Maximal oxygen uptake (VO₂max) is an important determinant of health-related physical fitness. In 2006, the Japan Ministry of Health, Labour and Welfare (JMHLW) officially declared a standard reference value and reference interval of VO₂max. However, these values were established on the basis of a systematic review of reports published in Western countries and were not based on actual VO₂max data of the Japanese population. Therefore, we conducted a study entitled “The study on a minimum zone of VO₂max as one of the determinants of health-related physical fitness in Japan” from 2004 to 2006 as a project of the Japanese Society of Physical Fitness and Sports Medicine (JSPFSM). In addition, we collected published VO₂max data of the Japanese population from the JSPEFM website. In the present study, we attempted to determine the reference interval of VO₂max with regard to age, gender, and different methods of exercise. Further, we established a cut-off value of VO₂max for determining metabolic syndrome (MS).
1. Reference interval of VO₂max
For both men and women, 325 and 364 values for the treadmill exercise, and 1175 and 2178 values for the cycle ergometer exercise, respectively, were collected. This data revealed a balanced distribution of VO₂max with regard to age. Data that satisfied the VO₂max criterion were used for the analysis. These data were regressed to age on gender and methods of exercise. The percentage of VO₂max was calculated using the following equation: %VO₂max = measured VO₂max × 100/age-estimated VO₂max. The iterative truncation method was used to calculate the reference interval of VO₂max (70%∼130% VO₂max) from the crude data of %VO₂max, and then converted to actual VO₂max. Thus, the reference interval of VO₂max for healthy Japanese was determined with regard to age, gender, and different methods of exercise.
2. Cut-off value of VO₂max for determining MS
Using the VO₂max data of subjects with body mass index (BMI) of ≧25kg/m² and ≧2 MS risk factors, and the data of subjects with normal BMI without any risk factors, we calculated sensitivity and specificity. The cut-off value was determined using the receiver operating characteristic curve. This cut-off value was defined as the critical value of VO₂max that should be maintained to avoid MS and remain healthy.