Olecranon Process

A battery of anthropometric measurements was taken according to standardized procedures. Stature and sitting height were measured without shoes using a Seca 213 portable stadiometer (Hamburg, Germany), with the participant’s head in the Frankfort Plane. Stature was measured with participant fully erect, feet together, and at the end of a deep inhalation, and sitting height was measured while seated on a table with legs hanging freely and arms resting on the thighs [24 ]. Waist circumference was measured at the end of gentle expiration with a non-elastic tape held midway between the lower rib margin and the iliac crest [25 ]. Mid-upper-arm circumference was measured on the right arm using a non-elastic tape held midway between the acromion and olecranon processes, with arm hanging loosely at the side of the body [24 ]. Each measurement was repeated, and the average used for analysis (a third measurement was obtained if the first two measurements were greater than 0.5 cm apart and the average of the two closest measurements was used for analysis).
The participant’s body mass, impedance and percentage body fat were measured using a portable Tanita SC-240 Body Composition Analyzer (Arlington Heights, IL) after all outer clothing, heavy pocket items and shoes and socks were removed. Two measurements were obtained, and the average was used in analysis (a third measurement was obtained if the first two measurements were more than 0.5 kg or 2.0% apart, for body mass and percentage fat, respectively, and the closest two were averaged for analysis). In addition, impedance values were recorded for future analyses. Due to harsh field conditions in some sites, a back-up scale was carried by the assessment team to ensure that body weight was obtained.
The Body Mass Index (BMI; body mass (kg)/height (m²)), waist-to-stature ratio, and sitting height-to-stature ratio were calculated.

Based on the static position sense experiment, the study selected initial and end position from five wrist positions to form a movement mode. Our study chose eight movement modes from 20 combinations (5*4). Eight movement modes are: extension small 1 (ES1), extension small 2 (ES2), extension small 3 (ES3), extension large (EL), flexion small 1 (FS1), flexion small 2 (FS2), flexion small 3 (FS3), and flexion large (FL) (Figure 4). The variables include direction (F or E) and range (S:60° or L:120°). When the prosthetic wrist moved within the perception range of the five positions, the corresponding stimulation channels were active. After the prosthetic wrist moved in the next range of the preestablished positions, the previous channels were inactive. For consistency with the static position sense experiment, the burst duration on each electrode also lasted for 0.5 s. Therefore, the total duration of stimulation of ES1, 2, and 3 and FS1, 2, and 3 was 1.5 s, while that of EL and FL was 2.5 s.
The movement experiment also includes learning and test sessions. During the learning session, the subjects were provided with three kinds of guidance: 1. the movement of the prosthetic wrist, 2. the stimulating channel map, and 3. the dynamic illustrations of wrist FE movements on a 22″ screen. The above guidance helped subjects establish the connection between electrotactile stimulation and wrist movement to achieve a better learning effect. The learning session lasted approximately 15 min. The paradigm of the test session is similar to that of the static position sense experiment. The test session consisted of 32 blocks of random movement modes. To simplify user input, we numbered E60∼F60 as indexes 1∼5. Similarly, the subjects were asked to respond to the perceived movement by a keyboard. They needed to press the first index on the keyboard to represent the initial position, then the cursor was automatically switched to the next dialog box in which the second index represents the end position, and they finally pressed the enter key to submit the answer (Figure 3C). Similarly, we recorded the input and DRTs of the subjects. For consistency of the stimulation electrode position on the forearm in the two experiments, we used multiple reference positions such as the styloid process of ulna, olecranon, etc. In addition, we took photos of each subject’s forearm and marked the position of each electrodes with a color pen that is harmless to the skin.
Subjects’ subjective feelings need to be considered. To evaluate the acceptance of the electrotactile scheme in this study, after each subject completed the movement experiment, we distributed a questionnaire and invited the subjects to use a score from 1 to 5, where 5 represents the highest outcome, to rate the following aspects: 1. degree of pain and numbness, 2. the resolution of each channel, 3. the comfort of electrotactile stimulation, 4. intuitiveness, and 5. ease of learning.

Participants’ height, weight, WC, systolic arterial pressure (SBP) and diastolic arterial pressure (DBP) were measured. Weight and height were measured by well-trained personnel while subjects were in light clothing and barefoot. Participants’ height was measured using a wall-mounted Harpenden Stadiometer Holtain Ltd. Their weight was measured with an electronic scale (SOEHNLE Professional 2755) to the nearest 0.1 kg. WC was measured twice, midway between the lowest border of rib cage and the upper border of iliac crest with the use of inextensible anthropometric tape while the child was standing with their arms at their sides and feet closed together [22 ]. All measurements were taken twice, and the two measurements were averaged for analysis.
SBP and DBP values were the mean of three measurements after a 5-min rest, with a 1-min interval between each measurement, and they were measured with a calibrated G-Care SP-800 sphygmomanometer. A pediatric cuff of proper size was chosen, so that its bladder width was at least 40% of the arm circumference midway between the olecranon and the acromion, and it covered 80 to 100% of the circumference of the arm [25 (link)]. BMI was calculated as weight (in kilograms) divided by height (in meters) squared.