There is strong evidence that the skeletal muscles of pinnipeds are adapted for an aerobic, lipid-based metabolism under the hypoxic conditions associated with breath-hold diving. However, regional variations in mitochondrial density are unknown, and the few fiber typing studies performed on pinniped skeletal muscles are not consistent with an aerobic physiological profile. Thus, the objectives of this study were to (1) reexamine the fiber type distribution throughout the primary locomotory muscles of the harbor seal, and (2) to better understand the density and distribution of mitochondria in the locomotory muscles. Multiple samples from transverse sections of the epaxial muscles and a single sample of the pectoralis muscle of wild harbor seals were analyzed using immunohistochemical fiber typing and electron microscopy. Fiber typing results indicated that harbor seal epaxial muscles are composed of 47.4% type I (slow twitch, oxidative) fibers and 52.8%, IIa (fast twitch, oxidative) fibers. No fast twitch, glycolytic (type IIb) fibers were detected in the epaxial muscles or the pectoralis muscle. Mean volume density of mitochondria [Vv(mt,f)] was 5.6%, which is elevated over what would be predicted for a terrestrial mammal of similar mass. The elevated Vv(mt,f) had a high proportion of intermyofibrillar mitochondria, a trait not normally found in the muscles of terrestrial mammals with elevated Vv(mt,f). These results provide further evidence that the elevated mitochondrial volume density in pinniped muscle decreases the oxygen diffusion distance between myoglobin and mitochondria to facilitate aerobic respiration in working muscles. In addition, analyses of heterogeneity revealed that the regions of the epaxial muscles that were located deep within the muscle showed a significantly higher Vv(mt,f) relative to those regions that were superficially-located. In contrast, there was no significant heterogeneity of fiber type detected in either plane of the epaxial muscles. Thus, there was a fine-scale pattern of spatial heterogeneity of Vv(mt,f) within the epaxial muscles that does not manifest in fiber type distribution, indicating that the fibers have similar oxidative capacities.

This study examined the informal learning strategies of individuals who were among the first to belong to the original small group of British Columbian recreational divers. These individuals included breath-hold divers, users of Oxygen Re-breathers, and users of Self Contained Underwater Breathing Apparatus (scuba). Through the narratives provided by the divers themselves and other corroborative evidence, this qualitative investigation looked at who the divers were and how they approached learning to dive in this context of informal learning: that is, how they learned about and acquired the skills and knowledge needed for diving, and the changes in attitude and aspirations they acquired which stemmed from those learning activities.

In scuba diving any problem that can be solved underwater will be solved underwater. This helps to prevent a dive from being disrupted. If a diver is separated from the group and is unable to find the group within a short time both the diver and dive group must surface to find each other and rejoin. To prevent the separation of divers a Stray Diver Alert System has been devised involving wireless communication to track the diver's position relative to the dive masters. Underwater communication holds many challenges that are not found in above water networks. Through simulation, it has been shown that the communication requirements for the Stray Diver Alert can be met with existing technology and protocols. This has been done by evaluating the resolution, power consumption and physical size of the device for three different communication protocols. This has shown that current technology is capable of meeting the requirements of the stray diver alert system.

Recreational SCUBA diving has grown tremendously along most of the southern Mozambican coastline in the last eight years. This growth was not accompanied with management actions, largely due to a lack of baseline information and appropriate regulations. A number of aspects of the industry were thus covered in this study to redress this shortfall. Information was collected on divers and diving pressure in southern Mozambique using questionnaires and dive log sheets distributed through local dive centres. The diving pressure was estimated at 42 500 dives in 2001 and 62 000 dives in 2002, and occurs at about 20 dive sites. More than 50% of the diving occurs on five reefs, three of which were included in the study. Surveys using visual techniques were conducted on six reefs subjected to different diving pressures, ranging from minimal ( 6 000 dives.year-I). Divers visiting southern Mozambique were found to be mostly educated South African males in their 30s. They are experienced and committed divers, satisfied with their diving experiences in the area and sensitive to reef conservation issues. The reefs differed in benthic composition, with three mam reef groups identified through multivariate analysis. All were typified by prolific soft corals but one included an abundance of branching Acropora and the other an abundance of foliose hard corals, thus differentiating the three groups. Reef fish communities also differed among the reefs. While prey species diversity was generally similar on all the reefs, two included high densities of piscivorous species. The present levels of SCUBA diving appeared to be having no deleterious effects on the reef communities, especially when compared to other disturbances such as storms and fishing. The sustainable diving capacity was estimated to be 7000 dives/year/dive site. The overall effects of recreational diving activities in southern Mozambique are discussed, along with future research needs and the management implications of the study. / Thesis (M.Sc.)-University of Natal, Durban, 2003.

A computer simulation model of a springboard and a diver was developed to investigate diving takeoff techniques in the forward and the reverse groups. The springboard model incorporated vertical, horizontal and rotational movements based on experimental data. The diver was modelled as an eight-segment link system with torque generators acting at the metatarsal-phalangeal, ankle, knee, hip and shoulder joints. Wobbling masses were included within the trunk, thigh and shank segments to allow for soft tissue movement. The foot-springboard interface was represented by spring-dampers acting at the heel, ball and toes of the foot. The model was personalised to an elite diver so that simulation output could be compared with the diver's own performance. Kinematic data of diving performances from a one-metre springboard were obtained using high speed video and personalised inertia parameters were determined from anthropometric measurements. Joint torque was calculated using a torque / angle / angular velocity relationship based on the maximum voluntary torque measured using an isovelocity dynamometer. Visco-elastic parameters were determined using a subject-specific angledriven model which matched the simulation to the performance in an optimisation process. Four dives with minimum and maximum angular momentum in the two dive groups were chosen to obtain a common set of parameters for use in the torque-driven model. In the evaluation of the torque-driven model, there was good agreement between the simulation and performance for all four dives with a mean difference of 6.3%. The model was applied to optimise for maximum dive height for each of the four dives and to optimise for maximum rotational potential in each of the two dive groups. Optimisation results suggest that changing techniques can increase the dive height by up to 2.0 cm. It was also predicted that the diver could generate rotation almost sufficient to perform a forward three and one-half somersault tuck and a reverse two and one-half somersault tuck.

No description available.

No description available.

No description available.

No description available.

No description available.