The sodium-potassium adenosine triphosphatase enzyme (Na+,K+ -ATPase) regulates muscle cell [Na+],[K+] and muscle membrane potential, therefore playing a fundamental
role in muscle excitability. This dissertation primarily examined the effects of acute exercise, training status and chronic inactivity on Na+, K+ -ATPase content and activity
in human skeletal muscle. Since Na+, K+ -ATPase activity also regulates plasma [K+] at rest and during exercise, a secondary focus of this thesis was to examine relationships
between muscle Na+,K+ -ATPase and plasma [K+] responses during and following exercise.