Changes in postural control in hemiplegic patients after stroke performing a dual task

Turning Ability in Stroke Survivors: A Review of Literature

The aim of this paper is to explore the research literature on the turning ability among stroke survivors. Stroke is one of the top five leading causes of death and disability in Malaysia. Stroke survivors reported a higher rate of fall incidences with turning while walking has been the major contributor in most of the incidences. The attentional task requires stroke survivors to have higher cognitive and attention function, and sound muscle coordination in order to perform multitask activities such as driving, walking and turning while talking, carrying an object (holding a plastic bag), navigating corners and overcoming obstacles within the base of support. Most of the previous studies have focused on the kinematic and gait parameters measurement of turning ability among stroke survivors. However, studies conducted on muscle activity using electromyography to evaluate the time pattern of muscle contraction during turning event is lacking. With regards to dual-task ability among stroke survivors, there is insufficient information or research into dual task (motor and cognitive) ability during turning. Further studies are needed to understand the effects of dual-task activity on muscle activity and gait parameters and how this impairment affects the turning ability. This needs to be addressed in order to prevent falls among stroke survivors.

Effect of a cognitive task during obstacle crossing in hemiparetic stroke patients

Stroke patients are at a higher risk of falling than the community-dwelling elderly, and many falls are due to contact with an obstacle. This study compared the effects of the simultaneous addition of a cognitive task during obstacle crossing between stroke patients and community-dwelling older adults (control subjects). Participants comprised 20 stroke patients who could walk with or without supervision and 20 control subjects matched for age and height with the stroke patients. Participants were asked to cross a 4-cm-high obstacle while walking at a self-selected speed. The number of failures and the spatial and temporal parameters were compared between a single-task condition (i.e., crossing task only) and a dual-task condition (i.e., verbal fluency task: listing vegetables or animals). Under the dual-task condition, six stroke patients (30%) and three community-dwelling elderly individuals (15%) failed to complete the motor task. Task failure was only due to heel-obstacle contact after toe clearance. In both groups, obstacle-heel distance after clearance was reduced, and the time from heel contact to toe clearance and stride time were significantly increased under dual-task condition versus single-task condition. In addition, group-task interaction for the time from heel contact to toe clearance of the obstacle was significant; this increase in time was significantly greater under dual-task condition in stroke patients than in control subjects. Obstacle crossing in stroke patients involved an increase in crossing performance time and a risk of heel-obstacle contact after crossing. These tendencies appeared stronger under the dual-task condition.

The effects of cognitive loading on balance control in patients with multiple sclerosis

The aim of this study was to compare the effects of concurrent cognitive task (silent backward counting) on balance performance between two groups of multiple sclerosis (MS) (n=23) and healthy (n=23) participates. Three levels of postural difficulty were studied on a force platform, i.e. rigid surface with eyes open, rigid surface with eyes closed, and foam surface with eyes closed. A mixed model analysis of variance showed that under difficult sensory condition of foam surface with eyes closed, execution of concurrent cognitive task caused a significant decrement in variability of sway velocity in anteroposterior direction for the patient group (P<0.01) while this was not the case for healthy participants (P=0.22). Also, the variability of sway velocity in mediolateral direction was significantly decreased during concurrent execution of cognitive task in patient group (P<0.01) and not in healthy participants (P=0.39). Furthermore, in contrast to single tasking, dual tasking had the ability to discriminate between the 2 groups in all conditions of postural difficulty. In conclusion, findings of variability in sway velocity seem to confirm the different response to cognitive loading between two groups of MS and healthy participants.

Interference between cognition, double-limb support, and swing during gait in community-dwelling individuals poststroke

BACKGROUND

Dual tasking can interfere with activity after stroke.

OBJECTIVE

The authors examined the interactions between 3 different cognitive tasks and the swing and double-limb support (DLS) components of the gait cycle in community-dwelling individuals poststroke.

METHODS

Acquisition of cognitive and gait data were synchronized to study the cognitive-motor interference effects during the different phases of the gait cycle. Participants performed 3 different cognitive tasks in isolation and in combination with walking as well as a single walking task. Tasks were performed continuously for 3 minutes, generating 131 +/- 39 gait cycles per person for analysis for each walking trial. Data were analyzed for 8 participants 7.6 +/- 4.2 months poststroke.

RESULTS

A significant increase was found in the proportion of the gait cycle spent in DLS in dual-task walking because of an increased duration of the DLS phase associated with paretic weight acceptance. There was a significant dual-task effect on nonparetic swing duration: participants reduced the amount of time in paretic single-limb stance in the 3 dual-task conditions. Temporal asymmetry of gait did not increase significantly under dual-task conditions. Reaction times were not affected by whether the stimuli were present during the swing or DLS phase of the gait cycle.

CONCLUSIONS

The findings from this pilot study provide evidence that cognitive-motor interference during gait may be influenced by the phase of the gait cycle, especially DLS involving paretic weight acceptance, which may affect community ambulators with hemiparetic stroke.

Decrease in postural sway and trunk stiffness during cognitive dual-task in nonspecific chronic low back pain patients, performance compared to healthy control subjects

STUDY DESIGN

A 2-group experimental design.

OBJECTIVE

To investigate the effect of a cognitive dual-task on postural sway of pelvis and trunk during unstable sitting in nonspecific chronic patients with low back pain (CLBP) compared to healthy control subjects.

SUMMARY OF BACKGROUND DATA

Higher cognitive systems as well as sensory processes contribute to postural control. An increase in postural sway due to a cognitive dual task could mean more need of cognitive systems to control balance.

METHODS

A total of 21 CLBP patients and 21 control subjects were included based on detailed clinical criteria. Every subject was submitted to 2 postural control tests in an unstable sitting position (easy test position: 2 feet on the ground and difficult test position: 1 foot lifted). Both tests were performed with and without cognitive dual-task. A 3-dimensional motion analysis system was used measure angular displacement of trunk and pelvis in the 3 cardinal planes.

RESULTS

In the most difficult balance position, postural sway increases in the control group when the cognitive dual-task is added, for 50% of the variables the increase is significant (P between 0.02 and 0.05). On the contrary, postural sway decreases, not significantly, in the CLBP group when the dual-task is added. These findings are the same for trunk as for pelvis deviations. The Pearson correlation coefficient between trunk and pelvis movement from the CLBP group are lower for all 3 movement directions in the dual-task condition (r between 0.441 and 0.988) compared to the single task condition (r between 0.982 and 0.995).

CONCLUSION

In nonspecific CLBP patients, a cognitive dual-task reduces both postural sway and trunk stiffness due to the distracting effect of the dual-task. This effect is only visible when the balance task is difficult.

Reduced sway during dual task balance performance among people with stroke at 6 and 12 months after discharge from hospital

BACKGROUND

Cognitive motor interference has been linked to poor recovery and falls. Little is known about recovery of dual-task balance ability poststroke.

METHODS

. In this experimental study, postural sway was examined while standing on a force plate in preferred stance, with feet together, and with eyes closed, at 6 and 12 months postdischarge from hospital. Sway was assessed in isolation and while participants performed a cognitive (shopping list) task.

RESULTS

. Seventy-six people with stroke (mean age 67 years; range, 21-91 years) took part. Fifty-four completed both assessments. When compared with the single task, sway during the dual-task condition was significantly lower in both the medial lateral (ML) and anterior posterior (AP) directions (both P < .0001). Sway in both directions was influenced by the difficulty of the balance task (both P < .0001). There was a trend of reduced sway at the 12-month assessment compared with the 6-month assessment: significant only in the ML direction (P = .0056). Repeat fallers swayed more than non-repeat fallers, with increases of 48% and 44% in the ML (P = .0262) and AP (P = .0134) directions, respectively. No significant variation in the dual-task reduction in sway was found: the dual-task effect was remarkably consistent over all the conditions tested, particularly in the AP direction.

CONCLUSIONS

. Sway decreased under dual-task conditions and changed as the difficulty of the balance task changed. Stroke fallers swayed more than nonfallers and there was evidence of a reduction in sway over time, particularly in the ML direction.