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 0022-3751Full text for this resource is not available from the Research Repository.
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–.
|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|
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|Citations in Scopus:||26 - View on Scopus|
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