Muscle function testing and 31P-NMR spectroscopy in fasted healthy volunteers

Abstract

The effects of a five-day fast on muscle function and 31P-NMR spectroscopy were examined in normal volunteers as a study preliminary to the application of these tests in assessing nutrient deprivation in critically ill patients. As a result of fasting, testing of the adductor pollicis muscle by ulnar nerve stimulation showed a decrease in the force of contraction at a stimulation frequency of 100 Hz and an increase in the ratio of the force of contraction at 10 Hz over that at 100 Hz, but no change in relaxation rate or fatiguability. 31P-NMR spectroscopy of the forearm muscles was performed at rest, immediately following four minutes of maximum voluntary exercise and during the recovery period. Fasting had no effect on the resting pH or the Pi/PCr ratio. There was also no significant change in Pi/PCr as a result of fasting in the immediate postexercise period. The pH was relatively higher immediately postexercise in the fasted state suggesting that less glycolysis had occurred. The alterations in muscle function and 31P-NMR spectroscopy seen after acute starvation in normals may serve as a basis for nutritional assessment in critically ill patients.