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Item The influence of external load during hiking on markers of joint stress and movement efficacy(Montana State University - Bozeman, College of Education, Health & Human Development, 2022) Rowland, Isaac Franco; Chairperson, Graduate Committee: Mary P. Miles; Mary Miles, David Graham, Ron June, Brian Bothner and Hunter Fausset were co-authors of the article, 'The influence of external load during hiking on markers of joint stress and movement efficacy' which is contained within this thesis.PURPOSE: Complications to lower extremity joints, including injury and inflammation, are prevalent issues that arise during prolonged external load-bearing exercise. Metabolomic blood analysis can provide insight into the metabolic processes that occurs during this type of exercise. METHODS: Eight healthy, active men and women participated in a series of blood sample collections and motion capture recording before and after completing a 7.2-mile hiking protocol under two separate conditions. Blood was collected prior to hiking, 15-20 minutes after hiking, 8-hours after, 24-hours after, and 48 hours after. Movement coordination and efficacy was measured with a motion capture system while performing the y-balance test and an obstacle clearance task. Hiking conditions were randomized as backpacking with 20% of body mass external load or daypacking with minimal external load for each participant and separated by two weeks. Serum was analyzed to detect differences in metabolite upregulation between conditions. Biomechanical data were analyzed for inter- and intra-differential values relevant to fatigue between conditions. RESULTS: Analysis found clear differences between conditional metabolite upregulation at all post-hike timepoints. The upregulation of cortisol was significant in backpacking conditions at the post-hike timepoint. Glycerophospholipids were significantly upregulated in backpacking at 8-hours post-hike All significant metabolite upregulation switched to daypacking conditions at 24-hours post-hike. Significant metabolite upregulation varied between conditions at 48-hours post-hike. The only findings of significance in movement coordination and efficacy were between the y-balance lateral leg movement. CONCLUSIONS: The presence of cortisol is consistent with the physiological and mental stress of external loadcarriage and alludes to exposure that can lead to decreased bone mineral content. Glycerophospholipid metabolism pathways play an important role in joint degradation, which could explain their upregulation in backpacking conditions. Ceramide, omega-3s, and fatty acid/triglyceride cycling are functions of cell proliferation and turnover which may be upregulated with more efficiency in daypacking conditions. Upregulation of anserine at 48-hours post-hike in daypacking supports the idea of more efficient exercise recovery occurring in this condition. While significant differences were not clear in motor control measures, the findings show potential reliability for future study designs.Item Patellofemoral joint loading in females during back squats of varying depth, weight load, and stance width(Montana State University - Bozeman, College of Education, Health & Human Development, 2019) Zavala, Linnea Joy; Chairperson, Graduate Committee: James P. Becker; Victoria Flores, Joshua Cotter and James Becker were co-authors of the article, 'Patellofemoral joint loading in females when using different depths and loads in the back squat' submitted to the journal 'Journal of applied biomechanics' which is contained within this thesis.; James Becker was a co-author of the article, 'Patellofemoral joint loading in females during back squats with varying stance widths' submitted to the journal 'Journal of orthopedic sports physical therapy' which is contained within this thesis.As a repetitive and loaded exercise, the back squat can lead to tissue injury. One concern is patellofemoral pain syndrome, a common knee diagnoses over twice as prevalent in females as in males. Patellofemoral joint stress is cited as a cause of the syndrome. To manage the syndrome, quadriceps strength is important. Although the back squat is a good exercise for quadricep strength, modifications to squat technique may be necessary to decrease patellofemoral joint stress. Two studies on female recreational athletes are addressed here: 1) how patellofemoral joint loading changes with squat depth and load and 2) how it changes with squat load and stance width. Depth-specific 1-repetition maximums were measured, and weight loads were based on percentages of the maximum. Peak knee extensor moments, patellofemoral joint reaction forces, and patellofemoral joint stresses were calculated using inverse dynamics and previously reported equations. First, participants squatted to 90°, ~°110, and ~135° of knee flexion with loads of 0%, 50%, and 85% of 1RM. A depth-by-load interaction was found such that within each depth, moments increased as load increased, while decreasing with increased depth. Patellofemoral joint reaction force had main effects of load and depth such that as load increased or depth decreased, reaction force increased. Another depth-by-load interaction was found such that within each depth, as load increased the stress increased, while increasing with increased depth. From these results, squats to full depth or loaded squats to less than 90° of knee flexion are recommended to minimize patellofemoral joint stress. Second, when squatting to ~110° with loads of 35% and 85% and stance widths of 90%, 100%, 110%, and 120% of natural stance, there was a main effect of load for knee extensor moment, patellofemoral joint reaction force, and patellofemoral joint stress. Although altering stance width does not appear to change joint loading, some research suggests that there may be a relationship between foot turnout and joint loading. Continuing relatively simple studies, like these, reveal trends which more individualized approaches can later use, accounting for individuals' anatomy to fully understand patellofemoral joint loading during the back squat.Item Evaluating determinants of psychophysiological stress in collegiate student-athletes(Montana State University - Bozeman, College of Education, Health & Human Development, 2016) Terry, Jennifer Lauren; Chairperson, Graduate Committee: Daniel P. HeilCollegiate student-athletes are a unique group of individuals who experience a vast array of cognitive and physiological stressors. In addition to the typical stressors of an average college student, such as homesickness, finances, academics, and social relationships, student-athletes must also cope with lack of free time, pressure to perform, relationships with coaches and teammates, and physiological stress due to training and competing. Student-athletes with unmanaged chronic stress are more likely to experience a plethora of negative health outcomes, effecting performance in the classroom, on the field, and in life. Currently, survey instruments exist to predict cognitive and physiological sources of stress in isolation, but no existing instrument integrates both cognitive and physiological stressors into a single measure of chronic stress. The current cross-sectional study compared magnitude and sources of stress, psychological and physiological, experienced by Montana State University student-athletes (n=30) and their non-athlete counterparts (n=22). In addition, associations between chronic stress (as indicated by hair cortisol concentration, or HCC) and subjective measures of psychological stress, physiological stress and sleep quality were assessed in a subgroup of participants (n=12 student-athletes; n=9 non-athletes). Student-athletes had significantly greater average weekly training load than the non-athlete students (P < 0.001), but all other indicators of psychological stress and sleep quality were not significantly different between the two groups. Of those participants who provided a hair sample, the student-athletes had greater average HCC (P = 0.027). Although no associations were observed between HCC and measures of psychophysiological stress or sleep quality, a significant correlation was observed between HCC and body fat percentage (r = -0.59, P < 0.045). Additional research is necessary to elucidate the role of body composition, as well as other factors, on chronic stress development in college student-athletes.