INCREASED NITROGEN INTAKE FOLLOWING HIP ARTHROPLASTY EXPEDITES MUSCLE STRENGTH RECOVERY
A.A. Ferrando, M.M. Bamman, S.E. Schutzler, H.J. Spencer, A.M. Dawson, R.P. Evans, R.R. Wolfe
J Aging Res Clin Practice 2013;2(4):369-375
Background: Objectives: The aim of this study was to investigate the effects of increased nitrogen intake, via amino acid supplementation, on strength and functional recovery after THA. Design: Prospective, randomized clinical trial. Setting: Academic medical center; orthopedic clinic. Participants: Patients scheduled to receive elective hip arthroplasty. Intervention: Patients were randomly assigned to receive usual care (UC; n = 8, 55 ± 7 (SD) y) or 15 g of essential amino acid supplementation 3 times per day (EAA; n = 8, 55 ± 8 y) for 8 weeks. Measurements: Leg strength (maximal voluntary contraction of the quadriceps) was measured by hand-held dynamometer, and function by 4 meter walk and a chair stand test pre-surgery, 2, and 8 weeks post-surgery. Results: Improvement in leg strength was greater in the EAA group, as was the rate of improvement from weeks 2 to 8 post-surgery. Improved strength was realized without an increase in lean mass. Both groups improved chair stand and 4 meter walk times. EAA supplementation increased total protein intake by 0.6g/kg/d (EAA 1.7 g/kg/d vs UC 1.1 g/kg/d). Conclusions: Increased nitrogen intake via amino acid supplementation improves the rate of recovery of leg muscle strength following THA. Key words: Essential amino acids, hip arthroplasty, paximal voluntary contraction, leg strength and function.