Kinesiology Department Dissertations Collection Copyright (c) 2013 University of Massachusetts - Amherst All rights reserved. http://scholarworks.umass.edu/kinesiology_diss Recent documents in Kinesiology Department Dissertations Collection en-us Tue, 26 Mar 2013 07:55:11 PDT 3600 The role of the upper body in human locomotion http://scholarworks.umass.edu/dissertations/AAI3545899 http://scholarworks.umass.edu/dissertations/AAI3545899 Wed, 16 Jan 2013 12:24:27 PST The arms and thorax are integral parts of the human body for locomotion. However, the legs have been the focus of study in a majority of research on human walking and running. The human body functions best when all the parts work together as a cohesive unit. The overall aim of these studies was to analyze changes in arm, thorax and pelvis interactions under various manipulations, and to relate those findings to angular momentum control. Manipulations used were: gait speed, arm and thorax kinematics (removal of arm swing and reduction of axial rotation), age and mode of locomotion (walking and running). In the first study, manipulating arm swing and axial rotation led to changes in thorax-pelvis coordination and upper and lower body angular momentum that were designed to maintain angular momentum control through adapted arm swing. Walking without arm swing resulted in an increase in the range of whole-body angular momentum. This increase in angular momentum could potentially lead to problems in maintaining balance. In the second study, older adults demonstrated a smaller change than young adults did in thorax-pelvis coordination with increasing speed. However angular momentum differences were apparent at slower speeds but not faster, indicating that older adults regulate angular momentum independently of coordination, and do so differently than young adults. In the third study, walking and running locomotion modes led to a different organization of thorax-pelvis coordination and arm swing. This resulted in an inverse relationship between coordination and angular momentum regulation. The more out-of-phase coordination pattern in walking had smaller arm swing, while a more in-phase coordination pattern in running was associated with greater arm swing. In both modes of locomotion, arm swing was used to generate angular momentum to counter that of the legs. The general finding from these studies is that angular momentum is a factor of human locomotion that is regulated regardless of the degree of thorax-pelvis coordination in order to allow the momentum of the arms to counter that of the legs. This balance of angular momentum is likely important for the energetics and control of walking, and is an indirect result of the linking of upper and lower body movements. Arm swing is important for regulating angular momentum and plays a key role in countering the momentum generated by the legs.^

]]> Baird, Jennifer L Refinement, Validation and Application of a Machine Learning Method For Estimating Physical Activity And Sedentary Behavior in Free-Living People http://scholarworks.umass.edu/open_access_dissertations/651 http://scholarworks.umass.edu/open_access_dissertations/651 Wed, 12 Dec 2012 07:38:25 PST 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 accelerometer.

Study 1 validated two versions of this method: sojourn-1x (soj-1x) and sojourn-3x (soj-3x). Soj-1x uses data from a vertical accelerometer sensor, while soj-3x uses r data from the vertical, anterior-posterior and medial-lateral accelerometer sensors. Seven participants were directly observed in the free-living environment for ten consecutive hours on three separate occasions. PA and SB estimated from soj-1x, soj-3x and a neural network previously calibrated in the laboratory (lab-nnet) were compared to direct observation. Compared to the lab-nnet, soj-1x and soj-3x improved estimates of MET-hours (lab-nnet: bias (95% CI) = 5.4 (4.6-6.2), rMSE = 5.4 (4.6-6.2), soj-1x: bias = 0.3 (-0.2-0.9), rMSE = 1.0 (0.6-1.3), soj-3x: bias = 0.5 (-0.1-1.1), rMSE = 1.1 (0.7-1.5)) and minutes in different intensity categories (lab-nnet: rMSE range = 10.2 (vigorous) - 55.0 (light), soj-1x: rMSE range = 4.0 (MVPA) - 50.1 (sedentary), soj-3x: rMSE range = 7.8 (MVPA) - 27.8 (light)). Soj-1x and soj-3x also produced accurate estimates of qualifying minutes, qualifying bouts, breaks from sedentary time and break-rate.

Study 2 evaluated the sensitivity of soj-1x and soj-3x to detect change in habitual activity. Thirteen participants completed three, seven day conditions: sedentary, moderately active and very active. Soj-1x and soj-3x were sensitive to change in MET-hours (mean (95% CI): soj-1x: sedentary = 19.8 (19.0-20.7), moderately active = 22.7 (22.0-23.4), very active = 27.0 (25.8-28.2), soj-3x: sedentary = 18.2 (17.7-18.8), moderately active = 22.3 (21.6-23.1), very active = 27.6 (26.4-28.7)) and time in different intensity categories.

Study 3 applied soj-3x to a free-living intervention to elucidate the effects of increased sedentary behavior on markers of cardiometabolic health. Eleven participants completed seven days of an active condition followed by seven days of an inactive condition. Insulin action significantly decreased 17% (5.4-30.2), while total cholesterol, LDL and HDL did not change from the active to inactive condition. This dissertation used novel methods to improve PA and SB estimation in a free-living environment and to improve our understanding of the physiologic response to increased free-living SB. These methods ultimately have the potential to broaden our understanding of how PA and SB dose are linked to health.

]]> Lyden, Kate Mechanics and Energetics of Footfall Patterns in Running http://scholarworks.umass.edu/open_access_dissertations/641 http://scholarworks.umass.edu/open_access_dissertations/641 Wed, 12 Dec 2012 06:20:23 PST 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 a difference in economy between footfall patterns in the FF group in which RF running was more economical. Therefore, there is no advantage of FF running for improving running economy.

The results of the second study indicated that there was a weak to moderate relationship between Achilles tendon (AT) moment arm length and running with either RF or FF patterns. AT force was greater during FF running, which may increase the risk of developing tendon injury.

The third study used a modeling approach to find that FF running resulted in greater elastic energy recoil in the gastrocnemius (GA) and the soleus (SO). However, greater mechanical work overall with FF running resulted in no difference in metabolic cost of the GA between footfall patterns but greater metabolic cost of the SO compared to RF running.

The fourth study found that shock attenuation was greater during RF running compared to FF running. Greater shock attenuation during RF running was a result of an increased load imposed on the system. Decomposing the vertical ground reaction force in the frequency domain revealed that RF running may have a greater reliance on passive shock attenuation mechanism whereas the FF pattern may have a greater reliance on active shock attenuation mechanisms.

These results suggest that previous speculation that the FF running pattern is more economical was not substantiated. It is likely that each footfall pattern exposes a runner to different types of injuries, rather than one footfall pattern being more injurious than another.

]]> Gruber, Allison H. Postures for Precision: An Ecological Approach to Marksmanship and the Issue of Warfighter Load. http://scholarworks.umass.edu/open_access_dissertations/618 http://scholarworks.umass.edu/open_access_dissertations/618 Tue, 11 Dec 2012 07:27:54 PST 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) under load all suggest reductions in the postural affordances for visual perception. The heaviest load was not the worst; as the asymmetrically loaded Vest configuration had greater negative effects on postural affordances. This was further supported by the increased power and frequency content in the Center of Pressure dynamics, suggesting much more difficult postural regulation in this configuration. The second study examined the effects of load on dynamic marksmanship performance using large loads on the torso and small loads on the extremities (night vision goggles and extremity armor on the arms) while establishing two different postures determined by target placement. Load and Posture both had negative impacts on the speed-accuracy trade-off, with larger loads affecting gross postural transitions and smaller loads degrading fine-aiming performance. The more challenging posture degraded accuracy on target substantially, suggesting that reorientation of multiple segments may be necessary for assessing the consequences of load on marksmanship performance. Increases in the total coordinative variability of Head-Trunk-Gun relations with load at a high target suggests that increased inertial and interactive forces during movement "push" the system out of the optimal segmental relations. Moreover, the results from Postural-Focal coupling suggest that load "freezes" previously available degrees of freedom, making the system more deterministic and less flexible in goal-directed achievement. The two previous paradigms are joined in the third study to understand perception-action coupling during movement cessation to marksmanship transitions, a ubiquitous task in combat. Increased time to discriminate targets was found with load and was related to peak head velocities and the inability to dissipate energy at the head/eyes under load. Again, Load and Posture had significant effects on the speed-accuracy trade-off, especially at the load most similar to that seen in current missions. Segmental coordination in this effort ballasts the findings in study 2, as significant shifts from optimal Head-Trunk-Gun relations were observed with load as well as increased variability that was detrimental to task performance. This dissertation demonstrates that science can be "Operationalized" in a way that maintains scientific integrity during complex task analysis; providing additional insight into the issue of load across multiple scales of analysis related to functional capability and survivability in combat and others encumbered by load.

]]> Palmer, Christopher Jay The influence of free-living activity and inactivity on health outcomes and responsiveness to exercise training http://scholarworks.umass.edu/open_access_dissertations/580 http://scholarworks.umass.edu/open_access_dissertations/580 Tue, 04 Sep 2012 07:00:12 PDT 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 reducing SB and the validity of PA monitors for measuring SB compared to direct observation (DO). Participants completed a 1-week baseline period and a 1-week intervention period, where they were instructed to decrease SB. The correlation between the AP and DO was R2=0.94 and the AG100 and DO sedentary minutes was R2=0.39. SB significantly decreased from 67% of wear time (baseline period) to 62.7% of wear time (intervention period) according to AP. Only the AP was able to detect reductions in SB and was more precise than the AG. Study Two was a 12-week randomized controlled study. There were 4-groups that were instructed to: 1) CON: maintain habitual PA and SB 2) rST: reduce and break-up SB and increase daily steps 3) EX: exercise 5-days per week for 40-minutes per session at moderate intensity 4) EX-rST: combination of EX and rST. Cardiovascular disease risk factors were assessed pre-and post-intervention. The AP was used to verify AP between-group differences in activity at four time-points. EX-rST had improvements in insulin action variables that EX did not. All other physiologic responses to training were similar between EX groups and rST has less robust changes than either EX group. These data provide validation of activity monitors for measuring SB and present preliminary evidence that activity outside of exercise training may influence the metabolic response to training. This dissertation shows that what is done outside of exercise training can and should be quantified using objective monitors that assess daily exposure to activity and inactivity behavior.

]]> Keadle, Sarah Kozey A comprehensive model of human neuromuscular function during repeated isometric contractions: Predicting the effect of age on fatigue http://scholarworks.umass.edu/dissertations/AAI3498334 http://scholarworks.umass.edu/dissertations/AAI3498334 Mon, 16 Apr 2012 14:14:48 PDT 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 model would include components that represent motor neurons and populations of muscle fibers that reflect the range of metabolic and contractile characteristics known to exist in human skeletal muscle. Consideration of joint and connective tissue mechanical properties will add translational value by predicting whole joint segment behavior that can be validated by in vivo experimentation. The proposed dissertation project involved the development of a computational model incorporating multiple components meant to represent the function of the intact neuromuscular system. The complete model combines previously-validated models of neural activation and contractile behavior with a control function that attempts to match torque output to a pre-determined task. The model uses experimentally-derived functions describing metabolic cost and force inhibition to predict the loss of force generating capacity during repeated activation. Once tested using data from a group of adult men, the parameters of this model were altered to reflect age-related changes in the human neuromuscular system. The model's ability to predict the well-established phenomenon of age-related fatigue resistance during isometric contractions was then tested. The results from this series of studies support the utility of a computational approach to the investigation of muscle fatigue, and provide useful tools for future studies.^

]]> Callahan, Damien M Adaptations to Stride Patterns and Head Movements During Walking in Persons With and Without Multiple Sclerosis http://scholarworks.umass.edu/open_access_dissertations/533 http://scholarworks.umass.edu/open_access_dissertations/533 Wed, 28 Mar 2012 09:19:16 PDT 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 definitions, measures of coordination between the swing foot and body CoM, and head movements as they pertain to field of view orientation during walking. Third, these novel measures were used to study the swing phase of walking in people with MS.

The first investigation revealed that the MS group walked with lengthened dual support times across all speeds, but shortened swing time and altered swing foot timing at fixed speeds in comparison to controls. Those with MS adopted a gait strategy with increased dual support time, despite forcing changes to swing that may reduce gait stability.

In the second investigation, novel measures of swing showed alterations to phases of swing and in coordination between the swing foot and CoM under different gait tasks. This study also showed that the field of view was closer to the body during obstacle condition steps compared with unobstructed gait.

In the third study, these novel measures showed that at all speeds the MS group shortened early swing and lengthened mid swing while late swing remained unchanged compared with controls. Coordination measures illustrated adaptations in swing foot dynamics that may partially ameliorate altered swing foot timing. The MS group oriented the field of view closer to the body earlier in swing compared with controls. Those with MS have functionally adapted swing to increase time over the stance foot and rely more on visual perception, yet shorter early swing may afford fewer opportunities to plan a step or cope with gait disturbances while walking.

]]> Remelius, Jebb Grigory A Comprehensive Model of Human Neuromuscular Function During Repeated Isometric Contractions: Predicting the Effect of Age on Fatigue http://scholarworks.umass.edu/open_access_dissertations/509 http://scholarworks.umass.edu/open_access_dissertations/509 Tue, 06 Mar 2012 10:02:54 PST 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 model would include components that represent motor neurons and populations of muscle fibers that reflect the range of metabolic and contractile characteristics known to exist in human skeletal muscle. Consideration of joint and connective tissue mechanical properties will add translational value by predicting whole joint segment behavior that can be validated by in vivo experimentation. The proposed dissertation project involved the development of a computational model incorporating multiple components meant to represent the function of the intact neuromuscular system. The complete model combines previously-validated models of neural activation and contractile behavior with a control function that attempts to match torque output to a pre-determined task. The model uses experimentally-derived functions describing metabolic cost and force inhibition to predict the loss of force generating capacity during repeated activation. Once tested using data from a group of adult men, the parameters of this model were altered to reflect age-related changes in the human neuromuscular system. The model's ability to predict the well-established phenomenon of age-related fatigue resistance during isometric contractions was then tested. The results from this series of studies support the utility of a computational approach to the investigation of muscle fatigue, and provide useful tools for future studies.

]]> Callahan, Damien Mark Effects of high-intensity interval training on muscle oxidative metabolism in young men http://scholarworks.umass.edu/dissertations/AAI3465034 http://scholarworks.umass.edu/dissertations/AAI3465034 Wed, 18 Jan 2012 12:10:48 PST The ability to supply cellular energy in the form of adenosine triphosphate (ATP) by oxidative phosphorylation is critical to maintaining muscle function and health. While conventional endurance exercise training has proven effective at increasing the maximal capacity for oxidative phosphorylation (Vmax ), it is not known whether exercise training stimulates mitochondrial ATP synthesis in resting muscle (Vrest). Recently, short-term high-intensity interval training (HIT) training has shown potent effects on Vmax. However, little is known about (1) the effects of short-term HIT on Vrest, and (2) the time course of adaptations in V rest and Vmax following short-term HIT. Healthy young males were recruited to participate in a 2-week training intervention (6 training sessions). Each session consisted of 4–6 bouts of 30-s sprints on a cycle ergometer. Phosphorus magnetic resonance spectroscopy was used to measure Vrest and Vmax in vivo in vastus lateralis: (i) prior to, (ii) 15 hours after a single session of exercise training, and (iii) after completing 6 sessions of exercise training. Two weeks of training increased peak whole-body oxygen consumption (35.8 ± 1.4 to 39.3 ± 1.6 ml·min−1·kg−1, p=0.01) and exercise capacity (217.0 ± 11.0 to 230.5 ± 11.7 W, p=0.04) on the cycle ergometer. While Vmax was unchanged after a single session of HIT, completion of six training sessions resulted in increased muscle oxidative capacity (p<0.004). In contrast, neither a single nor six training sessions altered Vrest (p=0.74). Metabolic flux through each pathway, during maximal voluntary contractions, remained unchanged after the first training session, but 6 training sessions increased the relative contribution of ATPOX (31 ± 2 vs. 39 ± 2 % of total ATP turnover, p<0.001), and lowered the relative contribution from ATP CK (49 ± 2 vs. 44 ± 1 %, p=0.004) and ATPGLY (20 ± 2 vs. 17 ± 1 %, p=0.03). This study provided novel information about the scope and timing of bioenergetic adaptations of skeletal muscle in young healthy men following high-intensity interval training. These results highlight the plasticity of skeletal muscle oxidative metabolism, which is critical for the design of future exercise training interventions for both clinical and healthy populations.^

]]> Larsen, Ryan Godsk Cellular and Molecular Changes Following Skeletal Muscle Damage: A Role for NF-kB and Muscle Resident Pericytes http://scholarworks.umass.edu/open_access_dissertations/449 http://scholarworks.umass.edu/open_access_dissertations/449 Tue, 06 Dec 2011 08:35:47 PST 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 muscle biopsies were taken from both legs 3 h post-EC. The sample from the non-EC leg served as the control. A well-powered transcriptomic screen and network analysis using Ingenuity Pathway software was first conducted on mRNA from the biopsy samples. Network analysis identified the transcription factor NF-kappaB (NF-kB) as a key molecular element affected by EC. Conformational qRT-PCR confirmed alterations in genes associated with NF-kappaB. A transcription factor ELISA, using nuclear extracts from EC and control muscle samples showed a 1.6 fold increase in NF-kB DNA binding activity following EC. Immunohistochemical experiments then localized the majority of NF-kB positive nuclei to cells in the interstitium, which stained positive for markers of pericyte cells and not satellite cells. To ascertain the mechanistic significance of NF-kB activation following muscle damage, in vitro analyses were carried out using a novel primary pericyte/myoblast co-culture model. Primary pericyte/myoblast co-culture experiments demonstrated that pericytes, transfected with a DNA vector designed to drive NF-kB activation, enhanced proliferation and inhibited myogenic differentiation of co-cultured skeletal muscle myoblasts. Furthermore, reduced NF-kB activation led to enhanced myogenic potential of primary pericytes. Taken together, the data in this dissertation suggest that NF-kB dependent signaling in pericytes regulates myogenic differentiation in a cell- and non-cell autonomous manner and may affect the early regenerative response following muscle damage by inhibiting differentition and promoting proliferation of muscle satellite cells.

]]> Hyldahl, Robert H.