Discussion
BLOOD
This study explored the impact of acute ingestion of the polyphenol epigallocatechin gallate (EGCG) on catecholamine, catecholamine metanephrine, systemic metabolic and cardio-respiratory variables during continuous incremental cycle exercise. To the authors’ knowledge, this study is the first to demonstrate that EGCG supplementation resulted in lowered circulating catecholamine concentrations. In addition, EGCG altered oxidative energy provision from lipid and carbohydrate at low exercise intensities.Increased physical exercise intensity elevated heart rate, ventilation, OUsing principles of stoichiometry to determine the lipid and carbohydrate proportions of energy utilisation during exercise at relatively similar metabolic domains, this study revealed a 32% decreased oxidation rate of lipids following EGCG supplementation at FATThe lipids (non-esterified fatty acids) oxidised during exercise are derived from intramuscular depots or adipose tissue. However, during exercise above the lactate threshold, circulating FFA amounts cannot meet the tissue oxidative needs and intramuscular triglyceride stores are used more [Many studies researching green tea extract or EGCG have explored oxidative energy provision with scant attention paid to non-oxidative pathways. We measured resting and exercising blood lactate concentration as an indicator of non-oxidative energy metabolism. As graded exercise was mostly performed in an oxidative isoenergetic domain, the noted difference in RER between PLAC and EGCG might indicate an increase in CHO utilisation. Increased CHO flux through non-oxidative glycolysis preceding oxidation might result in elevated pyruvate and lactate formation, with an increase in both these markers [There was no change in performance time or power output after EGCG supplementation. This is a similar finding to previous research [Green tea leaves contain components like caffeine that can alter circulating catecholamine concentrations in some [In conclusion, this study explored the impact of acute ingestion of the polyphenol epigallocatechin gallate (EGCG) on catecholamine, catecholamine metanephrines, systemic metabolic and cardio-vascular variables across a range of exercise intensities during graded cycle exercise in man. Circulating catecholamine concentrations and peak lipid oxidation were lower in response to a graded exercise test following acute EGCG supplementation.Study limitations: Blood samples collected at the end of each stage were able to be analysed for catecholamines and catecholamine metabolites; however, we established five metabolic time points which were examined to remove potential bias and mitigated this limitation, all samples were however analysed for plasma blood lactate and plasma blood glucose. Second, the lack of a post ingestion respiration sample, in any future study it would be beneficial to add this sample point to allow a more complete picture of any subtle changes which may have occurred during the rest period.
