Manual materials handling is a common occupational task associated with workplace falls. The aim of this study was to examine whether an anterior manual load impacts balance recovery via compensatory stepping. Step recovery following unpredictable perturbations to standing were compared with and without a manual load in 12 young healthy male and female adults. Recovery from forward perturbations was measured via the margin of stability during and following the step, as well as by step coordination in terms of maintaining lateral stability in shifting support between legs when stepping, along with step timing and placement. While the load did not affect forward destabilization during the step, it did delay the reversal of the falling motion after landing the foot. Moreover, the load disrupted lateral stability control such that a greater fall toward the unsupported step-leg side occurred but with no increase in step-width to compensate. Step-length was also unchanged, but the load did elicit slightly earlier step timing that in turn reduced the prestep interval to enact lateral weight shifts. These results show that a load compromises step recovery by delaying poststep restabilization and disrupting step coordination, identifying step response efficacy as a possible factor in fall risk associated with manual loads.

Balance reactions depend on sensing imbalances to direct recovery responses, though the role of vestibular feedback in scaling these responses remains uncertain. While vestibular input can alter anticipatory postural adjustments before a compensatory step (McMorran, Bent, and Zettel 2024), this study aimed to clarify whether this reflects vestibular-based scaling of step-recovery or if vestibular input acts as a stability reference in feedforward control of step execution. To investigate vestibular input's influence on step scaling, galvanic vestibular stimulation (GVS) was aligned to amplify or diminish the sense of perturbed postural motion in forward step recovery, through inducing the sensation of forward (FGVS) or backward (BGVS) postural motion. Effects of altered vestibular input was analyzed in terms of postural and step motion and restabilization. GVS modulated forward step responses asymmetrically, with BGVS exhibiting greater postural motion in advance of the step as indicated through forward stability, while FGVS evoked larger and faster forward steps relative to the body. Upon landing the step, these differences culminated as skewed stability according to GVS direction, with a smaller stability margin in BGVS compared to a larger one in FGVS. This stability shift continued post-recovery, with a forward-BGVS and backward-FGVS shift when re-establishing equilibrium. These results demonstrate step-recovery scaling according to the GVS direction, indicating vestibular-based modulation of compensatory stepping reactions.

Compensatory stepping reactions to recover balance are frequently performed, however, the role of sensory feedback in regulating these responses is not fully understood. Specifically, it is unknown whether vestibular input influences compensatory stepping. Here, we aimed to assess whether step responses utilize vestibular input by combining medio-lateral galvanic vestibular stimulation (GVS) with step-inducing balance perturbations via unpredictable anterior–posterior platform translations. Step responses were assessed for any lateral differences due to the illusory sense of left (LGVS) or rightward (RGVS) postural motion in terms of pre-step weight-shifts, center of mass (COM) motion and step-placement as well as lateral stability when recovering balance. GVS evoked clear differences from the pre-step phase onwards, in an asymmetrical pattern depending on the GVS direction relative to the right step-leg side. RGVS induced a leftwards postural shift to create a larger stability margin to the right ( p < 0.0007), opposing the illusory motion and reducing the fall towards the unsupported side during the step; however, RGVS caused no change in step-width. Conversely, LGVS evoked a leftward step placement ( p < 0.0001) in the direction of the mis-sensed motion, but without any rightward shift in postural motion. This asymmetry is consistent with vestibular input predictively modulating pre-step lateral weight-shifts and foot-placement in accordance with step mechanics, specifically in controlling frontal plane stability when lifting the foot to step.

Student Evaluations of Teaching (SETs) are a ubiquitous tool in higher education. Though they are not effective means of evaluating teaching ability, they are useful in formative teaching development of a teaching career. We characterise the current formative use of and attitudes towards SETs by instructors across all disciplines (STEM and non-STEM). We found that tenured instructors used SETs for formative development more than untenured, and that non-STEM instructors had more negative associations with SETs than STEM instructors. Based upon these data, we make recommendations to redesign the SET instrument and change the way in which the data are used to support formative teaching development.

Inter-segmental coordination patterns and mechanical energy transfer were compared between vertical jumping tasks which possess different countermovement characteristics. Thirteen participants completed squat (SJ), countermovement (CMJ) and drop (DVJ) vertical jumps. Inter-segmental coordination patterns became more out-of-phase with increases in countermovement velocity (DVJ > CMJ > SJ), at the ankle, hip and lumbar spine (all p < 0.05), but not at the knee. With countermovements, more inter-segmental energy transfer occurred at all joints (p < 0.05), but increasing the countermovement velocity (DVJ compared to CMJ) did not always increase energy transfer (p < 0.001 for the hip and knee, p > 0.05 for the ankle and lumbar spine). The relationship between mechanical energy transfer and inter-segmental coordination patterns during vertical jumping is not straightforward since the responses to these varying countermovement demands were not consistent across all joints.

Student evaluations of teaching (SETs) provide both summative and formative feedback. Although it is clear that SETs are used by administrators for summative purposes, such as providing data to support personnel decisions, it is uncertain how instructors use them for formative development such as to inform overall teaching practice. The objective of our study was to determine the frequency and nature of SET use for formative purposes, to explore the perception of SET utility to inform teaching practice, and to determine how perception of SET utility might be improved to enhance its use in a formative context. Participants were all biological sciences instructors at a large, research-intensive University. This research was conducted in two phases, using a combination of focus groups, interviews, and a survey to yield both qualitative and quantitative data. We found that while instructors generally perceive that SET feedback has formative utility, and that most instructors have used SET feedback for formative purposes at some point, there are many elements of SET administration that they are dissatisfied with, and they suggest several ways in which SETs could be improved (such as allowing in class time for SET administration or doing multiple administrations per semester) to yield more useable feedback that could inform their teaching. The results of this study can be used to further inform the ongoing debate about the role that SETs should play in higher education, as they demonstrate both the utility and concerns about using SETs for formative purposes.

Reaching movements generate reaction forces that affect postural stability, requiring sophisticated coordination between body and arm movement to maintain balance. In voluntary movement, this coordination involves feedforward shifts of posture, and such anticipatory postural muscle activity also accompanies the rapid modulation of an ongoing point to suddenly a shifting target (double-step). However, it is unknown if this early postural activity depends on target-shift predictability and whether arm and body motion are similar coordinated to voluntary movement. Body and arm motion coordination during double-step pointing movements from standing were done under differing conditions of target-shift predictability. In a proportion of trials, the pointing target was displaced, with the predictability of target-shift direction varied between two peripheral targets (target-shift direction known) and two central targets (target-shift direction uncertain). The target jump evoked an adjustment in the arm then body response, opposite to the pointing responses to the initial target. The triggered arm-then-body ordering was consistent across target-shift predictability, although known target-shift direction resulted in closer timing of arm and body onsets. The altered coordination in triggered corrections suggests that the body component in triggered reactions depend on response predictability, showing an altered control of arm and body motion.

Visuo-vestibular recalibration, in which visual information is used to alter the interpretation of vestibular signals, has been shown to influence both oculomotor control and navigation. Here we investigate whether vision can recalibrate the vestibular feedback used during the re-establishment of equilibrium following a perturbation. The perturbation recovery responses of nine participants were examined following exposure to a period of 11 s of galvanic vestibular stimulation (GVS). During GVS in VISION trials, occlusion spectacles provided 4 s of visual information that enabled participants to correct for the GVS-induced tilt and associate this asymmetric vestibular signal with a visually provided ‘upright’. NoVISION trials had no such visual experience. Participants used the visual information to assist in realigning their posture compared to when visual information was not provided (p < 0.01). The initial recovery response to a platform perturbation was not impacted by whether vision had been provided during the preceding GVS, as determined by peak centre of mass and pressure deviations (p = 0.09). However, after using vision to reinterpret the vestibular signal during GVS, final centre of mass and pressure equilibrium positions were significantly shifted compared to trials in which vision was not available (p < 0.01). These findings support previous work identifying a prominent role of vestibular input for re-establishing postural equilibrium following a perturbation. Our work is the first to highlight the capacity for visual feedback to recalibrate the vertical interpretation of vestibular reafference for re-establishing equilibrium following a perturbation. This demonstrates the rapid adaptability of the vestibular reafference signal for postural control.

Investigating an ecologically relevant upper limb task, such as manually transporting an object with a concurrent lateral change in support (sidestepping alongside a kitchen counter), may provide greater insight into potential deficits in postural stability, variability and motor coordination in older adults. Nine healthy young and eleven older, community dwelling adults executed an upper limb object transport task requiring a lateral change in support in two directions at two self-selected speeds, self-paced and fast-paced. Dynamic postural stability and movement variability was quantified via whole-body center of mass motion. The onset of lead lower limb movement in relation to object movement onset was quantified as a measure of motor coordination. Older adults demonstrated similar levels of stability and variability as their younger counterparts, but at slower peak movement velocity and increased task duration. Furthermore, older adults demonstrated asymmetrical motor coordination between left and right task directions, while younger adults remained consistent regardless of task direction. Thus, older adults significantly modulated movement speed and motor coordination to maintain similar levels of stability and variability compared to their younger counterparts.

A simultaneous turn and step motion is a vital component of many complex movements and may provide insight into age related balance and stability deficits during a weight transfer task. In this study, nine young adults and ten healthy, community dwelling older adults performed a simultaneous “turn and step” task from a quiet standing position under two self-selected speeds, self-paced and as quickly and efficiently as possible. Whole-body center of mass was estimated to investigate stability, segmental coordination, and variability. Older adults performed the task with greater variability, however they were unable to alter stability nor segmental coordination across the self-selected speeds; absence of this modulation portrays a trade-off between stability and manoeuvrability. An increase in variability with no observed directional differences suggests that the simultaneous turn and step task may be a sensitive discriminatory motor task helpful in elucidating the adoption of altered control strategies used by elderly populations.

A "reach and transport object" task that represents common activities of daily living may provide improved insight into dynamic postural stability and movement variability deficits in older adults compared to previous lean to reach and functional reach tests. Healthy young and older, community dwelling adults performed three same elevation object transport tasks and two multiple elevation object transport tasks under two self-selected speeds, self-paced and fast-paced. Dynamic postural stability and movement variability was quantified by whole-body center of mass motion. Older adults demonstrated significant decrements in frontal plane stability during the multiple elevation tasks while exhibiting the same movement variability as their younger counterparts, regardless of task speed. Interestingly, older adults did not exhibit a tradeoff in maneuverability in favour of maintaining stability throughout the tasks, as has previously been reported. In conclusion, the multi-planar, ecologically relevant tasks employed in the current study were specific enough to elucidate decrements in dynamic stability, and thus may be useful for assessing fall risk in older adults with suspected postural instability.

The objective of this work was to investigate the influence perturbation direction has on postural responses during overground gait, and whether these responses are age related. Differences in stepping patterns following perturbations of the support surface were examined in the frontal and sagittal planes during forward walking. Eleven young and 10 older adults completed Mini BESTest, hip strength tests, and 45 perturbed walking trials, triggered on heel contact. Lateral perturbations were more challenging to postural stability for both groups. Step length measures showed young adults recovered in the step proceeding the perturbation, while older adults needed additional steps to regain balance. Young adults arrested center of mass movement by producing larger step widths than older adults following the support surface perturbation.

Dysequilibrium of cervicogenic origin can result from pain and injury to cervical paraspinal tissues post-whiplash; however, the specific physiological mechanisms still remain unclear. Central sensitization is a neuradaptive process which has been clinically associated with conditions of chronic pain and hypersensitivity. Strong links have been demonstrated between pain hypersensitivity and postural deficits post-whiplash; however, the precise mechanisms are still poorly understood. The purpose of this study was to explore the mechanisms of cervicogenic disequilibrium by investigating the effect of experimentally induced central sensitization in the cervical spine on postural stability in young healthy adults. Sixteen healthy young adults (7 males (22.6 +/- 1.13 years) and 9 females (22 +/- 2.69 years)) performed 30-s full-tandem stance trials on an AMTI force plate under normal and centrally sensitized conditions. The primary outcome variables included the standard deviation of the center of pressure (COP) position in medio-lateral (M-L) and antero-posterior (A-P) directions; sway range of the COP in M-L and A-P directions and the mean power frequency (MPF) of the COP and horizontal ground shear forces. Variability and sway range of the COP decreased with experimental induction of central sensitization, accompanied by an increase in MPF of COP displacement in both M-L and A-P directions, suggesting an increase in postural stiffening post-sensitization versus non-sensitized controls. Future studies need to further explore this relationship in clinical (whiplash, chronic pain) populations. (C) 2015 Elsevier B.V. All rights reserved.

Balance disruptions induced by voluntary focal arm actions are accommodated via anticipatory postural adjustments, but how this coordinated control is organized by the central nervous system remains unclear: either as combined or separate streams of postural-focal motor commands. For example, a focal arm task that dictates extremely tight temporal constraints may induce a focal response in absence of an anticipatory postural adjustment, providing evidence for separate focal-postural control streams. This study sought to probe the organization of focal-postural control via an interceptive task with very little available response time, and to determine whether focal-postural coordination depends on temporal and/or spatial foreknowledge of the task. Ten healthy young adults (5 males and 5 females; 20-29 years) reacted to catch a ball when standing under four conditions of temporal and spatial foreknowledge. Response onset was characterized by muscle activity from both postural and focal arm muscles. The catching task resulted in rapid muscle responses, but there was no difference between the fastest focal and postural muscle onsets. As expected, temporal cuing resulted in faster focal and postural onsets compared to spatial and control cuing trials. The accompaniment and time-locking of focal and postural muscle onsets, suggests that postural-focal coupling remains intact even under external time constraints and provides evidence for a single combined command stream of postural and focal control under such circumstances.

Hemiparetic stroke patients commonly bear more weight on the non-paretic side which seems intuitively linked to unilateral control deficits. However, there is evidence that some post-stroke favour weighting the paretic side, which may be problematic given altered capacity of the paretic limb to contribute to the control of upright posture. This study explores the prevalence and clinical determinants of stance asymmetry, and the relationship between stance asymmetry and postural control among chronic stroke patients. Subjects (n=147; >6 months post-stroke) stood on two force plates in eyes-open and eyes-closed conditions; 59 were symmetric, 18 had paretic asymmetry (PA), and 70 had non-paretic asymmetry (NPA). Root mean square (RMS) of antero-posterior and medio-lateral centre-of-pressure under each limb and both limbs combined were compared. RMS of total medio-lateral centre-of-pressure was greater for both asymmetric groups compared with the symmetric group. PA subjects relied less on the loaded limb for control than NPA subjects and relied more on visual information for postural control than those who were symmetric. There were no differences in the characteristics of individuals between the PA and NPA groups. The loading of the paretic limb was not related to impaired postural control during stationary standing which was attributable, in part, to individuals relying on control from the non-paretic limb, in spite of lower vertical load, and a greater dependence on visual contributions. There was no evidence that greater loading on the paretic limb was related to persisting dyscontrol but may rather reflect a learned strategy.

Problem: Falling is a leading cause of serious injury, loss of independence, and nursing-home admission in older adults. Impaired balance control is a major contributing factor. Methods: Results from our balance-control studies have been applied in the development of new and improved interventions and assessment tools. Initiatives to facilitate knowledge-translation of this work include setting up a new network of balance clinics, a research-user network and a research-user advisory board. Results: Our findings support the efficacy of the developed balance-training methods, balance-enhancing footwear, neuro-prosthesis, walker design, handrail-cueing system, and handrail-design recommendations in improving specific aspects of balance control. Impact on Knowledge Users: A new balance-assessment tool has been implemented in the first new balance clinic, a new balance-enhancing insole is available through pharmacies and other commercial outlets, and handrail design recommendations have been incorporated into 10 Canadian and American building codes. Work in progress is expected to have further impact. (C) 2011 National Safety Council and Elsevier Ltd. All rights reserved.

Rapid step reactions evoked by balance perturbation must accommodate constraints on limb motion imposed by obstacles and other environmental features. Recent results suggest that the required visuospatial information (VSI) is acquired and stored "proactively", prior to perturbation onset (PO); however, the extent to which "online" (post-PO) visual feedback can contribute is not known. To study this, we used large unpredictable platform perturbations to evoke rapid step reactions, while subjects wore liquid crystal goggles that occluded vision: (1) prior to PO (forcing use of online-VSI), (2) after PO (forcing use of stored-VSI), or (3) not at all (normal-VSI). Subjects stood behind a barrier in which the location of a narrow slot, through which the foot had to be moved during forward step reactions, was varied unpredictably between trials. Within subjects who were able to do the task (6 of 8 young adults tested), responses in stored-VSI and normal-VSI trials were very similar. However, in online-VSI trials, the foot-off time for the step through the slot was delayed (by approximately 50 ms, on average). Presumably, this delay allowed more time to acquire and process online-VSI regarding the required foot trajectory, yet subjects were still more likely to select the "wrong" foot (contralateral to the slot location) and to contact the barrier while moving the foot through the slot, in online-VSI trials. These results suggest a critical role for stored-VSI during the earliest phase of the step, in selecting the step limb and planning the initial trajectory. Online acquisition and processing of the required VSI may be too slow to allow effective control of this early phase, particularly in situations where the demands for accurate foot motion are high.

BACKGROUND:Rapid stepping reactions are a prevalent response to sudden loss of balance and are thought to play a crucial role in preventing falls. Previous dual-task studies, involving concurrent performance of step reactions and a visuomotor tracking task, indicated that online visual attention was not required to guide the step, even when nearby objects increased demands for accurate foot movement. However, the planning and execution of the step apparently required attentional resources initially allotted to the tracking task. Reallocation of these resources ("attention switching") was delayed in older adults. The present study examined the influence of the competition for attentional resources by comparing trials performed with and without the concurrent task.METHODS:Unpredictable platform perturbations were used to evoke rapid forward stepping reactions in healthy young and older adults. Challenging obstacles and/or step targets increased demands for accurate foot motion in some trials. A concurrent tracking task was performed in half of the trials.RESULTS:Although participants looked down more frequently in the absence of the tracking task, the ability to clear the obstacle or land on the step target and other spatiotemporal features of the stepping reactions were largely unaffected. There was, however, one notable exception: In older adults, the duration and amplitude of the "anticipatory postural adjustment" that preceded foot lift were reduced in tracking trials, resulting in increased lateral center-of-mass motion.CONCLUSION:Impaired attention switching apparently compromised the control of lateral stability during stepping reactions in older adults, and may be an important contributor to increased risk of falling.

BACKGROUND:Rapid stepping reactions are a prevalent response to sudden loss of balance and play a crucial role in preventing falls. A previous study indicated that young adults are able to guide these stepping reactions amid challenging environmental constraints using "stored" visuospatial information. This study addressed whether healthy older adults also use "stored" visuospatial information in this manner, or are more dependent on "online" visual control.METHODS:Gaze behavior was recorded during rapid forward-stepping reactions evoked by unpredictable platform perturbation, as participants performed a concurrent task demanding visual attention. Challenging obstacles and/or step targets were used to increase demands for accurate foot motion. Twelve healthy older adults (61-73 years) were compared to 12 young adults (22-29 years) tested in a previous study.RESULTS:Similar to young adults, older participants seldom redirected gaze downward in response to the perturbation (11% of trials), yet were commonly able to clear the obstacle (74% of trials) or land on the target (41% of trials) while stepping to recover balance. The threat posed by the obstacle apparently prompted older adults to initiate early downward saccades during a small proportion (18%) of obstacle trials; however, this did not improve ability to clear the obstacle.CONCLUSION:Aging did not alter the predominant visual-control strategy used to guide the stepping reactions. Both young and older persons typically used stored visuospatial information, thereby allowing vision/attention to be switched to other demands during the stepping reaction and minimizing head/eye movements that could exacerbate the destabilizing effect of the balance perturbation.