The purpose of this paper was to design a simplified wind tunnel force balance for use in elementary aerodynamics/wind tunnel laboratory courses. The applied loads and moments were determined to be as follows: The design lift force is ± 20 lbs, the design drag force is ± 10 pounds, the design pitching moment is ± 20 inch-pounds. The force balance output accuracy was arbitrarily set at ± 5% since this would be sufficient for preliminary student work. The results of this work are as follows: The force balance is fabricated from a single bar of 2024 aluminum, machines and bent into an "L" shape, the applied forces and moments are sensed by strain gages bonded to machined surfaces on the bar, the output of the strain indicator equipment is transformed into uncorrected forces and moments by a system of three equations, the uncorrected forces and moments are transformed into true forces and moments by a system of force balance interaction equations, the design values for lift, drag, and pitching moment remain the same as originally proposed, the output error in lift is determined to be ± 3.5%, the output error in drag and pitching moment are determined to be ± 10%. The prototype has been in use for several months and its operation has been completely satisfactory.

MSc. Thesis, Ryan L. Rolick / Stream temperature, which influences many biogeochemical processes, is controlled by the exchange of water and energy across the stream surface, banks, and bed. A stream’s thermal sensitivity is its sensitivity to changes in air temperature and is increasingly important with projected warming in northern regions. As the thermal dynamics in permafrost underlain headwater streams are poorly documented, this study examines the thermal signals of two neighboring alpine streams (Granger Creek, GC and Buckbrush Creek, BB) within the Wolf Creek Research Basin (WCRB), Yukon Territory, and quantifies the dominant energy fluxes through an energy budget approach. A 1950 m study reach was established in each stream where water temperature, vertical streambed temperature, and stream discharge were measured. Distinct thermal heterogeneity is observed in each stream, with areas of persistent temperature decrease along their lengths, minimal downstream increase in stream temperature in GC, and an overall decrease in downstream temperature in BB. These observations are indicative of focused groundwater upwelling, low thermal sensitivity, and an increasing downstream influence of groundwater. This is inferred from increases in specific conductivity (2 μS/cm – 20 μS/cm) at locations of temperature decrease, and patterns in low (high) mean air-water linear regression slope (intercept) values. With distance downstream, regression slope (intercept) in GC went from 0.37 (1.2 ̊C) upstream to 0.33 (2.6 ̊C) at the outlet. Similarly, in BB regression slope (intercept) went from 0.37 (2.1 ̊C) upstream to 0.24 (3.3 ̊C) downstream. These patterns also indicate an overall lower thermal sensitivity and greater groundwater influence across the study reach of BB. Downwelling is observed at locations of vertical temperature profiles in each stream through efficient downward propagation of the diel temperature signal into the streambed, indicating hyporheic exchange. The energy balance indicates a large unaccounted for sink in BB, further denoting a larger groundwater influence in its study reach. These findings highlight the importance for continued study of thermal regimes and the complicated interconnections between heat exchange processes in alpine catchments in permafrost regions. / Thesis / Master of Science (MSc)

<p> This study deals with the use of mass balance and hydrodynamic/pollutant transport models for wetland restoration. The models were applied to Cootes Paradise marsh, located at the western end of Hamilton Harbour, Lake Ontario. Regulated water levels, excess nutrients and high suspended solids have contributed to declining vegetation and a subsequent change in wildlife in this wetland ecosystem. The Royal Botanical Gardens (RBG), which manages Cootes Paradise, has developed goals for the restoration of this wetland which focus primarily on improving water quality. </p> <p> A mass balance approach was applied to Cootes Paradise in order to gather more information on the inputs of phosphorus and suspended solids to the ecosystem. Although data were not complete for many aspects of the model, the mass balance calculations provided an acceptable agreement with field values. The mass balance models also revealed that more than 50% of the inputs of phosphorus and suspended solids were being contributed by the internal sediments. </p> <p> A two-dimensional depth averaged hydrodynamic/pollutant transport model provided an explanation for the movement of substances through the marsh as a result of wind and inflow generated currents. The resulting pollutant distribution patterns could be explained by environmental conditions in the marsh ecosystem. The computer model predicted phosphorus concentrations reasonably well, both for an overall average of the entire marsh and for individual sites. The model also simulated suspended solids and accounted for contributions of particulate matter due to carp and due to wind resuspension of the bottom sediments. Both overall averages and sample site comparisons for suspended solids were within one standard deviation of field values. According to data generated by the computer model for suspended solids, carp and wind are contributing to the concentrations in Cootes Paradise on an almost equal level; both contribute approximately one third to the overall concentration for suspended solids based on the available data. Further information is needed, however, to improve on the data set for Cootes Paradise in order to better validate the results produced by the mass balance and computer models. </p> / Thesis / Master of Engineering (ME)

People with Autism Spectrum Disorder (ASD) constitute the fastest-growing developmental disability population in North America, yet their employment outcomes are significantly poorer. Little attention has been given to the role of gender in shaping their employment experiences and the interface between their work and family demands. This qualitative research is intended to enable the ‘voice’ of people with autism to be heard through the content analysis of naturally occurring discourse in an on-line autism forum. The research is composed of three substantive studies. The first study investigated the role of gender in career exploration and job-seeking experiences. Guided by the Stages of Considering Work, the study examined how women and men with autism experienced three consecutive sets of vocational barriers related to contemplating employment, defining career goals, and finding jobs. The second study explored gender differences related to challenges in the workplace to maintain employment, including workplace mental health, social interaction, executive function, communication, disclosure, accommodation, sensory environment, and corporate cultures. The third study investigated the domestic experiences of women with autism as mothers, housekeepers, and caregivers, and how they negotiated the interface of work and family demands. Guided by the work/family border theory, the studyshowed how gender and disability identities significantly influenced their work-family experiences. Overall, this research informs gender-sensitive policies and practices to improve the employment and work-family balance experiences of individuals with autism. / Thesis / Doctor of Philosophy (PhD)

Athletes from an array of sports and military personnel often desire weight gain, ideally as lean body mass (LBM), to improve performance in sport or military operations. These athletic individuals are commonly encouraged to increase energy intake by ~500 kcal/day with an emphasis on adequate protein and carbohydrate (CHO) and judicious inclusion of healthy fat-containing energy-dense foods (including nuts/nut butters), along with rigorous resistance training (RT). These guidelines target gains of ~0.23 kg/wk (0.5 lb/wk). However, little is known about the efficacy of such regimens, particularly in female athletes. Purpose: 1) to evaluate the outcomes of a 10-wk diet and exercise regimen designed to promote healthy weight gain with excess energy from protein- or CHO-dominant foods, 2) to determine the predictors of weight gain under these conditions, and 3) to survey the methods that athletes currently use to achieve weight gain for athletic purposes. Methods: Two projects included 19 male and 13 female athletes (from a variety of athletic backgrounds with previous RT experience; mean age 25±6 years) who were randomly assigned to receive 500 additional kcal/day above weight maintenance diet through provision of either peanut-based whole foods/snacks (PNT group) or a similar, high-CHO, peanut-free snack (CHO group) along with a supervised RT regimen (60 to 120 min, 3 day/wk targeting major muscle groups). Body composition (via dual-energy x-ray absorptiometry), basic anthropometric measurements, resting metabolic rate, hormonal profile, muscular strength, aerobic fitness (VO2max), and food intake records were assessed at baseline (BSL) and post-intervention with some measurements also assessed at weeks 3 and 7. Predictors of weight gain were determined following the intervention. A third project included an online survey with targeted questions regarding athletes' habits for promoting weight gain. Results: 1) Total body mass (TBM) increased 2.2±1.3 kg with 1.5±1.1 kg as LBM after week 10. The PNT group (n=16; 10 men, 6 women) gained less TBM than the CHO group (n=16; 9 men, 7 women) (1.6±1.1 kg vs 2.7±1.2 kg, respectively, P=0.007) with no differences in LBM (1.2±1.1 kg vs 1.9±1.0 kg, P=0.136). 2) 15 (47% women) of 32 participants gained at least 2.27 kg after 10 weeks with 70% as LBM. Over time, from linear mixed effects models, increased free thyroxine (T4) and increased blood urea nitrogen concentration (as a marker of protein intake) predicted TBM and LBM gains. From general linear models, the CHO energy surplus was a significant predictor of TBM and LBM gains, while the female sex alone was significant for LBM gains at study completion. 3) 168 athletic participants (mean age 24±5 years; 29% female, 71% male) completed the survey and were actively attempting or had attempted weight gain in the last 12 months to gain muscle mass (87.5%), for aesthetic reasons (66.1%), or to improve athletic performance (63.7%). The most prevalent dietary strategies reported to help promote weight gain were consuming more energy than usual (88.0%) from mainly protein foods (83.9%) and using protein powders (67.3). 9.6% of participants reported using anabolic hormones. The main exercise change was increased RT (81.5%). Conclusions: 1) These results suggest that the addition of 500 kcal/day from whole foods/snacks in combination with a rigorous RT program promotes a similar weight gain of ~0.22 kg/week, primarily as LBM, over 10 weeks in both male and female athletes. However, snack macronutrient content may impact the effectiveness of this regimen. 2) Factors that predict ability to gain body weight as expected under these circumstances are incorporating a CHO-dominant energy surplus, consuming overall adequate protein (~1.6 g/kg/day), and free T4 status. Furthermore, athletic women are able to gain LBM as effectively as athletic men. 3) Results confirm that both male and female athletic individuals intentionally attempt to gain weight. Nutrition and exercise professionals may use the findings to be aware of these common dietary and exercise strategies and to better educate their athletic clients on appropriate methods that are evidence-based and not detrimental to health. / Doctor of Philosophy / Athletes from different sports, including military members, often want to gain weight, mainly as muscle, to improve their athletic performance (for example, strength and power) or to match the opposing team's size. Current sports nutrition recommendations include eating ~500 kcal more each day from carbohydrate (CHO), protein, and healthy fats in combination with hard weightlifting. These recommendations support a slow weight gain of about 0.5 lb to 1 lb per week, which should mostly be muscle. However, these recommendations have not been well studied, particularly in female athletes. Purpose: 1) to study purposeful overfeeding with weightlifting for 10 weeks to promote healthy weight gain with extra calories from either high-protein or high-CHO foods, 2) to figure out what factors are responsible for healthy weight gain under these conditions, and 3) to survey the methods that athletes currently use to achieve weight gain for athletic purposes. Methods: Two projects included 19 male and 13 female athletes (from a variety of athletic backgrounds with previous weightlifting experience; mean age 25±6 years) who overate 500 additional kcal/day from either peanut-based whole foods/snacks (PNT group) or a similar, high-CHO, peanut-free snack (CHO group) along with a supervised weightlifting regimen (60 to 120 min, 3 day/wk targeting major muscle groups). Body composition, metabolism, blood analyses, muscular strength, cardio fitness, and food intake records were done at the beginning and end with some measurements also done at weeks 3 and 7. Predictors of weight gain were studied later. A third project included an online survey with questions about athletes' habits for promoting weight gain. Results: 1) In all 32 participants, weight increased 4.8 lb (3.3 lb as muscle) after week 10. The PNT group (n=16; 10 men, 6 women) gained less weight than the CHO group (n=16; 9 men, 7 women) (3.5 lb vs 5.9 lb, respectively) with no differences in muscle (2.6 lb vs 4.2 lb). 2) An increased thyroid hormone (thyroxine) and increased blood urea nitrogen (as a marker of protein intake) predicted overall weight and muscle gains. From the beginning of the study, the CHO energy surplus was a significant predictor of weight and muscle gains, while the female sex alone was significant for muscle gains by the end of the study. 3) 168 athletic participants (mean age 24±5 years; 29% female, 71% male) completed the survey and were actively attempting or had attempted weight gain in the last 12 months to gain muscle (87.5%), to look better (66.1%), or to improve athletic performance (63.7%). The main dietary ways reported to help promote weight gain were eating more than usual (88.0%) from mainly protein-rich foods (83.9%) and using protein powders (67.3%). 9.6% of participants reported using anabolic hormones. The main exercise change was increased weightlifting (81.5%). Conclusions: 1) These results suggest that an extra 500 kcal/day from whole foods/snacks in combination with hard weightlifting promotes a similar weight gain of ~0.5 lb/week, mainly as muscle, over 10 weeks in both male and female athletes. 2) What affects healthy weight gain may be eating a CHO-dominant energy surplus, eating enough protein in general, and thyroid status. Furthermore, athletic women are able to gain muscle as effectively as athletic men. 3) Results confirm that both male and female athletic individuals try to gain weight. Nutrition and exercise experts may use these findings to be aware of these common nutrition and exercise strategies and to better educate their athletic clients on appropriate methods that are based on scientific experiments and not bad for health.

Short-rotation woody crops are becoming important supplies of hardwood fiber, but little is known about the early nutritional needs of these systems, especially on different site types. The study objectives were, on two young (ages 3-6) sweetgum plantations with contrasting soil types, to 1) determine the plant growth and foliar nutrition response to repeated nitrogen (N) fertilizer applications, 2) determine soil N supply, plant N demand, foliar N resorption, and soil and fertilizer uptake efficiencies, and 3) test a simple N supply model. In order to expand the findings to the range of sweetgum site types, the study objectives were also to 4) evaluate rapid methods for determining N mineralization potential, 5) characterize the soils of 14 sweetgum site types in the Atlantic coastal plain, and 6) review current N fertilizer prescriptions in forestry and recommend strategies for improvement. Two young sweetgum (Liquidambar styraciflua L.) plantations on a converted agricultural field and a pine cutover site in South Carolina were fertilized biannually with three rates of N fertilizer (0, 56, 112 kg N per ha). Fertilization doubled foliar biomass and leaf area on the cutover pine site in the years fertilizer was applied, and stem biomass increased 60%. Critical values, the N concentration required for 90% of optimum growth, is approximately 1.75%. Foliar N uptake increased at both sites when fertilizer was applied. Modeled annual soil N supply was within 20% of that measured on the two plantations even though monthly N supply was not accurately estimated. Potential N mineralization was accurately estimated with a 3-day incubation of rewetted soils that were previously dried, but not by hot salt extraction or anaerobic incubation. Across a spectrum of 14 sweetgum sites, the agricultural fields had lower mineralizable nitrogen (126 kg per ha) than the cutover sites (363 kg per ha). Current N fertilizer prescriptions are not sufficient for repeated fertilizer applications to fast-growing hardwood plantations, but simple models of soil N supply and an N-balance approach may improve prescriptions. / Ph. D.

Research Objectives The objective of this study was to evaluate if neuromusculoskeletal training (i.e., weight and balance training) for older adults could reduce the likelihood of slip-induced fall accidents. The study focused on evaluating biomechanics among the elderly at pre- and post-training stages during processes associated with slip-induced fall accidents. Motivations: Older adults are at a higher risk of falls due to deficient gait characteristics and postural control, especially when facing unexpected external perturbations such as slippery surfaces. The literature (Alexander et al., 1992; Englander 1996; Hausdorff, 2001; Rizzo 1998) indicates that falls among the elderly over 65 result in enormous economic and personal losses, therefore, the losses must be diminished. The results from this study can provide intervention strategies for researchers, health care individuals, and the elderly and their families in reducing the likelihood of slip-induced falls. Background: More than 25% of older adults fall every year (Sattin, 1992), and older adults and their family members fear their falls and fall-related injuries due to the associated high mortality rate (Jensen, 2003). The Center for Disease Control (CDC) reported in 2003 that emergency departments treated more than 1.6 million seniors due to fall-related injuries and, among them, 373,000 were admitted to the hospital. In 2002, The National Safety Council reported that 14,500 people died due to fall-related accidents, and 60 percent of them were 65 years of age and older. To minimize economic and personal losses, tribometric techniques for assessing shoe/floor interactions, the biomechanical responses in walking on slippery floor surfaces, and postural control were studied. Still, the elderly population is at a high risk of falling, severe enough that it is a major cause of hospitalization (CDC, 2003). Yet reasons for slip-induced fall accidents are not clear. Therefore, mechanisms involving fall accidents must be explored and, further, interventions to minimize fall accidents must be discovered and implemented. The occurrence of falls among the elderly are postulated to result from neuromusculoskeletal aging. The changes in neuromusculoskeletal components with advancing age are commonly accompanied with mobility problems and poor health status contributing to a decreased physical capability such as a reduction in lower extremity strength (Larsson et al., 1979; Lord et al., 1991 and 1994; Murray et al. 1985; Stalberg et al., 1989; Whipple et al. 1987) and insecure and unconfident balance (Manchester et al. 1989; Stelmach and Sirica, 1987; Teasdale et al. 1991; Thelen et al., 1998; Woolacott, 1986) leading to unstable dynamic postural control and poor gait dynamics (Alexander, 1994; Judge, 2003; Lockhart et al., 2003; Wolfson, 2001). Unstable dynamic postural control and poor gait dynamics influence the likelihood of falls among older adults (Guralnik et al.1994; Judge et al.1996; Lockhart et al., 2003; Tinetti et al. 1988). Therefore, in an effort to improve unstable dynamic postural control and poor gait dynamics, strength and balance training have been proposed and implemented. (Campbell et al., 1999; Day et al., 2002; Fiatarone et al., 1994; Neil, 1994; Shepard et al., 1993; Tinetti et al, 1994; Wolfson et al, 1993). Problem Statement: Although the significance of muscle strengthening and balance training in reducing falls for older adults has been addressed previously, most studies (Berg et al., 1992; Duncan et al., 1990; Guralnik et al.,1994; Hageman et al., 1995; Nashner, 1993; Nashner and McCollum, 1985; Nevitt et al., 1989; Overstall et al., 1977; Rikli and Jones, 1999; Tinetti, 1986) have focused on the effect of muscle strengthening and balance training on the static and dynamic postural control such as quite standing, one-leg stand, the sit-to-stand test, the test of precise movement, functional reaching, or the mobility test. Yet, research to evaluate the effectiveness of muscle strengthening and balance training on actual slip-induced fall events was lacking. This study were carried out to evaluate the likelihood of falls at pre- and post stages of training by incorporating and validating the effectiveness of training utilizing actual perturbations commonly associated with slips and falls. Method: 18 older adults participated in the study for 8 weeks: 6 individuals in balance group, 6 individuals in weight group, and 6 individuals in control group (social group). Each group met three times a week and each session lasted for 1 hour. Biomechanical dependent measures and psychosocial dependent measures were evaluated to the effects of training. Results: The results indicated that, overall, training resulted in improvements in biomechanical dependent measures. Further, regular social activities resulted in improvements in proprioception sensory sensitivity and in ankle dorsiflexion muscular strength. Conclusion: Balance training contributed to an improvement in ankle flexibility, whereas, weight training did not contribute to an improvement in ankle flexibility although either weight or balance training played a role in decreasing slip-propensity and the likelihood of slip-induced falls among older adults. An ability to integrate neuro-musculo-skeletal systems was improved by training and was a main contributor in reducing the likelihood of slip-induced falls. Proprioception sensitivity by itself did not play a role in decreasing the likelihood of slip-induced falls. In addition, the exercise training as well as social activities played a role in altering psychosocial behavior (i.e. fear of falling and independency) of older adults. The author concluded that an ability to integrate neuro-musculo-skeletal systems could be improved by either balance or weight training and could be a primary factor contributing to a reduction in the likelihood of slip-induced falls among older adults. In addition, the author concluded that the regular social activities also could contribute to an enhancement in the psychosocial characteristics of older adults. / Ph. D.

Obesity is associated with an increased risk of falls and subsequent injury. Most falls result from some type of postural perturbation. As such, it is important to understand how obesity influences balance recovery from a postural perturbation. There is limited information on the effects of obesity on balance recovery, and the limited available information is ambiguous. Therefore, the purpose of the research within this dissertation was to investigate the effects of obesity on balance recovery after a postural perturbation in young adults to better understand how obesity contributes to fall risk. Four separate studies make up this dissertation. The purpose of the first study was to investigate the effects of obesity on balance recovery ability using an ankle strategy in young adults. Normal-weight and obese participants recovered balance using an ankle strategy after three types of postural perturbations: an initial angular displacement, an initial angular velocity from the natural stance, and an initial angular velocity from a prescribed position. Obese participants were unable to recover balance using an ankle strategy as well as normal-weight participants when perturbations involved an initial angular velocity. However, no differences between obese and normal-weight participants were found when perturbations only involved an initial angular displacement. The effect of obesity on balance recovery in young adults was dependent on the perturbation characteristics, and may be explained by a possible beneficial effect of increased inertia on balance recovery after perturbations with little or no initial angular velocity. The purpose of the second study was to examine the effects of obesity on balance recovery by stepping in young adults. The ankle strategy has the benefit of simplifying the mechanics of balance recovery, but limits generalizability to more realistic fall scenarios where stepping to extend the base of support and recover balance is desired. Similar to the first study, participants attempted to recover balance following two types of postural perturbations: an initial angular displacement from an upright stance (by releasing participants from a static forward lean), and an initial angular velocity while in an upright stance (using a translating platform). In contrast to the first study, the ability to recover balance with a single-step did not differ between young normal-weight and obese adults. These results suggest that the reported increase in fall risk in obese adults is not a result of impaired balance recovery ability (at least among young adults that were tested here). The third study examined the effects of obesity on body kinematics immediately following a trip-like perturbation in young adults. Obesity was found to increase body angular velocity the perturbation, and that increases in body angular velocity were associated with an increased probability of a failed recovery. These results suggest that when a young obese and young normal-weight individual trip while walking at similar speeds, the young obese individual may be at a greater risk of falling following a trip because the young obese individual will experience a greater body angular velocity. This detrimental effect of obesity on the difficulty of recovering from a trip-like perturbation in young adults is most likely due to how mass is distributed throughout the body and not the amount of mass itself. The final study examined the relationship between relative strength and functional capability in young adults, and how obesity influences this relationship. To compare relative strength used during a functional task (i.e. balance recovery from a forward fall), the obese and normal-weight individual should complete the task with identical kinematics. Forward dynamic simulations were used to address this research question, instead of human subjects testing, to achieve identical kinematics. Differences in peak relative torques were found between the normal-weight and obese model, with the largest differences seen at the hip. These findings suggest that young obese individuals use greater relative strength at some joints than young normal-weight individuals to perform the time-critical task of balance recovery, and that these differences in relative strength demands may limit functional capability in young individuals who are obese. / Ph. D.

While human balance is known to be affected by altered sensory feedback, altered dynamics may also contribute to balance deficiencies in certain populations. The goal of this study was, therefore, to investigate the effects of altered dynamics, namely increased inertia and increased weight, on standing balance. Sixteen normal-weight male participants completed quiet standing in a custom-built backboard under four conditions: baseline, increased inertia only, increased weight only, and increased inertia and weight. Increased inertia did not affect body center of mass movement (COM) or center of pressure (COP) movement, suggesting that no additional ankle torque was necessary to control the increased inertial forces. Increased weight caused increased body COM movement (increased backboard angle range and angular speed) and greater acceleration of the COM (as evidenced by increased COP-COM), requiring an increased level of corrections needed to maintain upright posture (as evidenced by increased COP speed) and increased ankle torques (as evidenced by increased range of COP position). Increasing inertia and weight simultaneously had the same effects as increasing weight except that there was no increased COM movement when both inertia and weight were increased. This indicates that there may be a slight mediating effect of increasing inertia on the extreme changes in balance observed when only weight is increased. These results indicate that altered dynamics of the body have an effect on human standing balance, just as altered sensory function has an effect on balance. / Master of Science

Fall related injuries are a major public health concern due to their high associated medical costs and negative impact on quality of life. Obese and older adults are reported to fall more frequently than their normal-weight and young counterparts. To help identify potential mechanisms of these falls the purpose of the research within this dissertation was to investigate the effects of obesity and age on the likelihood of tripping and subsequent balance recovery. Four experimental studies were conducted. The purpose of the first study was to investigate the effects of obesity, age and gender on the likelihood of tripping during level walking. Likelihood of tripping was assessed with median minimum foot clearance (MFC) and MFC interquartile range (IQR). Obesity did not increase the likelihood of tripping suggesting the increased rate of falls among obese adults is not likely due to a greater likelihood of tripping over an unseen obstacle. Additional results suggested females and individuals of shorter stature have an increased likelihood of tripping compared to their male and taller counterparts. The purpose of the second study was two-fold. First, the effects of load carriage and ramp walking on the likelihood of tripping were investigated, followed by investigating the effects of age and obesity on the likelihood of tripping during load carriage and ramp walking. Again, likelihood of tripping was assessed with median MFC and MFC IQR. Load carriage increased the likelihood of tripping during both level and ramp walking and obesity and age increased the likelihood of tripping during selected combinations of load carriage and/or ramp walking. These results suggest that the increased rate of falls during load carriage and the increased rate of falls among obese and older adult workers reported elsewhere may be due in part to an increased likelihood of tripping. The third study proposed a new method for investigating the likelihood of tripping as a function of obstacle height. The proposed method aimed to clear up ambiguous results often encountered when using MFC central tendency and variability to quantify likelihood of tripping. The method used trip probability curves and a statistical bootstrapping technique to compare trip probability at specific obstacle heights between groups of interest. An additional benefit of this method was that it was able to identify effects of factors not identifiable by the commonly used ANOVA analysis using MFC central tendency and variability. The purpose of the fourth study was to investigate the effects of obesity, age and gender on balance recovery following a lab induced trip perturbation. Measures of balance recovery included fall rate, stepping strategy and characteristics, and trunk kinematics. Obese, older, and female adults fell more frequently after tripping and this higher fall rate may help explain the higher fall rates among obese, older and female adults reported elsewhere. Failed recoveries were associated with higher peak trunk angles and angular velocities in addition to the use of a lowering strategy. Obese, older, and female adults had higher peak trunk angles and angular velocities and older adults and females used lowering strategies more often. These alterations in trunk kinematics and stepping strategy may have contributed to the higher fall rate among these individuals. / Ph. D.