The association between different physical activity levels and flexion-relaxation phenomenon in women: a cross-sectional study

BACKGROUND: To investigate whether the flexion-relaxation phenomenon differs in women with different physical activity levels. METHODS: Seventy-two subjects were recruited for this study. The electromyographic activity of the erector spinae and multifidus muscles was recorded during a flexion task using a surface electromyographic device. The flexion-relaxation and extension-relaxation ratios were calculated. Participants were classified into different physical activity level groups based on their responses to the International Physical Activity Questionnaire. A Welch analysis of variance was conducted to compare the flexion-relaxation ratio and extension-relaxation ratio between groups. RESULTS: A significant difference in the flexion-relaxation and extension-relaxation ratio was observed in both the erector spinae and multifidus muscles between different levels of physical activity. CONCLUSIONS: In this study, we observed that female participants with high levels of physical activity showed a more pronounced flexion-relaxation phenomenon compared to those with moderate and low levels of physical activity. No significant difference was found between moderate and low physical activity levels. The findings of our study highlight the association between physical activity and the mechanics of the spinal stabilising muscles.