Abstract
This study was undertaken to compare and re-examine the relation of lactate threshold (LT) and ventilatory threshold (VT), using six objective determination methods proposed previously. Twenty-one young male subjects performed a cycle exercise test in which the work rate was increased by 150kg•m every 2min up to his limit of volitional fatigue. Through each test, gas exchange parameter measurements were made every 1min (every 30s at nearly maximal level), and the venous blood samples were taken from a warmed ear lobe at each work rate for determining blood lactate concentration. LT and its variance were determined by the intersecting straight lines regression. LT ranged from 0.72 to 1.40l/min in terms of VO2, and the mean value of S.D. for each LT was about 0.1l/min. Each objective method for determining VT used in this study was based on the simple modelling of the criterion for visual detection of VT, that is the non-linear increase in VE or the systematic increase in VE/VO2. When the relationship between LT and VT was examined, VT by the objective methods based on determining minimum value of VE/VO2 showed relatively high consistency with LT. Of 16-20 individuals out of all 21 subjects, there were VT within LT±0.2 in VO2. It is concluded that VE/VO2 is a more sensitive index for detecting VT than VE in the gas exchange parameters, and the objective VT determination method based on minimum value of VE/VO2 could facilitate estimation of LT within an error of±0.2l/min VO2 in most normal individuals.
