Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Phosphorous 31, nuclear magnetic resonance spectroscopy {dollar}(\sp{lcub}31{rcub}{dollar}P NMRS) was used as a non-invasive probe of forearm muscle metabolism in three studies of healthy men and women. Specific objectives of the studies were to: (1) observe the changes in high energy phosphates and intracellular pH in muscle, during a ramp exercise protocol, (2) study the effect of endurance training on muscle metabolism and evaluate the utility of the forearm ramp test as a means to assess muscle oxidative capacity, and (3) describe the kinetics of phosphocreatine (PCr) and inorganic phosphate (Pi) metabolism during the on and off transient response to moderate exercise.;In the first study, 18 subjects performed a forearm ramp exercise to fatigue. Exercise caused a biphasic increase in the Pi/PCr ratio of the muscle. Change in Pi/PCr was initially slow, followed by a rapid phase. The transition or threshold between the two rates corresponded to the onset of intracellular acidosis. Repeated testing of 6 subjects showed that this threshold was reproducible. These findings demonstrated the existence of a threshold in intracellular metabolism (IT), which was related to aerobic capacity.;In the second study, 4 older subjects trained the dominant forearm daily for 12 weeks, using a light weight. Muscle metabolism was evaluated using the ramp protocol and {dollar}\sp{lcub}31{rcub}{dollar}P NMRS before training and after 6 and 12 weeks of training. The onset of the IT was delayed 14%, and submaximal exercise endurance time was increased 58% by training. Muscle blood flow was not altered by training. The results indicated that endurance training improved forearm muscle oxidative capacity, and that the IT could be used to assess this change.;Finally, the kinetics of forearm muscle PCr metabolism were studied during the transition to, and the recovery from, moderate intensity work. Five young men completed 6 square wave exercise tests each. The results of these tests were combined and the changes in PCr and Pi modelled using an exponential growth or decay function. The time constants (scT) calculated for both metabolites were about 30 s, which is similar to the sc T reported for oxygen uptake during whole body exercise. These data suggest a first-order relationship between muscle oxygen consumption and substrate utilization during exercise transition states.



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