Background: Delivery workers repeatedly get in and out of trucks and walk or run to deliver packages during work. Iliotibial band syndrome (ITBS) is a well-known non-traumatic overuse injury of the lateral side of the knee caused by frequent knee flexion and extension. Hip muscle strength is among the factors that prevent lower extremity injuries. Although many studies have examined the relationship between ITBS and hip muscle strengths, there was no study comparing hip muscle strength and ratio between delivery workers with and without ITBS.
Objects: This study aimed to compare hip muscle strength and hip internal/external rotator and adductor/abductor strength ratios between delivery workers with and without ITBS.
Methods: Fourteen delivery workers with ITBS matched inclusion criteria in the present study among 20 participants. Because total sample size was required 28 subjects by G*power program (ver. 3.1.9.4; University of Trier), 14 delivery workers without ITBS were recruited. Hip muscle strengths were measured in a side-lying position using a Smart KEMA pulling sensor (KOREATECH Co. Ltd.). An independent t-test was used to compare hip muscle strengths and hip internal/external rotator and hip adductor/abductor strength ratios between delivery workers with and without ITBS.
Results: The adductor/abductor strength ratio was significantly greater in delivery workers without ITBS than in those with ITBS (p < 0.05). The strengths of the hip abductor, hip adductor, hip internal rotator, hip external rotator, and the ratio of internal/external rotator strengths were not significantly different between the delivery workers with and without ITBS (p > 0.05).
Conclusion: This study’s findings showed that delivery workers with ITBS had significantly lesser adductor/abductor strength ratio, while the strengths of the hip abductor and adductor muscles did not differ significantly. These results suggest that adductor/abductor strength ratio should be considered when evaluating and treating ITBS in delivery workers.

INTRODUCTION
MATERIALS AND METHODS
    1. Subjects
    2. Instruments
RESULTS
DISCUSSION
CONCLUSIONS
FUNDING
ACKNOWLEDGEMENTS
CONFLICTS OF INTEREST
AUTHOR CONTRIBUTION
ORCID
REFERENCES

• Eun-su Lee(Department of Physical Therapy, The Graduate School, Yonsei University, Kinetic Ergocise Based on Movement Analysis Laboratory)
• Oh-yun Kwon(Department of Physical Therapy, College of Software and Digital Healthcare Convergence, Yonsei University, Kinetic Ergocise Based on Movement Analysis Laboratory) Corresponding Author
• Il-kyu Ahn(Department of Physical Therapy, The Graduate School, Yonsei University, Kinetic Ergocise Based on Movement Analysis Laboratory)
• Hwa-ik Yoo(Department of Physical Therapy, The Graduate School, Yonsei University, Kinetic Ergocise Based on Movement Analysis Laboratory)
• Ui-jae Hwang(Department of Physical Therapy, College of Software and Digital Healthcare Convergence, Yonsei University, Kinetic Ergocise Based on Movement Analysis Laboratory)