Recent research has highlighted that information-movement couplings are unique to the constraints of the task, environment and performer. This recent research implies that skills should be developed in practice environments that are reflective of those found in competition. Representative environments should also allow the performer to attune to specifying information essential for success of a skill. However, in water polo, shooting practice is often conducted without the presence of a goalkeeper or defender. The aim of this study was to determine the effect of game-specific task constraints on the ball speed, accuracy and technique of the water polo shot. Ten male competitive level water polo players performed a total of forty shots comprising ten shots in each of four conditions from the 4m-penalty line. Conditions included all combinations of goalkeeper and defender (absent or present). Three Sony mini-digital cameras (50Hz) were placed perpendicular to the movement, giving rear, overhead and a right sagittal view. Ball speed was measured using a Radar-gun (Stalker Pro, USA). For each condition, means and standard deviations were determined for all outcome measures (shooting accuracy and ball speed) and technique variables. A repeated measures ANOVA was used to determine the effect (p<0.05) of the goalkeeper and defender individually as well as in combination on the dependent variables. Cohen's effect sizes were also used to determine the magnitude of the difference between conditions. The presence of a defender resulted in a significant increase in lateral trunk flexion at ball release, decreased the duration of the shot and selected swing sub-phases (i.e. pick-up to top of back swing time) and significantly altered the placement of the ball in the goal. When the goalkeeper only was present, this resulted in decreases in total shot time and pick-up to top of back swing time and significantly altered the placement of the ball in the goal. The presence of the defender and goalkeeper in combination brought about a moderate effect, decreasing the ball speed, significantly decreasing the success of the shots, scores achieved and significantly altering the placement of shots. Forward swing distance and selected swing sub-phases (i.e. total shot time, pick-up to top of back swing time, forward swing start to midway and forward swing start to release) were also significantly decreased in the presence of the defender and goalkeeper. These findings highlight the importance of maintaining appropriate task constraints during water polo shooting practice. In effect the removal of the defender and goalkeeper leads to the development of inappropriate information-movement couplings. Specifically, the presence of the defender and/or goalkeeper lead to reductions in the durations of selected swing sub phases, resulting in changes in the relative coordination and timing of the water polo shot. These findings indicate that in order to facilitate the development of this specific shooting skill, coaches should structure practice to replicate the perceptual information available during competition.

Grinding set-up in America's Cup sailing provides the power behind tacking and gybing, where the yacht crosses the wind to change direction. Grinding is also used for trimming the sails, which changes the angle on which the yacht is headed. This study provided a descriptive biomechanical overview of grinding on an America's Cup class yacht, and experimentally evaluated the influence of technique instruction on backward grinding performance. Inter-subject differences in body position (technique) throughout the grinding cycle, the ability to alter grinding technique within an eight-day technique intervention period, and the effect of technique on grinding performance as determined by power output were assessed. The quasi-experimental design, in which each of eleven Team New Zealand America's Cup grinders served as their own control, assessed four trials of backward grinding at baseline and post-biomechanical technique intervention testing sessions. Each trial was a maximal effort performed against a high load (250 W) and sustained over a period of eight seconds. Sagittal plane video was used to analyse joint kinematics (elbow, shoulder, trunk, hip, knee, ankle angles and joint centre positions) and to calculate the centre of body mass relative to the grinder pedestal. Height, weight, and limb lengths were obtained from each grinder using the ISAK protocol. Current backward grinding technique employed by the majority of grinders did not optimally use biomechanical principles. Recommendations for improvement were specific to each individual but focused on lowering trunk position and distancing the trunk from the grinding pedestal. Real-time visual feedback was provided to the grinder operators with the main focus being the position of their hip joint (viewed in the sagittal plane), and lowering the shoulder to be vertically level with the apex of the grinding handle cycle. During the intervention the grinders were given added correctional instruction relating to their body position according to perceived technique requirements. Recommendations were based on biomechanical principles regarding body position, and how body position could be altered to optimise the contribution of body weight and force production by the muscles of the upper limb in order to improve the torque applied to the handles. Altering grinding technique according to biomechanical principles produced 4.7% (p = 0.012) greater power during five seconds of grinding performance. Muscular strength, when measured using a 1RM bench pull (116.4 ± 9.8 to 117.3 ± 10.3), was unaffected by the intervention program, thus not contributing to the increased power output observed during grinding. Moderate changes to body position were observed after the eight-day intervention. Forward lean of the trunk decreased from 25° to 17° (p = 0.028) due to a lower hipy position (-0.09 m to -0.16 m below hub, p = 0.019). The more vertical trunk alignment resulted in the shoulderx position being further from the hub (0.33 m to 0.41 m, p = 0.013), producing a greater line of pull due to a more efficient shoulder vector angle (47° to 36°, p = 0.009). Variability (standard deviation and confidence intervals) decreased in all but four kinematic measures (which exhibited no change) indicating improved consistency in grinding technique. Regression analysis indicated the best predictors for high-load backward grinding performance were COMx position relative to the grinding pedestal and maximal strength. Changes in COMx position explained 40% (p = 0.166) of the variation in grinding performance, while maximal strength showed a relationship of 0.23% (p = 0.144) increase in performance per kilogram of bench pull 1RM. A one standard deviation difference in maximal strength altered the effect of COMx position by 0.26% per centimetre (p = 0.008). Weaker predictive factors were body weight, standing height, and pull angle, while brachial index did not appear to have any substantial influence on backward grinding performance. For future research greater subject numbers should enable more conclusive findings, especially in terms of the technique mechanisms and their relative levels of influence on performance.

During pregnancy the female body must accommodate the enlarging gravid uterus and increased mass. Therefore the maternal musculoskeletal system is required to adapt in both morphology and functional workload. After childbirth there is a rapid change in both mass and dimensions, requiring further adaptations. The objectives of the study were to investigate seated and standing upper body posture, the kinematics of seated and standing trunk motion, and the three dimensional kinematics and kinetics during rising to stand from a chair, as pregnancy progressed and in the early post-birth period. Nine maternal subjects (aged 28 to 40 years) were tested at less than 16 weeks, 24 weeks, 30 weeks, 38 weeks gestation and at 8 weeks postbirth. The subjects, fitted with 37 retroreflective markers, were filmed during upright sitting, quiet standing, and four trials each of maximum seated and standing trunk forward flexion, side to side flexion and during maximum seated axial rotation. Three trials each of constrained and free rising to stand from a height adjustable stool and with each foot placed on a forceplate were also recorded. An eight-camera motion analysis system was used to record movements of the body segments and synchronised force plate variables in three dimensions. Motion of the ankle, knee and hip joints, pelvic, thoracic and head segments and the thoracolumbar and cervicothoracic spines and shoulder joints were investigated. Twelve nulliparous subjects (aged 21 to 35 years) were used as controls to provide standard descriptive data and to investigate the consistency of the selected biomechanical variables with repeated testing. A repeated measures ANOVA was used to investigate the possibility of linear and quadratic trends showing systematic changes within the maternal group, over the four test sessions during pregnancy for each variable. Two tailed Student t-tests were used to compare the maternal postbirth variable results with the control group. There was no significant effect of pregnancy on the upper body posture during upright sitting and quiet standing. Postbirth, the pelvic segment had a smaller anterior orientation and the thoracolumbar spine was less extended, indicating a flatter spinal curve. The maternal subjects were similar to the control subjects in early pregnancy and postbirth for trunk segment motions during seated and standing forward flexion and side to side flexion and seated axial rotation. Strategies, such as increasing the width of the base of support and reducing obstruction to movements from other body parts, were used in late pregnancy in attempts to minimise the effects of increased trunk mass and circumference. For seated and standing side to side flexion, the strategies were successful and no significant decreases in range of motion were seen. For seated and standing forward flexion and seated axial rotation, motion of the thoracic segment and the thoracolumbar spine were significantly reduced, although movement of the pelvis was less affected. In early pregnancy and postbirth the kinematics and kinetics of the lower limbs and upper body segment kinematics during constrained and free rising were generally similar to the control subjects. As pregnancy progressed there were increases in mass and dimensions of body segments. The effect of increased mass was seen in increased ground reaction forces and sagittal plane lower limb joint external moments. An increased base of support width was found in association with an increased lateral ground reaction force and ankle inversion moment from each foot, which would move the body centre of mass medially. There was little change in the three dimensional kinematics of the thoracolumbar and cervicothoracic spine, although the contribution of the upper body segments differed for each rise condition. There were also few significant changes in the displacement of the ankle, knee and hip, and the angular velocity of ankle and knee joints. The maternal subjects were thus able to flex the upper body forward, raise the body and maintain stability as pregnancy progressed, regardless of whether the rise to stand was performed in a natural manner or under constrained conditions. The overall results show that, contrary to expectations as pregnancy progressed, maternal subjects minimised propulsion rather than increasing it to overcome the increased mass and possibly limited trunk flexion. A fear of postural instability may have made the subjects more cautious and as they were able to adequately flex the trunk forward, propulsion was minimised in favour of maintaining upright terminal balance.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 109-118).

Impairments of upper limb function can negatively impact an individual???s ability to carry out everyday tasks. Children with cerebral palsy can have limitations of upper limb movement due to physiological and structural changes in their body. Current treatment regimes for children with upper limb involvement of cerebral palsy are assessed using a variety of qualitative assessment tools. These measures rely on subjective input from the assessor, and can be insensitive to significant functional improvements. Research methods in upper limb motion analysis are developing towards use as clinical tools. To date, there is a paucity of knowledge on the quantitative measures of range of motion (ROM) and function of upper limbs in healthy children. There is also lack of agreement on repeatable functional tasks of the upper limb for 3D measurement. The identification of a repeatable task in healthy children would facilitate the use of upper limb 3D motion analysis to guide clinical practice and improve patient outcomes. This thesis aims to describe upper limb joint range of movement in each degree of freedom and present normative three dimensional kinematic data of upper limb movement in healthy children during a repeatable upper limb functional task. This will provide a basis for comparison to children with movement disorders for future research and clinical practice. The UNSW kinematic upper limb model was found to successfully measure three dimensional upper limb anatomical and functional movements in healthy children. Normative kinematic data are reported for anatomical movements and two functional tasks. The results of the studies undertaken showed that differences in dominant and non-dominant limbs were present during anatomical and functional movements. Joint angles measured were found to be repeatable in healthy children. The results suggest that methods used were reliable for investigating upper limb kinematics. Functional movement time-series data were found to be repeatable for the group with the exception of wrist flexion/extension during the hand to mouth movement for both the dominant and non-dominant limbs. These findings improve current knowledge on upper limb kinematics in healthy children. This knowledge can assist the investigation of movement disorders in children to facilitate clinical decision making.

Impairments of upper limb function can negatively impact an individual???s ability to carry out everyday tasks. Children with cerebral palsy can have limitations of upper limb movement due to physiological and structural changes in their body. Current treatment regimes for children with upper limb involvement of cerebral palsy are assessed using a variety of qualitative assessment tools. These measures rely on subjective input from the assessor, and can be insensitive to significant functional improvements. Research methods in upper limb motion analysis are developing towards use as clinical tools. To date, there is a paucity of knowledge on the quantitative measures of range of motion (ROM) and function of upper limbs in healthy children. There is also lack of agreement on repeatable functional tasks of the upper limb for 3D measurement. The identification of a repeatable task in healthy children would facilitate the use of upper limb 3D motion analysis to guide clinical practice and improve patient outcomes. This thesis aims to describe upper limb joint range of movement in each degree of freedom and present normative three dimensional kinematic data of upper limb movement in healthy children during a repeatable upper limb functional task. This will provide a basis for comparison to children with movement disorders for future research and clinical practice. The UNSW kinematic upper limb model was found to successfully measure three dimensional upper limb anatomical and functional movements in healthy children. Normative kinematic data are reported for anatomical movements and two functional tasks. The results of the studies undertaken showed that differences in dominant and non-dominant limbs were present during anatomical and functional movements. Joint angles measured were found to be repeatable in healthy children. The results suggest that methods used were reliable for investigating upper limb kinematics. Functional movement time-series data were found to be repeatable for the group with the exception of wrist flexion/extension during the hand to mouth movement for both the dominant and non-dominant limbs. These findings improve current knowledge on upper limb kinematics in healthy children. This knowledge can assist the investigation of movement disorders in children to facilitate clinical decision making.

Impairments of upper limb function can negatively impact an individual???s ability to carry out everyday tasks. Children with cerebral palsy can have limitations of upper limb movement due to physiological and structural changes in their body. Current treatment regimes for children with upper limb involvement of cerebral palsy are assessed using a variety of qualitative assessment tools. These measures rely on subjective input from the assessor, and can be insensitive to significant functional improvements. Research methods in upper limb motion analysis are developing towards use as clinical tools. To date, there is a paucity of knowledge on the quantitative measures of range of motion (ROM) and function of upper limbs in healthy children. There is also lack of agreement on repeatable functional tasks of the upper limb for 3D measurement. The identification of a repeatable task in healthy children would facilitate the use of upper limb 3D motion analysis to guide clinical practice and improve patient outcomes. This thesis aims to describe upper limb joint range of movement in each degree of freedom and present normative three dimensional kinematic data of upper limb movement in healthy children during a repeatable upper limb functional task. This will provide a basis for comparison to children with movement disorders for future research and clinical practice. The UNSW kinematic upper limb model was found to successfully measure three dimensional upper limb anatomical and functional movements in healthy children. Normative kinematic data are reported for anatomical movements and two functional tasks. The results of the studies undertaken showed that differences in dominant and non-dominant limbs were present during anatomical and functional movements. Joint angles measured were found to be repeatable in healthy children. The results suggest that methods used were reliable for investigating upper limb kinematics. Functional movement time-series data were found to be repeatable for the group with the exception of wrist flexion/extension during the hand to mouth movement for both the dominant and non-dominant limbs. These findings improve current knowledge on upper limb kinematics in healthy children. This knowledge can assist the investigation of movement disorders in children to facilitate clinical decision making.

Biomechanical models have been used in designing human work environments to evaluate potential risks to workers before a work environment is constructed. In order for work environments to be modeled correctly, most biomechanical models require as input, an accurate body posture of the worker. This information can be obtained by, either measuring the posture of workers for the task of interest, or estimating the posture. This research explores methods to estimate working postures by developing a model that can predict a worker's posture. The model in this thesis represents the body of the worker with ten links: neck, left and right forearms, left and right upper arms, body, left and right thighs, and left and right calves. The work task inputs consist of the magnitude and direction of the force applied to the hands, and the distances between the hands and the floor. By using these inputs, the model can predict a posture by optimizing an objective function of two criteria: Total Squared Moment and Balance. Model constraints also ensure that a predicted posture is feasible for human. The output of the model is the predicted posture in terms of ten body joint angles: neck, left and right elbows, left and right shoulders, hip, left and right knees, left and right ankles. These joint angles are defined as angles relative to horizontal. The prediction posture can be used as a base reference when inputting into other biomechanical models. By predicting posture from the model, one can obtain postures of the workers without direct measurement of postures from the workers, which can be expensive and time consuming. / Graduation date: 2002

In the Everest valley of Nepal, because of the rugged mountain terrain, the ‘roads' are nothing more than dirt mountain footpaths. Most of the material is conveyed over long distances by professional porters who carry impressive burdens in a wicker basket supported by a strap looped over their head. We measured the body weight and loads carried by the Himalayan porters passing along the busy footpath to Namche Bazaar, the main market place of the Everest region. On average, the porters were carrying loads equivalent to 90% of their body weight on the last day of a 7-9 day trip covering a horizontal distance of ~100 km with >8000 m of total ascents and >6300 m of total descents. Interestingly, these porters adopt a specific rhythm of walking: they generally walk slowly and make very frequent rest stops using a T-stick or stone-platforms built along the trail to support the load during the pause. It has been shown that African women could carry head-supported loads more economically than Western subjects because they have developed a mechanical energy-saving strategy. Similarly, Nepalese porters could also have developed a mechanism to carry economically their very heavy loads. To test this hypothesis, we measured the energy consumption and the mechanical work done during level walking under different loading and speed conditions in the Nepali porters and in Western subjects. We compared these results to those of the African women. Nepalese porters carry loads at a lower cost than either the control subjects or the African women. For example, for a load equivalent to 60% of body weight, western Caucasian subjects increases their metabolic rate by 60%, the African women by 40% and the Nepalese porters by only 30%. Contrary to the African women who are taking advantage of the load to reduce the work performed, Nepalese porters do not modify their gait while carrying a load. Consequently, the mechanical work performed is not reduced as compared to control subjects walking at same speed-load combinations. Yet the Nepalese porters are the most economical load-carriers measured to date, particularly while carrying heavy loads at walking speeds slower than 1.4 m/s, but the exact mechanisms by which they save energy are still unknown. G. J. Bastien et al. Eur J Appl Physiol 94, 76 (2005); G. J. Bastien et al. Science 308, 1755 (2005); G. J. Bastien et al. J Exp Biol submitted.

Thesis (M.Ed.)--North-West University, Potchefstroom Campus, 2008.