Using virtual reality simulation to study navigation in a complex environment as a functional-cognitive task; A pilot study.

BACKGROUND: Navigation skills are required for performance of functional complex tasks and may decline due to aging. Investigation of navigation skills should include measurement of cognitive-executive and motor aspects, which are part of complex tasks. OBJECTIVE: to compare young and older healthy adults in navigation within a simulated environment with and without a functional-cognitive task. METHODS: Ten young adults (25.6±4.3 years) and seven community dwelling older men (69.9±3.8 years) were tested during a single session. After training on a self-paced treadmill to navigate in a non-functional simulation, they performed the Virtual Multiple Errands Test (VMET) in a mall simulation. Outcome measures included cognitive-executive aspects of performance and gait parameters. RESULTS: Younger adults' performance of the VMET was more efficient (1.8±1.0) than older adults (5.3±2.7; p < 0.05) and faster (younger 478.1±141.5 s, older 867.6±393.5 s; p < 0.05). There were no differences between groups in gait parameters. Both groups walked slower in the mall simulation. CONCLUSIONS: The shopping simulation provided a paradigm to assess the interplay between motor and cognitive aspects involved in the efficient performance of a complex task. The study emphasized the role of the cognitive-executive aspect of task performance in healthy older adults.

A narrative review of texting as a visually-dependent cognitive-motor secondary task during locomotion.

Typing while walking is an example of people's ability to interact with technology while engaged in real life activities. Indeed, an increasing number of studies have investigated the typing of text messages (texting) as a dual task during locomotion. The objective of this review is to (1) describe the task requirements of texting-while-walking, (2) evaluate the measurement and psychometric properties of texting as a dual task, and (3) formulate methodological recommendations for researchers who use and report on texting-while-walking. Twenty studies which used texting as a dual task during gait were identified via a literature search. The majority of these studies examined texting among young healthy adults and showed that, like other dual tasks, texting-while-walking caused decrements in both gait and texting performance. The cause of these decrements was most likely related to increased visual task requirements, task-dependent cognitive requirements and fine motor skills. Texting-while-walking gait measures were repeatable, but texting performance showed poor reliability which further depended on skill. Preliminary results show that texting-while-walking performance may discriminate between populations (e.g., young vs. older adults) but no studies have yet examined its predictive validity (e.g., for fall risk). In conclusion, texting-while-walking is an ecologically-valid dual task for locomotion which has become much more commonly used in recent years. As opposed to other secondary tasks such as subtraction by 7 or generating words, texting may challenge various cognitive, visual and sensorimotor domains depending on its content. This imposes task-specific methodological challenges on future research, which are discussed.

Stability of gait and interlimb coordination in older adults.

Most falls in older adults occur when walking, specifically following a trip. This study investigated the short- and longer term responses of young (n = 24, 27.6 ± 4.5 yr) and older adults (n = 18, 69.1 ± 4.2 yr) to a trip during gait at comfortable speed and the role of interlimb coordination in recovery from tripping. Subjects walked on a self-paced treadmill when forward movement of their dominant leg was unexpectedly arrested for 250 ms. Recovery of center of mass (COM) movements and of double-support duration following perturbation was determined. In addition, the disruption and recovery of interlimb coordination of the arms and legs was evaluated. Although young and older subjects used similar lower limb strategies in response to the trip, older adults had less stable COM movement patterns before perturbation, had longer transient destabilization (>25%) after perturbation, required more gait cycles to recover double-support duration (older, 3.48 ± 0.7 cycles; young, 2.88 ± 0.4 cycles), and had larger phase shifts that persisted after perturbation (older, -83° to -90°; young, -39° to -42°). Older adults also had larger disruptions to interlimb coordination of the arms and legs. The timing of the initial disruption in coordination was correlated with the disturbance in gait stability only in young adults. In older adults, greater initial COM instability was related to greater longer term arm incoordination. These results suggest a relationship between interlimb coordination and gait stability, which may be associated with fall risk in older adults. Reduced coordination and gait stability suggest a need for stability-related functional training even in high-functioning older adults.

Age-related differences in lower-limb force-time relation during the push-off in rapid voluntary stepping.

BACKGROUND: This study investigated the force-time relationship during the push-off stage of a rapid voluntary step in young and older healthy adults, to study the assumption that when balance is lost a quick step may preserve stability. The ability to achieve peak propulsive force within a short time is critical for the performance of such a quick powerful step. We hypothesized that older adults would achieve peak force and power in significantly longer times compared to young people, particularly during the push-off preparatory phase. METHODS: Fifteen young and 15 older volunteers performed rapid forward steps while standing on a force platform. Absolute anteroposterior and body weight normalized vertical forces during the push-off in the preparation and swing phases were used to determine time to peak and peak force, and step power. Two-way analyses of variance ('Group' [young-older] by 'Phase' [preparation-swing]) were used to assess our hypothesis (P ≤ 0.05). FINDINGS: Older people exerted lower peak forces (anteroposterior and vertical) than young adults, but not necessarily lower peak power. More significantly, they showed a longer time to peak force, particularly in the vertical direction during the preparation phase. INTERPRETATIONS: Older adults generate propulsive forces slowly and reach lower magnitudes, mainly during step preparation. The time to achieve a peak force and power, rather than its actual magnitude, may account for failures in quickly performing a preventive action. Such delay may be associated with the inability to react and recruit muscles quickly. Thus, training elderly to step fast in response to relevant cues may be beneficial in the prevention of falls.

Cognitive load affects lower limb force-time relations during voluntary rapid stepping in healthy old and young adults.

BACKGROUND: Quick step execution may prevent falls when balance is lost; adding a concurrent task delays this function. We investigate whether push-off force-time relations during the execution of rapid voluntary stepping is affected by a secondary task in older and young adults. METHODS: Nineteen healthy older adults and 12 young adults performed rapid voluntary stepping under single- and dual-task conditions. Peak power, peak force, and time to peak force during preparatory and swing phases of stepping were extracted from center of pressure and ground reaction force data. RESULTS: For dual-task condition compared with single-task condition, older adults show a longer time to reach peak force during the preparation and swing phases compared with young adults (approximately 25% vs approximately 10%, respectively). Peak power and peak force were not affected by a concurrent attention-demanding task. CONCLUSION: Older adults have difficulty allocating sufficient attention for fast muscle recruitment when concurrently challenged by an attention-demanding task.