Effects of aging on whole body and segmental control while obstacle crossing under impaired sensory conditions

The ability to safely negotiate obstacles is an important component of independent mobility, requiring adaptive locomotor responses to maintain dynamic balance. This study examined the effects of aging and visual–vestibular interactions on whole-body and segmental control during obstacle crossing. Twelve young and 15 older adults walked along a straight pathway and stepped over one obstacle placed in their path. The task was completed under 4 conditions which included intact or blurred vision, and intact or perturbed vestibular information using galvanic vestibular stimulation (GVS). Global task performance significantly increased under suboptimal vision conditions. Vision also significantly influenced medial–lateral center of mass displacement, irrespective of age and GVS. Older adults demonstrated significantly greater trunk pitch and head roll angles under suboptimal vision conditions. Similar to whole-body control, no GVS effect was found for any measures of segmental control. The results indicate a significant reliance on visual but not vestibular information for locomotor control during obstacle crossing. The lack of differences in GVS effects suggests that vestibular information is not up-regulated for obstacle avoidance. This is not differentially affected by aging. In older adults, insufficient visual input appears to affect ability to minimize anterior–posterior trunk movement despite a slower obstacle crossing time and walking speed. Combined with larger medial–lateral deviation of the body COM with insufficient visual information, the older adults may be at a greater risk for imbalance or inability to recover from a possible trip when stepping over an obstacle.     

Athletic background is related to superior trunk proprioceptive ability,postural control,and neuromuscular responses to sudden perturbations

Trunk motor control is essential for athletic performance, and inadequate trunk motor control has been linked to an increased risk of developing low back and lower limb injury in athletes. Research is limited in comparing relationships between trunk neuromuscular control, postural control, and trunk proprioception in athletes from different sporting backgrounds. To test for these relationships, collegiate level long distance runners and golfers, along with non-athletic controls were recruited. Trunk postural control was investigated using a seated balance task. Neuromuscular control in response to sudden trunk loading perturbations was measured using electromyography and kinematics. Proprioceptive ability was examined using active trunk repositioning tasks. Both athlete groups demonstrated greater trunk postural control (less centre of pressure movement) during the seated task compared to controls. Athletes further demonstrated faster trunk muscle activation onsets, higher muscle activation amplitudes, and less lumbar spine angular displacement in response to sudden trunk loading perturbations when compared to controls. Golfers demonstrated less absolute error and variable error in trunk repositioning tasks compared to both runners and controls, suggestive of greater proprioceptive ability. This suggests an interactive relationship between neuromuscular control, postural control, and proprioception in athletes, and that differences exist between athletes of various training backgrounds.     

Residual attentional capacity amongst young and elderly during dual and triple task walking

Walking is considered an automatic function which demands little attentional resources. Thus a residual attentional capacity is available for a concurrent task (dual task). Minor age-related deficits in postural control may minimize the residual attentional capacity, however this may not be detected by a simple examination of the individuals gait performance. This study investigated the use of challenging dual task combinations to detect age related changes in gait performance. Eleven community-dwelling elderly (mean age 76 years) and 13 young subjects (mean age 26 years) participated in the study. The participants walked along a figure-of-eight track at a self-selected speed. The effect of introducing a concurrent cognitive task and a concurrent functional motor task was evaluated. Stride-to-stride variability was measured by heel contacts and by trunk accelerometry. In response to the cognitive task the elderly increased their temporal stride-to-stride variability by 39% in the walking task and by 57% in the combined motor task. These increases were significantly larger than observed for the young. Equivalent decreases in trunk acceleration autocorrelation coefficients and gait speed were found. A combination of sufficiently challenging motor tasks and concurrent cognitive tasks can reveal signs of limited residual attentional capacity during walking amongst the elderly.     

Distraction Affects the Performance of Obstacle Avoidance During Walking

In this study, dual-task interference in obstacle-avoidance tasks during human walking was examined. Ten healthy young adults participated in the experiment. While they were walking on a treadmill, an obstacle suddenly fell on the treadmill in front of their left leg during either midswing, early stance, or late stance of the ipsilateral leg. Participants were instructed to avoid the obstacle, both as a single task and while they were concurrently performing a cognitive secondary task (dual task). Rates of failure, avoidance strategy, and a number of kinematic parameters were studied under both task conditions. When only a short response time was available, rates of failure on the avoidance task were larger during the dual task than during the single task. Smaller crossing swing velocities were found during the dual task as compared with those observed in the single task. The difference in crossing swing velocities was attributable to increased stiffness of the crossing swing limb. The results of the present study indicated that divided attention affects young and healthy individuals' obstacle-avoidance performance during walking.     

Distraction affects the performance of obstacle avoidance during walking

In this study, dual-task interference in obstacle-avoidance tasks during human walking was examined. Ten healthy young adults participated in the experiment. While they were walking on a treadmill, an obstacle suddenly fell on the treadmill in front of their left leg during either midswing, early stance, or late stance of the ipsilateral leg. Participants were instructed to avoid the obstacle, both as a single task and while they were concurrently performing a cognitive secondary task (dual task). Rates of failure, avoidance strategy, and a number of kinematic parameters were studied under both task conditions. When only a short response time was available, rates of failure on the avoidance task were larger during the dual task than during the single task. Smaller crossing swing velocities were found during the dual task as compared with those observed in the single task. The difference in crossing swing velocities was attributable to increased stiffness of the crossing swing limb. The results of the present study indicated that divided attention affects young and healthy individuals' obstacle-avoidance performance during walking.     

Writing while walking: The impact of cognitive-motor multi-tasking on collision avoidance in human locomotion

BackgroundWhen moving in public space, individuals are challenged with having to master multiple cognitive and motor demands, either simultaneously or in short succession. Empirical evidence suggests that cognitive-motor multi-tasking during walking may impact one or both, cognitive and motor performance. These performance changes may result from unintentional task-interference effects, but also from strategic behavioral changes to cope with the multiple task demands. Strategic changes in human walking behavior have been uncovered in experimental scenarios, in which individuals avoid colliding with other individuals or objects in the environment. However, whether collision avoidance behavior is sensitive to cognitive-motor multi-task demands has remained underexplored, yet. Thus, with this study, we aimed at systematically studying cognitive-motor multi-task effects on collision avoidance during human locomotion.MethodsTen healthy participants (23.9 ± 4.3 years, 4 female) were walking at their preferred speed from a predefined start to end position under four experimental conditions: walking only (BL), walking while having to avoid a collision with another person (IO), writing a text message on a mobile phone while walking (cognitive-motor dual-task, DT), and writing while walking with collision avoidance demand (multi-task, MT). Parameters quantifying locomotor as well as collision avoidance behavior (path length, walking speed, minimum distance, path and speed adjustment) were assessed using optical motion tracking. In addition, performance in the writing task (errors, writing speed) was examined.ResultsParticipants' locomotor behavior was significantly affected by experimental conditions, with additive effects of multi-task demands on both path length (BL = DT < IO < MT) and walking speed (BL > IO > DT > MT). Further, participants showed an increased error rate and writing speed in the writing task when walking as compared to when standing still, independent of the presence of an interferer. Importantly, collision avoidance behavior was selectively influenced by cognitive-motor multi-task demands, with an increased minimum distance to the other person in the MT-condition, but no differences in path or speed adjustment.DiscussionOur results suggest significant multi-tasking effects of writing a message on the mobile phone while walking on both locomotor behavior and writing task performance. Collision avoidance behavior seems to be selectively affected by multi-task demands, reflected in an increased minimum passing distance, without overt changes in path or speed adjustments. This may be indicative for a strategic change in collision avoidance behavior towards a more cautious strategy to account for altered attention allocation and less visual feedback when writing while walking.     

The starting distance of obstacle circumvention did not affect intersegmental coordination in individuals with Parkinson's disease

BackgroundObstacle circumvention is a challenging task in Parkinson's disease (PD). Body segments adjustments, such as changing the direction of the trunk, followed by a change in the direction of the head, and modifications in the positioning of the feet, are necessary to circumvent an obstacle during walking. For that, individuals need to identify the distance to the obstacle, its characteristics (such as its dimension), and perform well-coordinated movements. However, PD is characterized by rigidity, which may be increased in the axial axis and compromise the task execution. Also, worsening sensory integration in PD may increase the time to perform these body segments adjustments, thus impairing the movement coordination when starting obstacle circumvention near to the obstacle.AimTo determine if the starting distance (1.5 m, 3 m, or 5 m) from the obstacle could modify the intersegmental coordination (specifically, the coordination between head, trunk, and pelvis) during the obstacle circumvention steps in individuals with PD.MethodsFourteen individuals with a diagnosis of idiopathic PD and 15 neurologically healthy individuals (CG) from the community were included in this study. The participants were evaluated in three different gait conditions, according to the starting distance from the obstacle: 1.5 m, 3 m, and 5 m away from the obstacle. Vector coding technique was employed to establish the coupling between head, trunk, and pelvis in the steps immediately before and during obstacle circumvention. Three-way ANOVA's (group, distance, and step) were calculated with the level of significance at p < 0.05.ResultsFor all couplings of coordination, there were no effects of distance. However, significant main effects of group and steps (p < 0.05) were found for all couplings with different patterns of coordination: head/pelvis (group: in-phase and anti-phase variables; steps: anti-phase variable), head/trunk (group: trunk variable; steps: in-phase and anti-phase variables) and trunk/pelvis (group: anti-phase; steps: trunk and pelvis). Finally, only head/trunk coupling showed an interaction between group*steps. Individuals with PD showed 7.95% lower head movement (p < 0.024) and 14.85% greater trunk movement than CG (p < 0.002). Also, individuals with PD performed 17.56% greater head movement in the step before the circumvention compared to the step during circumvention (p < 0.044).ConclusionThe starting distance from the obstacle did not influence the pattern of axial intersegmental coordination in both groups. However, how these segments interact in the preparation and during the obstacle circumvention are opposite in individuals with PD. While on the previous step to obstacle circumvention, the head movement was greater than the trunk, during the obstacle circumvention step, individuals with PD rotated the trunk more.     

The influence of proximal motor strategies on pianists' upper-limb movement variability

Repetitive movements are considered a risk factor for developing practice-related musculoskeletal disorders. Intra-participant kinematic variability might help musicians reduce the risk of injury during repetitive tasks. No research has studied the effects of proximal motion (i.e., trunk and shoulder movement) on upper-limb movement variability in pianists. The first objective was to determine the effect of proximal movement strategies and performance tempo on both intra-participant joint angle variability of upper-limb joints and endpoint variability. The second objective was to compare joint angle variability between pianist's upper-limb joints. As secondary objectives, we assessed the relationship between intra-participant joint angle variability and task range of motion (ROM) and documented inter-participant joint angle variability. The upper body kinematics of 9 expert pianists were recorded using an optoelectronic system. Participants continuously performed two right-hand chords (lateral leap motions) while changing movements based on trunk motion (with and without) and shoulder motion (counter-clockwise, back-and-forth, and clockwise) at two tempi (slow and fast). Trunk and shoulder movement strategies collectively influenced variability at the shoulder, elbow and, to a lesser extent, the wrist. Slow tempi led to greater variability at wrist and elbow flexion/extension compared to fast tempi. Endpoint variability was influenced only along the anteroposterior axis. When the trunk was static, the shoulder had the lowest joint angle variability. When trunk motion was used, elbow and shoulder variability increased, and became comparable to wrist variability. ROM was correlated with intra-participant joint angle variability, suggesting that increased task ROM might result in increased movement variability during practice. Inter-participant variability was approximately six times greater than intra-participant variability. Pianists should consider incorporating trunk motion and a variety of shoulder movements as performance strategies while performing leap motions at the piano, as they might reduce exposure to risks of injury.     

Gait adjustments in response to an obstacle are faster than voluntary reactions

It has been reported that obstacle avoidance reactions during gait have very short latencies. This raises the question whether the cortex can be involved, as it is in voluntary reactions. In this study, latencies of obstacle avoidance (OA) reactions were determined and related to latencies of voluntary stride modifications and simple reaction times (SRT) of hand and foot. Twenty-five healthy young adults participated in this study. While they were walking on the treadmill, an obstacle suddenly fell in front of their left leg. The first reaction to the obstacle was the moment at which the differentiated acceleration curve of the foot deviated from the control signal. Latencies of OA reactions were 122 ms (SD 14 ms) on average. Two very different avoidance reactions (lengthening and shortening of the stride) were noticed, but there was no avoidance strategy effect on OA latencies. OA latencies were significantly shorter as compared to latencies of voluntary stride modifications and simple reaction times of hand and foot. The short OA latencies could not only be explained from the dynamic nature of the task. It is suggested that subcortical pathways might be involved in obstacle avoidance.     

Age-related changes of arm movements in dual task condition when walking on different surfaces

The purpose of this study was to investigate whether the dual task paradigm would influence arm movements during walking. Furthermore, we examined the effects of different walking surfaces on arm movements while performing dual tasks. The effects of age and gender were also investigated. Fifteen young adults and 15 older adults were included in this study. Subjects were asked to perform the walking task alone (single-task trial) and walking in combination with a cognitive task (dual-task trial). Four walking conditions (1 single task and 3 dual task trials)×two walking surfaces were encountered. Both age groups had greater elbow and trunk movement in the sagittal plane under the dual task trials as compared to the single task trial (p<.05). Subjects had greater upper extremity and upper body movement on the soft floor than on the hard floor (p<.05). Subjects had greater movement amplitude when confronting a challenging environment, especially in the contralateral side. Among gender, there was a group-gender interaction: the older females had smaller upper extremity movement than the older males (p<.05) but the opposite was true for the young adults. The results suggest that different age groups of males and females use different balance control strategy to deal with the challenging conditions.     

Exercise training can improve spatial characteristics of time-critical obstacle avoidance in elderly people

Fall prevention programs have rarely been evaluated by quantitative movement analysis methods. Quantitative movement analyses could provide insight into the mechanisms underlying the effects of training. A treadmill obstacle avoidance task under time pressure has recently been used to evaluate a fall prevention exercise program for community-dwelling elderly people and it showed that participants improved their obstacle avoidance success rates. The mechanism, by which the increased success rates were achieved, however, remained to be determined. Participants were elderly who had fallen at least once in the year prior to participation. They were assigned to either the exercise or the control group. The control group did not receive any specific treatment. The exercise group was administered a five week exercise program, which consisted of exercises on a functionally oriented obstacle course, walking exercises, and practice of fall techniques. Pre- and post-intervention laboratory obstacle avoidance tests were conducted. Three possible determinants of success were investigated, namely avoidance reaction times, the distribution of avoidance strategies, and three spatial parameters (toe distance, foot clearance and heel distance). Analysis yielded significant TimexGroup interactions in heel distances. The exercise group increased heel distance, while the control group did not. Increased heel distance may result in reduced risk of heel contact with the obstacle and, consequently, larger success rates. The remaining parameters showed no effect of training. In conclusion, the training program was effective in improving time-critical obstacle avoidance skills. In every day life, these effects of training may contribute to less obstacle-related fall incidents in elderly. In addition, these findings could indicate that the execution of other time-critical events, like an actual fall, could also be improved by training.     

Development of the coordination between posture and manual control

Studies have suggested that proper postural control is essential for the development of reaching. However, little research has examined the development of the coordination between posture and manual control throughout childhood. We investigated the coordination between posture and manual control in children (7- and 10-year-olds) and adults during a precision fitting task as task constraints became more difficult. Participants fit a block through an opening as arm kinematics, trunk kinematics, and center of pressure data were collected. During the fitting task, the precision, postural, and visual constraints of the task were manipulated. Young children adopted a strategy where they first move their trunk toward the opening and then stabilize their trunk (freeze degrees of freedom) as the precision manual task is being performed. In contrast, adults and older children make compensatory trunk movements as the task is being performed. The 10-year-olds were similar to adults under the less constrained task conditions, but they resembled the 7-year-olds under the more challenging tasks. The ability to either suppress or allow postural fluctuations based on the constraints of a suprapostural task begins to develop at around 10 years of age. This ability, once developed, allows children to learn specific segmental movements required to complete a task within an environmental context.     

Three-dimensional kinematics of the scapula and trunk,and associated scapular muscle timing in individuals with stroke

Poor scapulothoracic control is a risk for developing shoulder pathology, but has received little attention so far in individuals with stroke (IwS). Trunk and scapular kinematics and surface muscle activity were measured in 15 healthy controls and 18 IwS during a low and high forward flexion (FF). Group-differences in trunk and scapular kinematics were assessed during low and high FF using a t-test (independent samples). Differences in muscle onset and offset time relative to movement start (both FF tasks) were determined using a mixed model taking into account the different groups and muscles. Recruitment patterns per group and task were described based on significant differences between muscles. In IwS, earlier lower trapezius and late infraspinatus offset were found during low FF, as well as a later onset and earlier offset of serratus anterior. For low FF, significantly more trunk axial rotation was found in IwS during both elevation and lowering. During high FF, IwS showed significantly less scapular posterior tilt during elevation and more scapular lateral rotation during lowering. IwS demonstrated adaptive muscle timing with earlier initiation and late inactivation of lower trapezius and infraspinatus, possibly to compensate for a late activation and early deactivation of the serratus anterior and to establish as such the correct pattern of scapulothoracic movement.     

Increasing task complexity and ice hockey skills of youth athletes

The objective of this pilot study was to investigate the effects on cognitive performance of progressively adding tasks specific to ice hockey (skating, stick handling, and obstacle avoidance) during a visual interference task (Stroop Color Word Test-interference condition). In addition, the effects on locomotor performance of progressively adding tasks of stickhandling, visual interference, and obstacle avoidance related to maximal skating speed and minimal obstacle clearance were investigated in eight male athletes ages 10 to 12 years. Results revealed decreased performance on both cognitive and physical measures with increased task complexity, suggesting that adding complexity to an environment influences hockey skill performance.     

Visuomotor error augmentation affects mediolateral head and trunk stabilization during walking

Prior work demonstrates that humans spontaneously synchronize their head and trunk kinematics to a broad range of driving frequencies of perceived mediolateral motion prescribed using optical flow. Using a closed-loop visuomotor error augmentation task in an immersive virtual environment, we sought to understand whether unifying visual with vestibular and somatosensory feedback is a control goal during human walking, at least in the context of head and trunk stabilization. We hypothesized that humans would minimize visual errors during walking – i.e., those between the visual perception of movement and actual movement of the trunk. We found that subjects did not minimize errors between the visual perception of movement and actual movement of the head and trunk. Rather, subjects increased mediolateral trunk range of motion in response to error-augmented optical flow with positive feedback gains. Our results are more consistent with our alternative hypothesis – that visual feedback can override other sensory modalities and independently compel adjustments in head and trunk position. Also, aftereffects following exposure to error-augmented optical flow included longer, narrower steps and reduced mediolateral postural sway, particularly in response to larger amplitude positive feedback gains. Our results allude to a recalibration of head and trunk stabilization toward more tightly regulated postural control following exposure to error-augmented visual feedback. Lasting reductions in mediolateral postural sway may have implications for using error-augmented optical flow to enhance the integrity of walking balance control through training, for example in older adults.     

A load on my mind: evidence that anhedonic depression is like multi-tasking

Multi-tasking can increase susceptibility to distraction, affecting whether irrelevant objects capture attention. Similarly, people with depression often struggle to concentrate when performing cognitively demanding tasks. This parallel suggests that depression is like multi-tasking. To test this idea, we examined relations between self-reported levels of anhedonic depression (a dimension that reflects the unique aspects of depression not shared with anxiety or other forms of distress) and attention capture by salient items in a visual search task. Furthermore, we compared these relations to the effects of performing a concurrent auditory task on attention capture. Strikingly, both multi-tasking and elevated levels of anhedonic depression were associated with increased capture by uniquely colored items, but decreased capture by abruptly appearing items. At least with respect to attention capture and distraction, depression seems to be functionally comparable to juggling a second, unrelated cognitive task.     

The influence of approach–avoidance motivational orientation on conflict adaptation

To deal effectively with a continuously changing environment, our cognitive system adaptively regulates resource allocation. Earlier findings showed that an avoidance orientation (induced by arm extension), relative to an approach orientation (induced by arm flexion), enhanced sustained cognitive control. In avoidance conditions, performance on a cognitive control task was enhanced, as indicated by a reduced congruency effect, relative to approach conditions. Extending these findings, in the present behavioral studies we investigated dynamic adaptations in cognitive control—that is, conflict adaptation. We proposed that an avoidance state recruits more resources in response to conflicting signals, and thereby increases conflict adaptation. Conversely, in an approach state, conflict processing diminishes, which consequently weakens conflict adaptation. As predicted, approach versus avoidance arm movements affected both behavioral congruency effects and conflict adaptation: As compared to approach, avoidance movements elicited reduced congruency effects and increased conflict adaptation. These results are discussed in line with a possible underlying neuropsychological model.     

Head and Trunk Control While Walking in Older Adults with Diabetes: Effects of Balance Confidence

Investigations of gait in older adults with diabetes mellitus (DM) have been primarily focused on lower limb biomechanical parameters. Yet, the upper body accounts for two thirds of the body's mass, and head and trunk control are critical for balance. The authors examined head and trunk control during self-selected comfortable, fast, and dual-task walking and the relationship between balance confidence and potential head-trunk stiffening strategies in older adults with DM without diagnosed diabetic peripheral neuropathy (DPN). Twelve older adults with DM without diagnosed DPN (DM group) and 12 without DM (no-DM group) were recruited. Walking speed, peak-to-peak head and trunk roll displacement, head and trunk roll velocity, and head-trunk correlation were measured while walking at a self-selected comfortable or fastest possible speed with or without a secondary cognitive task. The Activities-specific Balance Confidence scale measured balance confidence. Subtle group differences in axial segmental control (lower trunk roll velocity; higher head-trunk correlation) were apparent in older adults with DM even in the absence of DPN. Balance confidence was 19% lower in the DM group than in the no-DM group, and partially explained (34%) the group difference in head-trunk stiffening. These results emphasize the need for proactive monitoring of postural control and balance confidence before the onset of DPN.     

Regulating cognitive control through approach-avoidance motor actions

In two studies, the regulatory function of approach-avoidance cues in activating cognitive control processes was investigated. It was hypothesized that avoidance motor actions, relative to approach motor actions, increase the recruitment of cognitive resources, resulting in better performance on tasks that draw on these capacities. In Study 1, error rates on a verbal response mode version of the Stroop task were analyzed. On inconsistent Stroop trials, participants in the avoidance condition made significantly fewer errors than those in the approach condition. In Study 2, performance differences on a task switching paradigm were investigated. Crucially, approach and avoidance motor actions were manipulated within-subjects by alternating between approach and avoidance motor actions on 4 blocks of trials. Temporal switching costs were significantly lower while performing an avoidance, compared to an approach motor action. These results support our hypothesis that avoidance cues, relative to approach cues, lead to improved performance on cognitive control tasks.     

“The threat is in the head,not in the legs”: Activating negative age stereotypes generates extra cognitive load during walking

ObjectiveActivating negative age stereotypes has been consistently shown to impair cognitive performance in older adults, but not motor performance, especially on mobility tasks. We tested the hypothesis that older adults may still experience stereotype threat, even if mobility performance is not affected. To do so, we examined whether inducing negative stereotypes may increase cognitive load during a walking task.MethodThis question was investigated in a dual-task paradigm: older adults performed simultaneously a walking task and a Stroop task, in stereotype and control conditions.ResultsResults showed that the stereotype induction did not affect walking parameters but decreased performance on the Stroop task, indicating that this induction increased cognitive load during walking.DiscussionThese results suggest that negative age stereotypes may be damaging even if walking parameters are not affected, by altering older adults' attention to their walking environment. We conclude by highlighting theoretical and practical implications.