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1.
We tested the hypothesis that anxiety regarding the potential consequences of a possible fall would alter gait patterns differently between younger and older adults. Sixteen younger and fifteen older adults participated in this study. Participants walked at a self-determined velocity along a 7.2-m walkway under 4 different conditions of postural threat; the walking conditions varied depending on the width constraints of the walkway (0.60 m vs 0.15 m) and the height of the walking surface (floor vs elevated: 0 m vs 0.60 m). Results indicated that although both younger and older adults altered their gait patterns under conditions of increased postural threat, the movement adaptations observed among older adults were substantially different to those adopted by younger adults. These age-dependent differences were strongly evidenced in the joint kinematics and the variability of the gait pattern within each condition. Our findings also indicated that when postural threat increased, the level of muscle activation throughout the gait cycle was altered in the distal musculature (gastrocnemius m. and tibialis anterior m.) among older adults only. Based on the age-related differences observed, we believe that the gait pattern alterations observed among younger and older adults reflect central set modifications to postural control that are mediated by a heightened anxiety imposed by the constraints of the testing conditions. Based on the age-dependent differences in the observed gait pattern modifications, it appears that the effects of anxiety on the control of locomotion are more pervasive for older adults than for younger adults.  相似文献   

2.
This study investigated whether or not gait kinematics among healthy older individuals and Parkinson's disease (PD) patients are influenced by postural threat. Eight healthy older individuals and eight PD patients were examined while walking at self-selected velocities, under three conditions of postural threat: unconstrained floor; constrained floor (19 cm wide); constrained and elevated floor (19 cm wide by 10 cm high). Independent of the surface conditions, due to motor disturbances caused by the PD these patients walked slower, with shorter strides, and spent more time in the double support phase and less time in the swing phase than did their matched controls. Increases in postural threat resulted in altered gait kinematics for all subjects. Specifically, stride length, stride velocity, cadence, and heel contact velocity decreased, and stride duration and double support duration increased relative to increases in postural threat. All gait alterations were the result of participants’ attempts to facilitate locomotion control and maintain stability. The results of this study reveal that width and height constraints effectively perturbed the balance of all of the walking older individuals. The PD patients were able to modulate gait parameters when faced by a postural threat task.  相似文献   

3.
For some people, visual exposure creates difficulty with movement and balance, yet the mechanisms causing this are poorly understood. The altered visual environment is an obvious possible cause of degraded balance. We studied locomotion in normal healthy adults along a 22-cm-wide walkway at ground level and at a height of 3.5 m. This produced substantial changes in gait progression (velocity reduced by 0.34 ms(-1), P <0.01), proportion of time spent in double support more than doubled (P <0.01), and galvanic skin conductance, a measure of physiological arousal, increased significantly (P <0.01). Since increasing visual distance is known to destabilize balance, our primary question was whether the disturbing effects of height could be eliminated by replacing sight of the drop with a visual surround comparable to ground level while retaining the danger and knowledge of the risk. Removing visual exposure did not significantly change the gait progression (P = 0.65) or double support duration (P = 0.58) but produced a small, significant reduction in physiological arousal (P = 0.04). In response to postural threat, knowledge of danger rather than current visual environment was the dominant cause of cautious gait and elevated physiological arousal in response to postural threat. We conclude that the mechanisms disturbing locomotion, balance, and autonomic response occur at a high task level which integrates cognition and prior experience with sensory input.  相似文献   

4.
The simultaneous performance of a cognitive task while walking typically alters the gait pattern. In some populations, these alterations have been associated with an increased risk of falls, motivating study of this response from the clinical perspective. The mechanisms responsible for these effects are not fully understood. The concurrent requirement to control upright posture and stepping, a bilaterally coordinated rhythmic task, may be the cause of this so-called dual-tasking effect. To evaluate this possibility, the present study was designed to isolate the individual contribution of these two demands by assessing the effects of cognitive loading on standing (i.e., postural control without bilateral coordination of stepping), cycling (i.e., bilateral coordination similar to stepping, but with minimal postural demands), and walking. We also investigated the effects of aging and parkinsonism on the performance of these three tasks in response to cognitive loading, also referred to as a dual task. Twenty-one healthy young adults, 15 healthy older adults, and 18 patients with Parkinson’s disease were assessed while walking, standing, and cycling, with and without an additional cognitive load. In the young adults, the performance on the two motor tasks that involved bilateral coordination deteriorated significantly in response to the dual task, while standing was not impacted. Similar results, although less robust, were observed among the healthy older adults. In contrast, among the patients with Parkinson’s disease, the dual-task costs, i.e., the impact of the simultaneously performed cognitive task on the gait pattern, were high in all motor tasks. These findings suggest that walking is especially vulnerable to cognitive loading, in part, because of the unique sensitivity of bilateral coordination of limb movements to the effects of dual tasking.  相似文献   

5.
Visual information concerning characteristics of the environment is critical for safe navigation. The purpose of this study was to determine the importance of vision from the lower visual field for negotiating multi-surface terrain. Ten healthy young adults and ten healthy older adults walked across a walkway where the middle portion consisted of solid, rock, slippery, compliant, tilt, and irregular surfaces (i.e. multi-surface terrain). Participants performed the walking trials with and without special glasses that blocked the lower visual field. Head pitch angle along with step parameters were measured. Young and older adults demonstrated increased mean and maximum head pitch angle downward when the lower visual field was blocked suggesting the importance of vision from this area when stepping on multi-surface terrain. In addition, young and older adults altered their gait pattern by reducing gait speed and step length when the lower visual field was blocked. These results suggest that information from the lower visual field is normally used when walking across multi-surface terrain. The results have implications for those individuals who wear multi-focal glasses and who use them while walking in complex environments, which may challenge balance.  相似文献   

6.
Research on attention and gait stability has suggested that the process of recovering gait stability requires attentional resources, but the effect of performing a secondary task on stability during obstacle avoidance is poorly understood. Using a dual-task paradigm, the present experiment investigated the extent to which young adults are able to respond to a secondary auditory Stroop task (requiring executive attentional network resources) concurrently with obstacle crossing during gait when compared with performing unobstructed walking or sitting (control task). Our results demonstrated that as the level of difficulty in the postural task increased, there was a significant reduction in verbal response time from congruent to incongruent conditions in the auditory Stroop task, but no differences in gait parameters, indicating that these postural tasks require attention, and that young adults use a strategy of modulating the auditory Stroop task performance while keeping stable gait performance under the dual-task situations. Our findings suggest the existence of a hierarchy of control within both postural task (obstacle avoidance requires the most information processing resources) and dual-task (with gait stability being a priority) conditions.  相似文献   

7.
Human gait requires the simultaneous generation of goal-directed continuous movement (locomotion) and the maintenance of balance (postural control). In adults, the centre of mass (CoM) oscillates in the vertical plane while walking. During the single support phase of gait initiation, its vertical (vCoM) velocity increases as the CoM falls and is actively reversed prior to foot-contact. In this study we investigated whether this active control, which is thought to reflect balance control during gait initiation, is controlled by visual and somatosensory inputs (Experiment 1) and whether it is modified by a change in motor demands, two steps versus one step (Experiment 2). In all healthy adults, the vCoM velocity was braked, or controlled, by contraction of the soleus muscle of the stance leg. The elimination of visual input alone had no effect on braking, although its amplitude decreased when somatosensory inputs were disrupted (−47%), and further decreased when both visual and somatosensory inputs were disrupted (−83%). When subjects performed only one step, with no trailing of the stance foot, the vCoM velocity braking also decreased (−42%). These results suggest that active braking of the CoM fall during the transition to double support, an indicator of balance control, is influenced by both multisensory integration and the demands of the current motor program. The neural structures involved in this mechanism remain to be elucidated.  相似文献   

8.
Optic flow is a powerful visual cue for the control of locomotion. Considerable research has focused on how healthy young people use and perceive optic flow. However, little is known on how older adults use this type of visual motion to control walking. The purpose of this study is to investigate the ability of young and older adults to adjust their physical walking trajectory in response to a rotation of the optic flow presented in a virtual environment. Ten healthy young adults (mean age 23.49 ± 4.72 yr) and 10 healthy older adults (mean age 76.22 ± 3.11 yr) participated in the study. Subjects were instructed to walk straight in a virtual environment viewed within a head-mounted display unit as they walked overground for 5 m, while the focus of expansion was gradually rotated to the left or the right by 40°. All subjects responded with a similar strategy by rotating their head and body in the direction away from the orientation of the perturbation. The younger subjects achieved almost complete corrections and had very small net heading errors. In contrast, the older adults had delayed and smaller reorientations, particularly in the head, thus showing significantly larger heading errors compared with younger subjects. We conclude that older adults retain the ability to use optic flow to control their walking trajectory, although smaller, delayed head rotations and larger heading errors may indicate an age-dependent effect on sensorimotor coordination.  相似文献   

9.
Previous studies have shown significant effects of increased postural anxiety in healthy young individuals when standing quietly or performing voluntary postural tasks. However, little is known about the influence of anxiety on reactive postural control. The present study examined how increased postural anxiety influenced postural reactions to unexpected surface rotations in multiple directions. Ten healthy young adults (mean age: 25.5 yr, range: 22-27 yr) were required to recover from unexpected rotations of the support surface (7.5 degrees amplitude, 50 degrees/s velocity) delivered in six different directions while standing in a low postural threat (surface height: 60 cm above ground) or high postural threat (surface height: 160 cm above ground) condition. Electromyographic data from 12 different postural leg, hip, and trunk muscles was collected simultaneously. Full body kinematic data were also used to determine total body center of mass (COM) and segment displacements. Four distinct changes were observed with increased postural anxiety: increased amplitude in balance-correcting responses (120-220 ms) in all leg, trunk, and arm muscles; decreased onset latency of deltoid responses; reduced magnitude of COM displacement; and reduced angular displacement of leg, pelvis, and trunk. These observations suggest that changes in dynamic postural responses with increased anxiety are mediated by alterations in neuro-muscular control mechanisms and thus may contribute significantly to the pathophysiology of balance deficits associated with aging or neurological disease.  相似文献   

10.
Human walking is highly adaptable, which allows us to walk under different circumstances. With aging, the probability of falling increases, which may partially be due to a decreased ability of older adults to adapt the gait pattern to the needs of the environment. The literature on visuomotor adaptations during reaching suggests, however, that older adults have little problems in adapting their motor behavior. Nevertheless, it may be that adaptation during a more complex task like gait is compromised by aging. In this study, we investigated the ability of young (n = 8) and older (n = 12) adults to adapt their gait pattern to novel constraints with a split-belt paradigm. Findings revealed that older adults adapted less and more slowly to split-belt walking and showed fewer aftereffects than young adults. While young adults showed a fast adjustment of the relative time spent in swing for each leg older adults failed to do so, but instead they were very fast in manipulating swing speed differences between the two legs. We suggest that these changes in adaptability of gait due to aging stem from a mild degradation of cortico-cerebellar pathways (reduced adaptability) and cerebral structures (decreased ability to change gait cycle timing). However, an alternative interpretation may be that the observed reduced adaptation is a compensatory strategy in view of the instability induced by the split-belt paradigm.  相似文献   

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