[Show abstract][Hide abstract] ABSTRACT: Postural threat, manipulated through changes in surface height, influences postural control. Evidence suggests changes in attention may contribute to this relationship. However, limited research has explored where and how attention is reallocated when threatened. The primary aim of this study was to describe changes in attention when presented with a postural threat, while a secondary aim was to explore associations between changes in attention and postural control. Eighty-two healthy young adults completed tests of static (quiet standing) and anticipatory (rise to toes) postural control under threatening and non-threatening conditions. Participants completed an open-ended questionnaire after each postural task which asked them to list what they thought about or directed their attention toward. Each item listed was assigned a percentage value reflecting how much attention it occupied. Exit interviews were completed to help confirm where attention was directed. Five attention categories were identified: movement processes, threat-relevant stimuli, self-regulatory strategies, task objectives, and task-irrelevant information. For both postural tasks, the percentage values and number of items listed for movement processes, threat-relevant stimuli, and self-regulatory strategies increased under threatening compared to non-threatening conditions, while the percentage values and number of items listed for task objectives and task-irrelevant information decreased. Changes in attention related to movement processes and self-regulatory strategies were associated with changes in static postural control, while changes in attention related to threat-relevant stimuli were associated with changes in anticipatory postural control. These results suggest that threat-induced changes in attention are multidimensional and contribute to changes in postural control.
[Show abstract][Hide abstract] ABSTRACT: This pilot study examined whether an adapted gymnastics program, CAN-flip, could be a feasible activity for children with cerebral palsy (CP) leading to improvements in muscle fitness, motor performance, and physical self-perception. Four girls and 1 boy (9.8 ± 1.3 yr) with CP participated in this multiple-baseline across-subjects design and were randomly assigned to start either the 6-wk gymnastics or the 6-wk control period. Muscle strength, neuromuscular activation, range of motion, gross motor performance, balance, and physical self-perception were assessed at baseline, after the first 6-wk period, and at the conclusion of the study. The gymnastics program comprised two 1-hr individualized classes per week. All participants were able to complete the gymnastics classes without injury and showed improvement in specific gymnastics skills. In addition, 3 of the 5 participants registered for regular gymnastics classes after the study, demonstrating the program's usability as a link to inclusive gymnastic classes.
No preview · Article · Oct 2015 · Adapted physical activity quarterly: APAQ
[Show abstract][Hide abstract] ABSTRACT: The tendon tap reflex (T-reflex) is often evoked in relaxed muscles to assess spinal reflex circuitry. Factors contributing to reflex excitability are modulated to accommodate specific postural demands. Thus, there is a need to be able to assess this reflex in a state where spinal reflex circuitry is engaged in maintaining posture. The aim of this study was to determine whether a pendulum hammer could provide controlled stimuli to the Achilles tendon and evoke reliable muscle responses during normal stance. A second aim was to establish appropriate stimulus parameters for experimental use. Fifteen healthy young adults stood on a forceplate while taps were applied to the Achilles tendon under conditions in which postural sway was constrained (by providing centre of pressure feedback) or unconstrained (no feedback) from an invariant release angle (50°). Twelve participants repeated this testing approximately six months later. Within one experimental session, tap force and T-reflex amplitude were found to be reliable regardless of whether postural sway was constrained (tap force ICC=0.982; T-reflex ICC=0.979) or unconstrained (tap force ICC=0.968; T-reflex ICC=0.964). T-reflex amplitude was also reliable between experimental sessions (constrained ICC=0.894; unconstrained ICC=0.890). When a T-reflex recruitment curve was constructed, optimal mid-range responses were observed using a 50° release angle. These results demonstrate that reliable Achilles T-reflexes can be evoked in standing participants without the need to constrain posture. The pendulum hammer provides a simple method to allow researchers and clinicians to gather information about reflex circuitry in a state where it is involved in postural control.
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to examine whether explicit instruction would facilitate arm reactions in individuals with Parkinson's disease (PD). Individuals with (n=10) and without (n=15) PD responded to unexpected support-surface translations. To recover their balance, participants were required to either respond naturally (react natural) or to reach toward a nearby handrail (explicit instruction). Arm reactions were quantified from electromyographic (EMG) and arm kinematic recordings. Results showed that while explicit instruction led to earlier and larger arm reactions, the benefits were not different between individuals with and without PD. Specifically, when explicitly instructed to reach toward a handrail, shoulder EMG responses were 4% earlier (p=.005) and 32% larger (p<.001) compared to when instructed to react naturally. A 44% greater peak wrist medio-lateral velocity (p<.001) and a 29% greater peak shoulder abduction angular velocity (p<.001) were also observed when participants were instructed to direct their arms toward a handrail after an unexpected support-surface translation. Explicit instruction also led to a higher frequency of handrail contact and a 49ms earlier time to handrail contact compared to the react natural condition (p=.015). These results suggest that providing instruction to promote arm movement may help reduce falls in older adults with and without PD.
No preview · Article · Aug 2014 · Human Movement Science
[Show abstract][Hide abstract] ABSTRACT: Unlabelled:
BACKGROUND/STUDY CONTEXT: Indirect evidence suggests that concerns over the impressions made on others (self-presentational concerns) may be associated with balance-related outcomes in older adults, but no empirical evidence exists to support this speculation. The present study examined the relationship between self-presentational concerns (social anxiety, social physique anxiety, and self-presentational efficacy) and functional mobility, accounting for age, balance confidence, falls, and muscle strength.
Healthy women (60 years or older; N = 187) completed measures of self-presentational concerns, balance confidence, and fall history, and performed the timed up and go (TUG) test and a test of leg strength. Bivariate correlations were conducted. A hierarchical regression predicted TUG duration from the three self-presentational concerns, controlling for age, balance confidence, falls, and muscle strength to examine the unique variance in TUG duration explained by self-presentational concerns.
Self-presentational efficacy was a significant predictor of TUG duration over and above that of age, balance confidence, falls, and muscle strength. The results also showed significant correlations between social anxiety and self-presentational efficacy and TUG duration, between all three self-presentational concerns and balance confidence, and between social physique anxiety and self-presentational efficacy and falls.
Research is needed to examine the causal relationship between these outcomes. Investigating self-presentational concerns in older women may provide novel ways to impact balance-related outcomes in this population. Practical implications for clinicians are discussed, as the social and physical environment may influence self-presentational concerns in this population and subsequently impact assessment and treatment outcomes.
Full-text · Article · Jul 2014 · Experimental Aging Research
[Show abstract][Hide abstract] ABSTRACT: Verbal persuasion has been shown to influence psychological and behavioral outcomes. The present study had two objectives: (1) to examine the effect of verbal persuasion on task choice in a balance setting and (2) to evaluate the use of verbal persuasion as an approach to experimentally induce mismatches between perceived and actual balance. Healthy young adults (N=68) completed an 8-m tandem walk task without vision and then were randomly assigned to a feedback group (good, control, or poor), regardless of actual balance. Following the feedback, participants chose to perform the task in one of three conditions differing in level of challenge and also were required to perform the task under the same pre-feedback conditions. Balance efficacy and perceived stability were rated before and after each pre- and post-feedback task, respectively. Balance performance measures were also collected. Following the feedback, participants in the good group were more likely to choose the most challenging task while those in the poor group were more likely to choose the least challenging task. Following the feedback, all groups showed improved balance performance. However, balance efficacy and perceived stability increased for the good and control groups but balance efficacy decreased and perceived stability was unchanged for the poor group. Thus, these findings demonstrate that verbal persuasion can influence task choice and may be used as an approach to experimentally create mismatches between perceived and actual balance.
[Show abstract][Hide abstract] ABSTRACT: Despite the established relationship between low balance confidence and poorer balance and gait performance, discrepancies may occur between an individual's perceived and actual abilities. This study determined if trunk sway measures could assist in identifying potential discrepancies between perceived and actual balance. Older women completed the Activities-specific Balance Confidence (ABC) scale and performed a series of 16 stance, gait and tandem gait tasks. Duration (or completed steps for tandem gait tasks) and trunk pitch and roll angle and angular velocity were calculated. Low (mean ABC score≤70%, n=33) and high (mean ABC score≥90%, n=99) balance confidence groups were identified from a pool of 204 participants. The low balance confidence group had greater stance trunk pitch and roll sway, shorter one leg stance durations, reduced gait trunk roll sway, longer gait durations, less tandem gait trunk roll sway and completed fewer tandem gait steps compared to the high balance confidence group. Stepwise linear discriminant analysis identified four variables that were used to achieve a classification accuracy of 75.8% for low and 90.9% for high balance confidence groups. This study reinforces the influence of low balance confidence on stance and gait control and provides direction for the identification and treatment of individuals with discrepancies between perceived and actual balance.
[Show abstract][Hide abstract] ABSTRACT: The current thesis investigated the effects of a 12-week multifactorial exercise and balance training program on balance control in older adults. Participants completed a baseline testing session which included a series of questionnaires, anthropometric measures, and 18 stance and walking tests. Those who were randomly assigned to the exercise group participated in the 12-week training program while the comparison group was asked not to change anything in his/her lifestyle during the 12-week control period, but were invited to participate in the training program after his/her control period. The same testing protocol was repeated after the 12-week period. The results indicated that there were improvements in the time to complete the walking tests but no change in trunk sway in both the exercise and comparison groups. No changes in stance duration or trunk sway were observed. The findings suggest that the current training program showed no significant improvement in balance control in healthy older adults.
[Show abstract][Hide abstract] ABSTRACT: The authors investigated how the nervous system responds to dual task performance. Because dual tasking is associated with greater postural challenges, it was hypothesized that spinal excitability would be reduced when simultaneously performing 2 tasks. For this experiment, participants maintained a lying or standing posture with or without performing a concurrent cognitive task (i.e., reacting to an auditory tone). Spinal excitability was assessed by eliciting the soleus Hoffmann reflex (H-reflex). Results indicated that the H-reflex was 6.4 ± 2.3% smaller (p = .011) when dual compared to single tasking. The reduced H-reflex amplitude, indicating a depressed spinal excitability, when dual tasking is suggested to reflect a neural strategy that individuals adopt to maintain postural stability when cognitive resources are divided between 2 concurrent tasks.
No preview · Article · Aug 2012 · Journal of Motor Behavior
[Show abstract][Hide abstract] ABSTRACT: This study investigated modifications to standing posture in response to elevated postural anxiety evoked by a potential physical threat to stability. Sixteen young adults, 16 older adults and 16 patients diagnosed with Parkinson's disease (PD) stood with or without the expectation of a threat to their posture (i.e., external trunk perturbation). This method allowed for the assessment of the effects of anticipatory anxiety on standing posture associated with an ecologically valid and direct threat to stability. Our manipulation was successful as all participants, independent of age and disease, reported significant increases in postural anxiety when anticipating a threat to their posture. The trunk sway modifications observed in response to elevated postural anxiety were dependent on age and disease. Young adults showed increased trunk sway in both pitch and roll directions while older adults demonstrated decreased trunk sway but only in the roll direction when standing and expecting a threat to posture compared to standing without this threat. Individuals with PD showed no significant changes in trunk pitch or roll sway when anticipating a threat to posture compared to standing without this threat. Our findings suggest that the effects of postural anxiety on postural control are dependent on the context associated with the postural threat, and age and disease status.
[Show abstract][Hide abstract] ABSTRACT: Verbal feedback was used to alter balance efficacy to examine its effects on perceived and actual balance in young adults. Participants (N=61) completed a stance task, were randomized to either a high or low balance efficacy or control group, and then completed the same task. The results showed that balance efficacy was manipulated as the low balance efficacy group had decreases in balance efficacy. Although verbal feedback did not alter balance efficacy in the high balance efficacy group, perceptions of stability increased for these participants. No changes in actual balance were found. The nature of verbal feedback may differentially influence balance-related cognitions during a challenging stance task in young adults.
No preview · Article · Jul 2011 · Canadian Journal of Experimental Psychology
[Show abstract][Hide abstract] ABSTRACT: The 16-item Activities-specific Balance Confidence (ABC-16) scale is commonly used to assess balance confidence in older adults. Recent work has shown that a shortened version of this scale (ABC-6; includes the 6 most challenging balance tasks) can also be used as a valid and reliable measure of balance confidence in a sample of 35 community-living older adults and is more strongly related to falls than the original version of the scale. The present study replicates and extends this work in a larger sample. We investigated the validity and reliability of the ABC-6 in older adults. A total of 65 men and 174 women age 60 and older completed the ABC-16, performed the Timed Up and Go (TUG) test, and reported fall(s) that had occurred over the last year. The results showed that balance confidence was significantly lower on the ABC-6 (78%) compared to ABC-16 (87%); however, scores on the 2 versions of the scale were significantly correlated (r = 0.95). Both versions of the scale had high internal consistency (Cronbach’s alpha, ABC-16 = 0.94; ABC-6 = 0.88) and high test-retest reliability (intraclass correlation, ABC-16 = 0.79; ABC-6 = 0.79). The ABC-16 and ABC-6 were both significantly correlated to TUG scores (r = -0.39, r = -0.36, respectively) and falls (r = -0.28, r = -0.29, respectively). Each version of the scale was able to discriminate between men (ABC-16 = 91%, ABC-6 = 86%) and women (ABC-16 = 86%, ABC-6 = 75%), and between non-fallers (ABC-16 = 89%, ABC-6 = 80%) and multiple fallers (2 or more falls reported; ABC-16 = 75%, ABC-6 = 63%), and single fallers (1 fall reported; ABC-16 = 90%, ABC-6 = 81%) and multiple fallers. The results suggest that, similar to the original version of the scale, the ABC-6 is a valid and reliable tool that can be used to assess balance confidence in healthy community-dwelling older adults.
[Show abstract][Hide abstract] ABSTRACT: Previous research has shown that skill focused attention may be beneficial for the performance of complicated motor tasks in individuals with Parkinson's disease (PD). The objective of this study was to assess the impact of skill focused attention instructions on gait under temporal movement constraints that may reflect common challenges experienced in daily life. Eighteen patients with PD walked a straight pathway under two different attention focus conditions (no instruction, skill focused instruction) and two different walking speeds (preferred pace, as fast as possible). In the no instruction condition, patients were not told "where" attention should be directed. In the skill focused instruction condition, patients were told to focus on the foot contacting the floor with each step. Spatial and temporal gait measures, as well as, trunk sway were used to quantify walking performance. The results showed that when walking at a preferred pace, skill focused instructions benefited gait performance (e.g., increased gait velocity, larger steps, more trunk sway). However, when walking as fast as possible, skill focused instructions had the opposite effect on gait performance (e.g., decreased gait velocity, smaller steps, and less trunk sway). This study demonstrates that skill focused instructions may contribute to the prioritization of stability under imposed temporal movement constraints. Clinicians should be aware of the processes involved in prioritization of movement components versus task goals in PD and the potential application of an attention based instructional set in altering priorities in this population.
[Show abstract][Hide abstract] ABSTRACT: Biofeedback has been shown to improve balance in a number of different populations. As certain clinical populations have a tendency to fall in one direction, the provision of biofeedback in the impaired direction may improve balance in that direction but not in others. The purpose of this study was to determine the effects of uni-directional biofeedback on stance tasks in healthy young adults. Trunk sway was measured in 40 healthy young adults as they performed nine stance tasks with and without biofeedback. Participants received biofeedback about their trunk sway in either the anterior-posterior (AP) or medial-lateral (ML) direction using a multi-modal head-mounted biofeedback device. An overall effect of reduced sway angle and increased sway angular velocity was noted with biofeedback. Some of the effects of biofeedback were dependent on the direction in which biofeedback was given and whether vision was present during the stance task. These effects were strongest in the pitch direction for AP biofeedback with vision present. This study showed direction specific effects of biofeedback are greatest in the sagittal plane. These results are important clinically as the use of biofeedback during stance tasks, similar to gait tasks, appears to work best in the AP direction when vision is present.
[Show abstract][Hide abstract] ABSTRACT: Although it is well established that postural threat modifies postural control, little is known regarding the underlying mechanism(s) responsible for these changes. It is possible that changes in postural control under conditions of elevated postural threat result from a shift to a more conscious control of posture. The purpose of this study was to determine the influence of elevated postural threat on conscious control of posture and to determine the relationship between conscious control and postural control measures. Forty-eight healthy young adults stood on a force plate at two different surface heights: ground level (LOW) and 3.2-m above ground level (HIGH). Centre of pressure measures calculated in the anterior-posterior (AP) direction were mean position (AP-MP), root mean square (AP-RMS) and mean power frequency (AP-MPF). A modified state-specific version of the Movement Specific Reinvestment Scale was used to measure conscious motor processing (CMP) and movement self-consciousness (MSC). Balance confidence, fear of falling, perceived stability, and perceived and actual anxiety indicators were also collected. A significant effect of postural threat was found for movement reinvestment as participants reported more conscious control and a greater concern about their posture at the HIGH height. Significant correlations between CMP and MSC with AP-MP were observed as participants who consciously controlled and were more concerned for their posture leaned further away from the platform edge. It is possible that changes in movement reinvestment can influence specific aspects of posture (leaning) but other aspects may be immune to these changes (amplitude and frequency).
[Show abstract][Hide abstract] ABSTRACT: This study was designed to manipulate balance efficacy using verbal persuasion to investigate its influence on perceived and actual balance in healthy young adults (n=46). Participants completed two balance tasks and were then randomized to either a high (performance within the top 10% for age and gender) or low (performance within the bottom 10% for age and gender) balance efficacy group, regardless of actual balance. Following the performance feedback, participants completed the same two balance tasks. Participants rated their balance efficacy prior to all tasks, and their perceived stability following all tasks. Trunk movement was recorded during each task to provide an estimate of actual balance. Results showed that the manipulation failed to alter balance efficacy in either group. However, participants in the good balance information group reported greater stability than those in the poor balance information group following the performance feedback, despite no changes in actual balance. These results suggest that verbal persuasion, independent of changes in balance efficacy or actual balance, can modify perceptions of stability in healthy young adults.
[Show abstract][Hide abstract] ABSTRACT: This study was designed to improve the understanding of how standing at elevated surface heights and the associated changes in the visual field affect human balance control. Healthy young adults stood at four different surface heights (ground, 0.8, 1.6 and 3.2 m) under three different visual conditions (eyes open, eyes closed and eyes open with peripheral vision occluded). Mean position, Mean Power Frequency (MPF) and Root Mean Square (RMS) of centre of pressure (COP) displacements were calculated from 60s standing trials, and psychosocial and physiological measures of fear and anxiety were also collected. When standing at a height of 3.2 m, 10 of 36 participants reported an increase in anxiety and a robust fear response while the remaining 26 participants experienced only an increase in anxiety and no fear response. A between subjects analysis of the effect of surface height on postural control revealed that fearful and non-fearful participants adopted different postural control strategies with increased heights. Non-fearful participants demonstrated a postural response characterized by increased MPF and decreased RMS of COP displacements with increasing heights. In contrast, fearful participants demonstrated both increasing MPF and RMS of COP displacements with increasing heights. These findings demonstrate, for the first time, a direct relationship between fear of falling and the strategies used for human postural control.
[Show abstract][Hide abstract] ABSTRACT: This study investigated the effects of altering the base of support (BOS) at the turn point on anticipatory locomotor adjustments during voluntary changes in travel direction in healthy young and older adults. Participants were required to walk at their preferred pace along a 3-m straight travel path and continue to walk straight ahead or turn 40 degrees to the left or right for an additional 2-m. The starting foot and occasionally the gait starting point were adjusted so that participants had to execute the turn using a cross-over step with a narrow BOS or a lead-out step with a wide BOS. Spatial and temporal gait variables, magnitudes of angular segmental movement, and timing and sequencing of body segment reorientation were similar despite executing the turn with a narrow or wide BOS. A narrow BOS during turning generated an increased step width in the step prior to the turn for both young and older adults. Age-related changes when turning included reduced step velocity and step length for older compared to young adults. Age-related changes in the timing and sequencing of body segment reorientation prior to the turn point were also observed. A reduction in walking speed and an increase in step width just prior to the turn, combined with a delay in motion of the center of mass suggests that older adults used a more cautious combined foot placement and hip strategy to execute changes in travel direction compared to young adults. The results of this study provide insight into mobility constraints during a common locomotor task in older adults.
Full-text · Article · Jul 2008 · Experimental Brain Research
[Show abstract][Hide abstract] ABSTRACT: This study investigated the effects of postural threat on the cortical response associated with postural reactions to predictable and unpredictable perturbations to upright stance. Postural threat was manipulated by having individuals stand on an elevated surface to alter the context in which the postural task was performed. Ten healthy young adults experienced a series of predictable and unpredictable trunk perturbations when standing at ground level and at the edge of a platform located 3.2 m above the ground. Participants felt less confident, more fearful of falling, more anxious and less stable when standing at the high surface height. Unpredictable perturbations generated a large negative potential (N1) which was increased by 84% when standing at the high compared to low surface height. The magnitude of change in this potential was related to the magnitude of change in balance perceptions, such as confidence and fear. Predictable perturbations did not generate a N1 potential but instead produced an anticipation-related potential prior to the perturbation. This cortical activity observed in response to predictable perturbations was not influenced by postural threat. A large N1 potential was observed for a 'surprise' perturbation that followed a series of predictable perturbations. There was a trend for the amplitude of this potential to be increased when standing at the high compared to low surface height. The results of this study provide evidence for the modulating influence of psychological factors related to postural threat on the cortical activity associated with postural reactions to unpredictable perturbations.
Full-text · Article · May 2008 · Neuroscience Letters