Data analysis and statistics
The intention-to-treat principle was used for data analysis. Participant characteristics are described using means and standard deviations for continuous data. After confirming normality, we used repeated measures ANOVA and paired t-test to compare the paired data between the three time points and two time points, respectively. Statistical significance was defined as a two-sided P-value of < 0.05. All statistical analyses were performed using SAS version 9.4 (SAS Institute, Cary, NC, USA).
Three-dimensional segmentation of the lumbar extensor muscle