Lutz Schega

Brain activity during walking: A systematic review

BACKGROUND This systematic review provides an overview of the literature deducing information about brain activation during (1) imagined walking using MRI/fMRI or (2) during real walking using measurement systems as fNIRS, EEG and PET. METHODS Three independent reviewers undertook an electronic database research browsing six databases. The search request consisted of three search fields. The first field comprised common methods to evaluate brain activity. The second search field comprised synonyms for brain responses to movements. The third search field comprised synonyms for walking. RESULTS 48 of an initial yield of 1832 papers were reviewed. We found differences in cortical activity regarding young vs. old individuals, physically fit vs. physically unfit cohorts, healthy people vs. patients with neurological diseases, and between simple and complex walking tasks. CONCLUSIONS We summarize that the dimension of brain activity in different brain areas during walking is highly sensitive to task complexity, age and pathologies supporting previous assumptions underpinning the significance of cortical control. Many compensation mechanisms reflect the brains plasticity which ensures stable walking.

Towards clinical application: Repetitive sensor position re-calibration for improved reliability of gait parameters

While camera-based motion tracking systems are considered to be the gold standard for kinematic analysis, these systems are not practical in clinical practice. However, the collection of gait parameters using inertial sensors is feasible in clinical settings and less expensive, but suffers from drift error that excludes accurate analyses. The goal of this study was to apply a combination of repetitive sensor position re-calibration techniques in order to improve the intra-day and inter-day reliability of gait parameters using inertial sensors. Kinematic data of nineteen healthy elderly individuals were captured twice within the first day and once on a second day after one week using inertial sensors fixed on the subjects forefoot during gait. Parameters of walking speed, minimum foot clearance (MFC), minimum toe clearance (MTC), stride length, stance time and swing time, as well as their corresponding measures of variability were calculated. Intra-day and inter-day differences were rated using intra-class correlation coefficients (ICC(3,1)), as well as the bias and limits of agreement. The results indicate excellent reliability for all intra-day and inter-day mean parameters (ICC: MFC 0.83-stride length 0.99). While good to excellent reliability was observed during intra-day parameters of variability (ICC: walking speed 0.71-MTC 0.98), corresponding inter-day reliability ranged from poor to excellent (ICC: walking speed 0.32-MTC 0.95). In conclusion, the system is suitable for reliable measurement of mean temporo-spatial parameters and the variability of MFC and MTC. However, the systems accuracy needs to be improved before remaining parameters of variability can reliably be collected.

Pick-by-Vision: A first stress test

In this paper we report on our ongoing studies around the application of Augmented Reality methods to support the order picking process of logistics applications. Order picking is the gathering of goods out of a prepared range of items following some customer orders. We named the visual support of this order picking process using Head-mounted Displays “Pick-by-Vision”. This work presents the case study of bringing our previously developed Pickby-Vision system from the lab to an experimental factory hall to evaluate it under more realistic conditions. This includes the execution of two user studies. In the first one we compared our Pickby-Vision system with and without tracking to picking using a paper list to check picking performance and quality in general. In a second test we had subjects using the Pick-by-Vision system continuously for two hours to gain in-depth insight into the longer use of our system, checking user strain besides the general performance. Furthermore, we report on the general obstacles of trying to use HMD-based AR in an industrial setup and discuss our observations of user behaviour.

Effects of Intermittent Hypoxia on Cognitive Performance and Quality of Life in Elderly Adults: A Pilot Study

Background: Physical exercise has a positive effect on cognitive performance and quality of life (QoL). One reason for this is the upregulation of brain-derived neurotrophic factor, which improves brain plasticity. Intermittent hypoxia promotes first the proliferation of endogenous neuroprogenitors which leads to an increased number of newborn neurons and second the expression of brain-derived neurotrophic factor in the adult hippocampus. Intermittent hypoxia may, therefore, support synaptic plasticity, the process of learning and provoke antidepressant-like effects. Hence, intermittent hypoxia might also lead to improved cognitive functioning and QoL. Objective: This study aims to evaluate to what extent physical activity with preceded intermittent hypoxic training is more effective than solely strength-endurance training on cognitive performance and QoL. Methods: 34 retired people aged between 60 and 70 years were randomly assigned to a control group or intervention group. Contrarily to the control group, which was supplied with a placebo air mixture, the intervention group was supplied with an intermittent hypoxic training prior to a strength-endurance exercise program. The cognitive performance of individuals was examined using the d2 test and the Number Combination Test (ZVT) both before and after the exercise program. We assessed QoL with the Medical Outcomes Study Short-Form 36-Item Health Survey (SF-12) and Pittsburgh Sleep Quality Index (PSQI) and the strength-endurance capacity using the Spring test. Results: Regarding the d2 test, a time × group effect was observed. Speed of cognitive performance in seconds was measured using ZVT. Here, no interaction effect was discovered. An interaction effect was not found in the Physical Component Summary scores (SF-12). Regarding the Mental Component Summary, an interaction effect just failed to become statistically significant. Furthermore, we determined sleep quality with the PSQI. Here, an interaction effect was observed. The analysis of the strength-endurance test revealed no interaction effects. Conclusion: The data of the current study suggest that an additional intermittent hypoxic training combined with physical exercise augments the positive effects of exercise on cognitive performance and QoL in elderly humans.

Towards the importance of minimum toe clearance in level ground walking in a healthy elderly population

Tripping is presumed to be the principal cause for falls during walking. At minimum toe clearance, the potential for trip-related falls is considered to be highest. Thus, controlling minimum toe clearance is essential for walking without tripping. In theory, the central nervous system should therefore give priority to accurate control of the variability in minimum toe clearance, as compared to other gait parameters, since people tend to only modify variability in any given task if it interferes with the task performance. The aim of this study was to determine whether elderly individuals show less increase in variability of minimum toe clearance during a dual-task condition (where an increase of gait variability is provoked), while allowing a larger range of variability in the other gait parameters. Forty elderly participants walked back and forth on a 25 m long track for five minutes. They then walked a second time performing an additional cognitive task. The variability in stride time, stride length and minimum toe clearance as well as dual-task costs of each gait parameter were calculated for each walk. The variability in minimum toe clearance did not change during dual task-walking, whereas the variability of stride length and stride time increased, showing dual-task costs of about 66% and 84%, respectively. To avoid additional detrimental load on the central nervous system, the modification of task-irrelevant variability may be tolerated during dual-task conditions, whereas minimum toe clearance is controlled with high priority.

Evaluation of a visual feedback system in gait retraining: a pilot study.

Abnormal gait pattern of the frontal plane (i.e. Duchenne gait and Trendelenburg gait) may be caused by a variety of diseases. The aim of this pilot study was to evaluate the instantaneous effect of a visual feedback system on frontal plane pelvis and trunk movements in order to use it in patients with THR in subsequent studies. A total of 24 women (45-65 years) were included in the study. According to acute functional impairments the subjects were assigned to the control group (CG, no gait disorders, n=15, age=59±11 years, BMI=27±4) or to the intervention group (IG, n=9, age=61±4, BMI=29±5), respectively. First, in Measurement 1 (M1) kinematic reference values were captured in a standardized clinical gait analysis (MVN, XSens). Afterwards, the influence of a visual real-time feedback on gait pattern was examined while using the feedback system (M2). While there was a significant difference of IG vs. CG in M1 in the mean inclination regarding pelvis and trunk movements, this was not detected in M2. Therefore it is concluded, especially in subjects with abnormal gait pattern, that the visualization leads to an improvement of the movement pattern of pelvis and trunk in the frontal plane while using the device.

The Effect of a Six-Month Dancing Program on Motor-Cognitive Dual-Task Performance in Older Adults

Dancing is a complex sensorimotor activity involving physical and mental elements which have positive effects on cognitive functions and motor control. The present randomized controlled trial aims to analyze the effects of a dancing program on the performance on a motor-cognitive dual task. Data of 35 older adults, who were assigned to a dancing group or a health-related exercise group, are presented in the study. In pretest and posttest, we assessed cognitive performance and variability of minimum foot clearance, stride time, and stride length while walking. Regarding the cognitive performance and the stride-to-stride variability of minimum foot clearance, interaction effects have been found, indicating that dancing lowers gait variability to a higher extent than conventional health-related exercise. The data show that dancing improves minimum foot clearance variability and cognitive performance in a dual-task situation. Multi-task exercises (like dancing) might be a powerful tool to improve motor-cognitive dual-task performance.

A cognitive dual task affects gait variability in patients suffering from chronic low back pain

Chronic pain and gait variability in a dual-task situation are both associated with higher risk of falling. Executive functions regulate (dual-task) gait variability. A possible cause explaining why chronic pain increases risk of falling in an everyday dual-task situation might be that pain interferes with executive functions and results in a diminished dual-task capability with performance decrements on the secondary task. The main goal of this experiment was to evaluate the specific effects of a cognitive dual task on gait variability in chronic low back pain (CLBP) patients. Twelve healthy participants and twelve patients suffering from CLBP were included. The subjects were asked to perform a cognitive single task, a walking single task and a motor-cognitive dual task. Stride variability of trunk movements was calculated. A two-way ANOVA was performed to compare single-task walking with dual-task walking and the single cognitive task performance with the motor-cognitive dual-task performance. We did not find any differences in both of the single-task performances between groups. However, regarding single-task walking and dual-task walking, we observed an interaction effect indicating that low back pain patients show significantly higher gait variability in the dual-task condition as compared to controls. Our data suggest that chronic pain reduces motor-cognitive dual-task performance capability. We postulate that the detrimental effects are caused by central mechanisms where pain interferes with executive functions which, in turn, might contribute to increased risk of falling.

Effect of intermittent normobaric hypoxia on aerobic capacity and cognitive function in older people

OBJECTIVES Physical exercise, especially aerobic training, improves physical performance and cognitive function of older people. Furthermore, it has been speculated that age-associated deteriorations in physical performance and cognitive function could be counteracted through exposures to passive intermittent normobaric hypoxia (IH). Thus, the present investigation aimed at investigating the effect of passive IH combined with subsequent aerobic training on hematological parameters and aerobic physical performance (V˙O2max) as well as peripheral levels of the neurotrophin brain-derived neurotrophic factor (BDNF) and cognitive function. DESIGN Randomized controlled trial in a repeated measure design. METHODS 34 older participants were randomly assigned to an intervention group (IG) or control group (CG). While IG was supplied with passive IH for 90min, CG breathed ambient air. Subsequently, both groups underwent 30min of aerobic training three times per week for four consecutive weeks. Aerobic physical performance and cognitive function was tested with spiroergometry and the Stroop test. Blood samples were taken to measure hematological parameters and the peripheral serum BDNF-level. RESULTS We found increases in the values of hematological parameters, the time to exhaustion in the load test and an augmented and sustainable improvement in cognitive function within the IG of the older people only. However, in both groups, the V˙O2max and serum BDNF-level did not increase. CONCLUSIONS Based on these results, hypoxic training seems to be beneficial to enhance hematological parameters, physical performance and cognitive function in older people. The current hypoxic-dose was not able to enhance the serum BDNF-level or V˙O2max.

Towards the assessment of local dynamic stability of level-grounded walking in an older population.

Local dynamic stability is a critical aspect of stable gait but its assessment for use in clinical settings has not yet been sufficiently evaluated, particularly with respect to inertial sensors applied on the feet and/or trunk. Furthermore, key questions remain as to which state-space reconstruction is most reliable and valid. In this study, we evaluated the reliability as well as the ability of different sensor placement and state-spaces to distinguish between local dynamic stability in young and older adults. Gait data of 19 older and 20 young subjects were captured with inertial sensors twice within the first day as well as after seven days. 21 different signals (and combinations of signals) were used to span the systems state-space to calculate different measures of local dynamic stability. Our data revealed moderate or high effect sizes in 12 of the 21 old vs. young comparisons. We also observed considerable differences in the reliability of these 12 results, with intra-class correlation coefficients ranging from 0.09 to 0.81. Our results demonstrate that in order to obtain reliable and valid estimates of gait stability λ of walking time series is best evaluated using trunk data or 1-dimensional data from foot sensors.