## 2 Materials and Methods
### Protocol  
All participants completed a Characterization Sociodemographic and Clinical Questionnaire to identify possible exclusion criteria, which included personal data (2 items), training habits (1 item), and clinical background (9 items). Anthropometric measurements, including height and weight, were recorded to calculate body mass index (BMI). The study was carried out on the dominant upper limb. To identify the dominant upper limb, a test was carried out in which a ball (Kempa(r) Leo) was thrown at the participant, who had to return it using the upper limb [18]. Measurements were collected at baseline (M0) and immediately after the intervention (M1). The ULNT1 was administered to the dominant upper limb of each participant. Participants were positioned supine on a massage table (Posturarte(r) Olympic, Braga, Portugal), with their bodies aligned and the test forearm exposed for smartphone placement via an armband. A smartphone (iPhone 6, iOS 12.4.5, Apple Inc.) was used as a goniometer substitute and was calibrated in the neutral position (0\({}^{\circ}\) elbow extension) before starting the test. The device was secured to the forearm with a strap to ensure stability during measurements, and the Compass application was used to measure elbow extension. The smartphone's built-in motion sensors (tri-axial accelerometer, gyroscope, and magnetometer) allowed for the precise detection and quantification of angular movement. The lightweight design of the smartphone (129 g) minimized any potential influence on elbow range of motion. The use of smartphones as goniometers has been validated in previous studies, demonstrating high reliability and accuracy in measuring joint range of motion [19; 20; 21]. To ensure stability, the head and cervical spine were supported at the maximum comfortable lateral inclination using a foam pillow (LojaPro(r)) [22]. Before the application of the test, the quality of the coupling (e.g., the possibility of sliding the armband during elbow extension or the comfort of the armband) was assessed, ensuring its consistency and feasibility for carrying out the test. All participants were submitted to a previous application of the ULNT1 on the contralateral side to familiarize them with the mechanosensitive changes (stretching, resistance, pain, or paresthesia) that can occur during ULNT1. Participants were instructed to report the onset of symptoms, defined as the first sensation of stretching, resistance, pain, or paresthesia during the test, and the maximum tolerated range of motion during the test. The ULNT1 was executed in the following sequence: (1) maximal contralateral cervical inclination; (2) shoulder abduction to 90\({}^{\circ}\) while preventing scapular elevation; (3) external rotation of the shoulder to 90\({}^{\circ}\) combined with elbow flexion at 90\({}^{\circ}\) (establishing the initial position or 0\({}^{\circ}\) range of motion); (4) forearm supination; (5) extension of the wrist and fingers; and (6) elbow extension [4; 17; 23]. As an evaluation parameter, the elbow extension range of motion at the onset of symptoms and the maximum tolerated range of motion were selected (Figure 1). According to [PERSON] and [PERSON] (2016) [19], the assessment of the elbow extension at the maximum tolerated point of the ULTN1 through a smartphone app showed great intra-rater agreement. The ULNT1 demonstrated moderate (kappa = 0.54) to substantial (kappa = 0.76) inter-rater concordance to collect information on mechanosensitivity in the studies by [PERSON] et al. (2009) [5] and [PERSON] et al. (2003) [24], respectively. Regarding the instrument used to assess elbow extension, some studies have compared the measurement of range of motion with smartphones and universal goniometers, reporting a high correlation between them (\(r\) = 0.79-0.99) [16; 20] and similar results [20]. Neurodynamic tests are considered to have moderate to substantial reliability [5] and ULNTs have acceptable clinimetric priorities [5].