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First published online December 3, 2004
Journal of Experimental Biology 207, 4615-4621 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.5913

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Lactate availability is not the major factor limiting muscle glycogen repletion during recovery from an intense sprint in previously active fasted rats

Ghazala Raja¹, Sally Mills¹, T. Norman Palmer² and Paul A. Fournier^1,*

¹ School of Human Movement and Exercise Science, University of Western Australia, Crawley, Western Australia, Australia, 6009
² Department of Biochemistry and Molecular Biology, James Cook University, Townsville, Queensland, Australia, 4811

^* Author for correspondence (e-mail: fournier{at}cyllene.uwa.edu.au)

Accepted 12 October 2004

It is not clear whether the amount of accumulated lactate is the main factor limiting muscle glycogen accumulation during recovery from an intense sprint performed by previously active fasted laboratory rats. To address this question, groups of fasted rats swam at moderate intensity for 30 min, each animal with a lead weight equivalent to 0.5% body mass attached to its tail, followed by a 3 min high intensity swim with a 10% lead weight and a recovery period of up to 2 hours afterwards. Moderately intense exercise for 30 min caused a decrease in muscle glycogen levels in the mixed, white and red gastrocnemius and the mixed quadriceps muscles, and a further rapid fall occurred in response to the 3 min sprint effort. During recovery, glycogen increased to comparable or above pre-sprint levels across all muscles, and this occurred to a large extent at the expense of net carbon sources other than lactate, with these carbon sources accounting for at least 36–65% of the glycogen deposited. The sustained dephosphorylation-mediated activation of glycogen synthase, but not the changes in glucose 6-phosphate levels, most probably played an important role in enabling the replenishment of muscle glycogen stores. In conclusion, our findings suggest that the amount of glycogen deposited during recovery from high intensity exercise in fasted animals is not limited by the amount of accumulated lactate.

Key words: carbohydrate, exercise, glycogen, glycogen synthase, muscle, recovery, regulation, rat

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This article has been cited by other articles:

				G. Raja, L. Brau, T. N. Palmer, and P. A. Fournier Fiber-specific responses of muscle glycogen repletion in fasted rats physically active during recovery from high-intensity physical exertion Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2008; 295(2): R633 - R641. [Abstract] [Full Text] [PDF]