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 150 kg m every 2 min up to his limit of volitional fatigue. Through each test, gas exchange parameter measurements were made every 1 min (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 1.401/min in terms of V02 , and the mean value of S.D. for each LT was about 0.11/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/Voz. When the relationship between LT and VT was examined, VT by the objective methods based on determining minimum value of VE/Voz showed relatively high consistency with LT. Of 16-20 individuals out of all 21 subjects, there were VT within LT + 0.2 in Voz. It is concluded that VE/Voz 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/Voz could facilitate estimation of LT within an error of + 0.2 1/mmn Voz in most normal individuals.

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The construction of dental condition models is one of the useful methods for analysis of epidemiological surveys. The purpose of this investigation was to make a simple model with clear turning points for the longitudinal tooth-loss patterns of Japanese adults by means of multi-plane regression analysis. Since 1957, the Japanese Ministry of Health and Welfare has carried out national surveys of dental conditions every six years. The data of present tooth numbers by age (24-79 years) and sex from these surveys were used for this study. When there are turning points between two variables, intersecting straight lines regression is a valid means. However, a new method was developed so that the data of this study had three variables. The new three-dimensional model by multi-plane regression analysis seemed to fit tooth-loss patterns of Japanese adults within three phases. Younger subjects are represented in the first phase followed by the third phase of elders, where tooth loss was rather slow. However, in the second phase, middle-aged subjects, people lost their teeth rapidly. Thus, prolongation of the first phase could be an important factor to improve overall dental health.

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