We have known that aging causes higher morbidity rate of chronic diseases including diabetes mellitus or cardiovascular disease and aging-related problems such as decreased fitness level and function [1], [2], [3]. There also are clear evidence available that maintaining higher health-related fitness level on midlife is associated with a lower risk of later-life mortality and morbidity of chronic diseases including cardiovascular disease and coronary artery disease, and a higher health-related quality of life [4], [5], [6]. The health-related components of physical fitness are classified as muscular strength and endurance, cardiorespiratory fitness, body composition and flexibility by American College of Sports Medicine (ACSM) [7].

The National Fitness 100 is a standardized typical physical fitness test in Korea. The National Fitness 100 provides different testing methods to measure fitness levels depending on each age range (youth, adolescents, adults, and elders). Both health-related physical fitness components and skill-related fitness components are measured, and the awards are divided into 3 grades depending on the percentage of testing results to evaluate the comprehensive physical fitness level of each participant.

Although the National Fitness 100 provides physical fitness grades, the range between each grade is still too wide to accurately assess individuals’ physical fitness level. In addition, exercise testing normative data are presented in ACSM textbook to evaluate physical fitness levels by age range [8]. However, for individuals who are unfamiliar with exercise evaluation and prescription, it may be challenging to analyze comprehensive results of physical fitness tests.

Physical Fitness Age (PFA) is an estimated age that combines the results of fitness test variables and converts them into a specific age, which is considered to be a standardized indicator of the health status [9], [10]. Previous studies from other countries have been developing estimated equations of PFA using the comparison data between physical fitness test scores and the chronological age [9], [11], [12].

Since physical fitness varies by each country or race, different kinds of PFA models need to be developed. However, there is currently a lack of studies on estimated physical fitness age conducted for Korean populations. Also, the sample sizes of most previous studies from in and outside of countries were too small to generalize the whole population. Therefore, it is necessary to develop a standard criterion that can represent the Korean population using physical fitness data measured from National Fitness 100.

Therefore, the purpose of the study was to develop an estimated model of physical fitness age to standardize the fitness level of an individual using health-related physical fitness data of the representative population aged 40 and 64 years from the National Fitness 100 in Korea.