Moderate Intensity Exercise and Phenylketonuria

The indicator amino acid oxidation technique utilizes a carbon labeled isotope (L-\[13C\]) tracer that is ingested orally and is measured in expired breath. This method is based on the theory that if one essential amino acid is deficient, all other amino acids will be oxidized until a break-point is reached and at that time all amino acids will be incorporated into muscle protein synthesis. Using a randomized crossover design the investigators plan to investigate the effects of an acute bout of moderate intensity treadmill exercise versus sedentary activities on plasma amino acids in four subjects with PKU. The long-term goal of this novel research is to determine if exercise could be used as an adjunctive therapy to improve the management of plasma phenylalanine levels and promote a normal, healthy quality of life among patients with PKU. Patient Recruitment: Four post-pubertal participants ranging from 14-17 years of age with classical phenylketonuria (PKU), treated at Oregon Health \& Science University, will participate in this pilot study. Participants will be recruited during their routine clinic visit at Doernbecher Children's Hospital Metabolic clinic. Study Design: This randomized crossover clinical trial will compare the effects of moderate intensity exercise and sedentary activities on amino acid oxidation and plasma amino acid pools using the indicator amino acid oxidation technique. Each participant will be studied on two separate occasions over a one-month period.