doi.org/10.1016/j.gaitpost.2013.02.004 Get rights and content

Abstract

Mobility limitations and cognitive impairments, each common with aging, reduce levels of physical and mental activity, are prognostic of future adverse health events, and are associated with an increased fall risk. The purpose of this study was to examine whether divided attention during walking at a constant speed would decrease locomotor rhythm, stability, and cognitive performance. Young healthy participants (n = 20) performed a visuo-spatial cognitive task in sitting and while treadmill walking at 2 speeds (0.7 and 1.0 m/s).Treadmill speed had a significant effect on temporal gait variables and ML-COP excursion. Cognitive load did not have a significant effect on average temporal gait variables or COP excursion, but variation of gait variables increased during dual-task walking. ML and AP trunk motion was found to decrease during dual-task walking. There was a significant decrease in cognitive performance (success rate, response time and movement time) while walking, but no effect due to treadmill speed. In conclusion walking speed is an important variable to be controlled in studies that are designed to examine effects of concurrent cognitive tasks on locomotor rhythm, pacing and stability. Divided attention during walking at a constant speed did result in decreased performance of a visuo-spatial cognitive task and an increased variability in locomotor rhythm.

Highlights

► Effects of DT walking at constant speed on gait variables, stability and cognition. ► Average temporal gait variables or COP excursion were not affected by DT walking. ► Variation of temporal gait variables increased during DT walking. ► Trunk motion was found to decrease during DT walking. ► Cognitive performance decreased during DT walking.

Introduction

Successful aging has become one of the most important aspects of health care in the 21st century. As people live longer risks of cumulative illness, chronic disability increase [1], [2]. Mobility limitations and cognitive impairments, both common with aging, reduce levels of physical and mental activity, are prognostic of future adverse health events, and are associated with an increased fall risk [2]. Importantly, the link between cognitive impairment, mobility limitations and the tendency to falls is recognized in the literature [3].

Maintaining stability during walking through the environment is a complex, multi-dimensional process requiring higher level motor control, and cognitive flexibility to address balance threats, while attending to environmental demands and concurrent cognitive tasks [2]. A key factor in locomotor control is executive cognitive functioning and deficits are associated with increased risk of falling [3], [4]. Various dual task (DT) studies have affirmed that difficulty in assigning attention to each task simultaneously may contribute significantly to increased fall risks. Poor DT performance in either the motor or cognitive task could be caused by altered prioritization between the two tasks [5]. The most common and consistent finding of DT studies has been the reduction of gait speed [3], likely as a strategy for concurrent task processing or to avoid stability threat. Reduced speed is commonly observed in elderly, and when negotiating obstacles, irregular or unpredictable terrain [6].

Dual-task studies have utilized cognitive tasks, like animal enumeration or number subtraction that are typically only assessed qualitatively, do not involve the visuomotor system and are limited in recruitment of individual brain areas. Visual–spatial processing of object locations/motions and their spatial relations with respect to body and space are key aspects of balance and locomotor skills, and evidence supports visual–spatial processing as an important aspect of cognition to explore in mobility decline [7], [8].

Virtual environments, viewed during treadmill walking, have been used as an ecological approach to rehabilitation [9]. Computerized cognitive tasks and games have received interest from researchers and clinicians, both as a model for learning a broad range of cognitive tasks and as a means to examine training and transfer of skills to daily life activities [10], [11], [12]. A treadmill rehabilitation platform (TRP) was designed around a treadmill as it is an excellent choice for conducting gait training with dual-tasks. It can incorporate walking skills while interacting with computer-generated cognitive activities viewed on a standard LCD display [9]. DT treadmill walking has important advantages versus over ground walking as gait variables are significantly influenced by walking speed [13], [14] and reduced gait speed is a highly consistent strategy used during dual-task over-ground walking [3]. It is a convenient method to determine steady-state walking speed. It also allows gathering hundreds of consecutive steps in a few minutes. Data from 5–10 strides (i.e. in gait laboratories or during repeated walks over short, instrumented walkways) may reliably measure gait speed, but is not sufficient for measures of gait variability or periodicity, particularly during dual task walking and for older adults with mobility limitations [15], [16].

The purpose of this study was to further explore the interplay between cognitive and walking demands on task performance. Since previous studies have shown that gait speed is an important factor affecting gait parameters, the treadmill speed is held constant to prevent a strategy of slowing walking speed. The first objective was to evaluate the effect of walking speed on temporal gait parameters and measures of walking stability, amplitude and variation of center of foot pressure (COP) displacements and trunk motion. The objective was to examine whether divided attention during walking at a constant speed would decrease locomotor rhythm, stability, and cognitive performance. This study addresses three hypotheses:

(1)
Walking speed has a significant effect on temporal gait variables, and measures representing walking stability.
(2)
Stability, locomotor, and cognitive performance will significantly decline from single task to DT conditions during constant speed.
(3)
Cognitive performance will decline with increasing treadmill speed.

Section snippets

Methods

Twenty healthy young adults aged 20–30 years (mean age 26.3 ± 3.2 years) participated. Participants were excluded if they had past neurological impairment, musculoskeletal disorder or were taking medications that may have influenced their walking.

Instrumentation and data recording

Fig. 1 illustrates the experimental set-up. Participants were positioned on the treadmill 100 cm from the 30-inch monitor connected to a computer running the cognitive game. Vertical foot contact pressures were recorded from each foot using in-shoe pressure insoles. (Vista Medical Ltd, WPG. MB). The pressure insoles each consist of an array of 128 piezo-resistive sensors, calibrated to 300 mm Hg (12-bit). Pressure signals from left and right insoles were recorded at 35 Hz. The 3D Track STAR

Cognitive game task

Studies have used computer-based games to probe and evaluate cognitive function [11]. The Useful Field of View (UFOV) is a computer-based test that requires the ability to select relevant information and ignore irrelevant information (cognitive inhibition) [19]. Studies have found that older adults with slower cognitive speed of processing, as measured by the UFOV test, experienced the greatest mobility loss [20]. A modified version of the UFOV has been designed to evaluate visual–spatial

Protocol

Participants played the computer game using a standard optical mouse for 2 min in sitting to familiarize themselves with the cognitive task. The viewing height of the display during sitting and walking was maintained by placing an adjustable stool on the treadmill. A rest period of 2–3 min was given between test conditions. Participants walked on a level treadmill for 10 min at 0.7 m/s for treadmill acclimation. During testing, participants walked for 2 min at two treadmill speeds; 0.7 m/s (lower

Data analysis

Custom built scripts in MATLAB version 7.1 (The Math Works, Natick, MA) processed the pressure data of each insole array into footfall patterns. Time indices were computed for pressure onset and offset, stance and swing phases for each right and left step, and double support times. The average and coefficient of variation (COV) of stance time (ST), swing time (SW), and double support time (DS) were computed for each walk trial (45 steps per leg). These gait variables have been identified based

Statistical analysis

A two-way repeated measures ANOVA was used to determine the effects of treadmill speed and cognitive load (single vs. DT conditions) on temporal gait variables, COP and trunk excursion measures, and cognitive performance measures. The significance level was set at alpha level of 0.5.

Results

Group means and standard error of means (SEM) for average and COV of ST, SW, and DS are presented in Fig. 3. There was no significant difference in gait variables (average or COV) between left and right steps and therefore only results of analysis of right steps is presented in Table A1 (Appendix A). Average and COV of ST, SW and DS significantly decreased as a function of walking speed (p < 0.01). There was no significant effect of cognitive load for walk only versus DT walking on average ST,

Discussion

Treadmill speed had a significant effect on temporal gait variables (average and COV) in keeping with previous studies. The present results are consistent with Jordan et al. [13] and Kang and Dingwell [27] who observed a decrease in gait variability with increased walking speed. Measures of variability provide a perspective on the consistency of locomotor rhythm, and are often reported to represent walking stability. This view is supported by the present findings wherein the magnitude and

Funding

None.

Conflict of interest

There is no conflict of interest.

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Maintaining dynamic balance is an essential task during walking, with foot-placement playing a critical role. Dual-task studies analyzing steady-state walking with cognitive loads have found healthy adults prioritize cognitive task performance at the expense of maintaining control of their balance. However, few studies have focused on the influence of cognitive loads on more difficult motor tasks, such as walking with unexpected foot-placement perturbations. Individuals often recover from a loss of balance using an ankle or hip strategy; however, how cognitive loads affect these balance recovery strategies remains unknown.
How do individuals prioritize cognitive resources and does the balance recovery strategy used change following mediolateral foot-placement perturbations during steady-state walking when performing cognitive tasks of increasing difficulty?
Fifteen young healthy adults walked during unperturbed and perturbed conditions with increasing cognitive loads (no cognitive load, attentive listening, spelling short words backwards and spelling long words backwards). No specific task-prioritization instructions were given. Medial and lateral foot-placement perturbations were applied prior to heel-strike during random steps.
Cognitive performance decreased between the unperturbed and perturbed conditions. While balance control decreased during perturbed relative to unperturbed walking, the additional cognitive load had little effect on balance control during the perturbations. Lastly, the balance recovery strategy used, as measured by peak joint moments at the ankle and hip, was unaffected by the additional cognitive loads.
Individuals appear to prioritize their balance control over cognitive performance when experiencing foot-placement perturbations and do not change their balance recovery strategy with the addition of a cognitive load. These results highlight the flexibility of task-prioritization in young adults and provide a foundation for future studies analyzing neurologically impaired populations.
Effects of cognitive workload on heart and locomotor rhythms coupling
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Different physiological signals could be coupled under specific conditions, in some cases related to pathologies or reductions in system complexity. Cardiac-locomotor synchronization (CLS) has been one of the most investigating coupling. The influence of a cognitive task on walking was investigated in dual-task experiments, but how different cognitive tasks may influence CLS has poorly been investigated. Twenty healthy subjects performed a dual-task walking (coupled with verbal fluency vs calculation) on a treadmill at three different speeds (comfortable speed CS; fast-speed: CS + 2 km/h; slow-speed: CS-2 km/h) while cardiac and walking rhythms were recorded using surface electrodes and a triaxial accelerometer, respectively.
According to previous studies, we found a cognitive-motor interference for which cognitive performance was affected by motor exercise, but not vice-versa. We found a CLS at the baseline condition, at fast speed in both cognitive tasks, while at comfortable speed only for the verbal fluency task.
In conclusion, the cardiac and locomotor rhythms were not coupled at slow speed and at comfortable speed during subtraction task. Cognitive performances generally increased at faster speed, when cardiac locomotor coupling was stronger.
The influence of cognitive load on balance control during steady-state walking
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Citation Excerpt :
Walking performance has not necessarily been shown to take priority over cognitive performance, as some have observed successfully executed cognitive tasks at the expense of poorer gait performance (Plummer-D’Amato et al., 2008; Yogev-Seligmann et al., 2012), while others have seen a prioritization of gait performance (Hinton et al., 2020; Mersmann et al., 2013). The majority of DT studies have focused on gait speed as the primary outcome measure (Al-Yahya et al., 2011), with few studies focusing on balance control (e.g., Siragy and Nantel, 2020; Szturm et al., 2013; Tisserand et al., 2018). Whole-body angular momentum (H), which is a mechanics-based measure relating the linear and angular momenta of the body segments, must be tightly regulated in order to maintain dynamic balance during walking, and thus provides a useful measure of balance control that has been used to investigate a number of populations and walking tasks (Neptune and Vistamehr, 2019).
For an individual to successfully walk, they must maintain control of their dynamic balance. However, situations that require increased cognitive attention may impair an individual’s ability to actively control their balance. While dual-task studies have analyzed walking-while-talking conditions, few studies have focused specifically on the influence of cognitive load on balance control. The purpose of this study was to assess how individuals prioritize their cognitive resources and control dynamic balance during dual-task conditions of varying difficulty. Young healthy adults (n = 15) performed two single-task conditions (spelling-while-standing and treadmill walking with no cognitive load) and three dual-task conditions (treadmill walking with increasing cognitive load: attentive listening and spelling short and long words backwards). Cognitive performance did not change between the single- and dual-task as measured by spelling percent error and response rate (p = 0.300). Balance control, assessed using the range of whole-body angular momentum, did not change between the no load and listening conditions, but decreased during the short and long spelling conditions (p < 0.001). These results highlight that in young adults balance control decreases during dual-task treadmill walking with increased cognitive loads, but their cognitive performance does not change. The decrease in balance control suggests that participants prioritized cognitive performance over balance control during these dual-task walking conditions. This work offers additional insight into the automaticity of walking and task-prioritization in healthy young individuals and provides the basis for future studies to determine differences in neurologically impaired populations.
The Effect Of Visual Dual-Tasking Interference On Walking In Healthy Young Adults
2020, Gait and Posture
Citation Excerpt :
Gait stability is defined as maintaining the position of the body’s centre of mass(CoM) within the supporting surface without falling [11]. We defined gait stability as the ability to maintain mediolateral(ML) CoM displacement within a limited, dynamic trajectory whilst maintaining upright posture, so increasing ML COM reflects less stable gait while dual-tasking [13,14,15]. Previous studies investigating the effect of dual-task costs on the ML CoM displacement [13] and the ML trunk displacement [14] during walking showed significant increases in healthy adults.
Visual dual-task skills are essential for stable ambulation in everyday life such as walking while reading text. Gait analysis in a virtual environment can provide insight into altered walking performance while visual dual-tasking.
How visual dual-tasking including cognitive load of reading text and altered optical flow influences walking speed and stability in healthy adults? Also, is there a relationship between the mediolateral centre of mass(CoM) displacement and mediolateral trunk movement?
Nineteen able-bodied young adults performed self-selected walking on a treadmill in a virtual environment under the following three conditions; single-task walking, walking while viewing scrolling lines, and walking while reading text scrolling on the screen. Three-dimensional motion analysis was used to measure the effect of dual-tasking on gait velocity, step length, mediolateral CoM displacement, and mediolateral thorax inclination.
The effect of visual dual-tasking showed significantly increased walking speed and longer step length compared to single-tasking. The cognitive load of reading text while walking had a significant impact on reduced step length variability and greater mediolateral CoM displacement. This was related to the mediolateral thorax inclination.
A visual dual-task influences gait through altered optical flow and a cognitive load effect. Altered optical flow increased walking speed whilst the visual attention to read text affected foot placement and upright trunk posture, together with greater mediolateral CoM displacement. Thus, dual-tasking of reading text in a virtual environment substantially affected walking stability in healthy young people. This paradigm is therefore useful for assessment of walking stability in daily life and in the clinical setting.
Dual-task prioritization during overground and treadmill walking in healthy adults
2020, Gait and Posture
Citation Excerpt :
However, it is not clear whether these results will also apply to populations in whom dual-task effects on walking are more profound, such as in older adults or clinical populations [25]. It is also not clear whether these effects generalize to other dual-tasks, such visual attention tasks, which have previously been shown to exert dual-task effects on treadmill walking in healthy adults [26]. Examination of the role of task, and the difference between modalities in other populations, may provide insight into the factors which contribute the dual-task effect on walking.
The dual-task effect on walking performance is different during treadmill and overground walking, though the cause of this difference is unknown. This study examined the effects of task prioritization on overground and treadmill dual-task walking.
Twenty-two adults walked overground and on a treadmill under three dual-task conditions: prioritization of walking performance, prioritization of cognitive performance (serial subtraction in sevens), or no prioritization.
Compared to single-task walking, stride velocity was reduced and stride time variability was increased during dual-task overground walking. During treadmill walking, there was no dual-task effect on walking performance, but cognitive task performance was improved. Prioritization of the cognitive task reduced the dual-task effect on stride velocity during overground walking only, whilst prioritization of the walking task reduced cognitive task performance in both walking modalities.
These results corroborate recent findings that the dual-task effects on treadmill walking are not equivalent to those on overground walking. Healthy adults appear to prioritize cognitive task performance during treadmill dual-task walking without detrimental effects to gait. During overground walking however, allocation of attention to the secondary task reduces gait performance. These results indicate that treadmill based dual-task paradigms should not be used to infer factors which influence the cognitive control of overground walking.
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2019, Human Movement Science
Fluctuations in cyclic tasks periods is a known characteristic of human motor control. Specifically, long-range fractal fluctuations have been evidenced in the temporal structure of these variations in human locomotion and thought to be the outcome of a multicomponent physiologic system in which control is distributed across intricate cortical, spinal and neuromuscular regulation loops.
Combined with long-range correlation analyses, short-range autocorrelations have proven their use to describe control distribution across central and motor components.
We used relevant tools to characterize long- and short-range correlations in revolution time series during cycling on an ergometer in 19 healthy young adults. We evaluated the impact of introducing a cognitive task (PASAT) to assess the role of central structures in control organization.
Autocorrelation function and detrending fluctuation analysis (DFA) demonstrated the presence of fractal scaling. PSD in the short range revealed a singular behavior which cannot be explained by the usual models of even-based and emergent timing.
The main outcomes are that (1) timing in cycling is a fractal process, (2) this long-range fractal behavior increases in persistence with dual-task condition, which has not been previously observed, (3) short-range behavior is highly persistent and unaffected by dual-task.
Relying on the inertia of the oscillator may be a way to distribute more control to the periphery, thereby allocating less resources to central process and better managing additional cognitive demands. This original behavior in cycling may explain the high short-range persistence unaffected by dual-task, and the increase in long-range persistence with dual-task.

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The interacting effect of cognitive and motor task demands on performance of gait, balance and cognition in young adults

Abstract

Highlights

Introduction

Section snippets

Methods

Instrumentation and data recording

Cognitive game task

Protocol

Data analysis

Statistical analysis

Results

Discussion

Funding

Conflict of interest

The American Journal of Geriatric Psychiatry

Neuroscience and Biobehavioral Reviews

Neuropsychologia

Gait & Posture

Neurophysiologie Clinique = Clinical Neurophysiology

Gait & Posture

Journal of Neuroscience Methods

Trends in Cognitive Sciences

Cognition

Gait & Posture

Human Movement Science

Gait & Posture

Gait & Posture

Journal of Biomechanics

The lausanne cohort Lc65+: a population-based prospective study of the manifestations, determinants and outcomes of frailty

BMC Geriatrics