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Call number: LD2668 .T4 1984 M34 / Master of Science

Call number: LD2668 .T4 1984 P43 / Master of Science

The focus of this research was the reappraisal in physiological and psychophysical terms of current equivocal theories regarding the onset, course and termination of apneic bradycardia. Sixteen healthy male subjects participated in four separate testing sessions . Maximal oxygen consumption (VO₂ max) was measured on land and underwater using an identical direct, continuous progressive cycle ergometer test. On each of two other occasions subjects exercised in either environment at 50, 70 and 90% of the appropriate VO₂ max, during which time heart rate was continuously recorded. An initial apneic bout at each exercise intensity was followed by performance of the same workload without apnea for an equivalent period of time. Ratings of perceived exertion (RPE) were also monitored. While apneic bradycardia occurred at each exercise intensity studied underwater, it was apparent only at 50% VO₂ max on land. With the exception of between 50 and 90% VO₂ max on land, the mean apneic heart rates did not differ with varying exercise intensity (p<0.05); nor did the lowest heart rate recorded, although this was lower underwater than on land. Apart from 70% VO₂ max on land, apneic heart rates were lower than the equivalent values measured during exercise without apnea. Land and underwater heart rates during apneic and non-apneic conditions did not differ until 90% VO₂ max. The effects of increasing exercise intensity upon the onset of bradycardia were evident in that it occurred earlier at 50% VO₂ max underwater than at the heavier workloads, and only at 50% VO₂ max on land. The mean breath-hold duration did not differ between the land and underwater environments, nor was it affected by increasing exercise intensity. The order in which breath-holds was performed did not alter the length of apnea. Land and underwater RPE did not differ and increased with increasing exercise intensity in both environments. During apneic exercise RPE was greater than the equivalent exercise without apnea. Twelve of the original 16 subjects were divided equally into two groups on the basis of vital capacity expressed relative to body surface area. Vital capacity was measured during the first laboratory session. Neither the mean heart rate response to apneic exercise at 50% V0₂ max in both environments, nor the lowest heart rates recorded differed between groups, prompting the conclusion that lung volume did not affect apneic bradycardia. Despite a longer breath-hold duration for Group A (large relative lung volume) than Group B (small relative lung volume), the onset point of bradycardia was the same for either group when expressed relative to total breath-hold duration

Ergonomics aims to improve worker health and enhance productivity and quality. Knowledge and practical evidence of this relationship would be instrumental for optimising organisational performance particularly in industrially developing countries where the discipline is still in its developmental stages. Therefore this thesis set out to analyse the relationship between ergonomics deficiencies and performance. A survey was first conducted to establish the severity of quality problems in the South African manufacturing industry and to determine if these were related to Ergonomic deficiencies. The results indicated that quality problems continue to plague industry, a challenge associated with huge cost implications. Furthermore organisations were not cognisant of the fact that ergonomics deficiencies such as poor workstation design and awkward or constrained working postures are a major contributing factor to poor quality and performance decrements. This demonstrates that much is yet to be done in raising awareness about the benefits of ergonomics in South Africa and other industrially developing countries. However, for this to be effective, tangible evidence of these purported benefits is required. In lieu of this, a laboratory study was then conducted to establish the relationship between awkward working postures and the performance of precision tasks. Acknowledging that the task and the worker are interrelated elements, the impact of precision task demands on the postural strain experienced by the human was also investigated. A high and low precision task quantified positional precision while a force task (combination of pushing and pulling) was utilised to assess the ability to maintain a precise force over time. These three tasks were performed in eight different postures; namely seated, standing, stooping 300 and 600, working overhead, lying supine, and twisting to either side. A combination of the tasks and postures resulted in 24 experimental conditions that were tested on forty eight healthy male and female participants. The performance related dependent variables were movement time, deviation from the centre of the target, and the trend/slope followed by the force exerted. Muscle activity of eight arm, shoulder and back muscles, iii supplemented with heart rate and local ratings of perceived exertion, were utilised to quantify the impact of the tasks and the postures on the individual. The results revealed that awkward working postures do in fact influence performance outcomes. In this regard, awkward working postures (such as overhead work and lying supine and stooping) were evidenced to significantly affect movement time, deviations from the target and the ability to maintain a constant force over time. These variables have a direct relationship with organisational priorities such as productivity and quality. Furthermore, the results indicated that high precision demands augment postural strain elicited through high muscle activity responses and may have negative implications for the precipitation of musculoskeletal disorders. Essentially, the work done on this thesis reflected the complex nature of ergonomics by drawing on both macro and micro-ergonomics approaches. In so doing, challenges perceived to be relevant to industry as reported by organisations formed the foundation for further laboratory studies. Therefore, more collaborative research and knowledge transfer between industry and ergonomics researchers is a necessity particularly in industrially developing countries where ergonomics is still in its developmental stages.

This study analyzed an individual's ability to perceive levels of exertion of an isometric contraction. Two samples of college students were tested under magnitude production or magnitude estimation. A significant F was obtained for the magnitude production condition. An insignificant F was obtained for the magnitude estimation condition. This study concludes that subjects tested under magnitude production will perceive the 100 percent level with the least amount of error and that error will increase as the percentages descend from the 100 percent level. Subjects tested under magnitude estimation will be equally in error when perceiving percentages of a maximum contraction of the forearm flexors.

Human Resource Management (HRM) has undergone significant changes during the past twenty-five to thirty years in response to the demands made upon the Human Resource function. With the change in emphasis in HRM has come the need for human resource practitioners (HRPs) to adapt to the new demands made upon them to contribute directly to the bottom line success of their organisations It is argued that HRM is inherently ambiguous, attempting to meet both the needs of the business and the individual employee. This places pressure on HRPs to become "specialists in ambiguity" as they attempt to meet the demands of key stakeholders in the enterprise. The emphasis in the role of the HRP, has moved historically, from that of a welfare officer to that of a fully fledged member of the management team, held equally responsible for the success of the operation. As with most professions today, a price is exacted for participation in modem organisations in the form of increased work-related stress. Considerable research has been undertaken over the past thirty years into work-related stress among many professions~ but no identifiable, in depth studies into sources of work-related stress among HRPs were located. The significant shift that has taken place in the role of HRPs, from their original welfare orientated function, to the current role emphasis on contributing to direct bottom line success, provides the context for the increase in work related stress levels experienced by some HRPs. The study investigates the links between the career orientation of HRPs, role stress factors and burnout in an attempt to identify sources of stress among a sample of human resource practitioners drawn from the greater Durban area and the KwaZulu Natal coastal region. The report is diagnostic and not prescriptive in attempting to ascertain coping skills for stressed HRPs. The study model posits a juxtaposition between those HRPs who are "service" orientated with those who are "managemeng' orientated. The purpose is to establish in the current corporate environment, whether those who are more service orientated, would suffer greater work-related stress, in contrast to those who are more "management" orientated, who were conceived of as experiencing less work-related stress. No strong links are revealed between "service" and "general management' and Role Stress or Burnout. The combined effects of role stress and burnout are conceived in the study to illustrate work related stress. In contrast to the original study model, two other findings of significance emerged. Those HRPs who were entrepreneurially orientated showed the highest levels of workrelated stress. And, those who were technical/functional orientated were least likely to be affected by role stress and burnout. These findings are important in light of the current call for HRPs to be entrepreneurial and innovatively creative. Yet these HRPs reveal the greatest possibility of experiencing role stress and burnout. In contrast, those HRPs whose orientation is technical and functional are found to reveal the least possibility of suffering from work-related stress. These findings lead to a new paradigm revealing the presence of a different dilemma and tension for HRPs. Within the demand for a total business focus on the part of HRPs and HRM, emerges a tension between the more stressful entrepreneurial and innovative role and the more stable technical and functional role also demanded by the organisation. The study suggests that the ambiguity in HRM in practice presents itself in terms of dilemmas and contrasts with which the HRPs has to live. Role ambiguity and role overload appear to contribute most to the possibility of burnout. Role ambiguity has its origin in the very nature of HRM, which is shown to be inherently ambiguous. Role overload among management, is observed more as part of the nature of the modern work environment, whereas role ambiguity emerges as a feature of the nature of HRM. Role conflict is explained mostly as a normal element in the HRPs job of balancing competing demands in the work place. The ambiguous nature of HRM and the uncertainties which it generates adds to the work-related source of stress and leads to HRPs having to become "specialists in ambiguity". Role stress factors, rather than career orientation elements are shown to be the leading contributors to the possibility of increased levels of burnout The findings have implications for the selection and training of HRPs. The contemporary emphases require HRPs to balance a tough minded business focus with acceptable innovate approaches to the organisation's human resources and excellent ongoing functional services. This balancing of ambiguities needs to be accompanied by a sensitivity to people, without becoming the subject of role stress and raised levels of burnout. / Thesis (Ph.D.)-University of Natal, Durban, 2002.

Pushing and pulling research has yet to fully elucidate the demands placed on manual workers despite established epidemiological links to musculoskeletal disorders. The current study therefore aimed to quantify biomechanical and perceptual responses of male operators to dynamic pushing and pulling tasks. Three common push/pull techniques (pushing, one handed and two handed pulling) were performed at loads of 250kg and 500kg using an industrial pallet jack in a laboratory environment. Thirty six healthy male subjects (age: 21 ±2 years, stature: 1791 ±43 mm and body mass: 77 ±10 kg) were required to perform six loaded experimental and two unloaded control conditions. Hand force exertion, muscle activity and gait pattern responses were collected during 10m push/pull trials on a coefficient controlled walkway; body discomfort was assessed on completion of the condition. Horizontal hand force responses were significantly (p<0.05) affected by load, with a linear relationship existing between the two. This relationship is determined by specific environmental and trolley factors and is context specific, depending on factors such as trolley maintenance and type of flooring. Hand force exertion responses were tenuously affected by technique at higher loads in the initial and sustained phases, with pushing inducing the greatest hand forces. Comparison of the motion phases revealed significant differences between all three phases, with the initial phase evidencing the greatest hand forces. Muscle activity responses demonstrated that unloaded backward walking evoked significantly higher muscle activation than did unloaded forward walking whilst increased muscular activity during load movement compared to unloaded walking was observed. However increasing load from 250kg to 500kg did not significantly impact the majority of muscle activity responses. When considering technique effects on muscle activity, of the significant differences found, all indicated that pushing imposed the least demand on the musculoskeletal system. Gait pattern responses were not significantly affected by load/technique combinations and were similar to those elicited during normal, unloaded walking. Perceptually, increased load led to increased perception of discomfort while pushing resulted in the least discomfort at both loads. From these psychophysical responses, the calves, shoulders and biceps were identified as areas of potential musculoskeletal injury, particularly during one and two handed pulling. Pushing elicited the highest hand forces and the lowest muscle activity responses in the majority of the conditions whilst psychophysical responses identified this technique as most satisfactory. Current results advocate the use of pushing when moving a load using a wheeled device. Suitability of one and two handed pulling remains contradictory, however results suggest that one handed pulling be employed at lower loads and two handed pulling at higher loads.

Despite extensive research into musculoskeletal disorders (MSDs) they continue to plague workers. Manual materials handling (MMH), in particular the concurrence of load manipulation and awkward body posture, has been identified as a key factor in the onset of MSDs. Only a few studies have looked at the interaction between manipulation tasks and working posture during assembly tasks and as a result their relationship has not been widely explored. Assessing the stresses resulting from individual task factors and body posture in isolation and adding them together may be too simplified to estimate an overall risk profile, since this does not take into account that there may be a non-linear interaction in strain responses when manipulation task and body posture interact. Therefore, the present study investigated biophysical, physiological and psychophysical responses to combined tasks, rather than individual tasks of body posture and manipulative tasks. The objective of the research was to establish the interactive effects of constrained body postures and manipulative tasks and to identify whether a cumulative or compensatory reaction occurs during this interaction. Nine conditions were assessed in a laboratory setting, which included combinations of three working postures (standing, sitting and stooping) and three assembly tasks (torque wrenching, precision and no task). Thirty-six subjects were required to complete all nine conditions, with each condition lasting ninety seconds. Muscle activity was recorded for seven muscles from the upper extremity, trunk and lower extremity regions and was complemented by physiological (heart rate, tidal volume, minute ventilation, oxygen consumption, energy expenditure and breathing frequency) and psychophysical (body discomfort) data. At the completion of all nine conditions subjects completed a retrospective psychophysical rating questionnaire pertaining to discomfort felt during the conditions. Responses obtained for the different task and posture combinations revealed compensatory reactions (additive > combined) for most of the conditions assessed for the biomechanical and physiological responses. In the majority of cases for muscle activity, no significant differences were found between the combined and the additive effects (p < 0.05), while for the physiological responses there were mostly significant differences observed. Psychophysical responses indicated that there was a significant difference overall between the additive and combined effects. The results of this study demonstrate that in order to identify risk areas, manipulation tasks and constrained working postures may be considered either in isolation and added together (additive) or as a combined task, since there were very few significant differences observed between these two effects. Further studies are required, however, to provide conclusive evidence.

Fatigue is a state that, although researched for many years, is still not completely understood. Alongside this lack of a general understanding of fatigue is a lack of knowledge on the processes involved in the regulation of fatigue. The existing theories relating to regulation are focussed on mental effort regulation, suggesting that performance outcomes are co-ordinated by effort regulation that functions by making alterations to physiological processes and strategic adjustments at a cognitive level in response to cognitive demands and goals. Since fatigue is a multi-dimensional construct with psychological, physiological, and behavioural effects that respond to endogenous and exogenous variables, it follows then that fatigue assessment techniques ought to include multi-dimensional measures to acquire a holistic depiction of the fatigue symptom. This study aimed to assess whether or not a mechanism that regulated fatigue during sustained task execution could be identified and whether this mechanism resulted in regulation patterns that were distinct to a specific task. An additional aim of the study was on assessing whether the manner in which performance, psychophysical and subjective variables were modified over time followed a similar regulation pattern. The research design was aimed at inducing task-related fatigue twice on two different occasions in the same participants and evaluating the resultant changes in fatigue manifestation. This was done to assess the ability of participants to cope with fatigue as a result of previous experience. The research protocol included three tasks executed for an hour aimed at targeting and taxing the sensory, cognitive, motor resources, each task performed twice. 60 participants were recruited to participate in the current study, with 20 participants – 10 males and 10 females – randomly assigned to each of the three tasks. The cognitive resource task consisted of a memory recall task relying on working memory intended to evaluate the extent of reductions in memory and attention. The sensory resource task consisted of a reading task measuring visual scanning and perception designed to evaluate the extent of reduced vigilance. The motor resource task consisted of a modified Fitts’ stimulus response task targeted at monitoring the extent of movement timing disruption. Performance measures comprised of: response delay and the number of correctly identified digits during the cognitive resource task, the amount of correctly identified errors and reading speed during the sensory resource task, response time during the motor resource task, and responses to simple auditory reaction time tests (RTT) initiated at intervals during the task and then again at the end of each task. Physiological measures included ear temperature, eye blink frequency and duration, heart rate (HR), and heart rate variability (HRV). Subjective measures included the use of the Ratings of Perceived Exertion Category Ratio 10 scale (RPE CR 10) to measure cognitive exertion and the NASA-Task Load Index (NASA-TLX) to index mental workload. Eye blink frequency and duration, HR and HRV were sensitive to the type of task executed, showing differing response patterns both over the different tasks and over the two test sessions. The subjective measures indicated increasing RPE ratings over time in all tasks while the NASA-TLX indicated that each task elicited different workloads. Differing task performance responses were measured between the 1st test session and the 2nd test session during all tasks; while performance was found to improve during the 2nd test session for the motor and sensory tasks, it declined during the cognitive task. The findings of this research indicate that there was a regulatory mechanism for fatigue that altered the manner in which performance, psychophysical and subjective variables were modified over time, initiating a unique fatigue regulation pattern for each variable and each task. This regulation mechanism is understood to be a proactive and protective mechanism that functions through reducing a person’s ability to be vigilant, attentive, to exercise discernment, and to direct their level of responsiveness, essentially impacting how the body adapts to and copes with fatigue. The noted overall findings have industry implications; industries should consider accounting for the effects of this regulatory mechanism in their fatigue management interventions, specifically when designing job rotation and work/rest schedules because each cognitive task, having elicited a unique fatigue regulation pattern, ought to also have a different management program. / Microsoft� Office Word 2007 / Adobe Acrobat 9.54 Paper Capture Plug-in