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: 104/1/288    most recent 01037.2007v1 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 (4) Citing Articles via Google Scholar Google Scholar Articles by McKenna, M. J. Articles by Renaud, J.-M. Search for Related Content PubMed PubMed Citation Articles by McKenna, M. J. Articles by Renaud, J.-M.

INVITED REVIEW

HIGHLIGHTED TOPIC
Fatigue Mechanisms Determining Exercise Performance

Muscle K⁺, Na⁺, and Cl^– disturbances and Na⁺-K⁺ pump inactivation: implications for fatigue

¹Muscle, Ions and Exercise Group, School of Human Movement, Recreation and Performance, Centre for Ageing, Rehabilitation, Exercise and Sport, Victoria University, Melbourne, Victoria, Australia,² Copenhagen Muscle Research Centre, Institute for Sport and Exercise Sciences, University of Copenhagen, Copenhagen, Denmark; and ³Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada

Membrane excitability is a critical regulatory step in skeletal muscle contraction and is modulated by local ionic concentrations, conductances, ion transporter activities, temperature, and humoral factors. Intense fatiguing contractions induce cellular K⁺ efflux and Na⁺ and Cl^– influx, causing pronounced perturbations in extracellular (interstitial) and intracellular K⁺ and Na⁺ concentrations. Muscle interstitial K⁺ concentration may increase 1- to 2-fold to 11–13 mM and intracellular K⁺ concentration fall by 1.3- to 1.7-fold; interstitial Na⁺ concentration may decline by 10 mM and intracellular Na⁺ concentration rise by 1.5- to 2.0-fold. Muscle Cl^– concentration changes reported with muscle contractions are less consistent, with reports of both unchanged and increased intracellular Cl^– concentrations, depending on contraction type and the muscles studied. When considered together, these ionic changes depolarize sarcolemmal and t-tubular membranes to depress tetanic force and are thus likely to contribute to fatigue. Interestingly, less severe local ionic changes can also augment subtetanic force, suggesting that they may potentiate muscle contractility early in exercise. Increased Na⁺-K⁺-ATPase activity during exercise stabilizes Na⁺ and K⁺ concentration gradients and membrane excitability and thus protects against fatigue. However, during intense contraction some Na⁺-K⁺ pumps are inactivated and together with further ionic disturbances, likely precipitate muscle fatigue.

potassium; sodium; Na⁺-K⁺-ATPase; exercise excitability

This article has been cited by other articles:

				A. C. Petersen, M. J. Leikis, L. P. McMahon, A. B. Kent, and M. J. McKenna Effects of endurance training on extrarenal potassium regulation and exercise performance in patients on haemodialysis Nephrol. Dial. Transplant., September 1, 2009; 24(9): 2882 - 2888. [Abstract] [Full Text] [PDF]

				K. T. Murphy, I. Medved, M. J. Brown, D. Cameron-Smith, and M. J. McKenna Antioxidant treatment with N-acetylcysteine regulates mammalian skeletal muscle Na+-K+-ATPase {alpha} gene expression during repeated contractions Exp Physiol, December 1, 2008; 93(12): 1239 - 1248. [Abstract] [Full Text] [PDF]

				H. J. Green, E. Bombardier, T. A. Duhamel, R. D. Stewart, A. R. Tupling, and J. Ouyang Metabolic, enzymatic, and transporter responses in human muscle during three consecutive days of exercise and recovery Am J Physiol Regulatory Integrative Comp Physiol, October 1, 2008; 295(4): R1238 - R1250. [Abstract] [Full Text] [PDF]

				M. Amann, S. M. Marcora, L. Nybo, T. A. Duhamel, T. D. Noakes, V. Jaquinandi, J. L. Saumet, P. Abraham, B. T. Ameredes, M. Burnley, et al. Viewpoint: Fatigue mechanisms determining exercise performance: integrative physiology is systems physiology. J Appl Physiol, May 1, 2008; 104(5): 1543 - 1544. [Full Text] [PDF]