Reply to Boning and Pries

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Reply to Boning and Pries
  Reply to Böning and Pries James G. Hopker, 1 Damian A. Coleman, 2 and Louis Passfield 1 1  Endurance Research Group, School of Sport and Exercise Sciences, University of Kent, Kent, United Kingdom;and   2  Department of Sports Science, Tourism and Leisure, Canterbury Christ Church University, Kent, United Kingdom TO THE EDITOR : We thank Böning and Pries (2) for their interestand comment on our recently published study (3). We agreewith the main points they have raised in their letter on the needto carefully control for work rate and cadence effects in theassessment of cycling efficiency. However, Böning and Priesappear to have fundamentally misunderstood the statisticalanalysis of our efficiency data. Consequently, they have con-cluded incorrectly that training only has a “very limited” effecton cycling efficiency.We agree with Böning and Pries (2) that ideally comparisonsbetween subjects require the same absolute work rate to beused or a measure of efficiency that is not dependent on poweroutput. We do not think that this process is simple however. Inour recent study (3) we provide an important insight into thecomplexity of the interaction of those factors that determinegross efficiency. This is that the efficiency ratio does not scaleproperly across different work rates. Part of the reason for thisratio scaling issue may be attributable to the factors thatBöning and Pries highlight. Namely, that gross efficiency isinfluenced by changes in cadence as well as absolute andrelative work rate. But the optimal value for these parametersvaries between individuals, and this means there is no simplereference point for comparing between different populations.As is widely observed in the literature, our trained cyclistspreferred a higher cadence (91  6 revolutions/min) than theiruntrained counterparts (78    11 revolutions/min). Thereforewe made multiple measurements for comparison between ourdifferent populations. Furthermore, as these comparisons of the efficiency ratio are reliant on certain “statistical” as-sumptions, we for the first time account for these in ouranalysis. The method and further rationale for this areprovided in the paper (3).Allison et al. (1) recommend that where appropriate, andprior to analysis, values are rescaled with a log-linked allomet-ric model. To achieve this we used the log of energy expen-diture as a covariate in the model. Between group differencesfor work rates were assessed using a generalized linear modelwith energy expenditure and cadence included as covariates.Thus our analysis accounted for both the effects of work rateand cadence. Consequently, for the first time we provide astatistically robust method for comparing efficiency data.Relatively recently there have been several studies thatdemonstrate an effect of training on gross efficiency. Thesestudies have used both short interventional and longitudinalobservational designs. Those from our laboratory reportedchanges in gross efficiency of    5%. Studies from other re-search groups demonstrated improvements in cycling effi-ciency as large as 12% from training. Therefore we are gratefulfor this opportunity to explain how our and other recent robuststudies are debunking the myth that training has only a verylimited effect on the efficiency of exercise. DISCLOSURES No conflicts of interest, financial or otherwise, are declared by the author(s). AUTHOR CONTRIBUTIONS Author contributions: J.G.H., D.A.C., and L.P. drafted manuscript; J.G.H.,D.A.C., and L.P. edited and revised manuscript; J.G.H., D.A.C., and L.P.approved final version of manuscript. REFERENCES 1.  Allison DB, Paultre F, Goran MI, Poehlman ET, Heymsfield SB. Statistical considerations regarding the use of ratios to adjust data.  Int J Obes  19: 644–652, 1995.2.  Böning D, Pries AR.  Pitfalls of efficiency determination in cycling ergom-etry.  J Appl Physiol ; doi:10.1152/japplphysiol.01021.2013.3.  Hopker JG, Coleman DA, Gregson HC, Jobson SA, Von der Haar T,Wiles J, Passfield L.  The influence of training status, age and muscle fibertype on cycling efficiency and endurance performance.  J Appl Physiol  115:723–729, 2013.Address for reprint requests and other correspondence: J. Hopker, School of Sport and Exercise Sciences, Univ. of Kent, Chatham Maritime, Kent, UK(e-mail:  J Appl Physiol  115: 1863, 2013;doi:10.1152/japplphysiol.01061.2013.  Letter to the Editor 8750-7587/13 Copyright  ©  2013 the American Physiological Society 1863   b  y 1  0 .2 2  0 . 3  3 . 3  on S  e p t   em b  er 1  6  ,2  0 1  6 h  t   t   p:  /   /   j   a p. ph  y  s i   ol   o g y . or  g /  D  ownl   o a d  e d f  r  om 
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