Comparison of energy expenditure calculations

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Comparison of energy expenditure calculations
  A comparison of energy expenditure calculations M. Arkesteijn, S.A. Jobson, J. Hopker, L. Passfield University of Kent, UK  INTRODUCTION The determination of energy expenditure (EE) is central to many applications within exercise physiology. The quantification of EE is usually carried out using indirect calorimetry. This relies upon the accurate measurement of VO 2 and VCO 2 to determine the oxygen cost of the activity and the substrate oxidised. Energy expenditure is calculated using the formula: Total energy expenditure (kJ.min -1 ) = kJ per litre O 2 consumed x VO 2 , where kJ per litre of O 2 consumed is calculated from the thermal equivalents of oxygen for non-protein respiratory quotient (RQ). However, there is variation in the specific thermal equivalents used. The impact that this has on estimated EE has yet to be described. METHODS We examined 9 methods (Figure 1) for the determination of EE. Six (M1-M6) minor revisions and one major revision (M7) of the thermal equivalents tables of Lusk (1924) were used. The remaining two methods (M8-M9) used fixed values for the thermal equivalents of O 2 . The different methods for calculating EE were applied to data with a fixed VO 2 of 2.5 L.min -1 and RQ values between 0.71 and 1. Differences between methods were examined using a one-way ANOVA. DISCUSSION Variation in thermal equivalents values has a large impact on calculated EE. Fixed methods are overly simplistic as they do not take into account the substrate being oxidised. The figures of Peronnetet al. (1991) are preferable to those based upon Lusk’s early work as they are based on more accurate values of energy released from fat and carbohydrates. RESULTS Figure 1 illustrates the similarity of EE values based on the Lusk (1924) table (M1-M6) with variation of less than 1.1% at an RQ of 0.85 (P>0.05). The EE based on the Peronnetet al. table (M7) of non-protein respiratory quotient differed by 3.2% from M1-M6 ( P  <0.01). The fixed methods (M8-M9) showed a difference of up to 6.3% compared with M1-M6 ( P  <0.01). Overview of formulae used: M1 : EE (kJ) = Lusk Table of non-proteinrespiratoryquotientM2 : EE (kCal) = Lusk equation 1:(3.869 * VO 2 ) + (1.195 * VCO 2 )M3 : Linear interpolation of Lusk Table of non-protein quotientM4 : EE (Cal) = Weir Equation: 3.941 * (VO 2 *1000) + 1.106 * (VCO 2 *1000)M5 : EE (kJ) = Lusk equation 2:(1.232*RQ+3.815) * VO 2  /0.0143M6 : EE (kJ) = Garbyequation: (VO 2  /60) * (4940*RQ+16040)M7 : EE (kJ) = PeronnetTable of non-proteinrespiratoryquotientM8 : EE (kJ) = Assumed RQ of 0.96: VO 2 * 20.9M9 : EE (kJ) = Assumed RQ of 0.90: VO 2 * 20.6 0.70.750.80.850.90.9514849505152535455 Respiratory Quotient    E  n  e  r  g  y   E  x  p  e  n   d   i   t  u  r  e   (   k   J   )   Figure 1. Results of various methods for comparison of energy expenditure. See References for legend explanation. M1: Hopker et al. 2007: ApplPhysiolNutrMetab  ,32,1036-1042. M2: Cannon et al. 2007: EurJ ApplPhysiol  ,99,659-664.M3: Hunt et al. 2007: EurJ ApplPhysiol, 101,277-285.M4: Ulla Wergel-Kommertet al. 2001: ClinPhysiol, 21,135-140.M5:Tokui et al. 2007: EurJ ApplPhysiol, 101,565-570.M6:Noordhof et al. 2010: EurJ ApplPhysiol  ,109, 1209-1218.M7: Peronnetet al. 1991: Can J Sport Sci  ,16, 23-29.M8: Zameziatiet al. 2006: EurJ ApplPhysiol  ,96,274-281.M9: Martin et al. 2002: EurJ ApplPhysiol  , 86:245-250.Lusk 1924: J BiolChem  ,59,41-42. References
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