title: Exercise limitation in trained heart and kidney transplant recipients: central and peripheral limitations.
abstract: BACKGROUND
  To evaluate the role of central and peripheral contributions to exercise limitation after transplantation, we compared, during exercise, 2 groups of very well-trained heart transplants recipients (HTRs) and kidney transplant recipients (KTRs) with a group of control subjects (CSs), matched for physical level.
  
  
  METHODS
  Nineteen male subjects, 7 HTRs, 6 KTRs and 6 CSs, participated in the study. All transplant patients were in sinus rhythm and were matched for immunosuppressive therapy, none of whom had therapy with chronotropic effects. Exercise capacities were evaluated using a symptom-limited treadmill test. Oxygen consumption (VO2) and heart rate (HR) were measured continuously. Heart rate reserve (HRR) was defined as peak HR minus resting HR; resting HR was the stabilized HR measured in the supine position before the treadmill test.
  
  
  RESULTS
  Functional capacities were evaluated for all HTRs, KTRs and CSs, according to maximal VO2 (41.5 +/- 4.0, 52.0 +/- 8.7 and 50.6 +/- 9.0 ml/kg per min, respectively), maximal treadmill speed (9.9 +/- 1.2, 12.7 +/- 1.9 and 15.5 +/- 1.5 km/h) and HRR (65 +/- 17, 101 +/- 12 and 110 +/- 11 beats per minute [bpm]), which were significantly lower in the HTR group (p < 0.05). Regardless of type of organ transplant, both HTR and KTR patients had a similar VO2/treadmill speed relationship, significantly higher than in the CS group. HRR correlated with maximal VO2 for HTRs (r = 0.72, p < 0.05).
  
  
  CONCLUSIONS
  Despite regular training, the decreased mechanical efficiency reflected by an increased VO2/treadmill speed relationship suggests a peripheral limitation in both heart and kidney transplant patients. Furthermore, exercise limitations in HTRs likely arose from both central and peripheral factors, in view of their specific HRR reduction. These factors probably contributed to the decreased speed and VO2 observed in the HTR group.
authors.affiliation: Service de Physiologie et des Explorations Fonctionnelles, Hôpitaux Universitaires de Strasbourg, Strasbourg, France. ruddy.richard@physio-ulp.u-strasbg.fr
authors.forename: Ruddy
authors.initials: R
authors.lastname: Richard
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Verdier
authors.forename: Stéphane
authors.initials: S
authors.lastname: Doutreleau
authors.forename: François
authors.initials: F
authors.lastname: Piquard
authors.forename: Bernard
authors.initials: B
authors.lastname: Gény
authors.forename: Michel
authors.initials: M
authors.lastname: Rieu
mesh_terms: D000328:Adult; D017079:Exercise Tolerance / Q000502:physiology*; D006339:Heart Rate; D016027:Heart Transplantation / Q000502:physiology*; D006801:Humans; D016030:Kidney Transplantation / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D013318:Stroke Volume; D016277:Ventricular Function, Left