The comparison of the psoas muscle thickness and strength, and sagittal lumbopelvic alignment in female gymnasts with sway-back posture and normal posture

Objective: This study aims to investigate the thickness and strength of the psoas muscle, lordosis, and pelvic tilt in female gymnasts with SBP and normal posture.

Methods: This cross-sectional study involved 17 female elite artistic gymnasts, aged 22.1 ± 5.01 years. Among them, ten had SBP, while seven exhibited a normal posture. Ultrasonography, a manual dynamometer, a flexible ruler, and a manual inclinometer were used to measure muscle thickness, strength, lumbar lordosis, and pelvic tilt, respectively.

Results: The thickness of the psoas muscle at the levels L2-L3 and L3-L4 in female gymnasts with SBP was significantly less than in those with normal posture (L2-L3: p = .021, ηp2 = .327; L3-L4: p = .035, ηp2 = .281). However, the strength (p = .732, ηp2 = .009) and strength-to-thickness ratio of the psoas muscle (p = .356, ηp2 = .061), degrees of lordosis (p = .414, d = 0.41), and pelvic tilt (p = .323, d = 0.52) did not significantly differ between the two groups.

Conclusions: The present study revealed the thickness of the psoas muscle was significantly decreased in gymnasts with SBP while its strength was not different from the controls. This may be considered as a prelude for possible changes in bony alignments in the future. Future studies could potentially explore the implications of these findings for training and injury prevention strategies among gymnasts.