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Full-Text Articles in Life Sciences

Failures In Adaptive Locomotion In Healthy Young Adults, Michel J. H. Heijnen Apr 2016

Failures In Adaptive Locomotion In Healthy Young Adults, Michel J. H. Heijnen

Open Access Dissertations

Young adults fall most frequently when walking, and trips account for 25% of these falls (Heijnen & Rietdyk, 2016). Common approaches to understanding tripping include the examination of behavior when a stationary obstacle is crossed successfully, or to deliberately trip the participant with a covert obstacle. However, these approaches do not establish the underlying cause of failure; examining inadvertent failures does, as this occurs most often in the field (Heijnen & Rietdyk, 2016). In order to identify the behavior that results in obstacle contact, this dissertation examined gait characteristics during inadvertent failures and manipulated the sensory information available to guide the limb trajectory. Manipulating the availability of sensory information is important to determine the information used to successfully guide the limbs, particularly the trail limb. Three experiments were conducted to systematically examine the role of visual and somatosensory information in young adults ...


Recovery From Muscle Fatigue In Young And Older Adults: Implications For Physical Function, Stephen A. Foulis Sep 2013

Recovery From Muscle Fatigue In Young And Older Adults: Implications For Physical Function, Stephen A. Foulis

Open Access Dissertations

As adults age, skeletal muscles become smaller and weaker, which can ultimately lead to declines in physical function and disability. In general, older adults produce less isometric force and dynamic power than younger adults. The effects of this weakness are amplified following a series of muscle contractions that result in muscle fatigue. Since daily routines consist of repeated series of activity followed by rest, it is important to understand how muscle recovers from fatigue. In particular, muscle power has been shown to be related to physical function and balance. Thus, understanding the process of recovery from muscle fatigue will help ...


Postures For Precision: An Ecological Approach To Marksmanship And The Issue Of Warfighter Load., Christopher Jay Palmer Sep 2012

Postures For Precision: An Ecological Approach To Marksmanship And The Issue Of Warfighter Load., Christopher Jay Palmer

Open Access Dissertations

The goal of this dissertation was to understand the issue of load in a more operationally realistic way, while examining underlying segmental relations and postural regulation related to functional capability. The ecological approach provides a foundation for this work, as its approach seeks understanding across nested relations and at the level of the Organism-Environment system. First, a landing task was used to examine transitions from movement to upright stance, evaluating the effects of load on changes relevant to prospective control of action. Greater negative head angles, reductions in the field of regard, and reduced variability in orienting coordination (trunk-head relations ...


Mechanics And Energetics Of Footfall Patterns In Running, Allison H. Gruber Sep 2012

Mechanics And Energetics Of Footfall Patterns In Running, Allison H. Gruber

Open Access Dissertations

The forefoot (FF) running pattern has been recently advocated to improve running economy and prevent overuse injuries compared to the rearfoot (RF) pattern. However, these claims have not been supported by empirical evidence. The purpose of this dissertation was to investigate the potential advantages of RF and FF patterns to improve running economy and reduce injury risk in 20 natural RF and 20 natural FF runners.

The first study found that the RF group was more economical when performing the RF pattern at a slow, medium, and fast speed vs. FF running. Only running at the fast speed resulted in ...


Refinement, Validation And Application Of A Machine Learning Method For Estimating Physical Activity And Sedentary Behavior In Free-Living People, Kate Lyden Sep 2012

Refinement, Validation And Application Of A Machine Learning Method For Estimating Physical Activity And Sedentary Behavior In Free-Living People, Kate Lyden

Open Access Dissertations

There is limited knowledge of the dose-response relationship between physical activity (PA), sedentary behavior (SB) and health. Poor measures of free-living PA and SB exposure are major contributing factors to these knowledge gaps. The overall objective of this dissertation was to address these issues by refining, validating and applying a machine-learning methodology for measuring PA and SB for use in free-living people. By combining neural networks and decision tree analyses we developed a method better suited for use in free-living people. Our new method is called the sojourn method and it estimates PA and SB from a single hip mounted ...


The Influence Of Free-Living Activity And Inactivity On Health Outcomes And Responsiveness To Exercise Training, Sarah Kozey Keadle May 2012

The Influence Of Free-Living Activity And Inactivity On Health Outcomes And Responsiveness To Exercise Training, Sarah Kozey Keadle

Open Access Dissertations

On average, starting an exercise training program decreases one’s risk for chronic disease. However, there is remarkable individual variability in physiologic responses to exercise training. The activity and inactivity during the remaining 95% of the day (when the individual is not training) is rarely considered. The overall objective of this dissertation was to apply validated sedentary behavior (SB) and physical activity (PA) measurement techniques during an exercise training study to determine if time spent in SB and PA outside of training influences the physiological response to training. Twenty subjects participated in a pilot study to determine the feasibility of ...


Adaptations To Stride Patterns And Head Movements During Walking In Persons With And Without Multiple Sclerosis, Jebb Grigory Remelius Feb 2012

Adaptations To Stride Patterns And Head Movements During Walking In Persons With And Without Multiple Sclerosis, Jebb Grigory Remelius

Open Access Dissertations

Many people with multiple sclerosis (MS) have difficulty with walking, which can decrease their sense of mobility. Gait stability was investigated by studying stride parameters and head movements at preferred and fixed speeds in those with MS. First, walking gait data were recorded at preferred and fixed walking speeds from 19 individuals with MS and 19 controls. Traditional gait parameters were compared, as was swing foot to center of mass (CoM) timing at mid-swing. Second, walking gait data in healthy young adults (n=20) were recorded at preferred speed and while stepping over an obstacle. Study 2 developed novel swing ...


A Comprehensive Model Of Human Neuromuscular Function During Repeated Isometric Contractions: Predicting The Effect Of Age On Fatigue, Damien Mark Callahan Feb 2012

A Comprehensive Model Of Human Neuromuscular Function During Repeated Isometric Contractions: Predicting The Effect Of Age On Fatigue, Damien Mark Callahan

Open Access Dissertations

Repeated or prolonged activation of skeletal muscle results in an acute decline in the muscle's ability to produce force, which is typically referred to as fatigue. Muscle fatigue is likely related to the by-products of cellular metabolism, alterations in neural activation and diminished membrane excitability that have been shown to accompany repeated contractions. However, the complicated etiology of the fatigue process makes it difficult to understand the relative influence of these physiological responses. Computational modeling of the skeletal muscle response to repeated activation is an appealing means of gaining insight into the mechanisms of muscle fatigue. A reasonably comprehensive ...


Cellular And Molecular Changes Following Skeletal Muscle Damage: A Role For Nf-Kb And Muscle Resident Pericytes, Robert H. Hyldahl Sep 2011

Cellular And Molecular Changes Following Skeletal Muscle Damage: A Role For Nf-Kb And Muscle Resident Pericytes, Robert H. Hyldahl

Open Access Dissertations

Skeletal muscle is dynamic and actively regenerates following damage or altered functional demand. Regeneration is essential for the maintenance of muscle mass and, when dysregulated as a result of disease or aging, can lead to losses in functional capacity and increased mortality. Limited data exist on the molecular mechanisms that govern skeletal muscle regeneration in humans. Therefore, the overall objective of this dissertation was to characterize early molecular alterations in human skeletal muscle to strenuous exercise known to induce a muscle regenerative response. Thirty-five subjects completed 100 eccentric (muscle lengthening) contractions (EC) of the knee extensors with one leg and ...


Metformin And/Or Exercise Training Affect Metabolic Health In Men And Women With Prediabetes, Steven K. Malin May 2011

Metformin And/Or Exercise Training Affect Metabolic Health In Men And Women With Prediabetes, Steven K. Malin

Open Access Dissertations

Prediabetes is defined by elevated blood glucose concentrations not high enough to meet criteria for type 2 diabetes. Exercise or metformin, a common “anti-diabetes” medication, may attenuate the progression from prediabetes to type 2 diabetes by improving insulin sensitivity and cardio-metabolic health. Because each treatment has its primary action in different tissues, combining exercise (muscle) with metformin (liver) may further enhance insulin sensitivity and cardio-metabolic health. Purpose: To determine the efficacy of combining exercise training with metformin on insulin sensitivity and cardio-metabolic health in men and women with prediabetes. We hypothesized that the combined treatment would improve insulin sensitivity and ...


Adaptations To Running While Footwear Cushioning And Surface Are Manipulated, Trampas M. Tenbroek May 2011

Adaptations To Running While Footwear Cushioning And Surface Are Manipulated, Trampas M. Tenbroek

Open Access Dissertations

Minimal footwear sales have encountered rapid growth over the last several years. Minimal footwear are often constructed with thin basic uppers and thin, flexible midsoles. It is likely that running in minimal footwear will require adaptation and adjustments as the amount of cushioning and the geometry of the foot/ground interface will be substantially different than what many are accustomed to. This research investigated the effect footwear cushioning amount and the running surface had on running patterns. Study 1 (Chapter IV) utilized two different running footwear conditions and two different cushioned treadmill conditions, as well as a barefoot condition, to ...


Consequence Of Functioning At The End Range Of Joint Motion: Implications On Anterior Knee Pain, Pedro A. Rodrigues May 2011

Consequence Of Functioning At The End Range Of Joint Motion: Implications On Anterior Knee Pain, Pedro A. Rodrigues

Open Access Dissertations

“Excessive” and/or “delayed” subtalar joint (STJ) pronation has been linked to overuse injuries because of its influence on tibial internal rotation (TIR). The transfer of STJ pronation to TIR occurs via the talocrual joint, believed to have limited transverse plane motion. However, studies have shown the talocrural joint to have more transverse plane motion than once believed, therefore it is feasible that the STJ will only influence the motion of the tibia once this motion has been exhausted.

Currently, studies evaluating this relationship have focused on peak joint angles and excursion without reference to the amount of motion available ...


Optimal Control Of Human Running, Ross Herbert Miller May 2011

Optimal Control Of Human Running, Ross Herbert Miller

Open Access Dissertations

Humans generally use two modes of locomotion as adults. At slow speeds we walk, and at fast speeds we run. To perform either gait, we use our muscles. The central questions in this dissertation were: (1) Why do humans run the way they do, and (2) How do the mechanical properties of muscle influence running performance? Optimal control simulations of running were generated using a bipedal forward dynamics model of the human musculoskeletal system. Simulations of running and sprinting were posed as two-point boundary value problems where the muscle excitation signals were optimized to maximize an optimality criterion. In the ...


Muscle Weakness In Persons With Multiple Sclerosis, Linda Haiwon Chung Sep 2010

Muscle Weakness In Persons With Multiple Sclerosis, Linda Haiwon Chung

Open Access Dissertations

Skeletal muscle weakness is a problem for people living with Multiple Sclerosis (MS). Alterations in the central nervous system may be the primary source of muscle weakness because of the pathophysiology of MS. However, changes in peripheral mediators of force production may also contribute to muscle weakness in persons with MS. The main objective of the dissertation was to systematically identify key neural (motor unit discharge rates, spasticity) and muscular (muscle size, contractile function) mechanisms of force production that may explain lower isometric strength and dynamic power in persons with MS compared with age-matched controls. The knee extensor muscles of ...


Plantar Fasciitis: Biomechanics, Atrophy And Muscle Energetics, Ryan Chang May 2010

Plantar Fasciitis: Biomechanics, Atrophy And Muscle Energetics, Ryan Chang

Open Access Dissertations

Purpose: The purpose of this dissertation was to determine the effects of chronic plantar fasciitis on intrinsic foot structures with respect to biomechanics, muscle atrophy and muscle energetics. This was accomplished in three parts. Methods: In Part I, a three-dimensional motion capture system with a synchronized force platform quantified multi-segment foot model kinematics and ground reaction forces associated with walking. Healthy individuals were compared to individuals with chronic plantar fasciitis feet. Typical kinematic variables, measures of coupling, phase and variability were examined in rearfoot, forefoot and hallux segments. In Part II, foot and leg magnetic resonance images were taken in ...


"A"-Kids: Activity Kcal Intervention Daily Study. Effects Of 100-Kcal Daily Energy Expenditure On Total Moderate-To-Vigorous Physical Activity In 3rd Grade Children, Cheryl A. Howe Feb 2010

"A"-Kids: Activity Kcal Intervention Daily Study. Effects Of 100-Kcal Daily Energy Expenditure On Total Moderate-To-Vigorous Physical Activity In 3rd Grade Children, Cheryl A. Howe

Open Access Dissertations

A selection of common children’s games were measured in a laboratory-based study to be enjoyable and to elicit sufficient physical activity energy expenditure (PAEE) in 3rd grade children to combat the purported chronic energy surplus of childhood obesity (~100 kcal.day-1). PAEE during the games was similar for boys and girls, yet overweight children expended greater PAEE relative to body weight than healthy weight children. During a subsequent simulated recess program, the enjoyment declined over the 10-session program with no significant decline in PAEE. Using the enjoyable games of known energy cost in a structured recess program for 9 ...