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Revealing complexities within flat-water kayaking: injury prevention and biomechanical analysisFisher, Julia Marguerite January 2015 (has links)
Includes bibliographical references / Elite kayakers are required to perform repetitive movements that create strength and flexibility asymmetries in their bodies, making them susceptible to injury. The first portion of this thesis is dedicated to investigating whether a supervised, corrective pre-habilitation programme of the kinetic chain, conducted twice a week for 10 weeks, would reduce these predisposing factors. A group of 19 marathon paddlers were assessed before and after the intervention, with nine of them receiving the intervention. The 10-week intervention programme was found to significantly improve scapular position and kinesis, thoracic spine extension and single arm pulling ability, thus suggesting improved shoulder function and reduced risk of injury. The second portion of the thesis involved novel biomechanical analysis of kayaking on the water and on a kayaking-ergometer. It is the first objective description of the three dimensional movements of the kayak in the literature. Sprint and marathon paddlers performed a 180 metre time trial using an instrumented paddle with an accelerometer and gyroscope attached to the boat for analysis of boat movement characteristics and paddler-generated forces. Similar patterns for paddle torque, boat acceleration and pitch were observed between male sprint paddlers and male marathon paddlers. However, the direction and timing of the roll and the yaw of the boat during the water phase of the kayak stroke differed between these groups of paddlers. In addition, substantial individual variation existed within the group of male marathon paddlers. On the kayaking ergometer, activation patterns of the trunk and pelvic muscles were measured using electromyography during a maximal 200 metre time trial. Gluteus medius, lower trapezius and erector spinae were measured for the first time in maximal kayaking. The latissimus dorsi, pectoralis major and external oblique muscles were more active during the contralateral phase than has previously been reported. When these paddlers performed a single arm pull test on the same day, the muscle activation patterns changed, and muscle groups were active according to their anatomical function and what has previously been described. First, variation of movement, flexibility and segmental training of the kinetic chain may be advantageous when incorporated with kayaking training to prevent shoulder injury risk factors in paddlers. Second, individual evaluation of three-dimensional boat kinematics and muscle recruitment timing provides objective insight into an individual's kayak technique, with potential benefits for improving technical performance and mechanical efficiency.
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Respiratory mechanics during upper body exercise in healthy humansTiller, Nicholas B. January 2014 (has links)
The physiological responses to upper-body exercise (UBE) are well established. Few published studies, however, have attempted to elucidate the mechanical ventilatory responses to UBE. There is empirical evidence that respiratory function may be compromised by UBE during which the ventilatory and postural functions of the ‘respiratory’ muscles may be exacerbated. Therefore, the aims of this thesis were: 1) to characterise the mechanical-ventilatory responses to UBE in healthy subjects; 2) to explore the putative mechanisms that underpin the respiratory responses to UBE; and 3) to assess whether the mechanical-ventilatory stress imposed by UBE induces contractile fatigue of the respiratory muscles. Compared to lower-body exercise (LBE; leg cycling) at ventilation-matched work rates, UBE (arm-cranking) resulted in constraint of tidal volume, higher respiratory frequency, and greater neural drive to the respiratory muscles. Furthermore, end-expiratory lung volume was significantly elevated during peak UBE compared to LBE (39 ± 8 vs. 29 ± 8% vital capacity, p < 0.05) and was independent of expiratory flow limitation. In assessing the influence of cadence on cardiorespiratory function and respiratory mechanics, submaximal arm-cranking at high cadence (90 rev.min-1) induced significantly greater cardiorespiratory stress, a trend towards elevated intra-thoracic pressures and significantly greater perceptions of dyspnoea than at low cadence (50 rev.min-1). Furthermore, there was a greater prevalence of locomotor-respiratory coupling at high cadences (p < 0.05), suggestive of greater antagonistic loading of the thoracic muscles, likely the result of static postural contractions. Finally, there was objective evidence of abdominal muscle contractile fatigue in response to severe- but not heavy-intensity UBE. Specifically, there was a 22% decrease in gastric twitch pressure from pre- to post-exercise in response to magnetic stimulation of the thoracic nerves (p < 0.05). However, there was limited evidence of exercise-induced diaphragm fatigue, as assessed using magnetic stimulation of the phrenic nerves (p > 0.05). In conclusion, mechanical-ventilatory function may be compromised during UBE due to complex interactions between thoracic muscle recruitment, central neural drive and thoracic volume displacement. This thesis presents novel findings which may have important functional implications for clinical populations who report breathlessness during activities of daily living that involve the upper-body, as well as for athletes engaged in upper-body sports.
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