Relationship between Tibia Length Measurements and Standing Height: A Prospective Regional Study among Adolescents in Southern Region of Kosovo

The purpose of this research is to examine standing height in both Kosovan genders in the Southern Region as well as its association with tibia length, as an alternative to estimating standing height. A total of 225 individuals (120 male and 105 female) participated in this research. The anthropometric measurements were taken according to the protocol of ISAK. The relationships between body height and tibia length were determined using simple correlation coeffi cients at a ninety-fi ve percent confi dence interval. A comparison of means of standing height and tibia length between genders was performed using a t-test. After that a linear regression analysis were carried out to examine extent to which tibia length can reliably predict standing height. Results displayed that Southern Kosovan male are 178.60±5.73 cm tall and have a tibia length of 39.93±2.34 cm, while Southern Kosovan female are 165.33±4.45 cm tall and have a tibia length of 35.50±2.07 cm. The results have shown that both genders made Southern-Kosovans a tall group, but shorter than general Kosovan population. Moreover, the tibia length reliably predicts standing height in both genders; but, not reliably enough as arm span. This study also confi rms the necessity for developing separate height models for each region in Kosovo as the results from Southern-Kosovans don’t correspond to the general values.


Introduction
According to Komunat e Kosovës (2013), Kosovo is a democratic, multi-ethnic and secular republic which administratively is subdivided into seven districts (Ferizaj, Gjakova, Gjilan, Mitrovica, Peja, Pristina and Prizren) and fi ve regions (Eastern, Western, Northern, Southern and Central). Th is study analyzes the standing height and its estimation utilizing tibia length measurements in adolescents in southern region which contains fi ve municipalities (Dragas, Malisheva, Mamusha, Prizren and Suva Reka/Suharekë). Th is region ( Figure 1) covers the area of 1,397 square kilometers and has population of 331,670 inhabitants, while average density per square kilometer is 240 inhabitants (Komunat e Kosovës, 2013). Although Kosovo doesn't have too big territory, it has a very varied relief that mostly belongs to Dinarides range and the author assumed this fact might infl uence the main objective of this study, because of the type of the soil as well as other socio-economical and geographical characteristics as a potential infl uencing factors (Arifi , 2017;Arifi , Sermaxhaj, Zejnullahu-Raçi, Alaj, & Metaj, 2017b). Th ere are lots of scientifi c fi ndings which confi rms that the measurement of standing height is a vitally important variable when assessing nutritional status (cited in Arifi et al., 2017a;Datta Banik, 2011;, as well as when assessing the growth of children, evaluating the basic energy requirements, adjusting the measures of physical capacity and predicting the drug dosage and setting standards of physiological variables such as muscle strength, metabolic rate, lung volumes and glomerular fi ltration (Golshan, Amra, & Hoghogi, 2003;M. Golshan, Crapo, Amra, Jensen, & R. Golshan, 2007;Mohanty, Babu, & Nair, 2001;Ter Goon, Toriola, Musa, & Akusu, 2011). However, according to Quanjer and his collaborators (2014), the exact standing height cannot always be identifi ed and resolved in the usual way (e.g. paralysis, fractures, amputation, scoliosis and pain). Because of these factors, an estimate of standing height has to be acquired from other reliable anthropometric indicators such as hand and tibia lengths, foot lengths, knee height, length of the forearm, length of the sternum, vertebral column length, sitting height, length of scapula, arm span as well as cranial sutures, skull, facial measurements et cetera (cited in Gardasevic, Rasidagic, Krivokapic, Corluka, & Bjelica, 2017;Popovic, 2017;Popovic, Gardasevic, Masanovic, Arifi , & Bjelica, 2017;Masanovic, Gardasevic, & Arifi , 2018a;Masanovic, Gardasevic, & Arifi , 2018b). Th erefore, all these anthropometric indicators, which are used as an alternative to estimate standing height, are very important in predicting loss in standing height connected with aging. Also, to diagnose individuals with disproportionate growth abnormalities and skeletal dysplasia or standing height loss during surgical procedures on the spine (Mohanty et al., 2001), as well as to anticipate standing height in many older people as it is very diffi cult to measure it precisely, and sometimes impossible because of mobility problems and kyphosis (Hickson & Frost, 2003). Lastly, it is important to state that this knowledge fi nds its importance in sport science the standing height represents a signifi cant factor which infl uences the success in various sport disciplines (Popovic, 2017).
Several researches have reported the benefi t of using various body parameters in predicting standing height, and arm span happened to be one of the most reliable ones in adults (Hickson & Frost, 2003;Jalzem & Gledhill, 1993;Mohanty et al., 2001;Ter Goon et al., 2011), while some authors (Singh, Kumar, Chavali, & Harish, 2012) believe that foot length measurement is the most reliable predictor during adolescent age, due to the fact that ossifi cation and maturation occurs earlier in the foot than the long bones and standing height could be more accurately predicted from foot measurement as compared to long bones during adolescent age. In addition, the relationship of long bones and standing height was found to vary in diff erent ethnic and racial groups (Bjelica, Popovic, Kezunovic, Petkovic, Jurak, & Grasgruber, 2012;Brown, Feng, & Knapp, 2002;Popovic, Bjelica, Georgiev, Krivokapic, & Milasinovic, 2016;Popovic, Bjelica, Molnar, Jaksic, & Akpinar, 2013;Popovic, Bjelica, Tanase, & Milasinovic, 2015;Reeves, Varakamin, & Henry, 1996;Steele & Chenier, 1990) as well as various regions (Arifi , 2017;Arifi et al., 2017b;Milasinovic, Popovic, Matic, Gardasevic, & Bjelica, 2016;Milasinovic, Popovic, Jaksic, Vasiljevic, & Bjelica, 2016;Masanovic, Gardasevic, & Arifi , 2018c;Masanovic, Gardasevic, & Arifi , 2018d). Hence, researchers have derived a specifi c formula for calculating standing height from long bones for each ethnic/race group. Th e mentioned variations might be the case with tibia length predictions too, mostly due to the fact that the Dinaric Alps population has specifi c body composition than national as well as regional point of view (Popovic, 2017). Even though many studies with this essence are available on neighboring countries as well as worldwide population, only narrow data is available on Kosovan subjects, just one conducted by , and  that has covered whole Kosovan population, and one regional analyses that confi rmed Western-Kosovans have specifi c standing height/foot length ratio, comparing to general population in Kosovo . Considering rather sparse recent scientifi c literature, the purpose of this research was to examine the standing height in both Eastern-Kosovan genders and its association with tibia length.

Methods
Th e nature of this research gave extension to the 225 highschool students last year (120 male and 105 female) from Southern Region of Kosovo to be subjects. Two reasons which qualifi ed the selected individuals are: the fi rst is related to the fact that the growth of an individual ceases by this age, while the second is related to the fact that there is no age-related loss in standing height at this age. Th e average age of the male subject was 18.40±0.56 years old (range 18-20 years), while the average age of the female subject was 18.36±0.50 years old (range 18-20 years). It is important to underline that the researchers have excluded from the data analysis of the individuals with physical deformities as well as those without informed consent. Th e exclusion criterion was also being non-Southern Kosovan.
Th e anthropometric measurements, including standing height and tibia length, were taken according to the protocol of the International Society for the Advancement of Kinanthropometry (Marfell-Jones, Olds, Stew, & Carter, 2006). Th e trained measurers have measured selected anthropometric indicators (same measurer for each indicator), while the quality of their performance was evaluated against the prescribed "ISAK Manual". Lastly, the age of the each subject was reached directly from the birthdays.
Th e analysis were performed by using the Statistical Package for Social Sciences (SPSS) version 20.0. Means and standard deviations (SD) were obtained for both anthropometric variables. A comparison of means of standing height and tibia length between genders was performed using a t-test. Th e relationships between standing height and tibia length were determined using simple correlation coeffi cients at ninety-fi ve percent confi dence interval. Th en a linear regression analysis were carried out to examine the extent to which the tibia length can reliably predict standing height. Statistical signifi cance was set at p<0.05.

Results
A summary of the anthropometric measurements in both genders is shown in Table 1. Th e mean of the standing height for male was 178.60±5.73 centimeters and tibia length was 39.93±2.34 centimeters, while for female the standing height was 165.33±4.45 centimeters and tibia length was 35.50±2.07 centimeters. Th e sex diff erence between standing height and tibia length measurements was statistically signifi cant (standing height: t=19.183; p<.000. and tibia length: t=14.927; p<.000).

Figure 2. Scatter Diagram and Relationship between Tibia Length Measurements and Standing Height among Both Genders
In Table 2, the simple correlation coeffi cients and their ninety-fi ve percent confi dence interval analysis between the anthropometric measurements are displayed. Th e associations between standing height and tibia length were signifi cant (p<0.000) and high in this sample, regardless of gender (male: 0.734; female: 0.639).
Th e results of the linear regression analysis are shown in Table 3. Th e fi rst of all models were extracted by including age as a covariate. However, it was found that the contribution of age was insignifi cant and therefore the age was dropped and estimations were derived as a univariate analysis. Th e high val-ues of the regression coeffi cient (male: 0.734; female: 0.639) signify that tibia length notably predicts standing height in both Southern-Kosovan genders (male: t=11.740, p<0.000; female: t=8.432, p<0.000), which confi rms the R-square (%) for the male (53.9) as well as for the female (40.8).
Th e associations between tibia length measurements and standing height among the above models is sketched as a scat-ter diagrams (Figure 2).

Discussion
Th e assessment of standing height using various anthropometric measures is very typical from the past centuries and it has been attempted to be studied by many researchers. However, it is important to underline that the arm span has been obtained as the most reliable body indicator for predicting the standing height of an individual (Mohanty et al., 2001;Ter Goon et al., 2011), while tibia length is was very close (Khatun, Sharma, Jain, & Gupta, 2016;A. Kaore, B.P. Kaore, Kamdi, S. Kaore, 2012;Agnihotri, Smita, Jowaheer, & Pratap, 2009). In parallel, it is important to emphasize that the individual and ethnic variations referring to standing height and its association with tibia length might vary from ethnic group to ethnic group as well as race to race, because the racial and ethnic diff erences are aff ective on these measures and reduce the possibility of generalizing (cited in Bjelica et al., 2012). Th is fact confi rms the study conducted by authors (Agnihotri et al., 2009) who confi rmed a very high linear correlation between standing height and tibia length in both genders, while the research study conducted by Khatun and her collaborators (2016) shows signifi cant correlation between standing height and tibia length in both genders of Indian population. Th e highest correlation coeffi cient in this population was found for tibia length in males (r=0.67) as well as in females (r=0.58).
All above-mentioned have confi rmed the necessity for developing separate standing height models for each population on account of ethnic diff erences and the recent study conducted by Popovic and his collaborators (Popovic et al., 2017a; who have analyzed the entire Kosovan population and have found specifi c correlation coeffi cient standing height and foot length in Kosovan male (r=0.669) and female (r=0.625) population; however, some recent studies have also confi rmed the regional diff erences between the same ethnic groups too (Arifi , 2017;Arifi et al., 2017b;Popovic et al., 2017b;Milasinovic et al., 2016a;2016b), which caused the need for additional caution, mostly due to the reason one of them was sampled by Western-Kosovans. Th erefore, the main goal of this research was to test the hypothesis if above-mentioned facts are true for the Southern-Kosovans, that is, for the one of fi ve Kosovan regions. As the correlation between tibia length and standing height was signifi cant in both Southern-Kosovan genders, the tibia length measure therefore seems to be a reliable indirect anthropometric indicator for estimating standing height in both genders of Southern-Kosovan population.
Th e results of the study conducted by Popovic and his collaborators (Popovic et al., 2017a;Masanovic, 2017) confi rm the necessity for developing separate standing height models for both genders in Kosovo but the authors of the same study have recommended that further studies should consider dividing the population of this country to regional subsamples and analyze it separately, just to be sure there are no geographical diff erences (such as type of the soil) infl uencing the average standing height in both Kosovan genders as well as its association with tibia length. Th is concern was based on the fact that entire Kosovo doesn't fall into Dinaric Alps racial classifi cation. In parallel, this study confi rms the assumption mentioned above and also confi rms that it is necessary to develop separate standing height models for each population on account of regional variations in Kosovo.
Next to highlighted issue, the obvious constraint of this research might also be the composition of the measured sample that consisted of high school students. Th is limitation is based on the fact there are some studies which assumed the growth of an individual doesn't cease by this age (Grasgruber, P., personal communication, 2016;Jurak, G., personal communication, 2017). Th is assumption might be supported by the fact that university-educated individuals have been founded to be taller than the high school population in Bosnia and Herzegovina (Grasgruber et al., 2017;Gardasevic et al., 2017), Poland (Wronka & Pawlinska-Chmara, 2009) and Hungary (Szollosi, 1998). On the other hand, this wasn't the truth in Montenegro (Popovic, 2016) and comparing the average standing height measures of this study to the results of some study sampled by university students might give the science much precise conclusions. One more obvious limitation of this study is also the fact that both genders of Kosovo did not reach their full genetic potential yet, since various environmental factors controlled their development. Further continuous monitoring is necessary, mostly due to the reason it is expected the secular changes infl uencing standing height will ascend in the following two or three decades.