The trunk plays an important role in transferring energy to the distal body segments during sports gestures. This region can be assessed through the lumbar-pelvic stability test, where the degree of pelvic tilt is observed, and muscle weaknesses can be identified by the presence of pelvic drop. In swimmers, the factors associated with lumbopelvic stability are poorly understood, including the isometric muscle strength of the muscles of the trunk, shoulder, hip, and knee.

To evaluate the association between the lumbopelvic stability test and isometric muscle strength of regions of trunk, shoulder, hip, and knee in swimming athletes.

This is a cross-sectional study approved by the research ethics committee. The inclusion criteria were swimmers athletes of both sex, age between 18 and 60 years old, with competitive practice in the past one year, and regular training for at least twice a week. Lumbopelvic stability was assessed using the one-legged bridge test with spherical markers on the anterior superior iliac spines, where the pelvic tilt (in degrees) was observed and recorded. Two-dimensional analyses were conducted using Kinovea 0.9.5 software (Kinovea Open Source Project) for Windows®. Additionally, the peak of isometric muscle strength of the shoulder elevators, shoulder internal and external rotators, lower trapezius, serratus anterior, trunk extensors and flexors, hip extensors, abductors, and rotators (HIPSIT), hip flexors, and knee extensors were assessed using a hand-held dynamometer (Lafayette, Model 01165A). The association between the lumbopelvic stability test and strength was verified using multiple linear regression. Data analysis was performed using SPSS Inc., Chicago, IL version 23.0.

A total of 27 athletes participated in the study, with mean age of 32.78 ± 14.64, 6.96 ± 6.05 years of sports practice, and 15 (56 %) were men. The results of the lumbopelvic stability test showed a significant association (p = 0.026) with the muscle strength of the hip flexors, explaining 15% of the test. Additionally, the standardized beta (ß = -0.42) showed a negative result, indicating that the greater the strength of this muscle group, the smaller the pelvic tilt. All other muscles were not significantly associated with lumbopelvic stability tests.

The lumbopelvic stability test is associated with the muscle strength of the hip flexors in swimming athletes.

The study suggests the importance of thoroughly evaluating the strength of the hip flexor muscle group in swimming athletes, as it is the main influencing group in the lumbopelvic stability test, which can affect the pelvic tilt, leading to biomechanical imbalance and potentially becoming a risk factor for pain or injuries.