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Alkalosis and digoxin effects on plasma potassium, ionic homeostasis and exercise performance in healthy humans

Sostaric, Simon (2012) Alkalosis and digoxin effects on plasma potassium, ionic homeostasis and exercise performance in healthy humans. PhD thesis, Victoria University.

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Abstract

Muscle contractions induce cellular potassium (K+) efflux which may contribute to impaired muscle cell membrane excitability and fatigue. The magnitude of K+ changes are dependent on the size of contracting muscle mass, duration and intensity of exercise, and health and fitness status of participants. Activation of the sarcolemmal and t-tubular bound sodium-potassium adenosine 5’ triphosphatase enzyme (Na+,K+ATPase, NKA) mediates muscle cell K+ and Na+ active exchange, and is instrumental in the maintenance of muscle cellular and plasma K+ homeostasis during exercise. Therefore modulations of NKA function might enhance or impair exercise induced K+ disturbances, and theoretically can have a profound effect on muscle excitability and exercise performance. This thesis examined the effects of two interventions designed to induce acute or short term upregulation and downregulation of NKA activity on K+ homeostasis and exercise performance in healthy humans. Study 1 investigated the effects of metabolically induced alkalosis on plasma K+ regulation during submaximal finger flexion (small muscle mass) contractions and fatigue in healthy humans. Study 2 investigated the effects of a clinically relevant dose of digoxin administration on K+ regulation, during intermittent supramaximal finger flexion contractions (small muscle mass) and fatigue in healthy humans. Study 3 investigated the effects of digoxin on K+ regulation during progressive increasing intensity submaximal leg cycling exercise (large muscle mass) and fatigue in the same healthy participants as in study 2. A secondary focus of this thesis was to examine the ionic, metabolic and acid-base disturbances during small and large muscle mass exercise and in recovery. This included the regulatory role of NKA in active (study 1 and 2) and inactive tissue (study 3), during small (study 1 and 2) and large (study 3) muscle mass exercise.

Item Type: Thesis (PhD thesis)
Uncontrolled Keywords: blood plasma, alkalinity, alkaline, acidity, acid, glycoside, metabolism, enzymes, intense exercise
Subjects: FOR Classification > 1101 Medical Biochemistry and Metabolomics
FOR Classification > 1102 Cardiovascular Medicine and Haematology
FOR Classification > 1106 Human Movement and Sports Science
Faculty/School/Research Centre/Department > School of Sport and Exercise Science
Depositing User: VU Library
Date Deposited: 04 Jun 2012 04:43
Last Modified: 23 May 2013 16:58
URI: http://vuir.vu.edu.au/id/eprint/19414
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