The association of lower trunk muscle strength with low back pain in elite lightweight judokas is dependent on lumber spine abnormalities

BACKGROUND: Lumbar radiological abnormalities (LRA) and trunk muscle weakness are major causes of the low back pain (LBP). We reported that the prevalence of LRA was approximately 90% in middle- and heavyweight-judokas, independent to the occurrence of LBP. However, the trunk muscle weakness, especially the rotators, plays a key role in occurrence of LBP in heavyweight judokas. OBJECTIVE: To examine the trunk muscle strength (TMS) and LRA impact on LBP occurrence in lightweight judokas. METHOD: The strength of the trunk extensors, flexors, and rotators was measured in 32 lightweight male judokas. LBP and LRA were identified using a questionnaire, X-ray, and MRI. RESULTS: The occurrence rate of LBP and LRA were 40.6% and 62.5%, respectively, without any significant correlation. Among judokas without LRA, TMS of those with LBP were significantly lower than those without LBP (P< 0.05, the extensor; 60∘/s: ES [d] = 1.38, 90∘/s: ES [d] = 0.78, and 120∘/s: ES [d] = 0.37, flexor; 60∘/s: ES [d] = 1.48, dominant rotator; 60∘/s: ES [d] = 1.66, and 90∘/s: ES [d] = 1.87, non-dominant rotator; 90∘/s: ES [d] = 0.17, and dominant/non-dominant rotator ratio; 90∘/s: ES [d] = 1.55). Moreover, there were significant negative correlations between LBP severity and TMS (P< 0.05, the extensor; 90∘/s: r=-0.63, dominant rotator; 90∘/s: r=-0.648, and dominant/non-dominant rotator ratio; 90∘/s: r=-0.621) in judokas without LRA. RESULTS: The occurrence rate of LBP and LRA were 40.6% and 62.5%, respectively, without any significant correlation. Among judokas without LRA, the extensor (60, 90, and 120∘/s), flexor (60∘/s), dominant rotator (60 and 90∘/s), non-dominant rotator (90∘/s), and dominant/non-dominant rotator ratio (90∘/s) of judokas with LBP were significantly lower than those of the judokas without LBP. Moreover, there were significant negative correlations (P< 0.05) between LBP severity and the extensor (90∘/s; r=-0.63) and dominant rotator (90∘/s; r=-0.648) strength, and dominant/non-dominant rotator ratio (90∘/s; r=-0.621) in judokas without LRA. CONCLUSION: Weak trunk musculature may be a co-factor in the occurrence of LBP in lightweight judokas without LRA.