1. Foster, Carl PhD

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The exercise prescription is often written in terms of the relative intensity of exercise defined by %HRmax. However, many physiologists believe that an exercise intensity near the ventilatory threshold (VT) may be a more nearly optimal exercise training intensity. Various authorities have suggested that VT can be conveniently defined in terms of 80 %HRmax, although documentation of the closeness of this relationship is lacking.



This study was designed to evaluate how accurately a fixed %HRmax defined HR @ VT.



Healthy volunteers (age 18-44) (n = 22) (VO2max = 50 +/- 8 ml/kg) performed maximal treadmill exercise with gas exchange to define HRmax and HR @ VT. The %HRmax @ VT was compared to test the hypothesis that 80%HRmax could define VT.



VT was observed at a VO2 of 2.90 +/- 0.69 (66% VO2max). HR @ VT was 82 +/- 5 %HRmax, near the hypothesized value. However, the correlation between HR @ 80%HRmax and HR @ VT was not strong (r = 0.64) and the range of %HRmax @ VT (71-89 %) was quite wide.



We conclude that although 80% HRmax is a good average approximation of the intensity of VT, the relationship is not close enough for routine use in exercise prescription.