HR Index-A Simple Method for the Prediction of Oxygen Uptake

WICKS, J. R., N. B. OLDRIDGE, L. K. NIELSEN, and C. E. VICKERS. HR Index-A Simple Method for the Prediction of Oxygen Uptake. Med. Sci. Sports Exerc., Vol. 43, No. 10, pp. 2005-2012, 2011. Purpose: Energy expenditure measured in METs is widely used in cardiovascular medicine, exercise physiology, and nutrition assessment. However, measurement of METs requires complex equipment to determine oxygen uptake. A simple method to predict oxygen uptake on the basis of HR measurements without requirement for gas analysis, movement-recording devices, or exercise equipment (treadmills, cycle ergometers) would enable a simple prediction of energy expenditure. The purpose of this study was to determine whether HR can be used to accurately predict oxygen uptake. Methods: Published studies that reported a measured resting HR (HRrest), a measured activity HR (HRabsolute), and a measured oxygen uptake (mL O-2 center dot kg(-)center dot.min(-1)) associated with the HRabsolute were identified. A total of 220 data sets were extracted from 60 published exercise studies (total subject cohort = 11,257) involving a diverse range of age, pathophysiology, and the presence/absence of beta-blocker therapy. Net HR (HRnet = HRabsolute - HRrest) and HR index (HRindex = HRabsolute/HRrest) were calculated from the HR data. A regression analysis of oxygen uptake (expressed as METs) was performed against HRabsolute, HRnet, and HRindex. Results: Statistical models for the relationship between METs and the different HR parameters (HRabsolute, HRnet, and HRindex) were developed. A comparison between regression analyses for the models and the actual data extracted from the published studies demonstrated that the best fit model was the regression equation describing the relationship between HRindex and METs. Subgroup analyses of clinical state (normal, pathology), testing device (cycle ergometer, treadmill), test protocol (maximal, submaximal), gender, and the effect of beta-blockade were all consistent with combined data analysis, demonstrating the robustness of the equation. Conclusions: HRindex can be used to predict energy expenditure with the equation METs = 6HR(index) - 5.