title: The between and within day variation in gross efficiency.
abstract: Before the influence of divergent factors on gross efficiency (GE) [the ratio of mechanical power output (PO) to metabolic power input (PI)] can be assessed, the variation in GE between days, i.e. the test-retest reliability, and the within day variation needs to be known. Physically active males (n = 18) performed a maximal incremental exercise test to obtain VO2max and PO at VO2max (PVO2max), and three experimental testing days, consisting of seven submaximal exercise bouts evenly distributed over the 24 h of the day. Each submaximal exercise bout consisted of six min cycling at 45, 55 and 65% PVO2max, during which VO(2) and RER were measured. GE was determined from the final 3 min of each exercise intensity with: GE = (PO/PI) x 100%. PI was calculated by multiplying VO2 with the oxygen equivalent. GE measured during the individually highest exercise intensity with RER <1.0 did not differ significantly between days (F = 2.70, p = 0.08), which resulted in lower and upper boundaries of the 95% limits of agreement of 19.6 and 20.8%, respectively, around a mean GE of 20.2%. Although there were minor within day variations in GE, differences in GE over the day were not significant (F = 0.16, p = 0.99). The measurement of GE during cycling at intensities approximating VT is apparently very robust, a change in GE of approximately 0.6% can be reliably detected. Lastly, GE does not display a circadian rhythm so long as the criteria of a steady-state VO(2) and RER <1.0 are applied.
authors.affiliation: Department of Human Movement Sciences, VU University-Amsterdam, Van Der Boechorststraat 9, 1081 BT, Amsterdam, The Netherlands. d.noordhof@fbw.vu.nl
authors.forename: Dionne A
authors.initials: DA
authors.lastname: Noordhof
authors.forename: Jos J
authors.initials: JJ
authors.lastname: de Koning
authors.forename: Teun
authors.initials: T
authors.lastname: van Erp
authors.forename: Bart
authors.initials: B
authors.lastname: van Keimpema
authors.forename: Daan
authors.initials: D
authors.lastname: de Ridder
authors.forename: Ruby
authors.initials: R
authors.lastname: Otter
authors.forename: Carl
authors.initials: C
authors.lastname: Foster
mesh_terms: D000328:Adult; D002940:Circadian Rhythm / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology*; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D013647:Task Performance and Analysis
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