Theses and Dissertations at Montana State University (MSU)
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Item The Y-balance test in runners: relationships between performance and running mechanics, and the influence of fatigue(Montana State University - Bozeman, College of Education, Health & Human Development, 2020) Wilson, Charles Scott; Chairperson, Graduate Committee: James P. Becker; Allison Theobold, Sara Skammer, Sam Nelson and James Becker were co-authors of the article, 'A multivariate analysis between the Y-balance test and injury-linked running mechanics' submitted to the journal 'The American journal of sports medicine' which is contained within this thesis.; Sam Nelson, Sara Skammer and James Becker were co-authors of the article, 'The relationship between Y-balance test performance and running mechanics at the hip following fatigue' submitted to the journal 'The journal of orthopedic and sports physical therapy' which is contained within this thesis.The YBT is a widely known clinical movement screen used to measure strength, dynamic stability and neuromuscular control in a variety of athletic and clinical populations. The YBT is also used to predict injury risk across a range of sports. Strength and neuromuscular control of the muscles surrounding the hip are strong predictors of YBT performance. These same variables are also essential for running performance and the prevention of injury. Changes in injury-related running mechanics have been shown to occur along the course of a fatiguing run. Thus, the purpose of this thesis was twofold: 1) to evaluate the relationship between YBT performance and running mechanics and 2) to evaluate whether YBT performance can predict changes in injury-linked running mechanics after a run to fatigue. For the remainder of this paper the previous manuscripts will be referred to as Study 1 (A Multivariate Analysis of the Relationships Between Y-Balance Test Performance and Running Mechanics) and Study 2 (The Relationship Between Y-Balance Test Performance and Running Mechanics at the Hip Following Fatigue).Item Support moment distribution and induced acceleration analysis of the barbell back squat(Montana State University - Bozeman, College of Education, Health & Human Development, 2020) Goodman, William Wesley; Chairperson, Graduate Committee: David Graham and James P. Becker (co-chair); Victoria Flores, Joshua Cotter, David Graham and James Becker were co-authors of the article, 'Support moment distribution during the barbell back squat at different depths and loads in recreationally trained females' submitted to the journal 'Journal of strength and conditioning research' which is contained within this thesis.; James Becker and David Graham were co-authors of the article, 'An induced acceleration analysis of the barbell back squat at different depths in trained females' submitted to the journal 'Journal of strength and conditioning research' which is contained within this thesis.The barbell squat exercise is performed in settings ranging from rehabilitation through to developing muscle size, strength and power. Unfortunately, the lower extremity coordination producing the squat is not clearly understood. This thesis involves two studies evaluating how lower limb joints and muscles coordinate varied squat performance. Study one included 19 females who performed squats at three randomized depths (above parallel, parallel, below parallel) and three loads (unloaded, 50%, 85% 1 repetition maximum). Inverse dynamics analysis revealed that peak hip and ankle extensor moments varied with load but not depth and were greatest when using 85% 1 repetition maximum. Within each depth, as load increased so did peak knee extensor moments. Peak knee extensor moments were greatest when squatting below parallel with load. Within each depth as load increased contribution of the hip increased whereas the knee decreased. Ankle contribution was only influenced by load. When squatting to deep depths with load, the contribution of the hip decreased while the knee increased. In study two, 13 females squatted to the same 3 depths using 85% of their 1 repetition maximum at each respective depth. Performance was evaluated by estimating the individual muscle force production and the individual muscle contribution to whole body acceleration using a musculoskeletal model. The gluteus maximus and adductors increased peak force to parallel while the hamstrings and rectus femoris increased to below parallel. At deep depths, the vasti decreased peak force while the hamstrings and rectus femoris increased peak force. The induced acceleration of the vasti at transition decreased with depth while the hamstrings and rectus femoris increased. Because muscles can instantaneously accelerate all joints in the body, it's possible that at transition the hamstrings accelerated the hip and knee into extension while the rectus femoris also accelerated the knee and hip into extension while the soleus accelerated the ankle and knee into extension. In conclusion, a complex coordination of the lower extremity is used performing the squat. Varied coordination indicates that depth and load specificity is important and should be taken into consideration when programming based on the status and goals of the individual.Item The influence of a directional compression garment on muscle activity and performance in recreational alpine skiers(Montana State University - Bozeman, College of Education, Health & Human Development, 2018) Snyder, Cory James; Chairperson, Graduate Committee: John G. Seifert; John G. Seifert, James Becker and Ed Adams were co-authors of the article, 'The influence of a directioanl compression garment on muscle activity and performance in recreational alpine skiers' submitted to the journal 'Journal of sports sciences' which is contained within this thesis.Recent studies reported reduced muscle activity in competitive alpine skiers using directional compression (DC). It is not known whether the effects of DC are limited to competitive skiers, or if similar changes would be observed in recreational skiers during a full day of skiing. The purpose of this study was to examine changes in hip and leg muscle EMG patterns in recreational alpine skiers when skiing with and without a lower body DC garment. METHODS 11 intermediate and expert skiers volunteered for this study. Subjects completed 2 randomized trials, one in a DC garment, and one in a non-compressive (NC) base layer. EMG of the gluteus medius (GMED), gluteus maximus (GMAX), rectus femoris (RF), adductor longus (ADL), and vastus lateralis (VL) were recorded using EMG during three measurement runs with standardized turns on each visit. Standardized turns were used to compare EMG response between conditions and measurement runs. Subjects also completed self-paced skiing bouts (SP) between measurement runs. Skiing performance (heart rate, velocity, and skiing load (vertical/runs) were measured during the SP bouts. 2x3 repeated measures ANOVA's was used to compare kinematic and EMG changes during measurement runs, as well as performance during self-paced skiing between (p < or = 0.05). RESULTS Subjects skied more runs (DC 18.60 + or = 0.98, NC 13.55 + or = 1.06, p=0.001) and vertical (DC 4805.31 + or = 304.31 m, NC 2373.56 + or = 219.60 m, p=0.001) during free skiing with DC than NC. Heart rate and ski velocity were not different between SP bouts. Peak edge angle was lower in the DC treatment (DC 55.06 + or = 10.70°, NC 57.90 + or = 9.10°, p=0.008). Absolute muscle activity was lower in the DC condition for all muscles (p < or = 0.05), although no differences were observed in relative muscle activity. CONCLUSIONS No differences in relative muscle activity were detected, absolute muscle activity was lower in the DC condition. Subjects improved their self-paced skiing performance in the DC condition. There was also a trend towards lower RMS for all muscles in the DC treatment. Further research should investigate the influence of DC garments on repeated bouts of recreational alpine skiing on consecutive days.Item The effects of acute muscular fatigue on the functional ability of the knee joint(Montana State University - Bozeman, College of Education, Health & Human Development, 2005) Brown, Tyler Nolan; Chairperson, Graduate Committee: Michael E. Hahn.Results of preliminary data collection indicate an increase of electromyography (EMG) amplitude in fatiguing isokinetic contractions of the knee extensors. The primary purpose of this study was to determine if the EMG/Torque relationship of vastus lateralis changes as a result of fatigue. The second purpose of this study was to determine if tests of functional ability are affected by fatigue. Twenty-two subjects (13 males and 9 females) were sampled from two populations with different types of training (strength versus endurance) experience. The procedures included a five-minute self-selected warmup on a cycle ergometer, pre-fatigue functional ability tests, fatigue protocol and postfatigue functional ability tests. The functional ability test protocol included four singleleg hopping drills to assess the functional performance of the knee joint. Torque was measured on an isokinetic dynamometer at 60 degrees per second through a functional range of motion until acute fatigue was reached during the fatigue protocol. Surface EMG electrodes were placed over the vastus lateralis to develop an EMG/Torque ratio during the dynamic contractions. The results indicate training type did not significantly affect torque production (p = 0.373) or the EMG/Torque ratio (p = 0.744) during isokinetic knee extensions in response to acute muscular fatigue. The strength-trained sample tended to have a greater increase of the EMG/Torque ratio during the fatigue protocol. The results did indicate that there were two significantly different types of response to acute muscular fatigue (p < 0.001). There were significant differences between the preand post-fatigue functional ability tests for the M/L (p < 0.001) and Up/Down (p = 0.011) but not for 3-Forward (p = 0.408) or Figure-8 (p = 0.286). One group doubled their activation magnitude during the fatigue protocol, while another group did not increase their activation magnitude during the fatigue protocol. It is possible that the increase of activation magnitude seen during the fatigue protocol is a result of transition of fiber type utilization. Further study is needed to determine what is the primary cause of the muscleαs response to acute muscular fatigue.