Muscle fatigue: the role of metabolism.

This paper examined the role of metabolites in causing muscle fatigue. Previous studies have shown that Pi (H2PO4-, HPO4-2) and H+ may be important factors in causing fatigue. A key question is the potential interaction between metabolic end-products and calcium related excitation-contraction coupling fatigue (ECC).

Effect of prior exercise in Pi/PC ratio and intracellular pH during a standardized exercise. A study on human muscle using [31P]NMR.

Seven subjects underwent a standard localized exercise of calf muscles in order to investigate whether the metabolic exercise-induced steady-state, as revealed by the evaluation of inorganic phosphate/phosphocreatine ratio, depends on the conditioning of the muscle just prior to the exercise. The experimental protocols consisted of two separate experiments using first [31P]nuclear magnetic resonance spectroscopy and second (on 3 subjects) infrared oxyphotometry to respectively follow variation of energy metabolism and tissular deoxygenation. The exercise consisted of 240 successive plantar flexions (0.

Prediction by 31P-NMR of the irreversibility of ischemic injury in rat skeletal muscle after ligation of the femoral artery.

Rat leg muscles, rendered ischaemic 1 hour previously by ligation of the femoral artery, were submitted to 20 minutes exercise by electrical stimulation of the sciatic nerve. 31P-NMR spectroscopy was used to monitor the changes in high-energy phosphate content of the muscles before, during, and after exercise. Fifteen of the 35 studied muscles evolved toward total necrosis, whereas the others showed signs of recovery over a 2-5-hour postexercise period.

Reactive hyperemia monitored on rat muscle using perfluorocarbons and 19F NMR.

Perfluorinated blood substitutes can be detected by 19F NMR in vivo in small concentrations. Reactive hyperemia was induced in rat leg by the transient application of a tourniquet, causing a 50% increase in 19F NMR signal. These results show that this method can be used to monitor the kinetics of tissue perfusion.

[Effects of acute arterial occlusion on muscle energy metabolism. An experimental model using phosphorus NMR spectroscopy in the rat].

Phosphorus-31 MR spectroscopy allows non-invasive evaluation of the energy state of a tissue and was used to study effects of acute ischemia in rat skeletal muscle. Male Wistar rats were anesthetized with pentobarbital (50 mg.kg-1) and the femoral artery ligated on leaving the abdominal cavity.