Dual-task training reduces impact of cognitive task on postural sway

Motion Tracker: Camera-Based Monitoring of Bodily Movements Using Motion Silhouettes

Researchers in the cognitive and affective sciences investigate how thoughts and feelings are reflected in the bodily response systems including peripheral physiology, facial features, and body movements. One specific question along this line of research is how cognition and affect are manifested in the dynamics of general body movements. Progress in this area can be accelerated by inexpensive, non-intrusive, portable, scalable, and easy to calibrate movement tracking systems. Towards this end, this paper presents and validates Motion Tracker, a simple yet effective software program that uses established computer vision techniques to estimate the amount a person moves from a video of the person engaged in a task (available for download from http://jakory.com/motion-tracker/). The system works with any commercially available camera and with existing videos, thereby affording inexpensive, non-intrusive, and potentially portable and scalable estimation of body movement. Strong between-subject correlations were obtained between Motion Tracker's estimates of movement and body movements recorded from the seat (r =.720) and back (r = .695 for participants with higher back movement) of a chair affixed with pressure-sensors while completing a 32-minute computerized task (Study 1). Within-subject cross-correlations were also strong for both the seat (r =.606) and back (r = .507). In Study 2, between-subject correlations between Motion Tracker's movement estimates and movements recorded from an accelerometer worn on the wrist were also strong (rs = .801, .679, and .681) while people performed three brief actions (e.g., waving). Finally, in Study 3 the within-subject cross-correlation was high (r = .855) when Motion Tracker's estimates were correlated with the movement of a person's head as tracked with a Kinect while the person was seated at a desk (Study 3). Best-practice recommendations, limitations, and planned extensions of the system are discussed.

Effects of dual-task training on balance and executive functions in Parkinson's disease: A pilot study

The aim of this study was to analyze the efficacy of cognitive-motor dual-task training compared with single-task training on balance and executive functions in individuals with Parkinson's disease. Fifteen subjects, aged between 39 and 75 years old, were randomly assigned to the dual-task training group (n = 8) and single-task training group (n = 7). The training was run twice a week for 6 weeks. The single-task group received balance training and the dual-task group performed cognitive tasks simultaneously with the balance training. There were no significant differences between the two groups at baseline. After the intervention, the results for mediolateral sway with eyes closed were significantly better for the dual-task group and anteroposterior sway with eyes closed was significantly better for the single-task group. The results suggest superior outcomes for the dual-task training compared to the single-task training for static postural control, except in anteroposterior sway with eyes closed.

The effects of acute arm crank ergometry and cycle ergometry on postural sway and attentional demands during quiet bipedal standing

Current evidence suggests that acute bouts of lower limb exercise elicits a number of adverse effects on both sensory and motor components of postural control. The effects of acute exercise on quiet standing balance while concurrently performing an attentional task remains equivocal. This study aimed to compare the alterations in postural control and attentional demands elicited by upper and lower limb exercise. Twelve healthy young males (mean ± SD age, 22.2 ± 3.2 years) were examined on six separate occasions. The first two visits determined maximal aerobic fitness on an arm crank ergometer (ACE) and cycle ergometer (CYC). Subsequently, participant's postural sway was assessed during single- (ST) and dual-task (DT) conditions before and immediately after moderate- and high-intensity exercise engaging the upper or lower body musculature. The order of the four exercise tests was counterbalanced. The centre of pressure displacement in the anteroposterior (COPAP) and mediolateral (COPML) directions and the COP path length (COPL) were computed using a force platform. A time × mode interaction was observed for COPAP (ST; p = 0.011, DT; p = 0.018) and COPML (ST; p = 0.001). CYC elicited large (ES; 1.6-2.0) increases in COPAP and COPML, but there were no differences between aerobic and anaerobic tests (p > 0.05). The effect of cognitive load appeared to increase sway in the frontal plane following anaerobic CYC (p = 0.001) but not ACE (p < 0.05). Exercise has different effects on frontal and sagittal plane sway following different cognitive loads. In particular, COPML was increased at the cost of maintaining attentional performance following exercise.

Age-related cognitive task effects on gait characteristics: do different working memory components make a difference?

Background

Though it is well recognized that gait characteristics are affected by concurrent cognitive tasks, how different working memory components contribute to dual task effects on gait is still unknown. The objective of the present study was to investigate dual-task effects on gait characteristics, specifically the application of cognitive tasks involving different working memory components. In addition, we also examined age-related differences in such dual-task effects.

Methods

Three cognitive tasks (i.e. ‘Random Digit Generation’, ‘Brooks’ Spatial Memory’, and ‘Counting Backward’) involving different working memory components were examined. Twelve young (6 males and 6 females, 20 ~ 25 years old) and 12 older participants (6 males and 6 females, 60 ~ 72 years old) took part in two phases of experiments. In the first phase, each cognitive task was defined at three difficulty levels, and perceived difficulty was compared across tasks. The cognitive tasks perceived to be equally difficult were selected for the second phase. In the second phase, four testing conditions were defined, corresponding to a baseline and the three equally difficult cognitive tasks. Participants walked on a treadmill at their self-selected comfortable speed in each testing condition. Body kinematics were collected during treadmill walking, and gait characteristics were assessed using spatial-temporal gait parameters.

Results

Application of the concurrent Brooks’ Spatial Memory task led to longer step times compared to the baseline condition. Larger step width variability was observed in both the Brooks’ Spatial Memory and Counting Backward dual-task conditions than in the baseline condition. In addition, cognitive task effects on step width variability differed between two age groups. In particular, the Brooks’ Spatial Memory task led to significantly larger step width variability only among older adults.

Conclusion

These findings revealed that cognitive tasks involving the visuo-spatial sketchpad interfered with gait more severely in older versus young adults. Thus, dual-task training, in which a cognitive task involving the visuo-spatial sketchpad (e.g. the Brooks’ Spatial Memory task) is concurrently performed with walking, could be beneficial to mitigate impairments in gait among older adults.

Electronic supplementary material

The online version of this article (doi:10.1186/1743-0003-11-149) contains supplementary material, which is available to authorized users.

The effect of various dual task training methods with gait on the balance and gait of patients with chronic stroke

[Purpose] This study examined the effects of various dual task gait training methods (motor dual task gait training, cognitive dual task gait training, and motor and cognitive dual task gait training) on the balance and gait abilities of chronic stroke patients. [Subjects and Methods] Thirty-three outpatients performed dual task gait training for 30 minutes per day, three times a week, for eight weeks from June to August, 2012. Balance ability was measured pre-and posttest using the stability test index, the weight distribution index, the functional reach test, the timed up and go test, and the four square step test. Gait ability was measured by the 10 m walk test and a 6 min walk test before and after the training. The paired t-test was used to compare measurements before and after training within each group, and ANOVA was used to compare measurements before and after training among the groups. [Results] Comparisons within each group indicated significant differences in all variables between before and after the training in all three groups. Comparison between the groups showed that the greatest improvements were seen in all tests, except for the timed up and go test, following motor and cognitive dual task gait training. [Conclusion] In a real walking environment, the motor and cognitive dual task gait training was more effective at improving the balance and gait abilities of chronic stroke patients than either the motor dual task gait training or the cognitive dual task gait training alone.

Concurrent performance of a cognitive and dynamic obstacle avoidance task: influence of dual-task training

The performance of 2 or more attention demanding tasks simultaneously is poorly understood. The purpose of the study was to investigate optimal practice strategies for performing 2 simultaneous tasks. Eighteen young adults walked and stepped over either a static or dynamic obstacle, while responding to an auditory Stroop test. Participants were randomly assigned to 1 of 3 groups: one that practiced both tasks simultaneously, practiced only the cognitive task, or received no practice. Results indicate that only the dual-task practice group showed significantly more improvement in the locomotor task through reduced variability of gait velocity, obstacle clearance, and takeoff distance. Findings demonstrate that the practice of two concurrent, attention demanding tasks results in the best performance improvement for both tasks.

Effects of dual task training with visual restriction and an unstable base on the balance and attention of stroke patients

[Purpose] The purpose of this study was to examine the effects of the visual restriction and unstable base dual-task training (VUDT), the visual restriction dual-task training (VDT), and the unstable base dual-task training (UDT) on the balance and attention of chronic stroke patients. [Subjects and Methods] The subjects were 38 chronic stroke patients, who were divided into two groups of 13 patients each and one group of 12 patients. They were given dual-task training for 30 minutes per session, three times a week, for eight weeks. Their balance was measured using the center of pressure (COP) migration distances, functional reach test (FRT), and Berg balance scale (BBS), and attention was measured with the Trail Making Tests and the Stroop test. [Results] In comparisons within each group, all the three groups showed significant differences before and after the training (p<0.05), and in the comparisons among the three groups, the VUDT group showed more significant differences compared with the other two groups in all tests (p<0.05). [Conclusion] Dual-task training applied with visual restriction and an unstable base in which the subjects attempted to maintain their balance was effective in improving the balance and attention of stroke patients, and the VUDT was more effective than VDT or UDT.

"Postural first" principle when balance is challenged in elderly people

Human cognitive processing limits can lead to difficulties in performing two tasks simultaneously. This study aimed to evaluate the effect of cognitive load on both simple and complex postural tasks. Postural control was evaluated in 128 noninstitutionalized elderly people (mean age = 73.6 ± 5.6 years) using a force platform on a firm support in control condition (CC) and mental counting condition (MCC) with eyes open (EO) and eyes closed (EC). Then, the same tests were performed on a foam support. Sway path traveled and area covered by the center of foot pressure were recorded, low values indicating efficient balance. On firm support, sway path was higher in MCC than in CC both in EO and EC conditions (p < 0.001). On foam support, sway path was higher in CC than in MCC in EC condition (p < 0.001), area being higher in CC than in MCC both in EO (p < 0.05) and EC (p < 0.001) conditions. The results indicate that cognitive load alters balance control in a simple postural task (i.e. on firm support), which is highlighted by an increase of energetic expenditure (i.e. increase of the sway path covered) to balance. Awareness may not be increased and the attentional demand may be shared between balance and mental task. Conversely, cognitive load does not perturb the realization of a new complex postural task. This result showed that postural control is prioritized ("postural first" principle) when seriously challenged.

Effects of exercise on dual-task ability and balance in older adults: a systematic review

The interest in research on exercise and physical activity effects on dual-task performance has grown rapidly in the last decade due to the aging global population. Most of the available literature is focused on exercise benefits for the risk of falls, attention, and gait-speed; however, there is a lack of evidence reporting the exercise effects on balance in healthy older adults during dual-task performance. The objective of this study was to critically review the existing evidence of a potential relationship between exercise and improvement of static and dynamic balance during dual-task in healthy older adults and secondary outcomes in other physical and cognitive indices. A systematic search using online databases was used to source articles. Inclusion criteria included articles classified as randomized controlled trials (RCT), controlled trials (CT) and uncontrolled trials (UT). Moreover, the studies had to include an exercise or physical activity protocol in the intervention. Eight studies met the eligibility criteria and included 6 RCTs, 1 CT, and 1 UT. Several limitations were identified, mainly focused on the lack of a common and standardized method to evaluate the balance during the dual-task performance. Additionally, exercise protocols were extensively different, and generally lacked reporting measures. Preliminary findings show that the current body of evidence does not support that exercises used in these interventions entail clear and noteworthy benefits on static or dynamic balance improvements during dual-task performance. Innovative measures and exercise programs may need to be developed before efficacious screening and treatment strategies can be used in clinical settings.

A best practice fall prevention exercise program to improve balance, strength / power, and psychosocial health in older adults: study protocol for a randomized controlled trial

Background

With increasing age neuromuscular deficits (e.g., sarcopenia) may result in impaired physical performance and an increased risk for falls. Prominent intrinsic fall-risk factors are age-related decreases in balance and strength / power performance as well as cognitive decline. Additional studies are needed to develop specifically tailored exercise programs for older adults that can easily be implemented into clinical practice. Thus, the objective of the present trial is to assess the effects of a fall prevention program that was developed by an interdisciplinary expert panel on measures of balance, strength / power, body composition, cognition, psychosocial well-being, and falls self-efficacy in healthy older adults. Additionally, the time-related effects of detraining are tested.

Methods/Design

Healthy old people (n = 54) between the age of 65 to 80 years will participate in this trial. The testing protocol comprises tests for the assessment of static / dynamic steady-state balance (i.e., Sharpened Romberg Test, instrumented gait analysis), proactive balance (i.e., Functional Reach Test; Timed Up and Go Test), reactive balance (i.e., perturbation test during bipedal stance; Push and Release Test), strength (i.e., hand grip strength test; Chair Stand Test), and power (i.e., Stair Climb Power Test; countermovement jump). Further, body composition will be analysed using a bioelectrical impedance analysis system. In addition, questionnaires for the assessment of psychosocial (i.e., World Health Organisation Quality of Life Assessment-Bref), cognitive (i.e., Mini Mental State Examination), and fall risk determinants (i.e., Fall Efficacy Scale – International) will be included in the study protocol. Participants will be randomized into two intervention groups or the control / waiting group. After baseline measures, participants in the intervention groups will conduct a 12-week balance and strength / power exercise intervention 3 times per week, with each training session lasting 30 min. (actual training time). One intervention group will complete an extensive supervised training program, while the other intervention group will complete a short version ('3 times 3’) that is home-based and controlled by weekly phone calls. Post-tests will be conducted right after the intervention period. Additionally, detraining effects will be measured 12 weeks after program cessation. The control group / waiting group will not participate in any specific intervention during the experimental period, but will receive the extensive supervised program after the experimental period.

Discussion

It is expected that particularly the supervised combination of balance and strength / power training will improve performance in variables of balance, strength / power, body composition, cognitive function, psychosocial well-being, and falls self-efficacy of older adults. In addition, information regarding fall risk assessment, dose–response-relations, detraining effects, and supervision of training will be provided. Further, training-induced health-relevant changes, such as improved performance in activities of daily living, cognitive function, and quality of life, as well as a reduced risk for falls may help to lower costs in the health care system. Finally, practitioners, therapists, and instructors will be provided with a scientifically evaluated feasible, safe, and easy-to-administer exercise program for fall prevention.

Trial registration

ClinicalTrials.gov Identifier: NCT01906034

Dual-task training for balance and mobility in a person with severe traumatic brain injury: a case study

BACKGROUND AND PURPOSE

Attentional impairments following severe traumatic brain injury (TBI) are common and can lead to decreased functional mobility and balance, as well as deficits in previously automatic movements such as walking and stair climbing. The purpose of this case study was to determine the feasibility and potential value of incorporating a cognitive-motor dual-task training program into physical therapy for a patient with a severe TBI.

CASE DESCRIPTION

The patient was a 26-year-old woman who sustained a severe TBI during a motor vehicle accident 46 days prior to physical therapy evaluation. On the 8-level Rancho Los Amigos Cognitive Function Scale, her functioning was classified as level IV. She had impairments in attention, functional mobility, and balance, all of which limited her ability to participate in activities of daily living.

INTERVENTION

: Physical therapy was provided over 26 days within the inpatient rehabilitation setting. Interventions included mobility tasks such as walking, balancing, and stair climbing. Mobility training was paired with specific secondary cognitive and motor tasks.

OUTCOMES

Dual-task training may have contributed to improvements on outcome measures designed to test divided attention including the Walking While Talking Test and Trail Making Test and a greater rate of improvement in walking speed and time to descend stairs when compared to the baseline phase.

DISCUSSION

Addition of cognitive-motor dual-task training to standard physical therapy in the inpatient rehabilitation setting appears to be feasible and may have value for improving function in individuals with severe TBI.

VIDEO ABSTRACT AVAILABLE

(see Video, Supplemental Digital Content 1, http://links.lww.com/JNPT/A41) for more insights from the authors.

Ergonomic analysis of muscle activity in the forearm and back muscles during laparoscopic surgery: influence of previous experience and performed task

PURPOSE

The first aim of this study is to analyze the muscle activity in back and forearm muscles in surgeons during laparoscopic dissection and suturing maneuvers. The second aim is to determine the influence of the surgeons' previous experience in laparoscopic surgery.

METHODS

A total of 30 laparoscopic surgeons were divided in 3 groups: novice suturing, novice dissecting, and experts suturing. Electromyography data were collected from the trapezius, forearm flexors, and forearm extensors muscles, during the proposed tasks on physical simulator.

RESULTS

Muscle activity was significantly lower in the expert group. Moreover, muscle activity in the trapezius was significantly higher during the completion of intracorporeal suturing when compared with that during dissection.

CONCLUSIONS

Results obtained in this study show that the surgeons with a higher degree of laparoscopic experience exhibit a lower level of muscle activity when compared with the novice surgeons. Moreover, in accordance to our results, laparoscopic suturing involves a higher degree of muscle effort than during laparoscopic dissection.

Bimanual proprioceptive performance differs for right- and left-handed individuals

It has been proposed that asymmetry between the upper limbs in the utilization of proprioceptive feedback arises from functional differences in the roles of the preferred and non-preferred hands during bimanual tasks. The present study investigated unimanual and bimanual proprioceptive performance in right- and left-handed young adults with an active finger pinch movement discrimination task. With visual information removed, participants were required to make absolute judgments about the extent of pinch movements made to physical stops, either by one hand, or by both hands concurrently, with the sequence of presented movement extents varied randomly. Discrimination accuracy scores were derived from participants' responses using non-parametric signal detection analysis. Consistent with previous findings, a non-dominant hand/hemisphere superiority effect was observed, where the non-dominant hands of right- and left-handed individuals performed overall significantly better than their dominant hands. For all participants, bimanual movement discrimination scores were significantly lower than scores obtained in the unimanual task. However, the magnitude of the performance reduction, from the unimanual to the bimanual task, was significantly greater for left-handed individuals. The effect whereby bimanual proprioception was disproportionately affected in left-handed individuals could be due to enhanced neural communication between hemispheres in left-handed individuals leading to less distinctive separation of information obtained from the two hands in the cerebral cortex.

Training effects on motor–cognitive dual-task performance in older adults

This systematic review investigated whether healthy older adults benefit from training interventions in motor–cognitive dual-task (DT) situations and which specific aspects of the intervention and/or task selection contribute to training benefits. Training effects were analysed with regard to the training programme (e.g., general ST or DT training) and task conditions (e.g., standing or walking, complexity of secondary cognitive task). Literature was searched via OVIDsp (Medline, EMBASE, PsycINFO). DT studies were included by the following criteria: (1) investigation of at least one motor task, (2) assessment of DT performance outcomes on standing or walking, (3) conduction of an intervention, and (4) investigation of older adults in an experimental–control group design or an old–young comparison. Thirteen studies met all inclusion criteria. Four types of interventions were identified: (1) general single-task (ST) motor training, (2) specific ST motor training, (3) general DT training, and (4) task-related (specific) DT training. For DT standing conditions only DT interventions improved motor performance, whereas DT walking also benefits by ST training. Most benefits on motor and cognitive performance seem to be reached by DT training interventions whereas a GST produced lowest effects. Thus, balance orientated motor and cognitive DT performance in healthy older adults can be improved by performance related exercises. Furthermore, to reach beneficial effects, it seems necessary that the training intervention includes a certain level of exercise load such as rising difficulties, appropriate intensity and duration, a certain level of task specificity, and variable task prioritization. The transfer of training effects into everyday situations needs to be further investigated.

Cognitive and cognitive-motor interventions affecting physical functioning: a systematic review

BACKGROUND

Several types of cognitive or combined cognitive-motor intervention types that might influence physical functions have been proposed in the past: training of dual-tasking abilities, and improving cognitive function through behavioral interventions or the use of computer games. The objective of this systematic review was to examine the literature regarding the use of cognitive and cognitive-motor interventions to improve physical functioning in older adults or people with neurological impairments that are similar to cognitive impairments seen in aging. The aim was to identify potentially promising methods that might be used in future intervention type studies for older adults.

METHODS

A systematic search was conducted for the Medline/Premedline, PsycINFO, CINAHL and EMBASE databases. The search was focused on older adults over the age of 65. To increase the number of articles for review, we also included those discussing adult patients with neurological impairments due to trauma, as these cognitive impairments are similar to those seen in the aging population. The search was restricted to English, German and French language literature without any limitation of publication date or restriction by study design. Cognitive or cognitive-motor interventions were defined as dual-tasking, virtual reality exercise, cognitive exercise, or a combination of these.

RESULTS

28 articles met our inclusion criteria. Three articles used an isolated cognitive rehabilitation intervention, seven articles used a dual-task intervention and 19 applied a computerized intervention. There is evidence to suggest that cognitive or motor-cognitive methods positively affects physical functioning, such as postural control, walking abilities and general functions of the upper and lower extremities, respectively. The majority of the included studies resulted in improvements of the assessed functional outcome measures.

CONCLUSIONS

The current evidence on the effectiveness of cognitive or motor-cognitive interventions to improve physical functioning in older adults or people with neurological impairments is limited. The heterogeneity of the studies published so far does not allow defining the training methodology with the greatest effectiveness. This review nevertheless provides important foundational information in order to encourage further development of novel cognitive or cognitive-motor interventions, preferably with a randomized control design. Future research that aims to examine the relation between improvements in cognitive skills and the translation to better performance on selected physical tasks should explicitly take the relation between the cognitive and physical skills into account.

Use of dual-task methodology for skill assessment and development: examples from rugby league

We assessed the attentional demands of drawing and passing in rugby league players and investigated the effects of single-task and dual-task training on the acquisition, retention, and transfer of skill in these athletes. In Study 1, high-skilled and lesser-skilled rugby league players performed a standardized 2-on-1 drill under single-task (primary skill in isolation) and dual-task (primary skill while performing a secondary verbal tone recognition task) conditions. No differences were detected in primary task performance between groups, although the performance of the high-skilled players was more resistant to skill decrement under dual-task conditions. In Study 2, high-performance rugby league players were randomly allocated to either a single-task or dual-task training group. Each group underwent 8 weeks of training between the pre- and post-test sessions. While the mean improvement for draw and pass proficiency under dual-task conditions in the dual-task training group was greater than in the single-task training group (10.0% vs. 2.3%), the differences, while providing a moderate effect size (d = 0.57), were not statistically significant. These results suggest that the attentional demands of drawing and passing are reduced in high-skilled rugby league players compared with their lesser-skilled counterparts. In addition, compared with single-task training, dual-task training appears to improve the ability to perform dual-task draw and pass tasks (possibly through an improvement in time-sharing skills). Further studies are required to verify the efficacy of dual-task training as a training stimulus.

Effects of dual task balance training on dual task performance in elderly people: a randomized controlled trial

OBJECTIVE

To investigate the effects of dual task balance training in the elderly on standing postural control while performing a cognitive task.

DESIGN

A randomized two-group parallel controlled trial.

PARTICIPANTS

Forty-three subjects (all >65 years old) were enrolled in the study and were assigned randomly to either an experimental group (n = 21) or a control group (n = 22).

INTERVENTIONS

Subjects in the experimental group were given strength and balance training while performing cognitive tasks simultaneously. Subjects in the control group were given strength and balance training only. The training was administered twice a week for three months.

MEASUREMENTS

The Chair Stand Test, Functional Reach Test, Timed Up and Go Test and Trail Making Test were measured. The sway length of the centre of gravity was measured during standing while performing the Stroop task. The rate of Stroop task was also measured. All measurements were collected at baseline and after the training period.

RESULTS

There were no significant differences in Functional Reach Test, Timed Up and Go Test and sway length at baseline and after training between the two groups. However, the rate of Stroop task (P < 0.05) was significantly higher after training in the experimental group than in the control group.

CONCLUSIONS

These results suggest that dual task balance training in elderly people improves their dual task performance during standing postural control.

Effects of muscle fatigue on gait characteristics under single and dual-task conditions in young and older adults

BACKGROUND

Muscle fatigue and dual-task walking (e.g., concurrent performance of a cognitive interference (CI) while walking) represent major fall risk factors in young and older adults. Thus, the objectives of this study were to examine the effects of muscle fatigue on gait characteristics under single and dual-task conditions in young and older adults and to determine the impact of muscle fatigue on dual-task costs while walking.

METHODS

Thirty-two young (24.3 ± 1.4 yrs, n = 16) and old (71.9 ± 5.5 yrs, n = 16) healthy active adults participated in this study. Fatigue of the knee extensors/flexors was induced by isokinetic contractions. Subjects were tested pre and post fatigue, as well as after a 5 min rest. Tests included the assessment of gait velocity, stride length, and stride length variability during single (walking), and dual (CI+walking) task walking on an instrumented walkway. Dual-task costs while walking were additionally computed.

RESULTS

Fatigue resulted in significant decreases in single-task gait velocity and stride length in young adults, and in significant increases in dual-task gait velocity and stride length in older adults. Further, muscle fatigue did not affect dual-task costs during walking in young and older adults. Performance in the CI-task was improved in both age groups post-fatigue.

CONCLUSIONS

Strategic and/or physiologic rationale may account for the observed differences in young and older adults. In terms of strategic rationale, older adults may walk faster with longer strides in order to overcome the feeling of fatigue-induced physical discomfort as quickly as possible. Alternatively, older adults may have learned how to compensate for age-related and/or fatigue-induced muscle deficits during walking by increasing muscle power of synergistic muscle groups (e.g., hip flexors). Further, a practice and/or learning effect may have occurred from pre to post testing. Physiologic rationale may comprise motor unit remodeling in old age resulting in larger proportions of type I fibres and thus higher fatigue-resistance and/or increased muscle spindle sensitivity following fatigue leading to improved forward propulsion of the body. These findings are preliminary and have to be confirmed by future studies.

Benefits of cognitive dual-task training on balance performance in healthy older adults

BACKGROUND

There is growing evidence of the involvement of executive control in the maintenance of balance in old age. We examined whether healthy older adults who completed five sessions of nonmotor cognitive dual-task training would show significant improvements on measures of dual-task standing balance and mobility, compared with an untrained control group.

METHODS

Twenty healthy older adults were assigned to either training or control groups. In the pre- and post-training sessions, all participants performed tests of cognition, balance, and mobility (single-support balance, dynamic posturography, sit-to-stand, 40-foot walk) under single- and dual-task conditions. The training group completed five sessions of cognitive dual-task training spaced at least 2 days apart. The two tasks involved making two-choice decisions to visually presented stimuli. Participants completed multiple blocks of single-task (task A or B, blockwise) and mixed (A, B, or A + B) trials in each training session.

RESULTS

The training group showed significant improvements in body sway during single-support balance and center of gravity alignment during double-support dynamic balance. The control group showed no appreciable improvements.

CONCLUSIONS

This study is the first to demonstrate training-related benefits to gross motor performance stemming from cognitive dual-task training. The results support the view that motor control in aging is influenced by executive control and have implications for theories of cognitive training and transfer.

Removing the frontal lobes: the effects of engaging executive functions on perceptual category learning

The present study examined the impact of engaging frontal-mediated working memory processes on implicit and explicit category learning. Two stimulus dimensions were relevant to categorization, but in some conditions, a third, irrelevant dimension was also presented. Results indicated that in both implicit and explicit conditions, the inclusion of the irrelevant dimension impaired performance by increasing the reliance on suboptimal unidimensional strategies. With three-dimensional stimuli, a striking dissociation was observed between implicit and explicit category learning when participants performed a sequential working memory task. With explicit category learning, performance was impaired further, and there was an increased use of suboptimal unidimensional strategies. However, with implicit category learning, the performance impairment decreased, and there was an increased use of optimal strategies. These findings demonstrate the paradoxical situation in which learning can be improved under sequential-task conditions and have important implications for training, decision making, and understanding interactive memory systems.

Training-related changes in dual-task walking performance of elderly persons with balance impairment: a double-blind, randomized controlled trial

The purpose of this study was to compare the efficiency of three different balance training strategies in an effort to understand the mechanisms underlying training-related changes in dual-task balance performance of older adults with balance impairment. Elderly individuals with balance impairment, age 65 and older, were randomly assigned to one of three individualized training programs: single-task (ST) balance training; dual-task training with fixed-priority (FP) instruction; and dual-task training with variable-priority (VP) instruction. Balance control during gait, under practiced and novel conditions, was assessed by calculating the center of mass and ankle joint center inclination angles in the frontal plane. A smaller angle indicated better balance performance. Other outcomes included gait velocity, stride length, verbal reaction time, and rate of response. All measures were collected at baseline and the end of the 4-week training. Results indicated that all training strategies were equally effective (P>.05) at improving balance performance (smaller inclination angle) under single-task contexts. However, the VP training strategy was more effective (P=.04) in improving both balance and cognitive performance under dual-task conditions than either the ST or the FP training strategies. Improved dual-task processing skills did not transfer to a novel dual-task condition. Results support Kramer et al.'s proposal that VP training improves both single-task automatization and the development of task-coordination skills.

Comparisons of musculoskeletal complaints and data entry between a sitting and a sit-stand workstation paradigm

BACKGROUND

Seated working positions are often regarded as a cause for discomfort in the musculoskeletal system. Performing work in different working positions--that is, alternating between sitting and standing (sit-stand workstation paradigm)--could help reduce physical complaints.

OBJECTIVE

The questions were whether performing office work partly in a standing position leads to reduced complaints and whether standing would change the efficiency of data entry office work.

METHOD

We investigated the effect of a sit-stand workstation paradigmd during experimental data entry office work on physical and psychological complaints and data entry efficiency by conducting a randomized controlled trial with 60 male participants ages 18 to 35 years.

RESULTS

In this experiment, musculoskeletal complaints were reduced by a sit-stand workstation paradigm. A trend could be identified indicating a small but nonsignificant loss of efficiency in data entry while standing.

CONCLUSION

A sit-stand workstation paradigm reduces musculoskeletal complaints without considerably affecting data entry efficiency under the presented study conditions (young male participants, short duration, fixed and controlled sit-stand workstation paradigm, simulated experimental working condition).

APPLICATION

According to the present data, implementing a sit-stand workstation paradigm can be an effective workplace health intervention to reduce musculoskeletal complaints. This experiment encourages further studies on the effectiveness of a sit-stand workstation paradigm. Experimental research and field studies that prove the reduction of complaints when introducing a sit-stand workstation paradigm in the workplace could be the basis for evidence-based recommendations regarding such interventions.

The reliability of postural balance measures in single and dual tasking in elderly fallers and non-fallers

Background

The purpose of this study was to determine the reliability of a forceplate postural balance protocol in a group of elderly fallers and non-fallers. The measurements were tested in single and dual-task conditions, with and without vision.

Methods

37 elderly (mean age 73 ± 6 years) community-dwellers were included in this study. All were tested in a single (two-legged stance) and in a dual-task (two-legged stance while counting backwards aloud in steps of 7's) condition, with and without vision. A forceplate was used for registering postural variables: the maximal and the root-mean-square amplitude in medio-lateral (Max-ML, RMS-ML) and antero-posterior (Max-AP, RMS-AP) direction, mean velocity (MV), and the area of the 95% confidence ellipse (AoE). Reliability of the test protocol was expressed with intraclass correlation coefficients (ICC), with 95% limits of agreement (LoA), and with the smallest detectable difference (SDD).

Results

The ICCs for inter-rater reliability and test-retest reliability of the balance variables were r = 0.70–0.89. For the variables Max-AP and RMS-AP the ICCs were r = 0.52–0.74. The SDD values were for variable Max-ML and Max-AP between 0.37 cm and 0.83 cm, for MV between 0.48 cm/s and 1.2 cm/s and for AoE between 1.48 cm² and 3.75 cm². The LoA analysis by Bland-Altman plots showed no systematic differences between test-retest measurements.

Conclusion

The study showed good reliability results for group assessment and no systematic errors of the measurement protocol in measuring postural balance in the elderly in a single-task and dual-task condition.

Interaction between the development of postural control and the executive function of attention

The authors examined the interaction between the development of postural control and the development of the executive function of attention in 13 children and 6 adults in dual-task conditions. Participants performed an attentionally demanding cognitive task and a postural task simultaneously. The authors equalized the attentional load of the cognitive task across age groups. Comparative changes in the center of pressure in dual- and single-task conditions indicated that dual tasks interfered with postural performance in the wide stance (WS) and the modified Romberg stance (RS). Children at 4-6 years of age (but not children at ages 7-12 years of age or adults) experienced postural control interference in both stance positions, but interference was greater in the RS (p = .018). For all participants, cognitive task performance in RS was unchanged from that in WS. The knowledge gained from the results of this study will contribute to the design and implementation of academic and preacademic programming for young children. Their performance of an intentionally demanding cognitive task would be enhanced by the provision of appropriately sized desks and chairs or their use of an alternate, less demanding position.

The role of executive function and attention in gait

Until recently, gait was generally viewed as a largely automated motor task, requiring minimal higher-level cognitive input. Increasing evidence, however, links alterations in executive function and attention to gait disturbances. This review discusses the role of executive function and attention in healthy walking and gait disorders while summarizing the relevant, recent literature. We describe the variety of gait disorders that may be associated with different aspects of executive function, and discuss the changes occurring in executive function as a result of aging and disease as well the potential impact of these changes on gait. The attentional demands of gait are often tested using dual tasking methodologies. Relevant studies in healthy adults and patients are presented, as are the possible mechanisms responsible for the deterioration of gait during dual tasking. Lastly, we suggest how assessments of executive function and attention could be applied in the clinical setting as part of the process of identifying and understanding gait disorders and fall risk.

The effects of a concurrent cognitive task on the postural control of young children with and without developmental coordination disorder

The purpose of this study was to examine how dual-task performance affects the center of pressure (COP) sway characteristics and cognitive performance of children with developmental coordination disorder (DCD). Twenty-six children with DCD (mean age-5.1+/-0.59 years) and 20 typically developing children (mean age-5.0+/-0.57 years) participated in the study. The postural task consisted of standing quietly either on a firm or a compliant surface. The cognitive task involved naming simple objects appearing consecutively on a computer screen. Five tests were presented in random order, with the cognitive and the postural tasks tested either separately or concurrently. Mistakes in naming the objects were recorded, as were COP sway characteristics measured with a force-plate. Children with DCD demonstrated higher COP path-length velocity (PLV), and COP amplitude variability, as well as more mistakes in naming the objects in all stance conditions. A concurrent cognitive task increased all sway measures in both groups, with the effect on PLV greater in children with DCD. Cognitive performance was affected by dual tasking only in the control group. Young children with DCD demonstrated greater postural control activity than did the children in the control group during quiet stance, whether performed as a single or a dual task. This difference is accentuated during dual tasking when the children with DCD seem to prioritize the cognitive task.

Effects of Balance Status and Age on Muscle Activation While Walking Under Divided Attention

We examined the role of attention during different phases of the gait cycle by using a dual-task paradigm. Younger and older adults performed a self-paced treadmill walking task, a semantic judgment task, and both tasks simultaneously. We recorded vocal reaction time for the judgment task, and we recorded muscle activity by the use of electromyography. We derived dual-task costs from difference scores (single vs dual task). Our analysis of the judgment task showed that both groups responded more quickly during dual-task conditions than during single-task conditions. In five of eight muscle groups, stance-phase muscle activity decreased significantly from dual to single task. For older adults, individuals with poor balance increased their muscle activity during dual-task performance. These results suggest that, during moderately demanding walking and cognitive performance, poor balancers can compensate successfully for their motoric vulnerability.

Postural control during laparoscopic surgical tasks

BACKGROUND

Balance control during standing is essential while performing surgery. The postural sway must be controlled to enhance movement accuracy. Postural control was compared between novices and experts during standardized laparoscopic tasks.

METHODS

Seven novices with limited exposition to laparoscopy were compared with 7 expert surgeons. The subjects were requested to perform 4 laproscopic tasks on the McGill Inanimate System for Training and Evaluation of Laparoscopic Skills (MISTELS) and a quiet standing task while standing on 2 force platforms. An analysis of variance (ANOVA) with repeated measures was performed to compare groups and the different conditions. Significant level was set at P < .05.

RESULTS

The technical requirements of the laparoscopic tasks impacted on postural sway in both anteroposterior and mediolateral directions. Furthermore, results indicate that the experts have a significantly better postural balance for all tasks compared to novices.

CONCLUSION

Postural sway increases with the technical requirements of minimally invasive surgery. This study showed that postural control performance while standing improves with laparoscopic expertise.