Quantitative multi-parameter assessment of age- and gender-related variation of back extensor muscles in healthy adults using Dixon MR imaging

ObjectivesInvestigate sex differences in age-related back extensor muscle degeneration using Dixon MRI and analyze the relationship between quantitative muscle parameters and back muscle strength in healthy adults.Methods105 healthy subjects underwent lumbar Dixon MRI. Fat fraction (FF), cross-sectional area (CSA), functional CSA (FCSA), and relative FCSA (RFCSA) of multifidus muscle (MF) and erector spinae (ES) were quantified. Back extension muscle strength was measured using an external fixation dynamometer. ANOVA with post hoc Tukey correction was used for age group comparisons. Partial and Spearman's correlation analyzed relationships between age, muscle parameters, and muscle strength.ResultsMF and ES FF significantly increased with age in both genders (r = 0.55-0.85; p < 0.001). Muscle FF increased prominently for females (40-49 years, MF and 50-59 years, ES) and males (60-73 years, MF and ES). In females, total ES FCSA and RFCSA (r = - 0.42, - 0.37; p < 0.01) correlated with age. While in males, all MF and ES muscle size parameters, except total MF CSA, correlated with age (r = - 0.30 to - 0.58; p < 0.05). Back extension muscle strength correlated with mean FF, total CSA, and total FCAS for MF and ES individually (p < 0.001). The combined MF + ES FCSA correlation coefficient (r = 0.63) was higher than FF (r = - 0.51) and CSA (r = 0.59) (p < 0.001).ConclusionsAge-related back extensor muscle degeneration varies by muscle type and sex. FCSA has the highest association with back muscle strength compared to FF and CSA.

Automated summary

This study investigated the sex differences in age-related back extensor muscle degeneration using Dixon MRI and analyzed the relationship between quantitative muscle parameters and back muscle strength in healthy adults. The results showed that the fat fraction of multifidus muscle and erector spinae significantly increased with age in both genders. In females, the total erector spinae functional cross-sectional area and relative functional cross-sectional area correlated with age. In males, all muscle size parameters, except total multifidus muscle cross-sectional area, correlated with age. Back extension muscle strength correlated with muscle fat fraction, cross-sectional area, and functional cross-sectional area. The study concluded that functional cross-sectional area had the highest association with back muscle strength compared to fat fraction and cross-sectional area.