Deborah A. Jehu

Prioritizing attention on a reaction time task improves postural control and reaction time

Flexible and appropriate allocation of attention resources is important during dual-tasking to achieve task goals while maintaining postural safety. This pilot study aimed to examine the influence of explicit prioritization of attention on the dual-task paradigm by employing two levels of difficulty for the postural tasks and reaction time (RT) tasks in healthy young adults. The task entailed standing on a force platform on two feet or on one foot, attending to posture or RT, and completing a simple or choice RT task. Participants verbally responded “top” as soon as the light cue illuminated. In general, attending to RT produced faster RTs (F(1,19) = 30.9, p < 0.001) and improved center of pressure (COP) Displacement (F(1,19) = 5.1, p < 0.05) and 95% Area Ellipse (F(1,19) = 7.1, p < 0.05). These findings suggest that prioritizing attention away from posture may be beneficial for postural performance when completing a second task.

Continuous Cognitive Tasks Improve Postural Control Compared to Discrete Cognitive Tasks

ABSTRACT Research suggests that postural control synergies are sensitive to cognitive manipulations; however, the impact of different types of cognitive tasks on postural control remains inconclusive. The authors examined the effect of discrete and continuous tasks on postural control. Sixteen healthy young adults (M age = 22.7 ± 2.2 years) stood with feet together on a force platform while performing randomly assigned discrete and continuous cognitive tasks. Results demonstrated marked improvements in the area of 95% confidence ellipse and the standard deviation of the center of pressure in the anterior-posterior and medial-lateral directions for continuous compared to discrete tasks. This reinforces the notion that continuous tasks are sufficient in providing less opportunity to consciously attend to postural control, thereby facilitating automatic postural control.

Reaction Time Is Slower When Walking at a Slow Pace in Young Adults

ABSTRACT Limited research has examined attentional requirements of walking at various speeds. Twenty young adults were asked to walk 10 m at their preferred pace, 30% faster or 30% slower while verbally responding “top” as fast as possible to random auditory stimuli. Slow walking demonstrated significantly longer reaction time (RT; 457 ± 91 ms) than preferred (423 ± 80 ms) and fast (396 ± 73 ms) walking speeds, F(2, 38) = 13.4, p < .001; η2p = .414. Walking at a preferred pace also led to longer RT than walking at a fast pace (p < .05). Slower RT during slow walking may be attributed to increased task complexity, energy requirements and equilibrium demands. Faster RTs during fast walking could be due to familiarity of the task, higher arousal levels, and similar task instructions compared to slower speeds.

Balance and mobility training with or without concurrent cognitive training does not improve posture, but improves reaction time in healthy older adults

BACKGROUND AND AIMS The purpose was to determine whether balance and mobility training (BMT) or balance and mobility plus cognitive training (BMT+C) would reduce postural sway and reaction time (RT) and maintain these improvements after a 12-week follow-up in healthy older adults. METHODS Participants were allocated to the BMT (n=15; age: 70.2±3.2), BMT+C (n=14; age:68.7±5.5), or control group (n=13; age: 66.7±4.2). The BMT group trained one-on-one, 3×/wk for 12 weeks on a balance obstacle course. The BMT+C group trained one-on-one, 3×/week for 12 weeks on a balance obstacle course while completing cognitive tasks. Participants stood on a force plate for 30s in feet-apart (FA) and semi-tandem (ST) positions while completing simple RT and choice RT tasks at baseline, at the 12-week post-training, and at the 12-week follow-up. Participants were instructed to stand as still as possible while verbally responding as fast as possible to the auditory cues. RESULTS No group differences in center of pressure (COP) Area, COP Velocity, or Sample Entropy of the COP displacement were shown after the training or 12-week follow-up, but the BMT and BMT+C showed faster RT after training and maintained these improvements at the 12-week follow-up compared to the control group. No differences in postural sway or RT emerged between the BMT and BMT+C groups. CONCLUSION Both training groups improved RT after the interventions and sustained these improvements over 12 weeks, but showed no reductions in postural sway. Multi-task balance training likely results in reduced attention demand.

Impact of the Number of Steps on the Fukuda Stepping Test in Older Adults

ABSTRACT Aims: This study aimed to compare performance, within-subject variability and test–retest reliability between the 50-step and 100-step Fukuda test in healthy older adults. Methods: Fifty participants aged between 65 and 75 years performed three trials of both the 50- and 100-step tests on two separate sessions seven days apart. Their final foot position was measured relative to the starting line. Results: Absolute values of body rotation and lateral and longitudinal displacements were significantly larger on the 100-step than on the 50-step test. The mean standard deviations of these measures on the three trials were significantly larger on the 100- compared to the 50-step test, indicating larger within-subject variability. Intraclass correlation coefficients were similar for both tests, suggesting comparable test–retest reliability. Conclusion: The 50-step test is recommended over the 100-step as it may have reduced measurement error.

Letter to the Editor: On "Advantages and disadvantages of stiffness instructions when studying postural control" by C.T. Bonnet: You just can't win: Advantages and disadvantages of the postural stability requirement.

In the examination of postural control, instructions to stand as still as possible are common and promote a relatively unnatural sway pattern. The validity of the stability requirement is discussed in the present commentary in response to the discussion initiated by Cedrick T. Bonnet. The advantages of using the stability requirement include: evaluating unbiased postural control, reducing variability in postural sway, manipulating focus of attention, examining the ability to maintain an upright stance, and ecological validity of testing. The disadvantages include: constraining natural postural sway, increasing the complexity of the control condition, promoting an internal focus of attention, and reducing the ability to detect exploratory behaviour. After evaluating the aforementioned advantages and disadvantages, the present commentary suggests that researchers should strive to provide specific instructions to maintain feet, arm and eye position without specifically requiring participants to reduce their postural sway.

Medication and trial duration influence postural and pointing parameters during a standing repetitive pointing task in individuals with Parkinson’s disease

We aimed to determine the effects of levodopa medication on the performance of a repetitive pointing task while standing, and to investigate the optimal trial duration in individuals with Parkinson’s disease, and older adults. Seventeen individuals with Parkinson’s disease (5 freezers) and 9 older adults stood on force platforms for 30 s and 120 s while performing a bilateral repetitive pointing task, tracked by motion capture. Participants with Parkinson’s disease were assessed on and off medication and older adults were also assessed on separate days. The main findings were that: 1) on medication, participants with Parkinson’s exhibited greater center of pressure root mean square in the medial-lateral direction, greater velocity in the medial-lateral and anterior-posterior directions, and greater range in the medial-lateral direction than off medication; 2) longer trial durations resulted in greater center of pressure range in the medial-lateral and anterior-posterior directions and greater coefficient of variation in finger pointing on the least affected side; 3) Parkinson’s participants exhibited larger range in the medial-lateral direction compared to older adults; 4) off medication, freezers presented with less range and root mean square in the anterior-posterior direction than non-freezers; and 5) a correlation emerged between the freezing of gait questionnaire and pointing asymmetry and the coefficient of variation of pointing on the most affected side. Therefore, Parkinson’s medication may increase instability during a repetitive pointing task. Longer trials may provide a better depiction of sway by discriminating between those with and without neurological impairment. Individuals with Parkinson’s were less stable than older adults, supporting that they are at a greater risk for falls. The greater restrictive postural strategy in freezers compared to non-freezers is likely a factor that augments fall-risk. Lastly, the link between freezing of gait and upper-limb movement indicates that freezing may manifest first in the lower-limbs.

Fallers with Parkinson’s disease exhibit restrictive trunk control during walking

BACKGROUND The relationship between falls and static and dynamic postural control has not been established in Parkinsons disease (PD). The purpose was to compare the compensatory postural strategies among fallers and non-fallers with PD as well as older adults during static and dynamic movements. METHODS Twenty-five individuals with PD (11 fallers) and 17 older adults were outfitted with 6 accelerometers on the wrists, ankles, lumbar spine, and sternum, stood quietly for 30 s on a force platform, and walked back and forth for 30 s along a 15 m walkway. Root-mean-square displacement amplitude of the center of pressure (COP), COP velocity, gait spatial-temporal characteristics, trunk range of motion (ROM), and peak trunk velocities were obtained. RESULTS COP velocity in anterior-posterior was larger in older adults than those with PD (p < 0.05). Trunk frontal ROM and velocity were smaller in fallers and non-fallers with PD compared to older adults (p < 0.05). Trunk anterior-posterior ROM and velocity were smaller in fallers than non-fallers with PD and older adults (p < 0.05). In fallers with PD, negative correlations were shown between the sagittal trunk velocity and the COP velocity in the anterior-posterior direction as well as between trunk frontal velocity and COP velocity in both directions (p < 0.05). In non-fallers with PD, horizontal trunk ROM and velocity were positively correlated with COP ROM and velocity in the medial-lateral direction (p < 0.01). SIGNIFICANCE Dynamic postural control revealed better discrimination between groups than static. Fallers and non-fallers with PD and older adults adopted different compensatory strategies during static and dynamic movements; thereby providing important information for falls-risk assessment.BACKGROUND The relationship between falls and static and dynamic postural control has not been established in Parkinsons disease (PD). The purpose was to compare the compensatory postural strategies among fallers and non-fallers with PD as well as older adults during static and dynamic movements. METHODS Twenty-five individuals with PD (11 fallers) and 17 older adults were outfitted with 6 accelerometers on the wrists, ankles, lumbar spine, and sternum, stood quietly for 30 s on a force platform, and walked back and forth for 30 s along a 15 m walkway. Root-mean-square displacement amplitude of the center of pressure (COP), COP velocity, gait spatial-temporal characteristics, trunk range of motion (ROM), and peak trunk velocities were obtained. RESULTS COP velocity in anterior-posterior was larger in older adults than those with PD (p < 0.05). Trunk frontal ROM and velocity were smaller in fallers and non-fallers with PD compared to older adults (p < 0.05). Trunk anterior-posterior ROM and velocity were smaller in fallers than non-fallers with PD and older adults (p < 0.05). In fallers with PD, negative correlations were shown between the sagittal trunk velocity and the COP velocity in the anterior-posterior direction as well as between trunk frontal velocity and COP velocity in both directions (p < 0.05). In non-fallers with PD, horizontal trunk ROM and velocity were positively correlated with COP ROM and velocity in the medial-lateral direction (p < 0.01). SIGNIFICANCE Dynamic postural control revealed better discrimination between groups than static. Fallers and non-fallers with PD and older adults adopted different compensatory strategies during static and dynamic movements; thereby providing important information for falls-risk assessment.

Balance and Mobility Training With or Without Simultaneous Cognitive Training Reduces Attention Demand But Does Not Improve Obstacle Clearance in Older Adults

The purpose of this study was to determine whether balance and mobility training (BMT) or balance and mobility plus cognitive training (BMT + C) would improve obstacle clearance and reaction time (RT); whether further improvements would be exposed in the BMT + C group relative to the BMT group; and whether possible improvements would be sustained at the follow-up. Healthy older adults were allocated to the BMT (n = 15; age: 70.2 ± 3.2), BMT + C (n = 14; age: 68.7 ± 5.5), or control group (n = 13; age: 66.7 ± 4.2). The BMT and BMT + C groups trained one-on-one, three times per week for 12 weeks on a balance obstacle course. The BMT + C group also completed cognitive training. Participants walked onto and over six obstacles of varying heights while completing no RT, simple RT, and choice RT tasks at baseline, posttraining, and at the 12-week follow-up. Both the BMT and BMT + C groups improved RT and maintained these improvements at the follow-up. No meaningful improvements in obstacle clearance emerged following training. Thus, dual-task balance training likely reduces attention demand.