No description available.

No description available.

There is no abstract available for this dissertation. / Human Performance Laboratory

To determine whether pre-exercise muscle glycogen levels influence the ergogenic benefits derived from carbohydrate (CHO) feedings during exercise, eight experienced cyclists completed four, 1680 kJ isokinetic cycling trials as quickly as possible. Trials were conducted under the following pre-exercise muscle glycogen (vastus lateralis) and feeding conditions: 1) high glycogen (180.2 ± 9.7 mmol•kg ww-1) with carbohydrate feedings during exercise (HGCHO trial), 2) high glycogen (170.2 ± 10.4 mmol•kg ww-1) with placebo feedings during exercise (HG-PLA trial), 3) low glycogen (99.8 ± 6.0 mmol•kg ww-1) with carbohydrate feedings during exercise (LG-CHO trial), and 4) low glycogen (109.7 ± 5.3 mmol-kg ww-1) with placebo feedings during exercise (LG-PLA trial). The placebo feedings contained no CHO. The CHO feedings provided 116 ± 6 g CHO•trial-1 and prevented the fall in serum glucose that occurred during both placebo trials. Performance times for the HG-CHO, HGPLA, LG-CHO, and LG-PLA trials averaged 117.18 ± 1.44, 118.67 ± 1.84, 121.18 ± 1.88 (P<0.05 vs. HG-CHO), and 122.91 ± 2.46 (P<0.05 vs. HG-CHO, HG-PLA) min, respectively. There were no between trial differences in relative V02 (75 ± 2 % of V02 max) or self-selected pace (8.42 ± 0.14 min-120 kJ-1) during the initial 1200 kJ of exercise. During the remaining 480 kJ, pace was similar under the HG-CHO, HG-PLA, and LG-CHO conditions (8.59 ± 0.14 min-1 20 kJ-1) but was significantly slower over the final 240 kJ of the LG-PLA trial (9.67 ± 0.43 min. 120 kJ-1). In conclusion, when pre-exercise muscle glycogen levels were low, CHO feedings enabled subjects to maintain their optimal pace throughout the exercise bout, but when pre-exercise glycogen levels were elevated, CHO feedings provided no ergogenic benefit. / Human Performance Laboratory

It has been widely recognized that aging will cause a profound decrease in glucose tolerance end increase insulin resistance. These changes have been found to occur at a relatively early age. Narimiya [54], has documented these changes in younger rots end has shown alterations in glycogen metabolism to occur prior to nine months of age. Exercise in the form of running has been shown to attenuate these changes. In Vivo, glucose, insulin end muscle glycogen have interrelated functions. The role of muscle glycogen is to provide energy for the muscle's contractile process. Insulin is needed at rest to allow glucose to enter the muscle and be stored as glycogen. The purpose of this study is to pinpoint when changes in glycogen metabolism occur while looking at the influence of exercise end weight restriction on the process. METHODS: Male Sprague Dawley rats ages 1.5-4.0 months of age were divided into three groups control (CN), pairfed (PF), and exercise trained (ET). The ET cages were equipped with voluntary running wheels attached to an automatic revolution counter. At 1.5 months, a group of controls were sacrificed and treated as the 4 mo. animals described below. Following training the hindlimbs of CN, ET, end PF were surgically isolated and glucose uptake examined by perfusing them with a bovine blood preparation, which contained insulin and glucose. Pre and post samples of the soleus, plantaris, and red and white vastus were removed and assayed for glycogen. RESULTS: The 1.5 mo. CN had significantly greater glucose uptake then any other group for both the insulin and non-insulin infused groups. The ET had significantly greater uptake than the other 4 mo. groups at 90 and 120 min in the insulin infused group. In the 1.5 mo. CN when insulin is not present all muscles will break down glycogen. When insulin is present, glycogen is used in all but the white vastus. In the 4 mo. CN all muscles except the soleus break down glycogen. In the ET the glycogen breakdown pattern is similar regardless of whether insulin is present or not. In the PF, glycogen breakdown is depressed and decidely different from the other treatment groups. CONCLUSIONS: There is an age dependent decrease in glucose tolerance and insulin resistance at or before 4 mo. of age. Training prevented some of this loss but did not stop the decline. Weight restriction had a nominal, if any, benefit in reducing insulin resistance and raising glucose tolerance with aging.

The effect of intramuscular corticosterone injection on post mortem muscle metabolism and shear resistance of Pectoralis Major muscle was studied. Short term studies, conducted over an 8 hour post-injection period, showed no significant effect of injection until 6 hours post injection at which time shear values increased from those of the controls. Blood glucose levels rose significantly from 2 to 8 hours post injection. A comparison of shear values of P. Major muscle from 6 week-old broilers and 8 week-old broilers after both had received corticosterone injections showed that the only difference was due to the difference of age not to any alteration in the physiological handling of the injected corticosterone. The greatest difference in treatment effect was found between birds of different stress level. Stress level was subjectively evaluated with respect to the birds reaction to a person entering the range house and to the birds response to handling. Long term studies conducted over 5 and 15 days illustrated homeostatic adjustments to daily corticosterone injections and recovery after cessation of injections. Shear testing was performed on P. Major muscle which was chilled on the carcass and on muscle excised at death. Excised muscle displayed a greater reaction to injection and cessation of injection than did intact muscle due to a lack of skeletal restriction. Shear values decreased on initial injection and increased upon cessation of injection. Homeostatic adjustments returned values to near-normal between these times. Chemical tests were found to display a much more definite reaction to corticosterone injection than did shear testing. Blood glucose and tissue glycogen increased steadily on injection of corticosterone and decreased rapidly at cessation. As expected ultimate muscle pH decreased with muscle glycogen increase. Blood cholesterol increased during injection period as endogenous corticosterone production, for which it is a precursor, was not required. / Land and Food Systems, Faculty of / Graduate

Call number: LD2668 .T4 1985 A32 / Master of Science

Call number: LD2668 .T4 1985 C84 / Master of Science

Call number: LD2668 .T4 1985 X56 / Master of Science

The controversial condition of carbohydrate craving is believed by some researchers to be a defect in the regulation of food intake by an individual. This defect is believed to be responsible for the inability of some persons to control their food intake and therefore their weight. Research was conducted to test the hypothesis that, given a group of carbohydrate cravers and a group of noncravers, the cravers will experience a greater plasma insulin response (concentration and area under the curve) than will the noncravers, and that, because of this higher response, the cravers will experience equal or lower plasma glucose levels during a carbohydrate load. A second hypothesis was that, because of cephalic insulin response due to sensory stimuli, cookies would elicit a greater plasma insulin response than would a glucose solution. This higher plasma insulin response may in part explain the uncontrollable snacking that some individuals experience. The purpose of this research was to attempt to identify a biochemical distinction between persons who crave carbohydrates and persons who do not crave carbohydrates. Eleven overweight female subjects, age 30 to 40, were recruited and divided into two groups, five carbohydrate cravers and six noncravers, based on scores received on a questionnaire that was devised for this study to attempt to distinguish between the groups. A Restrained Eating questionnaire was also administered to the subjects. Both groups had similar, but high, restrained eating scores, indicating that all of the subjects were probably restrained eaters. The eating restraint, as supported by the reported frequency of dieting among the subjects, may well have influenced the subjects' responses to the carbohydrate craving questionnaire. Utilizing these two groups of subjects, two tests were administered. The oral glucose tolerance test was administered, utilizing 75 g of carbohydrate each in the forms of glucose solution and cookies, which were administered in a random order. The tests were administered during the premenstrual phase of the subjects' menstrual cycles, 0-10 days prior to the onset of menstruation. Blood was drawn and assayed for plasma glucose and insulin. The research showed that the cravers experienced a significantly greater plasma insulin concentration and area under the curve than the noncravers, particularly at the 30, 60 and 120 minute time points with the glucose treatment. For the glucose treatment, the cravers experienced plasma insulin concentrations that were 32% to 50% greater than those of the noncravers in the early portion of the test. This supports the hypothesis which states that cravers will experience a greater plasma insulin response to a carbohydrate load than will noncravers. This elevated plasma insulin level may be responsible for the carbohydrate cravings that the individuals experience. There was no significant difference in plasma glucose levels at any time point in either of the tests as compared between the cravers and noncravers, thus supporting the expectation that these levels would be similar between the groups. The hypothesis that cookies would elicit a greater plasma insulin response than would a glucose solution was not supported. Any cephalic insulin response which may have resulted from the sight and smell of the cookies, while not specifically measured, was not strong enough to override the physiological factors that control insulin release. Therefore, the glucose solution elicited a significantly greater plasma insulin concentration than did the cookies in the cravers during the first two hours of the tests, and a significantly greater area under the curve for the cravers at 60 minutes and both groups at 120 minutes. However, the cookies did have an effect on insulin release at the fasting point, causing elevated (x = 79%) plasma insulin levels in three of five subjects who were waiting while others were eating the cookies, as compared with these subjects' fasting insulin levels when they were not exposed to the cookies prior to their glucose test. Another finding was a difference between the groups in fasting plasma insulin concentrations over the 10 day premenstrual portion of their menstrual cycles. The noncravers experienced fasting plasma insulin concentrations that decreased as the onset of menstruation was approached, which would parallel the decrease in progesterone levels. However, the cravers experienced first a decrease in fasting plasma insulin levels to day 3 premenstrual, and then an increase to the level of that found 8-10 day premenstrual. This pattern is contrary to what would be expected as progesterone levels drop, and suggests an altered pattern of progesterone levels in the cravers, although progesterone was not measured in this study. To summarize, in a group of overweight women, carbohydrate cravers and non cravers, the cravers experienced a greater plasma insulin response than did the noncravers for the glucose treatment but not for the cookie treatment, and there was no significant difference between the groups for plasma glucose concentration for either treatment. / Graduation date: 1991