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The impact of Endurance Exercise and Carbohydrate feeding on hepatic enzymes in Ultra-endurance athletes / RUIYANG XIA
Swansea University Author: RUIYANG XIA
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Copyright: The Author, Ruiyang Xia, 2024 Distributed under the terms of a Creative Commons Attribution 4.0 License (CC BY 4.0).
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Abstract
Introduction: Ultra-endurance sports, such as ultramarathons, ultra-triathlons, and ultra-distance cycling, present extreme physiological and psychological demands, testing athletes' limits over prolonged periods of high-intensity exertion. From 1996 to 2018, global ultramarathon participation...
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Swansea University, Wales, UK
2024
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| Institution: | Swansea University |
| Degree level: | Master of Philosophy |
| Degree name: | M.Phil |
| Supervisor: | Bracken. R. M. |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa68881 |
| Abstract: |
Introduction: Ultra-endurance sports, such as ultramarathons, ultra-triathlons, and ultra-distance cycling, present extreme physiological and psychological demands, testing athletes' limits over prolonged periods of high-intensity exertion. From 1996 to 2018, global ultramarathon participation surged by 1,676%, reflecting the growing interest in these challenging events. Carbohydrates are the primary source of energy for ultra-endurance athletes, and carbohydrates with different glycaemic indices (GI) have markedly different effects on energy supply and liver function markers such as ALT and AST. High-GI carbohydrates, like maltodextrin, provide rapid energy boosts but can increase metabolic strain on the liver due to blood sugar fluctuations. In contrast, low-GI carbohydrates, such as isomaltulose, offer a slower, more stable release of energy, potentially reducing liver stress and improving endurance. Research indicates that prolonged high-intensity exercise increases liver enzyme levels, such as the key liver biomarkers alanine aminotransferase (ALT) and aspartate aminotransferase (AST), suggesting an increased burden on the liver. This study aims to examine the effects of different GI carbohydrates on liver function and metabolic recovery in ultra-endurance athletes following an acute endurance run and over a 28- day period of carbohydrate feeding. The findings provide insights into nutritional strategies for reducing liver strain, optimising performance, and enhancing recovery in ultra-endurance sports.Methods & Materials: This study employed a randomised crossover design to evaluate the impact of different dietary interventions on ultra-endurance athletes' performance. After obtaining ethical approval from the Swansea University Ethics Committee and informed consent from all participants, nine healthy adults aged 34 to 52 from local sports clubs participated in a 77-day study. The study consisted of two consecutive 28-day dietary interventions: one involving a low glycaemic index (GI)diet and the other a high GI diet, with a 14-day washout period in between. On testing days, participants arrived at the laboratory in a fasted state for baseline datacollection, followed by a 3-hour outdoor endurance run at 70% of their maximum heart rate. After the run, participants returned to the laboratory for a 3-hour rest and carbohydrate refeeding, then completed a treadmill endurance run at approximately 74% of their maximal oxygen uptake (V̇ O2max) until exhaustion. A carbohydrate-rich meal was provided post-activity. Data collected included anthropometric measurements, continuous heart rate monitoring, respiratory gas exchange via the Metamax 3B device, and glucose and lactate concentrations from capillary and venous blood samples taken pre- and post-exercise. All data were analysed for normality and subjected to repeated measures analysis of variance (ANOVA) and paired-sample t-tests using IBM SPSS statistical software.Results: Following a 28-day dietary intervention with two different glycaemic index (GI) carbohydrates, isomaltulose (low GI) and maltodextrin (high GI), the effects on participants' body weight, BMI, body fat percentage, and lean body mass (LBM) were analysed. Statistical analysis revealed no significant differences either pre- and post- intervention or between the two carbohydrate diets. In the 3-hour fixed-intensity outdoor running test, conducted in a fasted state, no significant differences were observed in running performance (including running distance, heart rate, percentage of maximum heart rate, and speed) before and after the interventions or between the two diets. Liver function biomarkers, including ALT, AST, GGT, and total bilirubin, showed no significant differences between the two dietary interventions, although AST levels significantly increased after both diets. Additionally, no significant changes were observed in blood glucose and lactate levels. The exercise performance test to exhaustion (measuring running time, V̇ O2, V̇ CO2, and heart rate) also revealed no significant differences. Overall, the 28-day intervention with different GI carbohydrates had no significant effect on participants' anthropometric data, liver function biomarkers, blood glucose, blood lactate, or exercise performance.Conclusion: This study systematically investigated the effects of different GI carbohydrates—isomaltulose (low GI) and maltodextrin (high GI)—on liver function and metabolic recovery in ultra-endurance athletes following an acute endurance run and a 28-day period of carbohydrate feeding. The results indicated that neither carbohydrate diet had a significant impact on key metabolic indicators such as blood glucose, lactate, ALT, GGT, or total bilirubin, nor did it result in notable changes in body composition or athletic performance. However, a slight but significant increase in AST levels was observed in both dietary groups, suggesting a mild degree of liver or muscle stress potentially related to post-exercise muscle micro-damage and its subsequent repair process. The study suggests that carbohydrate feeding does not affect liver enzymes in ultra-endurance athletes, though the observed rise in AST warrants further investigation to determine whether it is attributable to the different GI carbohydrates. Longer-term studies, controlling for exercise-induced liver stress, are needed to gain a more comprehensive understanding of the impact of carbohydrate intake on liver enzymes and metabolism in ultra-endurance athletes, in order toinform more personalised nutritional and recovery strategies. |
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| Keywords: |
Endurance exercise, Carbohydrate feeding, Hepatic enzymes, Ultra-endurance athletes |
| College: |
Faculty of Science and Engineering |