Background: Modern service-oriented occupations have increased concern regarding workrelated musculoskeletal disorders (WMSDs). Food service workers (FSWs) are at elevated risk of wrist-related WMSDs because their duties involve repetitive wrist movements during cooking, utensil handling, and tray carrying. Although ulnar deviation is frequently used in these tasks, ulnar-sided wrist pain (USWP) may be accompanied by direction-specific limitations and functional imbalance. Objects: This study aimed to compare radial and ulnar deviation strength and range of motion (ROM) between FSWs with and without USWP. Methods: Thirty FSWs were classified into USWP (n = 15) and non-USWP (n = 15) groups. USWP was defined as dominant-side pain lasting more than 3 months, a numeric pain rating scale score of ≥ 4 during work, and tenderness reproduced by the ulnar fovea sign test. Active wrist radial deviation ROM (WRDR) and ulnar deviation ROM (WUDR) were measured using a goniometer. Maximal voluntary isometric radial and ulnar deviation strengths were measured using a Smart KEMA strength sensor and normalized to body weight. ROM and strength asymmetry index (AI) were calculated to quantify directional imbalance. Results: The USWP group showed significantly lower WRDR (p = 0.002) and a higher ROM AI (p = 0.001) than the non-USWP group. Normalized radial deviation strength (p < 0.001) and ulnar deviation strength (p = 0.036) were also significantly lower in the USWP group, whereas the strength AI was significantly higher (p < 0.001). No significant between-group differences were observed in WUDR or raw ulnar deviation strength. Conclusion: USWP in FSWs was associated with reduced radial deviation ROM, lower normalized wrist deviation strength, and greater directional asymmetry. These findings suggest that USWP should not be viewed as localized ulnar-sided pain, but as a condition involving altered wrist deviation function. Pain-related limitation or neuromuscular factors may have contributed; however, causality requires caution.

INTRODUCTION
MATERIALS AND METHODS
    1. Participants
    2. Procedures
    3. Statistical Analysis
RESULTS
DISCUSSION
CONCLUSIONS
FUNDING
ACKNOWLEDGEMENTS
CONFLICTS OF INTEREST
AUTHOR CONTRIBUTIONS
ORCID
REFERENCES

• Seung-yoon Han(Department of Physical Therapy, The Graduate School, Yonsei University, Department of Physical Therapy, Kinetic Ergocise Based on Movement Analysis Laboratory, Yonsei University)
• Il-kyu Ahn(Department of Physical Therapy, The Graduate School, Yonsei University, Department of Physical Therapy, Kinetic Ergocise Based on Movement Analysis Laboratory, Yonsei University)
• Ha-yeong Baek(Department of Physical Therapy, The Graduate School, Yonsei University, Department of Physical Therapy, Kinetic Ergocise Based on Movement Analysis Laboratory, Yonsei University)
• Oh-yun Kwon(Department of Physical Therapy, Kinetic Ergocise Based on Movement Analysis Laboratory, Yonsei University, Department of Physical Therapy, College of Health Science, Yonsei University, Wonju, Korea) Corresponding author