ObjectivesElevated lumbar multifidus stiffness has been observed in populations with chronic low back pain (LBP). However, the modulation of deep (DLM) and superficial (SLM) lumbar multifidus stiffness, considering their distinct structural characteristics and functions, remains unaddressed, especially in athletes. This study aimed to compare differences in DLM and SLM stiffness in professional athletes from different sports with and without chronic LBP. DesignCross-sectional study. SettingThis study was conducted at a provincial sports training centre. ParticipantsNinety-nine professional athletes (age: 18-27 years) from weightlifting, badminton, and track and field teams were recruited. Thirty-eight had chronic bilateral LBP. InterventionsNot applicable. Main Outcome MeasuresUltrasound shear wave elastography (SWE) measured Young's modulus (stiffness indicator) of DLM and SLM at the L4/5 facet joint level. Two-way analysis of variance examined the effects of chronic LBP and sport type on DLM and SLM stiffness while considering proper confounders. Significance was set at p < 0.05. ResultsAthletes with chronic LBP demonstrated significantly higher DLM stiffness on the dominant (by 17.73%, mean difference (MD) = 2.52kPa, p = 0.001) and non-dominant sides (by 13.54%, MD = 1.83kPa, p = 0.046) compared to pain-free counterparts. SLM stiffness varied significantly among the three athlete groups. Post-hoc analyses revealed greater SLM stiffness on the non-dominant side in weightlifters than in badminton players (by 51.76%, MD = 8.97kPa, p = 0.010) or track and field athletes (by 72.01%, MD = 11.01kPa, p = 0.008). ConclusionsChronic LBP and sport type significantly impact multifidus muscle stiffness, suggesting the need for targeted clinical assessments and reconditioning strategies focusing on DLM for chronic LBP and SLM for athletes in trunk extension-intensive sports.
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