CUHK electronic theses & dissertations collection

In conclusion, the studies reported in this thesis suggested that the CHO amount, whether provided by a pre-exercise CHO meal or short-time, i.e., 3-day, CHO loading, plays a pivotal role in regulating the immune responses before, during, and after endurance exercise. Although GI and GL independently affect the exercise performance and immune responses, the amount of CHO consumed remains a determining factor. The potential benefits on immune system and endurance performance after the low GI and low GL diet (L-L) should be noted and warrant further investigation. Although the HGI and LGI meals demonstrated similar effects on endurance performance when large amount of CHO-electrolyte solution consumed during the exercise, pre-exercise LGI meal can hasten the IL-6 responses during the recovery. (Abstract shortened by UMI.)The aim of this thesis was to investigate the influence of pre-exercise carbohydrate (CHO) meal(s) with different glycemic index (GI) and glycemic load (GL) on endurance running performance, physiological, and immune responses.The first study (Chapter 4) examined the influence of a pre-exercise meal with different GI and GL on subsequent endurance running performance, physiological, and immune responses. Eight endurance-trained male runners completed three trials in a randomized order, separated by at least seven days. These responses were characterized by a lower CHO oxidation with a concomitant higher glycerol and FFA in the H-L trial. Consumption of a pre-exercise high CHO meal, i.e., H-H and L-L, resulted in less perturbation of circulating numbers of leukocytes, neutrophils, and T lymphocyte subsets, decreased elevation of plasma IL-6 concentrations immediately after exercise and during the 2 h recovery period when compared to the H-L trial. These responses were accompanied by an attenuated increase in plasma IL-10 concentrations and plasma cortisol concentrations at the end of 2 h recovery. It was concluded that the amount of CHO consumed 2 h before endurance exercise appears to be the main influencing factor on immune responses irrespective of its GI and GL value.The second study (Chapter 5) examined the influence of a 3-day CHO loading with different GI and GL meals on the supercompensation status, running performance, physiological and immune responses. Nine endurance-trained male runners were recruited in this study. The procedures basically involved a 3-day CHO loading with different GI and GL meal [CHO intake (% of energy intake), GI, and GL per day are 73%, 80, and 553 for the high-GI and high-GL (H-H); 73%, 42, and 249 for the low-GI and low-GL (L-L); 31%, 78.5, and 227 for the high-GI and low-GL (H-L) respectively] after a glycogen-lowering exercise. Two hours after the breakfast on day 4, participants performed the running protocol as described in the first study. There was no difference in time to complete the 10-km TT between the two trials with high-CHO loading, i.e., H-H and L-L (51.3 +/- 5.3 min vs 48.6 +/- 1.3 min, NS). These results suggested that 3-day CHO loading with low GI and low GL (L-L) is more effective in improving endurance performance when compared to a high GI but low GL diet (H-L). It appears that the amount of CHO consumed during the 3-day CHO loading remains the key influencing factor on immune responses despite of the differences in the GI and GL value.The third study (Chapter 6) investigated the influence of pre-exercise meal with different GI on subsequent endurance running performance and immune responses when CHO-electrolyte solution was consumed during exercise. Pre-exercise LGI meal attenuated the increases of cortisol when compared with CON and hastened the recovery of the IL-6 value to baseline when compared to that in HGI and CON trials during the first hour of the recovery. The results suggested that beside of CHO quantity (CHO content), the role of CHO quality (GI) in the diet consumed 2 h before exercise should be considered when investigating the influence of CHO supplementation on the exercise-induced transitory immunosuppressive effects.Chen Yajun."August 2006."Adviser: Stephen Wong Heung-Sang.Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1597.Thesis (Ph.D.)--Chinese University of Hong Kong, 2006.Includes bibliographical references (p. 199-225).Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.Abstracts in English and Chinese.School code: 1307