Are heart rate methods based on ergometer cycling and level treadmill walking interchangeable?

Introduction. The heart rate (HR) method is a promising approach for evaluating oxygen uptake (V̇O2), energy demands and exercise intensities in different forms of physical activities. It would be valuable if the HR method, established on ergometer cycling, is interchangeable with other regular activities, such as level walking. This study therefore aimed to examine the interchangeability of the HR method when estimating V̇O2 for ergometer cycling and level treadmill walking in submaximal conditions. Methods. Two models of HR-V̇O2 regression equations for cycle ergometer exercise (CEE) and treadmill exercise (TE) were established with 34 active commuters. Model 1 consisted of three submaximal intensities of ergometer cycling or level walking, model 2 included also one additional workload of maximal ergometer cycling or running. The regression equations were used for estimating V̇O2 with seven individual HR values based on 25-85% of HR reserve (HRR). The V̇O2 estimations were compared between CEE and TE, within and between each model. Results. Only minor, and in most cases non-significant, average differences were observed when comparing the estimated V̇O2 levels between CEE and TE. Model 1 ranged from -0.4 to 4.8% (n.s.) between 25-85 %HRR. In model 2, the differences between 25-65 %HRR ranged from 1.3 to -2.7% (n.s.). At the two highest intensities, 75 and 85 %HRR, V̇O2 was slightly lower (3.7%, 4.4%; P < 0.05), for CEE than TE. The inclusion of maximal exercise in the HR-V̇O2 relationships reduced the individual V̇O2 variations between the two exercise modalities. Conclusion. The HR methods, based on submaximal ergometer cycling and level walking, are interchangeable for estimating mean V̇O2 levels between 25-85% of HRR. Essentially, the same applies when adding maximal exercise in the HR-V̇O2 relationships. The inter-individual V̇O2 variation between ergometer cycling and treadmill exercise is reduced when using the HR method based on both submaximal and maximal workloads.FAA