Skeletal Muscle Fatigue: pH Effects on Contractile Function and Excitation-Contraction Coupling in Single Cells
Date of Award
Dissertation - Restricted
Doctor of Philosophy (PhD)
Fitts, Robert H.
As early as 1807 the correlation between fatigue and muscle acidity was observed by Berzelius in a fatigued deer and the acid involved was shown to be the same as that in sour milk (as cited in Needham, 1971). The degree of lactic acid accumulation and subsequent decrease in muscle pH is dependent on the duration, intensity, and type of muscle activity. Since the time of Berzelius there have been numerous research articles correlating fatigue with a pH change and many attempts to interpret a change in pH with a particular component of fatigue. Muscle fatigue is characterized by reduced force or power output of the cell. The cellular events underlying these changes in contractile function can be localized to the processes of excitation-contraction coupling or the events of the cross-bridge cycle. The experiments described within this dissertation were undertaken to examine the effect of pH on each of these components of muscle contraction. The experiments described in Chapter 2 investigated the effects of flow pH on excitation-contraction coupling by recording sarcoplasmic reticulum calcium transients in voltage clamped cut fibers utilizing micro spectrophotometry of the calcium binding dye, antipyralzo III. In Chapter 3, the events of the cross-bridge cycle were examined in skinned fibers by determining alterations in contractile properties due to the interaction of low pH and fiber temperature. The results from these studies contribute to the literature and the overall understanding of how lactic acid accumulation affects muscle function.