The goal of this observational study is to develop an upper extremity neurocognitive performance test battery, determine its reliability and validity, and investigate the effect of neurocognitive load on test performance in athletes and healthy volunteers aged 18-40.

The main questions it aims to answer are:

Are the developed upper extremity neurocognitive tests reliable and valid tool for assessment?

Does the addition of neurocognitive load significantly affect upper extremity physical performance scores?

Are the neurocognitive performance test results related to shoulder rotator cuff muscle strength, rate of force development, and shoulder function?

Researchers will compare the neurocognitive performance of athletes to healthy non-athlete individuals to see if the test battery can effectively differentiate between these two groups (discriminative validity).

Participants will:

Complete demographic forms and questionnaires regarding activity level and shoulder function.

Undergo shoulder range of motion and isometric strength/rate of force development assessments.

Perform a battery of 4 neurocognitive tests integrated with a light-based reaction system.

Perform the same functional tests without neurocognitive load to serve as a baseline for comparison.

(Athletes only) Attend additional sessions to evaluate the feasibility of the tests and to assess test-retest reliability with a one-week interval.

This study focuses on the integration of physical and cognitive components to assess athletic performance through the development of a specific Upper Extremity Neurocognitive Performance Tests. While traditional functional tests often focus on pre-planned motor tasks, this research aims to simulate real-world sports environments by incorporating reactive and cognitive demands. Study Methodology and Testing Protocol The research is conducted at the Hacettepe University, Department of Sports Physiotherapy and Rehabilitation.

The evaluation involves several specialized assessments:

Neurocognitive Performance Test Battery: Utilizing a light-based reaction system, four specific tests have been developed to measure reactive agility and decision-making under load:

Neurocognitive Closed Kinetic Chain Upper Quarter Stability Test (N-CKCUQST): Participants perform hand transfer tasks in a plank position while responding to specific target colors.

Neurocognitive Open Kinetic Chain 90-90 Wall Throw Test (N-OKCWTT): Participants perform rhythmic wall throws while reacting to light stimuli. Neurocognitive 90-90 Medicine Ball Drop Test (N-MBDT): Assesses reactive catching control and hand-eye coordination under cognitive load. Neurocognitive Upper Quarter Y-Balance Test (N-UQYBT): A modified version of the traditional Y-Balance test that incorporates a visual-motor response at 80% of the participant's maximum reach.

Physical Performance Comparisons: To isolate the impact of cognitive load, participants also perform traditional versions of these tests without the light-based reaction stimuli.

Strength and Power Metrics: Isometric strength and the Rate of Force Development (RFD) for the shoulder internal and external rotators are measured using the ForceFrame dynamometer. Additionally, the Athletic Shoulder (ASH) Test is utilized on a force platform to evaluate bilateral functional strength in the I, Y, and T positions.

Session Structure Athlete Group: Participation consists of three separate sessions. The first session focuses on feasibility and familiarization. The second session involves comprehensive evaluation and validity analysis. The third session, conducted one week later, is dedicated to test-retest reliability.

Control Group: Healthy, non-athlete volunteers participate in a single evaluation session to establish the discriminative validity of the test battery.

Safety and Data Integrity: All assessments are non-invasive and conducted by experienced physiotherapists. To ensure the accuracy of the performance evaluation, video recordings are taken during the neurocognitive tests, which are stored in encrypted digital environments and deleted five years after the study's completion. All participants are required to avoid high-intensity physical activity for 48 hours prior to testing.

Inclusion Criteria

General Inclusion Criteria (Both Groups):

• Individuals between the ages of 18 and 40
• No passive range of motion limitations in the shoulder joint
• Classified as healthy with no history of injury in the past year according to the Extended Nordic Musculoskeletal Questionnaire
• Volunteered to participate in the study[cite: 1].

Athlete Group Specific Criteria:

• Physically active individuals
• Currently active in sports clubs in Ankara and/or applied to the Hacettepe University Department of Sports Physiotherapy and Rehabilitation
• History of training or physical activity at least three times a week for the past year
• Participation in recreational or competitive above or below shoulder height sports

Control Group Specific Criteria:

• Healthy individuals who have applied to the Hacettepe University Department of Sports Physiotherapy and Rehabilitation Unit
• Does not engage in regular physical activity
• History of training or physical activity fewer than three times a week over the past year
• No participation in recreational or competitive sports

Exclusion Criteria

• Presence of symptomatic upper extremity pathology
• History of upper extremity and/or trunk injury or surgery in the last 12 months
• History of ongoing neck pain, neurological symptoms in any extremity, or back, hip, or knee pain in the last 12 months
• Presence of a health condition that could cause a decrease in shoulder strength, such as inflammatory arthritis or neurological disorders
• Presence of any systemic disease
• Presence of visual or hearing impairments

Participants are selected based on their availability and meeting specific inclusion criteria from targeted environments (sports clubs and clinics) rather than random selection from the general population.

Primary Location: The study is conducted at the Hacettepe University, Faculty of Physical Therapy and Rehabilitation, Department of Sports Physiotherapy and Rehabilitation in Ankara, Turkey.

Athlete Cohort: Participants are recruited from local sports clubs operating in Ankara and individuals who have applied to the same university.

Control Cohort: Healthy, non-athlete individuals are recruited from those applying to the same university who meet the specific activity-level requirements for the control group.

Geographic Context: The population is primarily composed of individuals residing in or around the Ankara who can visit the clinic for assessment.

Setting: All evaluations take place in a specialized clinical biomechanics and sports rehabilitation laboratory environment.

The research team has not yet established a definitive plan for sharing individual participant data (IPD). The decision will be finalized upon the completion of the study, following the analysis of the results and ensuring full compliance with the institutional policies of Hacettepe University and the specific conditions set by the Ethics Committee. Any potential data sharing will strictly involve de-identified data to ensure participant confidentiality and will be subject to a formal data use agreement.