Heart rate and oxygen uptake relationship: a comparison of loaded marching and running in women

Heart rate (beats · min^–1;f _c) measured during marching with a load is often used to predict the oxygen cost (1·min^–1; VO₂) of the activity. The prediction comes from thef _c/VO₂ relationship determined from laboratory measures off _c and VO₂ during treadmill running. Studies in men have suggested that this may not be appropriate although this has yet to be examined in women. This study, therefore, compared thef _c/VO₂ relationship between loaded marching and maximal running protocols in women. Sixteen female subjects [mean (SD), age 21.9 (2.3) years, height 6 (0.06) m, weight 62.6 (7.6) kg] had theirf _c (from three-lead chest electrodes) and VO₂ measured first during standard treadmill run protocols, and again 1 week later during loaded marching protocols. The slopes and intercepts determined from linear regression off _c on VO₂ for each individual for each protocol were compared as were the maximalf _c(f _cmax), VO₂ and ratings of perceived exertion (RPE) from the last work period of each protocol in pairedt-tests. The VO₂ slopes (P < 0.01) and intercepts (P < 0.05) differed significantly between loaded marching and running.f _cmax for loaded marching were 90% off _cmax for running (P < 0.01) and VO₂ for loaded marching were 80% of those for running (P < 0.01). However, RPE at the final levels for the two protocols were not significantly different. The data suggest that in women the VO₂ relationships for loaded marching and for running are different. This difference is similar to that found in men when speed is held constant and the load and gradient are varied. The results suggest that it would be erroneous to usef _c and VO₂ measured during running protocols in the laboratory to estimate energy expenditure and work intensity during loaded marching in the filed.