Date of Award

Fall 2002

Document Type

Dissertation - Restricted

Degree Name

Doctor of Philosophy (PhD)


Biological Sciences

First Advisor

Fitts, Robert

Second Advisor

Buchanan, James T.


The cause of muscular fatigue has been the quintessential question for exercise physiologists for over 100 years but despite intense efforts the etiology of the phenomenon remains elusive. Upon repeated high intensity stimulation muscular force and power output decline. A correlation between the build-up of metabolites and the decline in force and power output has been demonstrated. Additionally, elevating inorganic phosphate and hydrogen ions in skinned single muscle fibers depresses force and power output. These findings lead authors to conclude the build up of metabolites such as Pi and H+ were the major cause of fatigue. However, more recently authors have questioned the role of these ions based on the temperature-dependence of their depressive effects. The present investigation re-examined the role of elevations in Pi and H+ at low temperatures and at temperatures approaching mammalian physiological values. Efforts were also made to approximate the conditions experienced during fatigue. Chapter two examines the effect elevations in Pi on single fiber force, power and velocity. Chapter three examines the effect of elevated Pi on calcium sensitivity of single fibers. Finally Chapter four addresses the effect of simultaneous elevations in Pi and H+ on single fiber force, power and velocity. The results are interpreted in terms of the implication for muscular fatigue.



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