Association between the Ventilatory Treshold and the Break-point in the Heart Rate/Work Rate Relationship: Comparison with the Break-point in the Double Product/Work Rate

Abstract

The aim of this study was to assess the usefulness of the break-point in the heart rate/work rate relationship (HRBP). Ninety-seven middle-aged and elderly people performed a ramp-fashion incremental exercise test on a cycle ergometer. Breath-by breath O2 consumption and CO2 production data and beat-to-beat systolic blood pressure and heart rate data were obtained during the test, and work rate and heart rate corresponding to ventilatory threshold (VT), double product break point (DPBP), and HRBP were obtained by a linear regression analysis. Work rate and heart rate at HRBP correlated significantly with the corresponding values at VT (r=0.773, r=0.858, both P<0.0001), as work rate and heart rate at DPBP did (r=0.873, r=0.905, both P<0.0001). Work rate at DPBP and HRBP (60±13 and 61±13 watts) did not significantly differ from work rate at VT (61±13 watts), whereas heart rates at DPBP and HRBP (105±14 and 106±13 bpm) were significantly lower than that at VT (108±14 bpm, P<0.05). However, there was no significant difference in error from heart rate at VT between heart rate at DPBP and heart rate at HRBP. These results suggest that, in middle-aged and elderly people, HRBP could be determined as a nearly consistent point with DPBP, and might be a useful marker of VT.