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

Sostaric, Simon and Skinner, Sandford L and Brownn, Malcolm J and Sangkabutra, Termboon and Medved, Ivan and Medley, Tanya and Selig, Steve E and Fairweather, Ian and 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: 26 - View on Scopus

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