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Open Access
The effects of sertraline, alone and in combination with exercise on energy balance and eating behaviour in overweight women
(1996) Murphy, Kim; Lambert, Vicki
An 18-week, double blind, placebo controlled trial was conducted on 31 overweight females to determine the effects of sertraline (STL) alone and sertraline in combination with exercise (EX) on body weight, body composition and total daily energy expenditure (24-hr-EE). Sedentary, non - depressed female volunteers were placebo (EX,PLC); . exercise randomly plus assigned sertraline to 4 groups:-exercise, (EX,STL); placebo (SED,PLC) and sedentary plus sertraline (SED,STL). Each group received dietary counselling for food energy and dietary fat restriction. After a 2-week placebo period, the sertraline groups received a 50mg.dai1 dose of sertraline which was up titrated to 200mg.dai1 over the 8-week trial period. The subjects in the exercise groups attended a 1-hour exercise (70-80% max) session, 3 times per week, for the 8-week intervention period. All measurements were repeated 8 weeks after withdrawal of treatment. Body weight decreased in all groups (P<0.05). Although the groups receiving sertraline lost significantly more weight than those receiving placebo (5.5±1.3 and 5.9±1.1 vs 2.5±1.1 and 2.1±1.1 for EX,STL and SED,STL vs. EX,PLC and SEO.PLC.), body fat decreased similarly in all groups (P<0.05). Resting metabolic rate (per kg.FFM-1) did not change significantly. Estimated 24 hr-EE, as determined using individual heart-rate-energy expenditure regression equations and 24-hr heart rate monitoring, increased significantly in the STL groups compared to PLC groups (P<0.01). Estimated 24hr energy expenditure increased in the EX, STL group following the intervention from 11.3 ± 0.5 MJ to 14.9 ± 0.5 MJ and 10.6 ± 0.7 MJ to 12.2 ± 0.05 MJ in the SEO, STL group. At follow up, 24 hr-EE decreased again in the STL groups. Reported food energy intake decreased in all groups (P<0.01), but there were no significant differences between groups. The Three Factor Eating Inventory showed an increase in Factor One or cognitive restraint and a decrease in Factor Three or hunger in all groups (P<0.01); Factor Two or disinhibition decreased significantly only in the groups receiving sertraline (P<0.01). Quality of life was not significantly affected by the drug or exercise treatment in these non-depressed subjects. These results suggest that the administration of STL to exercising and sedentary non - depressed women may result in significant weight loss, which may be attributed, in part, to an increased 24 hr-EE and greater control of energy intake.
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Open Access
Exercise-associated muscle cramps in distance runners: the role of serum electrolytes both during and following an ultra marathon and IEMG activity in the recovery phase post-cramp
(1996) Nicol, Jeremy Colin Howard; Schwellnus, Martin
Exercise associated muscle cramps (EAMC) is a serious condition that can interfere with athletic performance. The scientific literature reveals very little well documented published research on the aetiology, pathophysiology, prevention and management of the condition. For the purposes of this thesis, EAMC is defined as involuntary, painful, electrically active and visible contraction of skeletal muscle, that is of sudden onset, lasts for seconds to minutes and occurs during or within 24 hours of a bout of exercise. The historical perspective, epidemiology, risk factors for EAMC, pathophysiology, prevention and management of EAMC are discussed initially. The hypothesis in the first study is that EAMC is not associated with serum electrolyte concentrations and hydration status. In this study, a group of 72 runners competing in the 56 km Two Oceans Marathon were prospectively studied to determine whether acute EAMC in distance runners is related to serum electrolyte concentrations and hydration status. This group of 72 runners consisted of a group of 45 runners who regularly suffer EAMC (Chronic Crampers) and a group of 27 runners with a history of no previous EAMC (Non-cramping group). Of the original cohort of 72 runners, 21 runners suffered EAMC during of within 60 minutes of completing the race (EAMC group) and 23 runners suffered no EAMC during or within 60 minutes of completing the race (CON group). Twenty-eight runners were excluded for not following the protocol. Body weight (BW) was measured and blood samples for blood glucose, serum electrolyte concentrations, serum osmolality, haemoglobin and haematocrit were collected from all runners 75 mins before the race and immediately on completion of the race and 60 mins after the race (T 50). Both groups had similar (mean± SD), age (years), (CON : 42 ± 8, EAMC : 37 ± 8), pre-race BW (kg) (CON : 73 ± 8, EAMC : 78 ± 11 ), and race finishing times (min) (CON : 304 ± 36, EAMC : 309 ± 41 ). Runners with EAMC were treated only with rest, passive stretching and oral fluids, and all were cramp free by T60. Serum electrolyte concentrations (mmol/I), blood glucose(mmol/I), osmolality (mosm/I) and hydration status (calculated as % change in BW (% BWC) and % change in plasma volume (%PVC) were compared in the EAMC and CON groups. There were no significant differences in the serum electrolyte concentrations, blood glucose, osmolality and hydration status between the EAMC (%BWC: -2.9 ±1 .2, %PVC: 0.2 ± 6.3) and the CON (%BWC: -3.6 ±1 .2, %PVC: -0.7 ± 8.6) group. The results of this study support the hypothesis that EAMC is not associated with in serum electrolyte concentrations and hydration status. The hypothesis of the second study is that recovery from an acute EAMC in distance runners will be associated with a decrease in integrated electromyographic (IEMG) activity, while demonstrating no association with to serum electrolyte concentrations. Eleven subjects with acute severe EAMC after a 56km race were compared to controls (Control elec, n=11) for serum electrolyte concentrations and Controls (Control EMG, n = 7) for IEMG activity. Controls for the serum electrolyte concentrations (Control elec) were runners matched for age, gender and finishing time who completed the 56 km race without EAMC. Controls for the IEMG (Control EMG) were runners with no EAMC after a 35km run. IEMG was recorded 1) in the affected muscle (quadriceps (Q), gastrocnemius (G)) of the subjects in the EAMC group on admission (To) and after recovery (T60) during periods when the runners were not experiencing a spontaneous muscle contraction and ii) in the Control (EMG) group in the Q and G muscles after the 35km run and 60 min later (T60). EMG data was expressed as% change in IEMG (TO to T60). There was no significant difference in the EAMC group and control group with respect to initial and 60-minute post-race serum electrolyte concentration. The % decrease (mean(SD) (To vs T 60) in IEMG for the EAMC group (52 ± 25) was significantly greater (p<0.05) than the Control (EMG) group (12~7). The results support the hypothesis that, i) EAMC is associated with a decrease in IEMG activity during recovery from EAMC), ii) there is no association between recovery from EAMC and serum electrolyte concentrations. This study also indicated that during the post-race period runners with EAMC have greater baseline IEMG activity than control runners. The third study examines the effects of passive stretching on IEMG activity during acute episodes of EAMC in four distance runners. This study demonstrates i) increased IEMG activity during an acute EAMC, ii) that passive stretching is associated with a rapid decrease in IEMG activity during an acute EAMC, iii) increased baseline IEMG activity in the cramping muscle between acute episodes of cramping. Conclusion: Serum electrolyte concentrations and hydration status are dissociated from EAMC before and after the race and during the recovery period of EAMC. Recovery from EAMC is associated with decreased IEMG activity in the involved muscle. Passive stretching of a muscle in acute EAMC is associated with a rapid decrease in IEMG activity of that muscle.
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Open Access
Physical activity, change in blood pressure and predictors of mortality in older coloured South Africans: a 24-month prospective study
(1997) Charlton, Karen Elizabeth; Steyn, Krisela
An historical cohort study was undertaken in a representative sample of the older coloured population in Cape Town to (1) investigate the prevalence of hypertension and identify associated risk factors; (2) to validate a questionnaire to assess habitual physical activity patterns; (3) to characterize the current physical activity patterns of subjects who were still alive using the validated instrument at 24-month follow-up; (4) to assess the association between physical activity, blood pressure and body composition, as well as changes in these parameters over 24 months, and (5) to identify predictive risk factors for 24-month mortality in the baseline sample. In 1993, a random sample of 200 free-living subjects aged ~ 65 years of age, resident in urban Cape Town, was drawn using a two-stage cluster design. The survey procedure included a dietary assessment using a quantified food frequency questionnaire method, anthropometric measurements and the drawing of blood for plasma lipid, haematological and biochemical analyses and a 2-hour glucose tolerance test. Blood pressure was determined according to the American Heart Association's recommendations. The prevalence of hypertension (systolic pressure ~ 160 mmHg and/or diastolic ~ 95 mm Hg) was 66, 7 % (95 % Cl: 57,3 - 76, 1 %) for men and 76,5 % (95 % Cl: 68,3 - 84, 7 %) for women. Isolated systolic hypertension ( ~ 160/ < 95 mm Hg) was identified in 33,8 % (95 % Cl: 18,2 - 30,2 %) of the hypertensive subjects. Over a third of hypertensive subjects (37 ,3 %) were previously undiagnosed. Only half of the hypertensives were being treated for the condition, 72 % of whom still had blood pressure levels .::: 160/95 mmHg. No association was found between either systolic or diastolic pressure and plasma lipids, salt intake, or alcohol intake. The prevalence of diabetes found in this study is amongst the highest in elderly populations worldwide and was of a similar order as that found in older South African Indians and Mauritian Creoles. The prevalence of anaemia (13 %) is of the same order of magnitude as that previously reported in this population. Over half (54 %) of the anaemic subjects had haemopoeitic nutrient deficiencies, with folate and vitamin B, 2 being more common than iron deficiency. An analysis of biochemical parameters related to liver function suggests that the high prevalence of hyperferritinamia found in the men (11 %) was related to an excessive alcohol intake. Obesity prevalence was found to be high in the women (47,5 %), according to age-adjusted body mass index (BMI: weight/height2) values, whereas over half of the men were classified as underweight. The results of the baseline study suggest an inadequate diagnosis and poor management of hypertension, diabetes and anaemia in the elderly coloured population. Improved medical care and preventive strategies regarding the early diagnosis, treatment and monitoring of these conditions requires special attention in this age group. There is a paucity of data on energy expenditure, habitual physical activity patterns and the association between activity and health status in free-living older South Africans. To date, no survey instruments used to assess physical activity have been validated in this population. The instrument used to assess physical activity levels in the baseline survey lacked sensitivity to detect participation in activities of low intensity, such as household chores (food preparation, dish-washing, laundry, etc.), time spent sitting or standing during the day, as well as activities of daily living (dressing, bathing, shopping, etc.), care-taking activities and yardwork. The information collected using this crude assessment instrument was limited to a narrow range of responses. In order to develop an instrument to accurately assess physical activity levels of subjects at follow-up, a sub-study was undertaken six months after the baseline survey to assess the construct validity of the questionnaire used in the Yale Physical Activity Survey for Older Persons (YPAS) in estimating energy expenditure associated with physical activity. A convenient sub-sample of 21 subjects from the baseline survey was drawn for a validation sub-study (10 men; 11 women; mean age = 76 (SD = 6) years). Resting metabolic rate (RMR) was measured in fasting subjects and individualized regression equations were calculated to assess the heart rate:oxygen consumption association. Heartrate monitoring was conducted over a 24-hour period and total daily energy expenditure (TDEE) was calculated from resting data and the regression equations. The YPAS was administered by trained interviewers and two composite indices of physical activity were estimated: weekly energy expenditure (PAR, kcal/day) and a Summary Index score (units/month). Both indices were significantly associated with total daily energy expenditure (r = 0,82, p < 0,0005 and r = 0,68, p < 0,01, respectively) and with the energy expenditure associated with physical activity (PAEE) (r=0,86, p<0,0001 and r=0,56, p<0,05, respectively). YPAS scores were approximately 37 % lower than those of a sample of North Americans of the same age, the population for whom the questionnaire was originally developed. The findings suggest that the Yale Physical Activity Survey provides a valid measure of energy expenditure associated with physical activity for use in a sample of older South Africans. Two years following the baseline survey, subjects were revisited in their homes. The validated YPAS questionnaire was administered to all subjects who were traced, and blood pressure and anthropometrical measurements were repeated by trained standardized fieldworkers. At follow-up, 142 of the subjects (Men (N = 66); Women (N = 76)) were traced and measurements collected. Thirty-two subjects were reported, by relatives living in the same household, to have died during the interim period (Men (N = 22); Women (N = 10)). The mortality rate was 16 % (95 % Cl: 10,9 - 21,2 %). More men than women had died (P < 0,05). The remaining twenty-six subjects had either moved out of the area, were unavailable on three occasions, or refused to participate in the follow-up study and were therefore classified as being lost to follow-up. Reported levels of habitual energy expenditure associated with physical activity were about two-thirds lower than that reported in a sample of North Americans of the same age (2 583 (3 027) kcal/week vs 7 613 (4 506) kcal/week, respectively). Both systolic and diastolic BP decreased over time, by about 8 mm Hg. BMI and waist:hip ratio also decreased over time in both men and women. An inverse association between age and total weekly energy expenditure (TWEE) (r =-0,31; P< 0,001) was found, and a positive association between BMI and TWEE (r =0,29; P< 0,005) was found in both men and women. The lack of an association between physical activity and either systolic or diastolic pressure at follow-up is inconsistent with findings from other studies. This may be explained by a number of reasons: ( 1) homogeneity of physical activity levels, (2) activity levels were not of sufficient intensity to have a physiological effect on blood pressure levels, (3) the measures of either activity or blood pressure lacked validity, or (4) the association was confounded by unmeasured variables. Potential sources of bias in the study may include a healthy survivor selection bias at baseline; observer bias which may have influenced the comparability of the repeat blood pressure measurements taken at baseline and follow-up (the measurements were not repeated by the same observer); and diurnal variation and intra-individual variability in blood pressure measurements which questions the reliability of an average measurement taken at one occasion only, at each visit. The use of antihypertensive medications or other medications which may affect blood pressure measurements, together with the presence of other conditions which may influence blood pressure (co-morbidity), are potential sources of confounding. Further, the duration of hypertension was not considered. It is possible that subjects with the highest blood pressure levels may have decreased their activity levels due to ill health. Conversely, known hypertensive subjects who were receiving treatment may have increased activity levels as a result of patient education regarding lifestyle modification. This is, however, unlikely since control of blood pressure in known hypertensives at baseline was poor. Regarding risk factors for mortality during the 24-month follow-up period, in men, systolic BP at baseline tended to be lower in those subjects who had died at follow-up compared to those still alive (difference approaching significance; P = 0 ,063), however in women no such trend was seen. In men, a trend for a greater proportion of subjects in the lowest BMI tertile at baseline to have died was seen (difference approaching significance; P=0,069), whereas in women, a greater proportion of subjects in the upper waist:hip ratio tertile had died at follow-up (p<0,05). Variables, collected at baseline, which were entered into forward stepwise logistic regression models to investigate the predictive factors for mortality at 24 months included: (i) continuous variables: age, systolic BP, diastolic BP, self-perceived health score, BMI, serum albumin, serum ferritin, fasting plasma glucose, haemoglobin, triglycerides, total cholesterol, HDL-C, LDL-C; and (ii) categorical variables: sex, presence of diabetes, tertiles of waist:hip ratio. The outcome (dependent) variable was mortality status at follow-up (dead or alive/lost-to-follow-up). Neither age, blood pressure (systolic or diastolic), nor BMI at baseline differed between men and women who were traced and those lost to follow-up, therefore the two groups were combined for the purpose of the regression analyses. For the total sample, low serum albumin, being male, having diabetes and a raised serum ferritin concentration were found to be independent risk factors for mortality during the 24month follow-up. When stratified according to sex, and including age and smoking in the models as possible confounders, in men higher serum albumin levels were associated with a reduced risk of mortality (OR = 0,85 (P< 0,05), whereas serum ferritin was positively associated with increased risk of death. For every 100 µg increase in ferritin, risk of death increased by 15 % (OR = 1, 15; 95 % Cl = 1,01 - 1,32). In women, being diabetic (OR = 4,27; P=0,056) and having a waist:hip ratio in the upper tertile (OR = 3,26; P=0,058) appeared to be associated with mortality. Although a high prevalence of hypertension was identified in the sample at baseline, no association was found between mortality after 24 months of follow-up and either systolic or diastolic blood pressure. Potential sources of bias which may have influenced the association between the variables of interest and mortality at 24-month follow-up may be an assumption that the subjects lost-to-follow-up were still alive and a lack of validation of mortality status through death certification records. The presence of underlying conditions associated with weight loss which may not have manifested at the time of the survey would further confound the analyses. Similarly, a reliable measure of functional disability is required in such studies of older adults; in this regard, the use of self-reported health status as a proxy for functional status in the present study may not have been an indicator of sufficient sensitivity. Nevertheless, this three-part study has yielded some important information which may be incorporated into the planning and provision of health services, particularly health promotion activities, for the elderly. The findings suggest a need for health education on behaviour modification in this age group, particularly with regard to the high prevalence of hypertension, diabetes and obesity (in women) identified in the baseline survey. The findings of the validation sub-study have shown that the adapted Yale Physical Activity Survey provides a valid measure of energy expenditure associated with physical activity for use in samples of older coloured South Africans and may be used to assess activity levels either in screening those subjects who are most in need of intervention (i.e. physical activity programmes) or for epidemiological research. The identification of predictors for mortality allows the screening of subjects at high risk, for whom medical intervention may be appropriate. In men, low serum albumin, raised serum ferritin, and a low BMI appear to be the best predictive factors of mortality during a 24-month follow-up period, whereas in women, the presence of diabetes and a high waist:hip ratio appear to be associated with increased risk of death. Simple anthropometric assessments, together with serum albumin determinations, may be useful to screen the general health risk of older adults at primary care level and may provide a tool to identify those to whom medical or social welfare intervention should be targeted. The findings suggest that strategies for the early detection and effective management of diabetes, particularly in women, may reduce premature mortality. Finally, the high prevalence of raised serum ferritin concentrations in men in this population and an apparent association with increased mortality risk warrant further investigation into the underlying causes of hyperferritinaemia.
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Open Access
Analysis of heart rate variability
(1997) Donovan, Reece Garethe; Scott-Millar; Rob
Instantaneous heart rate is the reciprocal of the time interval between adjacent QRS complexes in the ECG signal. Heart rate variability analysis is the study of changes in instantaneous heart rate over time. Decreased heart rate variability has been shown to be a powerful predictor of sudden cardiac death syndrome and is also associated with a variety of both pathologic and non-pathologic conditions. A comprehensive literature survey was conducted on the physiological aspects of heart rate control and the techniques used for generating and analysing the heart rate variability signal. Four ECG databases were created from appropriately selected Holter ECG recordings. A computer-based heart rate variability analysis system was then developed. This accepts both single and dual channel ECG signals for processing. The system allows for review and correction of the processed signal. A number of analysis techniques were selected from the literature and implemented. These include time domain measures (mean, standard deviation, SDANN, SDANNi, variance, rMSSD, pNN50 and coefficient of variation), frequency domain techniques (Fourier and auto-regressive modelling for power spectral analysis) and non-linear analytic techniques (histogram, return maps, recurrent plot analysis). The system was calibrated to ensure correct operation. A pilot study was performed to check the QRS detection module. The overall sensitivity results indicate a 99.14 % detection success and a 1.36 % detection failure. The system developed provides a platform for clinical studies of heart rate variability.
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Open Access
Application of the biomatrix model to education systems design - with special reference to South Africa
(1997) Dostal, Elisabeth; Jaros, GG; Bridger, B; Ashley, M
The research problem of the thesis arose from the author's ongoing involvement in organisational and societal transformation. It refers to the need of finding a comprehensive approach to the (re)design of large social systems such as an education system, which is both theoretically sound and can be applied in practice. More specifically, the research of this study was undertaken • to increase understanding of systems change and insight regarding systems design in general and with respect to education specifically; • to develop a comprehensive framework for the analysis and design of systems and to apply it to education; • to contribute to existing design methods and to apply them to the education system with special reference to education in South Africa. The biomatrix model, which is a process based general systems model, was chosen as the underlying theory on which to base this study. It was found to be appropriate because it integrates the most important general systems concepts developed by various systems thinkers and relates them to each other in a coherent and explanatory manner and describes generic organisational patterns which are applicable to various scientific disciplines. It may therefore be regarded as a comprehensive systems approach. Based on the biomatrix model, three methods were developed and applied to education systems design, namely design methods I and II and telentropy analysis. • Design approach I uses the various concepts and generic patterns of organisation of the biomatrix as "lenses" through which to view a system. The education system is seen as a system which spans various levels (i.e. from the societal to the molecular level) and different dimensions at the societal and individual levels. More specifically it is described as a system that provides, taps, internalises, integrates and applies learning opportunities. This method utilises existing data (e.g. education theories, policy documents, educational trends, etc.) which are viewed through the biomatrix model, thereby yielding different perspectives of the system. The generic organisational patterns of the biomatrix model contribute insights and recommendations for an ideal system. The South African education system was used as a case study. • Design method II uses the biomatrix as a multi-dimensional and multi-leveled framework within which systems problems can be identified and ideals can be brainstormed and integrated into a coherent design. This method was applied in a group context and is presented as a case study for an ideal design of South Africa's education system. • Telentropy analysis aims at identifying problems (i.e. telentropy) within the various parts of the system, classifying them and tracing their impact through the system by following the systems dynamic inherent in the biomatrix model. Problems within South Africa's education system were identified in a group context, using the biomatrix as a multi-dimensional and multi-leveled framework of inquiry. The development of the biomatrix model, as well as its application fall within the methodological context of new paradigm research and need to be evaluated accordingly. More specifically, the research methodology followed a dialectic process between induction and deduction, between a search for universal principles and patterns and their specific manifestations, between theory and application, superimposed by a process of self-reflection by the author as well as by a biomatrix research group. The thesis contributes insights into the current education policy debate and makes some recommendations regarding an ideal design. It also represents a further development of process-based systems thinking, as well as making methodological contributions to the general systems field. The biomatrix model was found to provide theoretical insights, a comprehensive framework and practical approaches for the inquiry into and the design of an education system.