title: Stability of the K4b² portable metabolic analyser during rest, walking and running.
abstract: This study investigated the stability of the measurement of respiratory variables during rest, walking and running using the K4b(2) portable metabolic analyser in ten active males (age 31 ± 11 years; VO₂ peak 42.1 ± 2.6 ml · min(-1) · kg(-1)). Following a 10 min rest, participants completed three discontinuous incremental exercise tests on a treadmill while walking (4, 5 and 6 km · h(-1)) and running (8, 10, 12, 14 and 16 km · h(-1), or until volitional exhaustion). Participants completed 3 min of exercise at each speed, followed by a 3 min recovery after each stage above 10 km · h(-1). The respiratory variables were measured using either a laboratory-based metabolic cart as a reference method (Oxycon Pro, OP), a K4b(2) calibrated immediately before the test (K4b(2)), or a K4b(2) calibrated 1 h before the test (K4b(2)DEL). Compared to the OP, carbon dioxide production (VCO₂) and V(E) were not different when measured by K4b(2) or K4b(2)DEL. There was no difference in VO₂ between OP and K4b(2) tests (P = 0.19, mean difference = 38 ml · min(-1) and limits of agreement (LOA) = 208 to -285) although K4b(2)DEL overestimated VO₂ (P = 0.05, mean difference = 84 ml · min(-1) and LOA = 302 to -469). These data suggest that a drift in measurement accuracy appears to cause the K4b(2) to overestimate VO₂ in tests lasting longer than 1 h.
authors.affiliation: a School of Life Sciences , Kingston University, Kingston upon Thames , UK.
authors.forename: Christopher C F
authors.initials: CC
authors.lastname: Howe
authors.forename: Richard O
authors.initials: RO
authors.lastname: Matzko
authors.forename: Fabio
authors.initials: F
authors.lastname: Piaser
authors.forename: Yannis P
authors.initials: YP
authors.lastname: Pitsiladis
authors.forename: Chris
authors.initials: C
authors.lastname: Easton
mesh_terms: D000328:Adult; D002138:Calibration; D005221:Fatigue; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000502:physiology; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D015203:Reproducibility of Results; D012146:Rest / Q000502:physiology*; D012420:Running / Q000502:physiology*; D016138:Walking / Q000502:physiology*; D055815:Young Adult