**3. Materials and methods**

#### **3.1. Subjects**

A convenience sample of 100 TU students were recruited for this study (n = 59 females and 41 males). Their ages ranged from 18 to 40 years old. Subjects were excluded if they had any lower limb or back injury that prevented the subject standing for the duration of data collec‐ tion, any vestibular problems that prevented the subject maintaining normal balance for the duration of data collection or a known allergy to self‐adhesive stickers when in contact with the skin. Ethical approval was granted by Teesside University School of Health and Social Care ethics committee.

#### **3.2. Instrumentation**

The Middlesbrough Integrated Digital Assessment System (MIDAS) (**Figure 1**) is a tool for acquiring a static 3‐D computer recording of a physical object. A counterbalanced mechanical arm has optical sensors in each joint for X, Y, Z coordinate awareness with a mean accuracy of 0.23 mm. A footplate was created with marks to standardize foot position and a chart was placed on the wall in front of the subject with markers to focus on [11–13].

Through assessment with an anatomical mannequin this system demonstrated very high intra‐rater reliability (ICC > 0.999, p < 0.0001) [12], with a sample of 50 human subjects (r = 0.92–0.99, p < 0.001). Further intra and inter rater reliability were also found excellent when evaluated by McAlpine et al. [14]. Additionally previous work has found improvements Limits of Normality and Symmetry in Standing Back Shape and Posture: 3D Mapping and Analysis of Young Adults http://dx.doi.org/10.5772/intechopen.69575 7

**Figure 1.** The microscribe digitizer in resting position.

in repeat measurements with foot and vision standardization [10]. The MIDAS was placed on an adjustable tripod for positioning and connected via a serial port to a laptop PC for data storage. A set of scales and a stadiometer were used to obtain weight and height measure‐ ments of subjects.
