Date of Award


Document Type

Dissertation - Restricted

Degree Name

Doctor of Philosophy (PhD)


Biological Sciences

First Advisor

Robert H. Fitts

Second Advisor

Elliot A. Stein

Third Advisor

Brian R. Unsworth


The effect of 6 weeks of hindlimb immobilization on cable properties, resting and action potentials was examined in the slow twitch, type I soleus (SOL), fast twitch type IIA and IIB extensor digitorum longus(EDL) and fast twitch, type IIB superficial vastus lateralis (SVL). With immobilization (Im), membrane capacitance (Cm) decreased (p<.O5) in all fiber types (4.82uF/cm2 vs 2.96uF/cm2 SOL; 4.24uF/cm2 vs 2.26uF/cm2 EDL; 3.SuF/cm2 vs 2.O6uF/cm2 SVL). The length and time constants also declined significantly with immobilization. Membrane resistance (Rm) showed a tendency to increase with Im but was not significantly altered, while the conductance of the membrane (Gm) was significantly depressed in the fast-twitch muscles. Examination of the action potential (AP) revealed that immobilization significantly increased the rate of rise of the AP (253.3V/s vs 239.3V/s SOL; 457.lV/s vs 444.SV/s EDL; 657.6V/s vs 646.BV/s SVL. Resting membrane potential (RMP) was depolarized in Im (p<.O5) and significant fiber type
differences were observed. These changes were associated, with alterations in (Na)i and (K)i concentrations. In general Im altered' the electrical properties and electrolyte concentrations of fast and slow skeletal muscle in a similar pattern as seen with denervation. This suggests that the maintenance of the electrical properties of all three fiber types is at least, in part, dependent on a normal pattern of contractile activity.



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