31-Phosphorous, nuclear magnetic resonance spectroscopy studies of exercising human muscle.

摘要

Phosphorous 31, nuclear magnetic resonance spectroscopy ;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 ;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.;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.