The impact of divided attention on automatic postural responses: A systematic review and meta-analysis

Dual-task interference of reactive stepping kinematics for balance recovery strategies in older adults

OBJECTIVE

To characterize the interference of reactive stepping kinematics related to the increase or maintenance of the number of steps in response to a large perturbation during dual tasks among older adults.

METHODS

This was a cross-sectional study that included 52 community-dwelling healthy older adults. Reactive stepping performance was analyzed after forward balance loss during a single task and a second cognitive task. The number of steps taken to recover balance and dual-task interference (DTI) for muscular onset latency, anteroposterior (AP) center of pressure (COP) displacement and velocity before step initiation, and step temporal and spatial variables were measured. The DTI of the variables was compared between the participants who increased versus those who maintained the number of steps taken during the dual task relative to the single task.

RESULTS

Twenty-eight (53.8 %) participants increased their steps during dual tasks relative to a single task. In older adults, the AP COP peak velocity (P < 0.001) and step length (P < 0.001) were significantly worse during dual tasks than during a single task. However, this was not observed for older adults who did not increase their steps. The DTI for the AP COP peak velocity and step length were significantly larger for the older adults who increased their steps than those who did not (AP COP peak velocity; P = 0.044, step length; P = 0.003). Both groups showed a significant muscular onset delay during dual tasks than during a single task (P < 0.001), and no significant differences were found between the groups.

CONCLUSIONS

Our findings suggest that reactive stepping strategies in older adults after a large external perturbation during secondary cognitive tasks can be attributed to interference with COP control before step initiation and step length.

The effect of cognitive tasks on reactive stepping in young and older adults

BACKGROUND

Divided attention is commonly required in daily life, and to prevent falls, balance must be recovered when a person experiences unexpected perturbations. Previous studies have shown that additional cognitive tasks in postural responses negatively affect automatic postural responses. However, the effect of dual-tasking on reactive stepping performance is still not clearly understood. This study investigated the effect of dual-tasking on reactive stepping induced by a large perturbation in older adults and characterized the effect of dual-tasking by comparison with young adults.

RESEARCH QUESTION

How does the effect of dual-tasking on reactive stepping performance differ between young and older adults?

METHODS

Twenty-nine older adults and twenty-two young adults were prospectively exposed to external perturbations to induce forward reactive steps. Perturbations were delivered under simple front fixed gaze (single-task condition) and modified Stroop task (dual-task condition). Measures of the time to foot-off and reach stability, step length, velocity, and number of steps were based on force plate data for both the single- and dual-task conditions.

RESULTS

Young and older adults showed a delay in foot-off time during the dual-task condition compared with that during the single-task condition. The reach stability time, step length, and number of steps were worse in the dual-task condition than in the single-task condition for older adults, but not for young adults. The deficits in reactive stepping performance during dual-tasking could reflect the reactive balance capacity in real life.

SIGNIFICANCE

The findings of this study highlight the increased risk of falls with age.

The perceived control model of falling: developing a unified framework to understand and assess maladaptive fear of falling

BACKGROUND

fear of falling is common in older adults and can have a profound influence on a variety of behaviours that increase fall risk. However, fear of falling can also have potentially positive outcomes for certain individuals. Without progressing our understanding of mechanisms underlying these contrasting outcomes, it is difficult to clinically manage fear of falling.

METHODS

this paper first summarises recent findings on the topic of fear of falling, balance and fall risk-including work highlighting the protective effects of fear. Specific focus is placed on describing how fear of falling influences perceptual, cognitive and motor process in ways that might either increase or reduce fall risk. Finally, it reports the development and validation of a new clinical tool that can be used to assess the maladaptive components of fear of falling.

RESULTS

we present a new conceptual framework-the Perceived Control Model of Falling-that describes specific mechanisms through which fear of falling can influence fall risk. The key conceptual advance is the identification of perceived control over situations that threaten one's balance as the crucial factor mediating the relationship between fear and increased fall risk. The new 4-item scale that we develop-the Updated Perceived Control over Falling Scale (UP-COF)-is a valid and reliable tool to clinically assess perceived control.

CONCLUSION

this new conceptualisation and tool (UP-COF) allows clinicians to identify individuals for whom fear of falling is likely to increase fall risk, and target specific underlying maladaptive processes such as low perceived control.

Effects of gender on dual-tasking and prioritization in older adults

BACKGROUND

The ability to produce effective posture and balance while distracted (dual-tasking; DT), is critical for mobility. In particular, individuals implicit prioritization across posture and secondary, distracting stimuli may impact fall risk. However, the impact of gender on DT and prioritization during gait is poorly understood.

RESEARCH QUESTION

Does gender impact DT effects or prioritization while DT walking?

METHODS

One hundred older adults participated. The timed up and go (TUG) was completed with and without a secondary cognitive task (counting backwards by 3's). Gait (time to complete the TUG), and cognitive (rate of correct numbers listed) performance was recorded during both single tasks and while dual-tasking. DT effects were calculated for cognitive and gait performance. Prioritization was calculated as the difference between cognitive and gait DT effects. The effect of gender on DT and prioritization was assessed, controlling for age and cognitive ability.

RESULTS

Gender by condition (single vs. dual-task) interaction effects were observed (Gait: F_1,96 =8.7; p = 0.004; Cognition: F_1,96 =5.2; p = 0.024) such that, compared to male participants, females exhibited smaller cognitive DT effects, and larger gait DT effects. Further, females exhibited significantly larger prioritization scores (F_1,95 =10.0, p = 0.002), indicating a cognitive prioritization compared to males.

SIGNIFICANCE

Given the link between posture-second strategies and falls, the current findings may provide some insight into previous results suggesting an increased fall-risk in older-adult women. However, this study did not investigate falls. Therefore, additional work is necessary to confirm current findings and further investigate the relationship between gender, prioritization, and falls; and its possible clinical relevance.