HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 103/1/331    most recent 01170.2006v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by Stewart, R. D. Articles by Green, H. J. Search for Related Content PubMed PubMed Citation Articles by Stewart, R. D. Articles by Green, H. J.

Protection of muscle membrane excitability during prolonged cycle exercise with glucose supplementation

Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada

Submitted 17 October 2006 ; accepted in final form 2 April 2007

To determine if exercise-induced depressions in neuromuscular function are altered with oral glucose supplementation, 15 untrained participants (O_{2 peak} = 45 ± 2 ml·kg^–1·min^–1, mean ± SE) performed prolonged cycle exercise at 60% O_{2 peak} on two occasions: without glucose supplementation (NG) and with oral glucose supplementation (G). The oral G began at 30 min of exercise and was administered every 15 min (total ingested = 1.23 ± 0.11 g carbohydrate/kg body mass). Quadriceps isometric properties and membrane excitability were assessed prior to exercise, after 90 min of exercise, and at fatigue. Cycle time to fatigue was greater (P < 0.05) in G compared with NG (137 ± 7 vs. 115 ± 6 min). Progressive reductions (P < 0.05) in maximal voluntary contraction (MVC, N) were observed for NG at 90 min (441 ± 29) and at fatigue (344 ± 33) compared with pre-exercise (666 ± 30). At fatigue in G, the reduction in MVC was not as pronounced (P < 0.05) as in NG. Motor unit activation assessed with the interpolated twitch technique during an MVC following exercise was not different between conditions. During cycling, the G condition also resulted in a higher (P < 0.05) muscle compound potential (M-wave) amplitude (mV) at both 90 min (+50%) and at fatigue (+87%) compared with NG. Similar effects were also found M-wave area (mV/ms). These results suggest that the ergogenic effect of glucose supplementation occurs not as a result of decreased neural activation but to improved muscle function, possibly as a consequence of protection of muscle membrane excitability.

quadriceps; compound muscle action potential; blood glucose; fatigue; central and peripheral fatigue

This article has been cited by other articles:

				S. P. Cairns and M. I. Lindinger Do multiple ionic interactions contribute to skeletal muscle fatigue? J. Physiol., September 1, 2008; 586(17): 4039 - 4054. [Abstract] [Full Text] [PDF]

				M. Hargreaves Fatigue mechanisms determining exercise performance: integrative physiology is systems biology J Appl Physiol, May 1, 2008; 104(5): 1541 - 1542. [Full Text] [PDF]

				T. J. Fairchild Protection of muscle membrane excitability during cycling in humans: a role for SGLT3? J Appl Physiol, January 1, 2008; 104(1): 315 - 315. [Full Text] [PDF]

				H. Green Reply to Fairchild J Appl Physiol, January 1, 2008; 104(1): 316 - 316. [Full Text] [PDF]

				M. J. McKenna, J. Bangsbo, and J.-M. Renaud Muscle K+, Na+, and Cl disturbances and Na+-K+ pump inactivation: implications for fatigue J Appl Physiol, January 1, 2008; 104(1): 288 - 295. [Abstract] [Full Text] [PDF]

				D. G. Allen, G. D. Lamb, and H. Westerblad Impaired calcium release during fatigue J Appl Physiol, January 1, 2008; 104(1): 296 - 305. [Abstract] [Full Text] [PDF]

				T. A. Duhamel, H. J. Green, R. D. Stewart, K. P. Foley, I. C. Smith, and J. Ouyang Muscle metabolic, SR Ca2+-cycling responses to prolonged cycling, with and without glucose supplementation J Appl Physiol, December 1, 2007; 103(6): 1986 - 1998. [Abstract] [Full Text] [PDF]