title: Reliability and day-to-day variability of peak fat oxidation during treadmill ergometry.
abstract: BACKGROUND
  Exercising at intensities where fat oxidation rates are high has been shown to induce metabolic benefits in recreational and health-oriented sportsmen. The exercise intensity (Fatpeak) eliciting peak fat oxidation rates is therefore of particular interest when aiming to prescribe exercise for the purpose of fat oxidation and related metabolic effects. Although running and walking are feasible and popular among the target population, no reliable protocols are available to assess Fatpeak as well as its actual velocity (VPFO) during treadmill ergometry. Our purpose was therefore, to assess the reliability and day-to-day variability of VPFO and Fatpeak during treadmill ergometry running.
  
  
  METHODS
  Sixteen recreational athletes (f = 7, m = 9; 25 ± 3 y; 1.76 ± 0.09 m; 68.3 ± 13.7 kg; 23.1 ± 2.9 kg/m(2)) performed 2 different running protocols on 3 different days with standardized nutrition the day before testing. At day 1, peak oxygen uptake (VO2peak) and the velocities at the aerobic threshold (VLT) and respiratory exchange ratio (RER) of 1.00 (VRER) were assessed. At days 2 and 3, subjects ran an identical submaximal incremental test (Fat-peak test) composed of a 10 min warm-up (70 % VLT) followed by 5 stages of 6 min with equal increments (stage 1 = VLT, stage 5 = VRER). Breath-by-breath gas exchange data was measured continuously and used to determine fat oxidation rates. A third order polynomial function was used to identify VPFO and subsequently Fatpeak. The reproducibility and variability of variables was verified with an intraclass correlation coefficient (ICC), Pearson's correlation coefficient, coefficient of variation (CV) and the mean differences (bias) ± 95 % limits of agreement (LoA).
  
  
  RESULTS
  ICC, Pearson's correlation and CV for VPFO and Fatpeak were 0.98, 0.97, 5.0 %; and 0.90, 0.81, 7.0 %, respectively. Bias ± 95 % LoA was -0.3 ± 0.9 km/h for VPFO and -2 ± 8 % of VO2peak for Fatpeak.
  
  
  CONCLUSIONS
  In summary, relative and absolute reliability indicators for VPFO and Fatpeak were found to be excellent. The observed LoA may now serve as a basis for future training prescriptions, although fat oxidation rates at prolonged exercise bouts at this intensity still need to be investigated.
authors.affiliation: University Outpatient Clinic, Center of Sports Medicine, Potsdam University, Potsdam, Germany ; Swiss Federal Institute of Sport Magglingen, Magglingen, Switzerland.
authors.forename: Raul
authors.initials: R
authors.lastname: De Souza Silveira
authors.affiliation: University Outpatient Clinic, Center of Sports Medicine, Potsdam University, Potsdam, Germany ; Department of Health Sciences, University of Education Schwaebisch Gmuend, Schwaebisch Gmuend, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Carlsohn
authors.affiliation: University Outpatient Clinic, Center of Sports Medicine, Potsdam University, Potsdam, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Langen
authors.affiliation: University Outpatient Clinic, Center of Sports Medicine, Potsdam University, Potsdam, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Mayer
authors.affiliation: University Outpatient Clinic, Center of Sports Medicine, Potsdam University, Potsdam, Germany ; Department of Medical Oncology, National Center for Tumor Diseases (NCT), Heidelberg University Hospital, Heidelberg, Germany.
authors.forename: Friederike
authors.initials: F
authors.lastname: Scharhag-Rosenberger
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D003187:Compliance; D016552:Ergometry; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D050356:Lipid Metabolism / Q000502:physiology*; D008297:Male; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D015203:Reproducibility of Results; D012420:Running; D016896:Treatment Outcome; D016138:Walking
keywords: Peak fat oxidation; Reliability; Running; Treadmill ergometry; Variability
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