Age effects on serum amino acids in endurance exercise at the aerobic anaerobic threshold in patients with neuromuscular diseases

We have measured concentrations of 26 serum amino acids in 46 subjects (age d 17-75 years), with the following neurological diseases: amyotrophic later al sclerosis, n = 7; peripheral neuropathy, n = 5; muscular dystrophy, n = 7; mitochondriopathy, n = 3; metabolic myopathy (others), n = 2; inflammato ry myopathy, n = 4;, mononeuropathy, n = 3; controls (patients with symptom s suggesting neuromuscular system dysfunction without objective evidence of neuromuscular disease), n = 15, before and after prolonged muscular effort . Tests were done on a bicycle ergometer at the individual aerobic/anaerobi c threshold determined for each subject in preliminary tests. Using a stepw ise multiple linear regression model, age emerged as a significant negative predictor (P < 0.05) of the post/before ratio of the levels of five amino acids. We conclude that an increase in recovery time and a reduction in tra ining capacity with aging could be linked to these changes. The cause is as sumed to be principally a reduction in glycogen storage in muscle with incr easing age; this situation could possibly be improved by consumption of car bohydrate before or during exercise, or also during rehabilitation exercise or training in neuromuscular or other diseases. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.