## 2 Materials and Methods
### Testing Procedures
#### 2.3.3 Cervical Range of Motion--Cervical Strength  
Testing Position  
Both cervical ROM and strength were assessed from a standardized sitting position to minimize errors and movement compensation. In the present study, we placed special emphasis on the selection of the proper chair used for the ROM and strength measurements. More specifically, the chair should meet the following criteria: (a) it should be stable without wheels and armsets, (b) it should have a back for better lumbar spine support (not a softback), and (c) it should be a height-adjusted chair depending on the height of the participants (feet flat on the floor, with knee angle approximately 90\({}^{\circ}\)). During the measurements, the participants were positioned in a sitting position with their backs straight and stabilized with Velcro straps in the back of the chair, their hands on the thighs of their legs, and their feet flat on the floor (Figure 1). At the beginning of every trial, the participant started from a fixed point with his/her head in the neutral position. Range of Motion Measurement  
Cervical ROM was assessed in 4 directions: (a) extension, (b) forward flexion, (c) lateral flexion (right and left), and (d) rotation (right and left) using an electronic goniometer (K-force Sens, Kinvent, France) and the values demonstrated in degrees (Figure 2). A pre  
Figure 1: Setup of the participant during the cervical ROM and strength measurements. vious study [55] reported very good reliability and validity for the measurement of wrist range of motion in young healthy adults (21-27 years old) using the electronic goniometer (K-force Sens, Kinvent, Seattle, WA, USA). Furthermore, in our study we found high intrasession reliability (reliability among trials in the same testing occasion) for the measurement of cervical range of motion using the electronic goniometer (K-force Sens, Kinvent). In the total sample, we found high reliability in cervical forward flexion (ICC = 0.987; 95% CI: 0.911-0.995; SEM% = 1.94), extension (ICC = 0.991; 95% CI: 0.952-0.997; SEM% = 1.66), lateral flexion (ICC = 0.987; 95% CI: 0.906-0.996; SEM% = 2.28 for the right side and ICC = 0.988; 95% CI: 0.924-0.996; SEM% = 1.95 for the left side), and rotation (ICC = 0.989; 95% CI: 0.929-0.996; SEM% = 1.20 for the right side and ICC = 0.985; 95% CI: 0.865-0.995; SEM% = 1.25 for the left side). In the present study, the examiner placed and stabilized the electronic goniometer with a Velcro strap at the center of the participant's forehead. For each direction of movement, the participant performed 3 maximal trials with 20 s rest between each trial and 1 min rest between each direction of movement, and the best score (at each direction) was considered for analysis. Maximal isometric cervical strength was assessed in three directions: (a) forward flexion, (b) extension, and (c) lateral flexion (right and left) using a handheld dynamometer (K-Force Dynamometer, Kinvent, France) (Figure 3). A previous study [56] demonstrated that the Kinvent k-force handheld dynamometer has good to excellent intra- and inter-rater reliability for almost all the upper (shoulder, elbow, wrist) and lower (hip, knee) limb movements assessed in young males and females (18-30 years old), except for ankle dorsiflexion, where the reliability was moderate in all assessments. Furthermore, [PERSON] et al. [57] also found that the Kinvent k-force handheld dynamometer is reliable and valid for strength and torque measurement during the athletic shoulder test. During the measurements, the investigator placed the handheld dynamometer in the appropriate position, and then he held resistance with both hands (to the participant's strength) so that the head and neck remained in the neutral position. In more detail, the handheld  
Figure 2: Cervical range of motion measurements: (**A**) extension, (**B**) forward flexion, (**C**) lateral flexion, and (**D**) rotation.