# Secular Trends of Adult Population and Their Impacts in Industrial Design and Ergonomics
## 4 Discussion  
Secular trends have been documented in many countries since the 19 th century [36; 37; 38; 39; 40]. Height increases were registered in southern Europe [41; 42]. [PERSON] et al. (1997) [43] found secular trends in Europe during the last decades of the 20 th century ranging from 3 mm/decade in Scandinavia to 30 mm/decade in parts of southern and eastern Europe.  
Although height in the Netherlands [44] and Scandinavia appears to be close to a plateau, the increase is likely to continue for some decades to come in southern Europe [45]. The existence of secular trends can be considered a global phenomenon [9; 46; 47; 48]. In this regard, our research complements a number of other studies carried out in the recent past in Slovakia and various neighboring countries. Comparing the results of our research to the results of other research studies is difficult for a variety of reasons, such as the different sample sizes, specific measurement methods, demographic coverage, ethnic mix, or health status of the participants.  
Regarding the Czech population, Reference [46] confirmed an acceleration in the growth of the average body height and weight from 1955 in young men aged 18-25, and this trend has been slowing down since the 1980s. [PERSON] et al. (2006) [49] registered that the average height of 13-year-oldCzech boys has increased by 19.4 cm, and the average height of Czech girls has increased by 18.3 cm since 1895.  
Very interesting results regarding the secular trends in heights, weights, and body mass index (BMI) in young Romanian students aged 18-24 years were reported by [PERSON] et al. (2014) [50]. The authors registered secular growth stagnation for males and females in height accompanied by a significant increase in BMI values in accordance to overall European trends.  
Similar to Slovakia and the Czech Republic, the results of other research from other geographical areas confirm the existence of a secular trend in different parts of the world: the US and North America [51; 52; 53; 54; 55; 56]; northern Europe [57; 58]; south and southeastern Europe [59; 60; 61; 62; 63]; western Europe [22; 43; 44; 64] or Asia [19; 65; 66; 67]. In addition, some globally oriented reviews support the idea of secular growth trends in the height of the human population during the 20 th century [68].  
Although some indications about the contemporary slowdown or stagnation of secular trends in heights (similar to the mentioned Romanian study) were reported for some regions and populations [9; 69; 70; 71], the positive secular trend in central and eastern Europe probably still prevails.  
Several possible explanations of the positive secular trend in Slovakia are possible. First of all, the current generation is affected by the events that have taken place over the last three decades in Slovakia (the fundamental change in political regime, entry of Slovakia to the European Union). The economic prosperity of the population resulting from economic and political changes (the purchasing power more than doubled compared to 1989), the influence, availability, and quality of diet, adherence to healthy lifestyle, or availability of vitamins and medicines all could also have an impact. In addition, the positive change in healthcare greatly impacts such trends.  
[PERSON] et al. (2016) [72] in their worldwide reviews found that the most important factors affecting the heights in human populations is consumption of protein-rich food and the human development index (as the measure of society wealth) which are most strongly associated with tall statures. This issue is also dealt by authors [PERSON] and [PERSON] (2016) [73]. Both factors were increased or improved in Slovakia, especially after the country's entry into EU, due to favorable economic development.  
Moreover, the social status and the achieved education--one of the factors influencing the development of body physical dimensions of the human population--were improved for many families in Slovakia [74].