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Muscle triglyceride and glycogen in endurance exercise: implications for performance

Citation

Johnson, NA and Stannard, SR and Thompson, MW, Muscle triglyceride and glycogen in endurance exercise: implications for performance, Sports Medicine, 34, (3) pp. 151-164. ISSN 0112-1642 (2004) [Refereed Article]

DOI: doi:10.2165/00007256-200434030-00002

Abstract

The importance of muscle glycogen as a metabolic substrate in sustaining prolonged exercise is well acknowledged. Being stored in proximity to the site of contraction and able to sustain high rates of adenosine diphosphate (ADP) phosphorylation, glycogen is viewed as the primary fuel for the maintenance of exercise of a moderate to intense nature. As such, to ensure optimal exercise performance, endurance athletes are encouraged to maximise the availability of muscle glycogen through the ingestion of a high carbohydrate (CHO) diet prior to competition. The skeletal muscle cell also contains significant quantities of triglyceride. Recent improvements in the ability to measure these intramyocellular triglyceride (IMTG) stores have confirmed that IMTG acts as a significant fuel substrate during prolonged exercise. While early research of the role of muscle glycogen in endurance exercise provided clear prescriptive information for the endurance-trained athlete, no such direction for optimising exercise performance is yet apparent from research concerning IMTG. In this article, we review the processes of muscle glycogen and triglyceride storage and metabolism. Attention is given to the effects of short-term alterations in diet on muscle substrate, particularly IMTG storage, and the implications of this to endurance exercise performance and competition preparation. We demonstrate that like glycogen, IMTG formation may be relatively rapid, and its storage predominates under conditions that promote minimal glycogen formation. This observation suggests that the role of IMTG is to maintain a readily available substrate to ensure that physical activity of a moderate nature can be performed when glycogen availability is not optimal. Under these conditions, IMTG may offer a similar availability of energy as glycogen in the endurance-trained athlete. Given the potential value of this substrate, the possibility of maximising IMTG storage without compromising glycogen availability prior to competition is considered.

Item Details

Item Type:Refereed Article
Research Division:Medical and Health Sciences
Research Group:Human Movement and Sports Science
Research Field:Exercise Physiology
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Environmental Sciences
Author:Johnson, NA (Dr Nathan Johnson)
ID Code:32816
Year Published:2004
Web of Science® Times Cited:22
Deposited By:Health Sciences A
Deposited On:2005-05-11
Last Modified:2005-05-11
Downloads:0

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