Mahnaz Emami - Department of Physiotherapy, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
Nahid Rahmani - Pediatric Neurorehabilitation Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
Mohammad Ali Mohseni Bandpei - ۲ Pediatric Neurorehabilitation Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran ۳ University Institute of Physical Therapy, Faculty of Allied Health Sciences, University of Lahore, Lahore, Pakistan
Akbar Biglarian - Department of Biostatistics, Social determinants of health and research center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran

Background: Trunk muscles play an important role in providing both mobility and stability during dynamic tasks in athletes.The purpose of this study was to evaluate the within-day and between-day reliability of ultrasound (US) in measuringabdominal and lumbar multifidus muscle (MF) thickness in athletes with and without hamstring strain injury (HSI).Methods: Fifteen male soccer players (18-30 years old) with and without HSI were evaluated using two US probes (50mm linear 7.5 MHZ and 70 mm curvilinear 5 MHz). The abdominal muscle thickness as well as the cross sectional area(CSA) of the MF was measured. To determine within and between days reliabilities, the second and third measurementswere repeated with two hours and one week intervals, respectively.Results: Intraclass correlation coefficients for athletes with and without HSI demonstrated good to high reliabilityfor the abdominal muscle thickness (0.82 and 0.93) and CSA of the MF muscle (0.84 and 0.89, respectively).Conclusion: Our results indicated that US seemed to be a reliable instrument to measure abdominal and lumbarmultifidus muscle thickness in soccer players with and without HSI. However, further studies are recommended tosupport the present study findings in other athletes.Level of evidence: III

Lower limb, Strain, Ultrasound imaging