Medical implications of the lactate and ammonia relationship in anaerobic exercise

The genesis of the modern ischemic forearm exercise test (IFET) employing the measurement of lactate and ammonia as countervailing metabolites is briefly reviewed, along with the application of the lactate ammonia exercise ratio in the diagnosis of myoadenylate deaminase deficiency and disorders of glycolysis and glycogenolysis. Two cases are presented to illustrate the response patterns elicited, their reproducibility, the types of parameters that can be quantified, and the role the IFET may play in the differential diagnosis of fitness failures. The role of the ammonia measurement is emphasized here because the lactate response is more familiar. The roles of hypoxanthine responses and of muscle ammonia measurements in the evaluation of cases are examined, and some pertinent and recently introduced analytic methods are cited. The applications of newer approaches, such as aspiration biopsy and N-14 NMR spectroscopy, are discussed, along with an example of the new clinical defects in enzymes and membrane carriers that should be anticipated during the utilization of the IFET.