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Alkalosis increases muscle K+ release, but lowers plasma [K+] and delays fatigue during dynamic forearm exercise

Sostaric, Simon, Skinner, Sandford L, Brownn, Malcolm J, Sangkabutra, Termboon, Medved, Ivan, Medley, Tanya, Selig, Steve E, Fairweather, Ian, Rutar, Danny and McKenna, Michael J (2006) Alkalosis increases muscle K+ release, but lowers plasma [K+] and delays fatigue during dynamic forearm exercise. The Journal of Physiology, 570 (1). pp. 185-205. ISSN 0022-3751

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Abstract

Alkalosis enhances human exercise performance, and reduces K+ loss in contracting rat muscle. We investigated alkalosis effects on K+ regulation, ionic regulation and fatigue during intense exercise in nine untrained volunteers. Concentric finger flexions were conducted at 75% peak work rate (3 W) until fatigue, under alkalosis (Alk, NaHCO3, 0.3 g kg–1) and control (Con, CaCO3) conditions, 1 month apart in a randomised, double-blind, crossover design. Deep antecubital venous (v) and radial arterial (a) blood was drawn at rest, during exercise and recovery, to determine arterio-venous differences for electrolytes, fluid shifts, acid–base and gas exchange. Finger flexion exercise barely perturbed arterial plasma ions and acid–base status, but induced marked arterio-venous changes. Alk elevated [HCO3–] and PCO2, and lowered [H+] (P < 0.05). Time to fatigue increased substantially during Alk (25 ± 8%, P < 0.05), whilst both [K+]a and [K+]v were reduced (P < 0.01) and [K+]a-v during exercise tended to be greater (P= 0.056, n= 8). Muscle K+ efflux at fatigue was greater in Alk (21.2 ± 7.6 µmol min–1, 32 ± 7%, P < 0.05, n= 6), but peak K+ uptake rate was elevated during recovery (15 ± 7%, P < 0.05) suggesting increased muscle Na+,K+-ATPase activity. Alk induced greater [Na+]a, [Cl–]v, muscle Cl– influx and muscle lactate concentration ([Lac–]) efflux during exercise and recovery (P < 0.05). The lower circulating [K+] and greater muscle K+ uptake, Na+ delivery and Cl– uptake with Alk, are all consistent with preservation of membrane excitability during exercise. This suggests that lesser exercise-induced membrane depolarization may be an important mechanism underlying enhanced exercise performance with Alk. Thus Alk was associated with improved regulation of K+, Na+, Cl– and Lac–.

Item Type: Article
Uncontrolled Keywords: muscle, alkalosis, exercise performance, fatigue, ionic regulation
Subjects: RFCD Classification > 320000 Medical and Health Sciences
Faculty/School/Research Centre/Department > School of Sport and Exercise Science
Depositing User: Ms Phung T Tran
Date Deposited: 16 Feb 2009 18:05
Last Modified: 06 Jul 2011 01:25
URI: http://vuir.vu.edu.au/id/eprint/1753
DOI: 10.1113/jphysiol.2005.094615
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Citations in Scopus: 38 - View on Scopus

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