# The Impact of Technical Error of Measurement on Somatotype Categorization
## 1 Introduction  
Variation in biological or mechanical (equipment) factors can result in measurement error in experimental environments [1; 2]. The true value of any measurement will be one that is free of measurement error [2]. In reality, continuous measurements will always include some magnitude of error [1] but the key is to try to minimize this error in order to identify actual differences or changes in performance.  
Anthropometry is susceptible to measurement error due to variations in technique, equipment issues and human error [3]. It is important to try to minimize this error to ensure measurements are as reliable and accurate as possible. The International Society for the Advancement of Kinanthropometry (ISAK) have provided standardized techniques for the measurement of anthropometric variables [4]. The provision of standardized protocols with exactly defined landmarks to determine a measurement, and the associated training provided by ISAK can help to decrease the imprecision and inconsistency that accompanies measurement by individuals with poor technique [5; 6]. Reliability is often assessed using the intra-tester technical error of measurement (TEM) [7; 8], which determines the magnitude of the difference between repeated measures on the same participant by the same measure. Calculation of the TEM for any anthropometric dimension will allow further computation of confidence intervals around the actual value [8]. This will help to assess how accurately the sample mean reflects the mean in the population, giving boundariesaround which the true value should fall [9]. The calculation of TEM is also considered to represent absolute reliability within the sample population and therefore preferential to measures of relative reliability such as intra-class correlation coefficients (ICC) [10].  
Somatotype is a numerical representation of physique, quantifying the morphology and characteristics of the human body [11]. Somatotypes are commonly reported in terms of their dominant components, with 13 categories providing detailed grouping [12]. However, it is also possible to simplify these 13 categories into four simple groups, each representing the dominance of endomorphy (relative adiposity), mesomorphy (musculo-skeletal robustness), or ectomorphy (linearity), or central (no dominance) [13]. Many studies have identified that somatotype components are highly related to performance in certain sports including combat sports [14; 15], rowing [16], basketball [17], volleyball [18] and endurance and ultra-endurance events including Ironman [19]. It has also been established that the task-specific nature of sports such as soccer, basketball and volleyball require discrete positional somatotypes with detailed grouping [17; 18; 20]. Somatotype has also been linked to functional capacity [21; 22; 23]. Given the propensity for researchers to assign populations to somatotype groups, establishing the reliability of this grouping is important to confirm the observations made. Despite the need for reliability in anthropometric measures, authors rarely report measurement errors in human populations [24] particularly in somatotype research [25; 26; 27; 28; 29; 30; 31]. No other study has outlined the impact of error on somatotype categorization. Measurement error needs serious consideration if statistical methods are to remain uncompromised and grouping of individuals is to remain correct [32]. This study aims to demonstrate the influence of intra-tester technical error of measurement (TEM) on somatotype categorization in a large population of participants with different somatotypes. The objective is to give researchers confidence in their categorization of participants.