Posture assessment is widely used in sports medicine, physiotherapy, and rehabilitation to identify body alignment problems and support clinical decision-making. Mobile applications have become increasingly popular because they are fast, inexpensive, and easy to use. However, these applications must be shown to provide accurate and reliable measurements before they can be recommended for clinical or sports use.

The purpose of this observational study is to evaluate the validity and reliability of the DeepClinic mobile application for posture assessment in physically active adults. Approximately 50 participants will undergo standardized posture photography from the front, back, and side views. The images will be analyzed using both the DeepClinic application and the validated APECS posture analysis system. The agreement between the two systems will be examined to determine validity. To evaluate test-retest reliability, posture assessments will be repeated after one week under the same standardized conditions.

No treatment or intervention will be provided as part of this study. The findings are expected to provide scientific evidence regarding the accuracy and reliability of the DeepClinic application and its potential use as a practical posture assessment tool in clinical practice, sports science, and rehabilitation.

Inclusion Criteria:

• Adults aged 18-45 years.
• Regular participation in sports or physical activity (minimum 3 sessions per week).
• Able to stand independently during posture assessment.
• Willing and able to provide written informed consent.
• Able to complete both baseline and one-week follow-up posture assessments.

Exclusion Criteria:

• Current musculoskeletal injury or pain affecting standing posture.
• History of spinal, lower extremity, or neurological disorders that may influence postural alignment.
• Previous spinal or lower extremity surgery within the past 12 months.
• Pregnancy.
• Inability to complete the posture assessment protocol or poor-quality photographs unsuitable for analysis.

Approximately 50 physically active adults aged 18-45 years who regularly participated in sports were recruited to evaluate the validity and test-retest reliability of the DeepClinic mobile application for posture assessment. Participants were assessed under standardized testing conditions and compared with the validated APECS posture analysis system.