PREDICTING THE ENERGY COST OF STEEP UPHILL TREADMILL WALKING: A CROSS-VALIDATION
PREDICTING THE ENERGY COST OF STEEP UPHILL TREADMILL WALKING:
E.Davila1, E.C. Ranta1, L.M. Whalen1, D. Weishar2, A. Blake2, D.E. Lankford2, & D.P. Heil, FACSM1.
1Montana State University, Bozeman, MT; 2Brigham Young University, Rexburg, ID
INTRODUCTION: There are a growing number of commercially-available electronic monitoring devices that claim to predict the energy cost of exercising as a function of one or more predictive metrics. Devices relying upon global positioning satellite (GPS) data, for example, can predict the energy cost of walking and running outdoors by determining real-time changes in travel speed and surface incline. These data can then be combined with a laboratory-derived prediction algorithm, but the algorithm must include both steep uphill and downhill inclines to remain ecologically valid. A well-known formula by Minetti et al. (JAP 2002), considered valid for inclines between -45% and +45%, would seem well suited but does not appear to have been cross-validated in the literature. The purpose of this study was to cross-validate the original Minetti formula for predicting relative energy cost (CW, J/kg/m) between -5% and +30% for treadmill walking using a broad range of healthy adults. METHODS: 31 recreationally-active adults (18 men: (Mean±SD) 28 ± 8 yrs, 20-45 yrs, and 23.0±3.3, 21.0-34.4 kg/m2; 13 women: 29 ± 3 yrs, 25-35 yrs, and 23.1±2.8, 19.1-29.8 kg/m2) were recruited to walk on a treadmill at 53.6 m/min (2.0 MPH) at one of four lower inclines (-5%, -2.5%, 0%, +8%) and one of four steeper inclines (+15%, +19%, +22.5%, +30%) across four separate lab visits for 20 mins at each incline. Steady-state oxygen consumption (VO2), recorded via standard indirect calorimetry procedures, were averaged from the end of each 20-min test. Net VO2 (exercise VO2 – resting VO2) was then converted to CW using the measured non-protein RER, body mass, and treadmill speed. Predicted CW, as determined from the original Minetti formula, was compared to measured CW using a two-factor repeated measures ANOVA, including a comparison by gender, at each incline (0.05 alpha). RESULTS: Mean predicted CW was statistically similar between genders for both measured and predicted CW. In contrast, measured CW was significantly lower (P<0.001) than predicted CW at the lower inclines (≤ +15%), statistically similar at the +19% incline, and significantly higher at the steepest inclines (+22.5% and +30%; P<0.001). CONCLUSIONS: The Minetti formula for predicting CW for steep downhill and uphill walking was derived using well-trained men accustomed to mountain running. The present study, in contrast, used a more diverse adult population (i.e., recreationally active, men and women, wide range of BMI) which suggests that the Minetti formula may lack a broad generalizability for the range of inclines tested (-5% to +30%) for populations dissimilar to the original validation sample.
Davila, E.; Ranta, E.C.; Whalen, L.M.; Weishar, D.; Blake, A.; Lankford, D.E.; and Heil, D.P.
"PREDICTING THE ENERGY COST OF STEEP UPHILL TREADMILL WALKING: A CROSS-VALIDATION,"
International Journal of Exercise Science: Conference Proceedings: Vol. 8
, Article 65.
Available at: https://digitalcommons.wku.edu/ijesab/vol8/iss2/65