Introduction

China became an “aging society” in 2000 and its elderly population has been increasing rapidly on the road to a “super aging society”. As a primary task of public health care system, The National Physical Fitness Surveillance, practically among elderly population plays a critical role in improving the citizen life quality (Dai 2011). Both overweight and underweight are regarded as dangerous factors threatening human health for developing countries (Villamor et al. 2006). Deficits in physical fitness potentially impairs life quality, shortens life span and cause various clinical disease such as coronary heart disease, cardiopathy disease and diabetes (Krzysztoszek 2015). There is debates about association between regional economic level and physical fitness condition of local people. Some studies (General Administration of Sport of China2014) show that the physical fitness of adult in economically developed region are superior to those in less developed region. Among them, Jiang et al. (Jiang et al. 2004) reported that the physical fitness in Jiangsu province which was regarded as developed economy regions are obviously superior to that in less developed regions, while the difference of physical fitness between the developed economy areas and less developed areas are not obvious in Jiangsu province. That’s indicated the physical fitness level and economic and social development is not coordinated in the similar level of economic development regions. Studies such as Fan et al. (Fan et al. 2012; Okafor et al. 2014;) have shown that the higher the standard of living, the more likely to suffer from chronic diseases which caused by over nutrition and exercise too little. Jiang (Jiang et al. 1998) have suggested to institute a regional evaluation standards, integrating the national physical fitness into the social development evaluation index that the purpose is arouse people’s attention to exercise.

The concept of “Health Industry” was initially defined by the Massachusetts General Hospital (Cobb 2010). Subsequently, based on Pareto theory (Pareto 1971; Liu et al. 2014), Liu et al. (Liu et al. 2013; Liu 2013) reported that the healthy function of human body constituted Pareto network and divided body function as necessary function, key-unnecessary function and normal-unnecessary function. Moreover, they strictly defined the concept of Health, Sub-health and Disease based on the Arndt-Schulz Principle (Martius 1923). The aim of health industry (Cobb 2010) is to reconstruct sub-health/disease and eventually improve health, which is consistent with the notion of “Pre-disease treatment” in Chinese medicine. Today, the knowledge of health management is also an essential element in health industry (Cobb 2010), which requires researchers to effectively estimate human body function for both healthy and sub-healthy population.

P-value method has been commonly used for data statistics in analyzing results of The National Physical Fitness Surveillance (Dai 2011; Krzysztoszek 2015; Jiang et al. 2004; Jiang et al. 1998; Liu 2011; Li 2011). However, statistical significance is not the same as biological importance (Whitlook 2015). Compared with this traditional statistical method, Liu et al. (2017) proposed the concept of Quantitative difference (QD) which is calculated as the absolute value of golden logarithmic of the ratio between intergroup averages. For genomics and protein omics, the biological importance has been assessed with the well-known expression thresholds, 1.5-fold and 2.0-fold. In order to extend the ratio threshold, Liu et al. have introduced the QD, $1=|\log \tau (\overline{x}/\overline{y})|(\tau =\sqrt{5}-1)/2\approx 0.618$M3 \documentclass[10pt]{article} \usepackage{wasysym} \usepackage[substack]{amsmath} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage[mathscr]{eucal} \usepackage{mathrsfs} \usepackage{pmc} \usepackage[Euler]{upgreek} \pagestyle{empty} \oddsidemargin -1.0in \begin{document} \[ 1 = |\log \tau (\bar{x}/\bar{y})|(\tau = \sqrt{5} - 1)/2 \approx 0.618 \] \end{document} . This advanced method solved the limitation of traditional method uncapable of addressing biological differences (Liu et al. 2016). This study used QD method to estimate the effects of progressive economic level on physical fitness condition among elderly population based on the annul data collected in the event of The National Physical Fitness Surveillance in 2014.

Methods

13 cities recruited in The National Physical Fitness Surveillance in Hebei province in 2104 were classified as capital city, high city, and general city according to the development of economy:

• Capital City (CC) – polity and culture center with developed economy – Shijiazhuang;
• High Level (HL) – economy developed – Tangshan, Qinhuangdao, Handan, Baoding, Cangzhou, Langfang;
• General Level (GL) – economy less developed – Xingtai, Zhangjiakou, Chengde, Hengshui, Dingzhou, Xinji.

Information of sample size are listed in Table 1.

QD is defined as the absolute value of golden logarithmic of the ratio between intergroup averages (Liu et al. 2016). It was found that there is QD thresholds (α, β) so that it is significant if α ≤ l < β and extraordinarily significant if l ≥ β. The QD thresholds (α, β) at the level of body, the level of organs or tissue and the level of cells, molecules or central nervous systems are (0.27, 0.47), (0.47, 0.80), (0.80, 1.22). According to the properties of testing indexes and the functional coverage, the indexes were classified as:

1. QD threshold at body level (Liu et al. 2016; Lin et al. 2014) is (0.27, 0.47): height, weight, body mass index, BMI, sit and reach (SR), grip strength (GS), single-leg standing while eyes closed (SSEC);
2. QD threshold at organic or tissues level (Liu et al. 2016; Lin et al. 2014) is (0.47, 0.80):
   1. Anthropometry: Chest circumference, waist circumference, hip circumference, skinfold thickness of upper arm (STUA), skinfold thickness of scapula (STSC), skinfold thickness of abdomen (STAB);
   2. Cardiovascular function: Heart rate (HR), systolic pressure (SP), diastolic pressure (DP);
   3. Lung function: Vital capacity (VC).
3. QD threshold at cellular/molecular level (Phycology-neuro function) (Liu et al. 2016; Sun et al. 2007; Chen et al. 2004; Page et al. 1999) is (0.80, 1.22): Choice reaction time (CRT).

This study has been approved by the Human Ethics Committee of Sports Scientific Research Institute of Hebei Province.

Results

Table 2 displays the overall physical function and QD threshold at body level of male participants. The male participant from CC and GL showed consistent balance ability, which was very significantly lower than the ability of male participants from HL. Although those from CC and HL showed difference in grip strength, it failed to reach significance level. As to sit and reach, GL has insignificant and significant difference compared with HL and CC, respectively. There was no difference in height, weight and BMI between cities.

Table 3 displays the overall physical function and QD threshold at body level of female participants. The balance ability of female participants is comparable with that of male participants. Significance level are more obvious between CC and HL than between CC and GL. Difference in SSEC between HL and GL is not significant. Similarly, there is no significant difference in SR between CC and GL as well as HL and GL. The female participants also showed difference in GS between CC and GL but without significance. Other indexes exhibited to be equivalent.

It can be seen from Table 4 that the anthropometry, cardiovascular function, and lung function of male participants are equivalent. The STUA and STSC of this group showed to be highest in HL, followed by GL and lowest in CC. The STAB showed to be highest in HL, followed by CC and lowest in GL. Sebum content of male participants from HL is at the highest level compared to participants from the other two cities.

It can be seen from Table 5 that anthropometry and cardiovascular function of female participants are equivalent. As to the lung function. The index of vital capacity exhibited significant difference between CC and HL. The STUA, STSC, and STAB of this group showed consistent order as: highest in CC, followed by HL and lowest in GL. Sebum content of female participants from HL is at the highest level compared to participants from the other two cities.

As shown in Tables 6 and 7, there was no difference in CFT between different cities among both male and female participants. The index level showed same order as: highest in CC, followed by GL, and lowest in HL.

Discussion

Statistical analysis showed that the indexes of anthropometry and grip strength at body level, cardiovascular function at organic tissues level, and choice reaction time at cellular/molecular level were comparable without significance between cities with different economic development degrees. The BMI for both male and female exceeded normal standard, suggesting overweight trend among the elderly population in Hebei Province.

The effect of economic level is not significant on the ability of sit and reach. For both male and female from capital city, the performance in single-leg standing while eyes closed showed worst, indicating that the government of this city should take instructive actions to encourage the residents to participate in physical actives that aims to improve balance ability. The combined outcomes of the thickness of subcutaneous fat with the index of BMI indicates that elderly male from high level city and female from capital city should increase the intense and frequency of participating in physical actives to prevent various diseased due to high body fat percent. BMI is a reliable index reflecting body substantial (Wang et al. 2006), therefore, it is highly associated with obesity. Normally, BMI less than 18.5 is regarded as thin level, among 18.5–23.9 is regarded as healthy level, higher than 24 is regarded as overweight, and higher than 28 is regarded as obesity (Ministry of health of China 2009). Previous studies have evidenced that higher level of BMI may cause various chronic disease and is very likely to increasing the risk of cancer (Følling et al. 2014; Taghizadeh et al. 2015). Furthermore, the data also showed a higher BMI in elderly female than in male population, modestly, it can be speculated that the prevalence risk of cardiovascular disease such as hypertension, hyperlipidemia, diabetes, and coronary heart disease is higher among female population.

In general, there were no obvious differences in the indexes extracted from The National Physical Fitness Surveillance in Hebei province in 2014, which implies that the regional economic development is not a sensitive factor affecting physical fitness of elderly population. This means that the economic level failed to induce stress for elderly population in terms of the public physical health condition. According to the Arndt-Schulz law (Martius, 1923), with the amplified signal, the biological function increased gradually, and when it reaches to the peak, the plateau would arise, then decreased gradually. Moreover, the stable function during plateau is able to resistant the amplified signal, which demonstrates the existence of negative feedback mechanism in order to maintain function stability. The latter is called function-specific homeostasis, FSH (Liu et al. 2013). A function in and far from its FSH is called a “normal/dysfunctional function”. In this study, the relationship between regional economic level and physical fitness condition could be expounded as that the simulation of improvement of economic level on the elderly health remains plateau.

The indexes collected from physical fitness testing directly explains the human health condition. As documented, anthropometry and fitness has been classified as normal-unnecessary function, while body function has been classified as key-unnecessary function (Liu et al. 2013). There was no significant difference in anthropometry between three regions, and QD presented uniform features at body function level and organic tissues level. This consistency demonstrated that it is anastomotic for the definition of the three levels of threshold in studies concerning human health function. However, the percentage of antilog of the threshold with regard to 0.27, 0.47, 0.80, and 1.22 is 88%, 80%, 68%, 55.6%, respectively. It is clear that although the definition of threshold interval is sufficiently wide in the application of health-related research. For studies with different purpose, higher or lower order of magnitudes of threshold can be discussed.

There are limitations of this study. First, with data collected in one year, it is difficult to infer the trend of physical fitness condition of the population for a certain period. Liu et al. (Liu et al., 2013) analyzed data of physical examination collected repeatedly and calculated variation coefficient of health indexes to deduce the health condition of subjects. In order to make a further step for estimating the variation of physical fitness condition of elderly people during years, data collected in The National Physical Fitness Surveillance after the year of 2014 should also be analyzed. Second, this study only detected QD for average values, however, evaluation of QD for ratios of index level may contribute to expounding the boundary of health and sub-health as supplement, which is another worthy direction of further study.

Conclusions

For both male and female population, single-leg standing while eye closed exhibited favorable consequence among people from high level cities, indicating that attentions for improving balance ability of elderly people from general cities and capital city should be paid. The elderly female from capital city showed worst performance in vital capacity, suggesting that aerobic exercises may be targeted for them to improve the lung function. Regardless of gender, the elderly population presented consistent outcome of thickness of subcutaneous fat and choice reaction time, indicating similar status of phycology-neuro function. Although insignificant, the male elderly from high level cities and the female elderly from capital city should take more physical activities due to thicker subcutaneous fat.