Lori Vallis - Academia.edu (original) (raw)

Papers by Lori Vallis

Investigative Ophthalmology & Visual Science, Sep 26, 2016

Applied Physiology, Nutrition, and Metabolism, Dec 1, 2020

This study compares sleep outcome measures obtained using normal- and low-frequency extension (LF... more This study compares sleep outcome measures obtained using normal- and low-frequency extension (LFE) settings (Actilife). Forty-two children (aged 3–6 years) were instructed to wear an ActiGraph GT3X+ accelerometer on their hip for 7 days, 24 h/day. Total sleep time (min), sleep efficiency (%), and number and cumulative length (min) of awakening were used to compare the settings. Results suggest that the LFE setting results in significant but relatively small reductions in the sleep metrics of children. Trial registration no.: clincialtrials.gov (ID no. NCT02223234) Novelty LFE setting, available through ActiGraph, estimates a significantly reduced total sleep time and efficiency.

IEEE Sensors Journal, Apr 1, 2022

Recently, there has been a notable shift to increasingly more sedentary lifestyles, yet it remain... more Recently, there has been a notable shift to increasingly more sedentary lifestyles, yet it remains unclear whether inexpensive accelerometers, such as those contained in Actigraph devices, can provide consistent measurements of low magnitude accelerations. This study sought to explore the ability of two Actigraph models to differentiate low frequency oscillations, in reference to higher-end accelerometers with the idle sleep mode disabled (ISM) (Part 1) and enabled (Part 2) in a controlled environment. Eight GT9X, fifteen wGT3X-BT and two higher-end accelerometers (Triaxial ICP) were mounted to a 6-degree of freedom robot, which introduced frequencies ranging from 0.5-2.0 Hz (Part 1) and 0.5-4.0 Hz (Part 2). To compare the models, the minimum, maximum and range of outputs were calculated for each of the frequencies. Part 1 revealed that the Actigraph monitors were able to detect low frequency oscillations; the captured output was similar across the different Actigraph models but was significantly greater than the higher-end devices. Part 2 demonstrated that amplitudes greater than the described 40 m g (0.392 m/s2) threshold were required for the Actigraph monitors to wake up. This study demonstrates that the GT9X and wGT3X-BT Actigraph accelerometers can detect low magnitude movements when the ISM is disabled.

Experimental Brain Research, Jan 28, 2021

Humans integrate visual information about their surrounding environment to properly adapt their l... more Humans integrate visual information about their surrounding environment to properly adapt their locomotion to step over or around obstacles in their path. We know that cognition aids in the execution of locomotion and in complex maneuvers such as obstacle avoidance. However, the role of the cognitive system in performing online adjustments to an obstacle avoidance strategy during locomotion has not yet been elucidated. Nineteen young adults instrumented with kinematic markers were asked to step over or circumvent an obstacle to the left or right. In half of these trials, participants were required to adjust this strategy when cued by LED lights two steps prior to obstacle crossing. In 75% of trials, a cognitive task was simultaneously presented (incongruent or congruent auditory Stroop cue, or neutral cue). Center of mass position and velocity was estimated and gait metrics (eg. step length) were calculated to quantify how individuals performed this last-minute direction change and determine how these responses changed when simultaneously performing a cognitive task. Results showed statistically shorter crossing steps, where the trailing limb was placed further from the leading edge and the lead limb was placed closer to the trailing edge when responding to the auditory Stroop task. Performing these avoidance strategy changes also decreased cognitive task performance. Our findings suggest that visually integrating a new stepping pattern to cross an obstacle is a complex locomotor maneuver, and requires the aid of the cognitive system to be performed effectively in a young adult population.

European Journal of Applied Physiology, May 4, 2019

PurposeWe hypothesize that training older adults with a structured visual attention task will res... more PurposeWe hypothesize that training older adults with a structured visual attention task will result in improved balance and mobility, potentially reducing their risk for falls.MethodsHealthy older adults aged 70 + took part in the study (mean age 80.3 ± 6 years). In this randomised control trial (NCT02030743), 15 participants were randomly assigned to a visual attention training group and 15 to a control group. Visual attention training was undertaken twice a week (45 min sessions) for 3 weeks (= six sessions) using versions of a selective attention useful field of view test and attended field of view test. The outcome measures were postural sway using a force plate, the Mini-Balance Evaluation Systems Test, the One-Legged Stance test, the 5 Meter Walking test, the Sit to Stand test, the Timed Up and Go test without and with a concurrent cognitive task.ResultsThere was a greater improvement in visual attention after training in the intervention group compared to the control group (p < 0.01). However, a mixed ANOVA (2× groups, 2× visit) showed no main effect of visit or group or any interaction for any of the force plate parameters. T tests of the changes over time between the intervention group and the control groups for the other balance and mobility assessment tools showed no improvement after the visual attention training.ConclusionIt was found that there was no improvement in either mobility or balance after the visual attention training and no difference between the intervention and the control groups.

Journal of Applied Gerontology, Dec 19, 2013

Gait & Posture, May 1, 2018

Background: Maintaining the centre of mass (CoM) of the body within the base of support is a crit... more Background: Maintaining the centre of mass (CoM) of the body within the base of support is a critical component of upright balance; the ability to accurately quantify balance recovery mechanisms is critical for many research teams. Research question: The purpose of this study was to investigate how exclusion of specific body segments in an anthropometric CoM model influenced a dynamic measure of postural stability, the margin of stability (MoS), following a support-surface perturbation. Methods: Healthy young adults (n = 10) were instrumented with kinematic markers and a safety harness. Sixteen support-surface translations, scaled to ensure responses did not involve a change in base of support, were then issued (backwards, forwards, left, or right). Whole-body CoM was estimated using four variations of a 13segment anthropometric model: i) the full-model (WFM), and three simplified models, ii) excluding upper limbs (NAr); iii) excluding upper and lower limbs (HTP); iv) pelvis CoM (CoMp). The CoM calculated for each variant was then used to estimate extrapolated CoM (xCoM) position and the resulting MoS within the plane of postural disturbance. Results: Comparisons of simplified models to the full model revealed significant differences (p < 0.05) in MoS for all models in each perturbation condition; however, the largest differences were following sagittal plane based perturbations. Poor estimates of WFM MoS were most evident for HTP and CoMp models; these were associated with the greatest values of RMS/maximum error, poorest correlations, etc. The simplified models provided low-error approximates for frontal plane perturbations. Significance: Findings suggest that simplified calculations of CoM can be used by researchers without reducing MoS measurement accuracy; however, the degree of simplification should be context-dependent. For example, CoMp models may be appropriate for questions pertaining to frontal plane MoS; sagittal plane MoS necessitates inclusion of lower limb and HTP segments to prevent underestimation of postural stability.

Gait & Posture, Jun 1, 2005

Chapter 2. Ageing and Conclusion: The elderly are lacking in their ability to utilize ankle stiff... more Chapter 2. Ageing and Conclusion: The elderly are lacking in their ability to utilize ankle stiffening to protect themselves from perceived risk of falling in the forward direction. References [1] Carpenter MG, Silcher CP. Surface height effects on postural control: A hypothesis for a stiffness strategy for stance. J Vestib Res 1999; 9:277 86. balance control I• Dynamic electromyographic activities of lower extremity muscles in patients with osteoarthritis of the knees

Experimental Brain Research, Jun 6, 2007

The aim of this research was to describe agerelated changes in locomotor adjustments during obstr... more The aim of this research was to describe agerelated changes in locomotor adjustments during obstructed gait and expand and build from the current body of literature describing single obstacle avoidance strategies by including trials in which the subjects stepped over two identical obstacles placed in series. We observed young adults (YA: N = 8; aged 23.1 § 2.0 years) and older adults (OA: N = 8; aged 76.1 § 4.3 years) as they walked along a 5 m long instrumented pathway (GAITRite) and stepped over one or two obstacles that were scaled to their lower leg length. Infrared markers, tracked using the Optotrak motion analysis system (60 Hz; Northern Digital Inc, Canada), were Wxed to subjects' trunk and feet, and several anatomical landmarks were digitized for each segment (e.g. toes). Data analyses included lead and trail toe clearance values, take-oV and landing distance, step time, length, width and velocity, and three-dimensional trunk angles. Both age groups were able to successfully complete the obstacle avoidance task, and the presence of a second obstacle did not aVect clearance strategies of either OA or YA. OA crossed the obstacles with a reduced step velocity and stepped closer to the trailing edge, although take-oV distances were not diVerent between the age groups. Additionally, OA used similar ranges of trunk motion as YA when crossing the obstacle, but did so while using smaller step lengths and step widths compared to YA, eVectively, using a narrower base of support. Together, these Wndings suggest that older adults adopted a more cautious crossing strategy in that they reduced their crossing step velocity. However, other aspects of the avoidance strategy used by the older adults, speciWcally the shortened landing distances and the use of similar ranges of trunk motion within a narrowed BOS, could potentially put them at risk for tripping or imbalance when stepping over an obstacle.

BACKGROUND Chronic stress is an important risk factor in the development of obesity. While resear... more BACKGROUND Chronic stress is an important risk factor in the development of obesity. While research suggests chronic stress is linked to excess weight gain in children, the biological or behavioural mechanisms are poorly understood. OBJECTIVE The objectives of the Family Stress Study are to examine behavioural and biological pathways through which chronic stress exposure (including stress from COVID-19) may be associated with adiposity in young children, and to determine if factors such as child sex, caregiver-child relationship quality, caregiver education and caregiver self-regulation moderate the association between chronic stress and child adiposity. METHODS The Family Stress Study is a prospective cohort study of families recruited from two Canadian sites: University of Guelph in Guelph, Ontario and McMaster University in Hamilton, Ontario. Participants will be followed for 2 years and were eligible to participate if they had at least one child (age 2-6) and no plans to move from the area within the next 3 years. Study questionnaires and measures were completed remotely at baseline and will be assessed using the same methods at 1- and 2-year follow-ups. RESULTS The study sample includes 359 families (359 children; 359 female caregivers;179 male caregivers). Children’s mean (SD) age is 3.9 (1.2) years and 51% are female. Approximately 74% of children and 80% of caregivers identify as white. Approximately 34% of caregivers have a college diploma or less and nearly 93% are married or cohabitating with a partner. Nearly half (47%) of the families have an annual household income ≥$100 000 CAD. CONCLUSIONS Despite public health restrictions from COVID-19, the Family Stress Study was successful in recruiting and using remote data collection to successfully engage families in the study. Results from this study will help identify the direction and relative contributions of the biological and behavioural pathways linking chronic stress and adiposity. These findings will aid in the development of effective interventions designed to modify these pathways and reduce obesity risk in children. CLINICALTRIAL This study has been retrospectively registered with the ‘Clinicaltrials.gov, Protocol and Results Registration System (ID: NCT05534711) as of September 8, 2022.

Measurement in Physical Education and Exercise Science, Dec 26, 2021

Experimental Gerontology

It has been suggested that the most frequent cause of falls in assisted-living facilities is due ... more It has been suggested that the most frequent cause of falls in assisted-living facilities is due to incorrect weight shifting. Lateral instability and weakness have also been linked to falls risk. The objective of this study was to evaluate balance responses to weight shifting during walking and to investigate age-related changes in movement and strength. Thirty-two participants (16 young, 16 older) completed 12 straight walking trials and 6 trials in each condition where a weight shift was required to grasp a handrail. Instructions were to walk down the pathway and, if cued, grasp the handrail as quickly as possible. Conditions included left and right grasping trials, with and without prior knowledge about the movement direction. Kinematic data were recorded and center of mass (COM) was calculated to examine whole body movements. A clinical balance test, strength, and body composition measures were captured to facilitate exploration into the relationship of these measures with reactive movements used during weight transfers. Young adults had quicker lateral COM velocities and reached peak velocity earlier. Males completed the task quicker than females and, for everyone, having knowledge about direction enabled quicker responses. Grip strength was correlated to most performance metrics in this study; more-so than body composition. Slower reactive movements might reflect a more cautious strategy in the older adults or it may highlight changes that occur with increased age and strength changes.

Journal of Exercise, Movement, and Sport, 2011

Individuals inherently walk towards open spaces and avoid colliding with obstacles to reduce the ... more Individuals inherently walk towards open spaces and avoid colliding with obstacles to reduce the risk of injury 1 . Research has demonstrated that young adults use body-scaled information to alter their movements when walking through confined spaces 2,3 . Young adults consistently require a safety margin greater than or equal to 1.3 times their shoulder width (termed Critical Point ) in order to pass through an aperture without changing their actions 2 . It is unknown as to whether individuals maintained similar body-scaled strategies when controlling their actions in situations where they are not obligated to walk through a confined space. The current study was designed to test the action strategies of young adults during an unconfined goal-directed locomotor task. The unconfined space consisted of a vertically oriented goal at the end of a 10m pathway and two vertically oriented obstacles placed half way (i.e. 5m from start) along the pathway on either side of the pathway's mi...

Journal of Sports Sciences, 2015

Abstract Research examining our ability to avoid obstacles in our path has stressed the importanc... more Abstract Research examining our ability to avoid obstacles in our path has stressed the importance of visual input. The aim of this study was to determine if athletes playing varsity-level field sports, who rely on visual input to guide motor behaviour, are more able to guide their foot over obstacles compared to recreational individuals. While wearing kinematic markers, eight varsity athletes and eight age-matched controls (aged 18–25) walked along a walkway and stepped over stationary obstacles (180° motion arc). Visual input was manipulated using PLATO visual goggles three or two steps pre-obstacle crossing and compared to trials where vision was given throughout. A main effect between groups for peak trail toe elevation was shown with greater values generated by the controls for all crossing conditions during full vision trials only. This may be interpreted as athletes not perceiving this obstacle as an increased threat to their postural stability. Collectively, findings suggest the athletic group is able to transfer their abilities to non-specific conditions during full vision trials; however, varsity-level athletes were equally reliant on visual cues for these visually guided stepping tasks as their performance was similar to the controls when vision is removed.

Physiological Reports

This case characterizes the clinical motor, perceived fatigue, gait and balance, cardiovascular, ... more This case characterizes the clinical motor, perceived fatigue, gait and balance, cardiovascular, neuromuscular, and cardiopulmonary responses after cycling 7850 km over 85 days in a physically active 57‐year‐old male with idiopathic Parkinson's disease (PD). The participant cycled 73/85 days (86%); averaging 107.5 ± 48.9 km/day over 255.4 ± 108.8 min. Average cycling heart rate was 117 ± 11 bpm. The Unified Parkinson Disease Rating Scale (UPDRS) Part III motor score decreased from 46 to 26 (−44%), while the mean Parkinson Fatigue Scale (PFS‐16) score decreased from 3.4 to 2.3 (−32%). Peak power output on a maximal aerobic exercise test increased from 326 to 357 W (+10%), while peak isotonic power of single‐leg knee extension increased from 312 to 350 W (+12%). Maximal oxygen uptake following the trip was 53.1 mL/min/kg or 151% of predicted. Resting heart rate increased from 48 to 71 bpm (+48%). The systolic and diastolic blood pressure responses to a 2‐min submaximal static hand...

Journal of Biomechanics, Oct 1, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Background Body movement-controlled video games involving physical motion and visual attention ma... more Background Body movement-controlled video games involving physical motion and visual attention may have the potential to train both abilities simultaneously. Our purpose was to determine the associations between performance in these games and visual attention, balance and mobility in a group of older adults. The long-term goal is to identify the optimal type of interactive games with regards to training potential. Methods Fifty healthy adults aged 65 + years participated in this cross-sectional study. Visual attention was measured with static and dynamic versions of a useful field of view (UFV) and a multiple object tracking (MOT) test. Balance was measured with a force plate in bi-pedal quiet stance test (QST) and one-legged stance (OLST). Gait variability and walking speed were assessed with the Five Meter Walk Test (5MWT). Four Microsoft™ Xbox® 360 Kinect™ interactive video games were chosen based on the apparent levels of visual attention demand. Results Visual attention (UFV an...