Grinding is integral to tacking and gybing manoeuvres in America’s Cup sailing. Grinding is a standing position cyclic upper body task requiring manual arm cranking of winches, which control movement of the mast and sails. Limited information exists on biomechanical factors involved in grinding performance. This thesis determined technique and muscular performance characteristics of sailors related to grinding performance, and effects of a training intervention on grinding performance. Reliability of grinding ergometer performance testing was evaluated across direction, load and heel conditions. In all conditions relative performance between individuals was consistent (r = 0.84-0.99) and the grinding performance test differentiated well between individuals. External work had lower overall variation (1.6-3.9%) than peak power (1.3-5.4%), especially when grinding against greater loads. Grinding performance was less consistent in heeled conditions (4.6-6.9%) than on the flat, but grinding direction did not affect reliability. Performance changes over 4% could be interpreted with confidence. Peak torque occurred at 95° (77 N m) and 35° (69 N m) for forward and backward grinding respectively (0° = grinding crank vertically up). Torque of >50 N m was maintained through 72% of the cycle during forward grinding but only 47% for backward grinding. Differences were attributed to a greater spread of active muscles throughout the cycle for forward grinding, and contrasting movements contributing most to torque – upper body push for forward grinding and pull for backward grinding. Variant characteristics of the two grinding directions provide some explanation for the significant advantage (+8.0%, p<0.001) when grinding in pairs with an anterior-posterior heel compared to a medio-lateral heel. Movement characteristics did not readily explain why an anterior-posterior heel may be more advantageous under higher grinding loads (1.0%, p = 0.254), while medio-lateral heel is better at lower loads (2.0%, p = 0.017). Muscular performance of sailors, examined using an instrumented Smith machine, showed force and 1RM strength were greater in the bench press by ~17%. Velocity and power output were greater for the bench pull across the range of loads with the difference increasing exponentially as load increased to over 400% higher at 1RM load. Bench press 1RM and maximum force capability demonstrated strongest correlations with forward grinding performance (r = 0.88-0.99 and 0.87-0.99 respectively) with the relationship increasing with grinding load. There was a strong relationship for backward grinding with bench pull maximum power (r = 0.85-0.98) in addition to 1RM (r = 0.90-0.95) and maximum force (r = 0.87-0.95). Backward grinding performance showed greater improvements in the power-focussed training group than the control group for moderate (+1.8%) and heavy load (+6.0%) grinding in the intervention study. Changes in maximum power output and power at 1RM had large correlations (r = 0.56-0.61) with changes in both moderate and heavy load grinding performance. Time to peak force explained 70% of the change in heavy load grinding performance. Performance benefits from the training intervention were not entirely clear, but the likelihood of a detrimental effect was low (<5%), therefore further training intervention was recommended.

Grinding is integral to tacking and gybing manoeuvres in America’s Cup sailing. Grinding is a standing position cyclic upper body task requiring manual arm cranking of winches, which control movement of the mast and sails. Limited information exists on biomechanical factors involved in grinding performance. This thesis determined technique and muscular performance characteristics of sailors related to grinding performance, and effects of a training intervention on grinding performance. Reliability of grinding ergometer performance testing was evaluated across direction, load and heel conditions. In all conditions relative performance between individuals was consistent (r = 0.84-0.99) and the grinding performance test differentiated well between individuals. External work had lower overall variation (1.6-3.9%) than peak power (1.3-5.4%), especially when grinding against greater loads. Grinding performance was less consistent in heeled conditions (4.6-6.9%) than on the flat, but grinding direction did not affect reliability. Performance changes over 4% could be interpreted with confidence. Peak torque occurred at 95° (77 N m) and 35° (69 N m) for forward and backward grinding respectively (0° = grinding crank vertically up). Torque of >50 N m was maintained through 72% of the cycle during forward grinding but only 47% for backward grinding. Differences were attributed to a greater spread of active muscles throughout the cycle for forward grinding, and contrasting movements contributing most to torque – upper body push for forward grinding and pull for backward grinding. Variant characteristics of the two grinding directions provide some explanation for the significant advantage (+8.0%, p<0.001) when grinding in pairs with an anterior-posterior heel compared to a medio-lateral heel. Movement characteristics did not readily explain why an anterior-posterior heel may be more advantageous under higher grinding loads (1.0%, p = 0.254), while medio-lateral heel is better at lower loads (2.0%, p = 0.017). Muscular performance of sailors, examined using an instrumented Smith machine, showed force and 1RM strength were greater in the bench press by ~17%. Velocity and power output were greater for the bench pull across the range of loads with the difference increasing exponentially as load increased to over 400% higher at 1RM load. Bench press 1RM and maximum force capability demonstrated strongest correlations with forward grinding performance (r = 0.88-0.99 and 0.87-0.99 respectively) with the relationship increasing with grinding load. There was a strong relationship for backward grinding with bench pull maximum power (r = 0.85-0.98) in addition to 1RM (r = 0.90-0.95) and maximum force (r = 0.87-0.95). Backward grinding performance showed greater improvements in the power-focussed training group than the control group for moderate (+1.8%) and heavy load (+6.0%) grinding in the intervention study. Changes in maximum power output and power at 1RM had large correlations (r = 0.56-0.61) with changes in both moderate and heavy load grinding performance. Time to peak force explained 70% of the change in heavy load grinding performance. Performance benefits from the training intervention were not entirely clear, but the likelihood of a detrimental effect was low (<5%), therefore further training intervention was recommended.

Study Design: Methodological study. Objectives: To examine the agreement and validity of using observational risk screening guidelines to evaluate ACL injury risk factors. Background: Post-pubescent females have an increased risk of anterior cruciate ligament (ACL) injury compared with their male counterparts partly due to their high-risk landing and cutting strategies. There are currently no scientifically-tested methods to screen for these high risk strategies in the clinic or on the field. Methods and Measures: Three physiotherapists used observational risk screening guidelines to rate the neuromuscular characteristics of 40 adolescent female soccer players. Drop jumps were rated as high risk or low risk based on the degree of knee abduction. Side hops and side cuts were rated on the degree of lower limb 'reaching'. Ratings were evaluated for intrarater and interrater agreement using kappa coefficients.3D motion analysis was used as a gold standard for determining the validity of ratings. Results: Acceptable intrarater and interrater agreement (k^0.61) were attained for the drop jump and the side hop, with kappa coefficients ranging from 0.64 to 0.94. Acceptable sensitivity (^0.80) was attained for the side hop and the side cut, with values ranging from 0.88 to 1.00. Acceptable specificity (^0.50) was attained for the drop jump, with values ranging from 0.64 to 0.72. Conclusion: Observational risk screening is a practical and cost-effective method of screening for ACL injury risk. Based on levels of agreement and sensitivity, the side hop appears to be a suitable screening task. Agreement was acceptable for the drop jump but its validity needs further investigation.

No description available.

This thesis examines the psychological processes dancers experience while learning choreography through a phenomenological hermeneutic lens. This investigation took place at Scripps College Dance Department where I composed a choreographic work to explore the outer expressivity of internal experiences. By measuring psychological experiences of flow, the research identifies when dancers do or do not experience positive mental states of being in flow while engaged in the choreographic process of making concert dance. Data was collected using the Event Experience Scale (FSS-2) and the Performance Competency Evaluation Measure (PCEM), as well as additional comments from the participants. This thesis challenges the notion that the psychological experiences of creating dance cannot be investigated qualitatively.

Healthy aging is associated with an increased incidence of injuries such as low back pain and falling. Age-related changes in trunk neuromuscular activation patterns could potentially explain uncontrolled trunk motion, a risk factor for these injuries. The purpose of this study was two-fold: i) to establish if trunk neuromuscular activation patterns differ between older and younger adults, and ii) to identify if increased cognitive load can alter the activation patterns used by older adults. Participants performed a controlled dynamic transfer task known to challenge trunk musculature by continuously changing the external moment experienced by the spine. In this thesis, the transfer task was altered by increasing the external moment and cognitive load to address purpose i) and ii) respectively. Three dimensional trunk and pelvis motion and surface electromyograms for 24 trunk muscle sites were collected in two experiments. In the first experiment 26 younger adults, and 17 older adults, performed the transfer task at two physical task intensities. In a second experiment, eight of these older adults performed the dynamic transfer task while performing a simultaneous cognitive dual-task. An analysis of amplitude and temporal characteristics of EMG waveforms, using principal component analysis, showed that older adults had altered trunk neuromuscular activation patterns compared to younger adults. In particular, after accounting for physical task intensity, older adults have increased antagonist co-activation, less temporal variation to changing external moments, and changes in the synergistic relationships between trunk muscle sites. Increasing the cognitive load had no influence on the trunk neuromuscular activation patterns used by healthy active older adults. However, as cognitive performance was not measured in the dual-task it cannot be excluded that i) the cognitive task did not represent enough challenge to result in competition of cortical resources, or ii) the cognitive resources necessary for the successful completion of the transfer task were prioritized in older adults.

With a prevalence of 17% in men and 4% in women, Femoroacetabular Impingement (FAI) of type cam is characterized by a decreased femoral head-neck offset and/or asphericity of the lateral femoral head, associated with groin pain and reduced hip range of motion. Since the aetiology is still unclear, the mechanisms of development, progression and degeneration of FAI are largely investigated. Musculoskeletal modeling can support the development of a biomechanical framework to advance the research on FAI pathomechanisms, expand the knowledge about hip contact load distribution in FAI population, and relate the muscle and hip contact forces to the alterations observed during functional tasks. Therefore, this thesis is composed of two parts: the development of a methodological framework, and its application to the investigation of FAI pathomechanisms. The variability of the modelling outcomes (i.e.., body kinematics, torques, contact and muscle forces) to different marker sets, pelvic marker misplacements, and hip joint center (HJC) location was investigated within an inverse kinematic framework. The findings from such studies supported the modelling choices for the clinical investigation of FAI pathomechanisms. In particular, the performance of three different marker sets (Plug-in-Gait, University of Ottawa Motion Analysis Model and a 3-marker-cluster marker set) was compared, and absolute and relative reliability indices were calculated with the purpose of finding a simple yet reliable marker set to be used within an inverse kinematic framework in a clinical study. Thereafter, the sensitivity of joint angles, moments and hip contact forces to simulated inaccurate pelvic tilt was analyzed. The resulting variability indices were high with variations up to 1.3 times the body weight in hip contact forces. The kinematic variations propagated non-linearly to all planes and joints, showing the importance of adjusting possible pelvic misalignments. A methodology was presented to correct the pelvic alignment when the relative position of surface pelvic markers with respect to bony landmarks is known from medical images. The HJC location is a crucial modelling parameter in the analysis of hip kinematics and forces. A certain degree of customization could be introduced in the model by using HJC measured from medical images. Therefore, the performance of a generic musculoskeletal model with customized or non-customized HJC was compared during walking. Hip contact forces were highly sensitive to HJC location, especially because of the dependency of muscle moment arms to HJC changes. However, the variation of HJC without consistent muscle anatomy customization introduced artifacts that could potentially produce inaccurate muscle and joint contact forces estimation. When HJC cannot be measured from medical images, regression equations can be used instead. Therefore, the validity of two popular HJC regression equations (Harrington and Davis) was tested on FAI participants using non-parametric statistical and Bland-Altman tests. The results indicated that the equations were valid for FAI population. In addition, skin thickness measurements were provided for pelvic bony landmarks, and their correlation with body mass index was proposed for systematic error reduction. New adult-specific regression equations were developed from medical images. The described methodological framework was then applied to investigate the functional alterations observed in FAI population. The differences in muscle and hip contact forces were compared between FAI and healthy control groups during level walking. The FAI group showed reduced muscle and hip contact forces, which were linked to the lower normalized walking speed and shorter step length. These results can be interpreted as a protective mechanism developed by FAI patients to prevent high compression at the site of impingement, given that the compressing hip contact force was directed towards the anterior-superior quadrant of the acetabulum, consistent with the localization of the cam-type deformity and the cartilage and labrum damages. Based on these findings, a possible FAI pathomechanism was proposed, which could be used to support the development of preventive treatment and intervention for symptomatic FAI patients.

No description available.

When it comes to actor training in higher education, an extremely strong emphasis is placed on understanding the voice and interpreting the text. While some institutions do incorporate movement courses into the curriculum of the students, many do not serve the learning actor in the most effective way. The work of Rudolf Laban is a way to strengthen the curriculum taught to actors, specifically in regards connecting actors to their bodies. This thesis discusses and analyses the use of Laban’s movement theory in the movement classroom, and focuses on the most effective way of presenting the material to the student. Included is research on Laban’s theories, the structure of a Laban for the actor course, feedback from participants, exercises crafted to better suit the learning actor, and connections to other acting and movement practitioners. The aim is to provide actors with a well-rounded toolbox that will assist them in creating more dynamic and livable characters. This thesis hopes to serve as a guide for both instructors of movement and students alike, providing all with a resource to refer to when working with the body on or off the stage.

Rudolf Laban: Father of Modern dance, revolutionary within the field of movement studies, and inventor of Labanotation. His work is so universal it has been applied to dancing, acting, industrial work, and movement therapy. This thesis will specifically discuss the use of his system as it applies to actor training. However before that it is important for me as a teacher to understand the potential ideologies and historical implications that are associated with a theory or body of work before passing it on, lest we unknowingly propagate a system of thought that is associated with destructive ideologies. This becomes particularly significant in the case of Laban. From 1933 until 1936 Laban’s movement analysis and choreographic skills were an integral and leading part of the Reich Chamber of Culture’s division of dance. Many of his contemporaries labeled him a Nazi, and many scholars today struggle to extricate his work from the Nazi stain. If his work, as his contemporaries claimed, was fascist in nature and his work was uniquely expressive of the German volk, as Goebbels had instructed him it should be, then we as teachers have a moral obligation to be judicious in our applications of his system. Therefore in this thesis I will first examine the time Laban spent working for the Third Reich, and only after concluding that his actual system of understanding movement had little to do with the politics during that time of his life will I then go on to discuss how Laban Movement Analysis can be an integral tool for actor training, and discuss the ideologies that I, as a teacher, bring to the table.