1. This series of studies was undertaken to examine the adrenergic regulation of carbohydrate metabolism during exercise. Recreationally active males were tested during moderate to intense exercise on a stationary cycle ergometer. Venous and arterial plasma obtained from indwelling catheters was analysed for hormonal and metabolite responses, and hepatic glucose production and glucose uptake were measured using the tracer-dilution method with stable isotopes. Muscle samples were obtained by the needle biopsy technique to examine muscle glycogen utilisation and the flux of related muscle metabolites using enzymatic, fluorometric and radioisotopic techniques. 2. During moderate exercise adrenaline infusion induced a marked hyperglycemia and this was due to reduced glucose uptake rather than enhanced hepatic glucose production. The reduction in glucose uptake was most likely mediated by a decrease in glucose phosphorylation, as indicated by the accumulation of glucose 6-phosphate with adrenaline infusion. 3. The hyperglycemic response to intense exercise was prevented by the administration of α- and β-adrenergic antagonists. Adrenergic blockade was without effect on hepatic glucose production whereas glucose uptake was enhanced when compared with control subjects. These data support the notion that adrenergic mechanisms are more important in restraining glucose uptake than enhancing hepatic glucose production during intense exercise. Other glucoregulatory factors are responsible for the increase in glucose production during intense exercise. 4. Elevated plasma adrenaline levels during moderate exercise in untrained men increases skeletal muscle glycogen breakdown and PDH activation which results

Thesis (D.P.E.)--Springfield College, 2002. / Includes bibliographical references.

Thesis (M.S.)--University of Montana, 2007. / Title from title screen. Description based on contents viewed Oct. 3, 2007. Includes bibliographical references (p. 50-57).

Thesis (M.A.(MHS))-University of Pretoria, 1999. / Summary in English and Afrikaans.

There exist a wide variety of metabolic responses to different types of carbohydrates and their influence on metabolism during endurance training. Recent studies revealed that the physiological responses to food are far more complex than was previously appreciated. The rapid release of insulin and the decline in blood sugar levels during the first stages of endurance training are linked to the Glycemic Index of foods. Researchers cannot still make use of the old distinction between starchy and sugary food or simple and complex carbohydrates. These distinctions are based on the chemical analysis of the food, which does not totally reflect the effects of these foods on the body. The Glycemic Index is a more reliable guideline to apply in nutritional management for endurance athletes. The major object of the study was to indicate the importance of utilizing the Glycemic Index (GI) as part of the nutritional preparation for endurance events. The study investigated the advantages of ingesting a Low Glycemic Index meal prior to exercise and compared it with the ingestion of a High Glycemic Index meal. A pretest-posttest design was used. Twelve healthy, male and female cyclists participated in the study. Subjects were selected according to their level of training. The total test period consisted of 14 days, which included two different dietary interventions of 7 days each. Diet -and training analysis were done on the subjects prior to the commencement of the study. Each subject completed three exercise trials. The first exercise trial consisted of a V02max test until exhaustion. Two submaximal trials (65 - 70 % of V02max) followed and were preceded by two dietary interventions. The dietary interventions (7 days each) had the same amount of CHO, fat and protein but differed in the Glycemic Index of the pre-exercise meals. The first pre-exercise meal was a High Glycemic Index (HGI) meal. The second pre-exercise meal was a Low Glycemic Index (LGI) meal. The results of the study indicated the advantages of ingesting a Low Glycemic Index meal prior to endurance exercise. The drop in blood glucose levels significantly differed (p<0.05) with an average of 0.68 mmol/L between the two tests after 10 minutes of cycling. It took 20 minutes for the blood sugar level of the first testto reach the same level of the blood sugar level of the second test. After the ingestion of the High Glycemic Index meal in Test 1, the blood lactate levels were significantly higher (p<0.05) during the first 15 minutes. The total distance covered by the subjects was 22.86 km after the first dietary intervention (High glycemic Index food) and 27.43 km after the second dietary intervention (Low glycemic Index food) although it is not statistically significant due to the small sample size. The difference in the distance covered of the two tests is 4.57 km in a period of 50 minutes. Subjects indicated that they experienced more physical strain (higher RPE values) in Test 1 (High Glycemic Index food) than in Test 2 (Low Glycemic Index food) (p<0.05). The study results support the fact that Low glycemic index food may confer an advantage when eaten prior to prolonged strenuous exercise by providing a slow¬releasing source of glucose to the blood without causing extensive hypoglycemia. Proper preparation and the correct choice of the pre-exercise meal can exclude the occurrence of sudden drops in the blood sugar levels. The Glycemic Index can also be successfully applied during and after events to improve performance. / Dissertation (MA (MHS))--University of Pretoria, 2007. / Arts, Languages and Human Movement Studies Education / unrestricted

[Truncated abstract] Obesity is now a major public health problem worldwide. More than half the Australian population is now overweight. This is an important public health concern primarily because of the impact of overweight and obesity on risk of diabetes, hypertension and cardiovascular disease. Many strategies have been proposed to fight the obesity epidemic. One possible strategy involves understanding of the role of dietary components in the control of food intake. In this regard, dietary protein and fibre appear to be the most satiating nutrients. Foods enriched in protein, replacing energy from carbohydrate, or dietary fibre can increase satiety and reduce energy intake in the short-term. Longer-term trials suggest benefits of increasing protein or fibre intake on weight loss and features of the metabolic syndrome. The effects of dietary approaches which increase both protein and fibre at the expense of refined carbohydrate are uncertain. A practical approach to increasing both protein and fibre content of processed foods is to incorporate high protein and fibre ingredients into high carbohydrate foods. Lupin kernel flour is a novel food ingredient derived from the endosperm of lupin. It contains 40 to 45% protein, 25 to 30% fibre, and negligible sugar and starch. Lupin kernel flour can be incorporated into refined carbohydrate rich foods such as bread to increase protein and fibre content at the expense of refined carbohydrate. ... Body weight was measured every 2 weeks throughout the 16 week intervention, and these data were analysed to determine whether there was any between group difference in the rate of change in weight over 16 weeks. Over 16 weeks, lupin bread compared to white bread resulted in a significant increase in protein (13.7 (2.3, 25.0) g/d) and fibre (12.5 (8.8, 16.2) g/d) intakes, and a decrease in carbohydrate intake (-19.9 (-45.2, 5.5) g/d). There was a significant difference between groups in the rate of weight change over the 16 weeks (P=0.05). However, at 16 weeks there was no significant effect on body weight (-0.4 (-1.3, 0.6) kg), fat mass (-0.5 (-1.2, 0.2) kg) or fat free mass (0.2 (-0.5, 0.8) kg). Plasma adiponectin and leptin were not altered. Mean 24 hour systolic blood pressure (-2.4 (-3.4, -1.3) mm Hg) and pulse pressure (-3.1 (-3.9, -2.3) mm Hg) were lower for lupin relative to white bread, but diastolic blood pressure was not significantly different between groups. Apart from a lower HDL cholesterol for lupin relative to white bread (-0.09 (-0.17, -0.01) mmol/L), there were no significant differences in other blood lipids and glucose and insulin concentrations. Interpretation of the results was not influenced after adjustment for potential confounding factors. These studies assessed effects of bread enriched in lupin kernel flour relative to white bread, resulting in a higher protein and fibre intake and lower refined carbohydrate intake. This increased satiety and reduced energy intake acutely, but did not significantly influence body weight over 16 weeks. Systolic blood pressure and pulse pressure were significantly reduced. There were no significant improvements in blood lipids or glucose and insulin concentrations. Therefore, increasing protein and fibre intake at the expense of refined carbohydrate using lupin kernel flour may benefit satiety and blood pressure. Longer-term trials incorporating weight loss may be needed to observe benefits on body weight.

Adolescent athletes of this era are more pressurized than adolescents of previous generations to perform at an optimum level (Micheli & Jenkins 2001, p49). The importance of winning can result in adolescent athletes developing inappropriate nutritional practices such as neglecting hydration and consuming insufficient carbohydrate (Micheli & Jenkins 2001, p57). Consuming insufficient fluid leads to dehydration which reduces a soccer player’s ability to continue training. Consuming inadequate carbohydrate reduces performance and blood glucose levels during training. This study aimed to determine the hydration status, fluid and carbohydrate intake of male, adolescent soccer players during training. A cross-sectional study was conducted among 122 amateur male, adolescent soccer players (mean age = 15.8 ± 0.8 years; mean BMI = 20.4 ± 2.0 kg/m2). The players’ hydration status before and after training, was measured using urine specific gravity and percent loss of body weight. Their carbohydrate intake, as well as the type and amount of fluid consumed, were assessed before, during and after training. A questionnaire was administered to determine the players’ knowledge regarding the importance of fluid and carbohydrate for soccer training. The study had an 87.1% response rate. The mean environmental conditions did not predispose players to heat illness. However, the players were at risk of developing heat illness during six of the 14 training sessions. Although the mean urine specific gravity indicated that players were slightly dehydrated before and after training, 43.8% of players were very or extremely dehydrated before training and 53.6% after training. A few (3.3%) were extremely hyperhydrated before training and after training (7.0%). On average players lost less than 1% of body weight during training and less than 3% of players dehydrated more than 2%. Players consumed mainly water before (289.17 ± 206.37 ml), during (183.20 ± 158.35 ml) and after (259.09 ± 192.29 ml) training. More than 90% stated that water was the most important fluid to consume before, during and after training. Very few (4.7%) correctly stated that carbohydrate should be consumed before, during and after training. Players were found to be slightly dehydrated before and after training and therefore were not consuming enough fluids during training. Players consumed inadequate amounts and types of fluid and carbohydrate. This not only compromises their performance but also health. Players were not aware of the importance of fluid and carbohydrate for soccer training. This study is unique in that it focused on the carbohydrate and hydration practices of socioeconomically disadvantaged adolescent soccer players during training. The study sample therefore represents a high risk group about which there is limited published data both locally and internationally. This study generated important baseline information which was lacking before on the hydration status, fluid and carbohydrate intake of adolescent soccer players in South Africa. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.