Skeletal muscle enzyme activities and metabolic substrates during exercise in patients with postoperative fatigue

Abstract

Abstract Subjective fatigue was quantified before and 20 days after uncomplicated elective abdominal surgery in 12 patients and compared with changes in heart rate, enzyme activities and skeletal muscle substrates before and after bicycle exercise for 10 min at 65per cent of patients' preoperative maximum work capacity. Fatigue increased from a mean(s.e.m.) preoperative level of 2·5(0·5) arbitrary units to 4·6(0·5) on postoperative day 20 (P<0·01). Body-weight, triceps skinfold thickness and arm circumference decreasedpostoperatively (P<0·02). Postoperative values of muscle enzyme activities indicative of oxidative phosphorylation capacity (citrate synthase and 3-OH-acyl coenzyme A dehydrogenase) were lower than preoperative values (P<0·05). Lactate dehydrogenase was unaltered and resting values of muscle glycogen and adenosine triphosphate were higher after operation (P<0·05). In response to exercise, heart rate, muscle glucose, glucose-6-phosphate and lactate increased (P<0·05), while muscle glycogen and creatine phosphate decreased (P<0·05). Increase in postoperative fatigue correlated with the increase in heart rate (P<0·05), while no significant correlations were found between fatigue and muscle parameters. Our results suggest that lack of exercise and malnutrition may be of importance in the decrease in work capacity and in fatigue after operation.