Abstract. The activity of muscle metabolic enzymes depends on the amount and type of physical training. We examined muscle enzyme adaptation to prolonged training followed by a period of lowered activity in spinal-cord-injured individuals (SCI). Ten SCI [mean age 35(SEM2)years , mean body mass 78(SEM4)kg, mean time post-injury 12(SEM2)years and range of lesion C5T4] were given 12months of functional electrical stimulation of an upright cycling motion for 30min a day, threetimes a week, followed by 6months of training once a week. Activities of glycolytic (hexokinase HK, lactate dehydrogenase LDH) and oxidative (citrate synthase CS, 3-hydroxyacyl-CoA dehydrogenase HAD) enzymes were determined in biopsies of the vastus lateralis muscle taken at 0, 3, 6, 12, and 18months of training. The degree of sympathoadrenergic activity was evaluated from arterial concentrations of catecholamines in response to acute exercise. Training threetimes a week induced increases (P0.05) in HK (150%), LDH (40%), CS (100%), and HAD (70%) activities that reached a plateau after 3months. Peak oxygen uptake and power output during exercise by electrical stimulation rose continuously over the first 12months. After reducing the amount of training by two-thirds, HK, LDH and CS activities remained elevated above basal levels (P0.05), whereas HAD, power output and maximal oxygen uptake returned to pretraining levels (P0.05). It is concluded that most improvements in glycolytic and mitochondrial oxidative enzyme activities induced by long-term training can be maintained in spinal-cord-injured individuals despite a marked reduction in training frequency unrelated to performance or to the degree of sympathoadrenergic impairment.