VALIDATION DATA

The overall internal consistency of the scale was evaluated using the Cronbach’s α coefficient  which showed α = 0.727. α > 0.70 indicates that the scale has high reliability. After removing each individual item, the α coefficients maintained between 0.692 and 0.717, with no significant change.

Spearman’s correlation coefficient was used to evaluate the test-retest reliability of the scale. The results showed high test-retest reliability for each item, for each factor, as well as for the total score, r > 0.5, which signifies high test-retest reliability of the SSFS

The results of this study showed an excellent test-retest reliability of the total score (r = 0.914, P < 0.01), as well as good test-retest reliability of the postural assessment factor (r = 0.800, P < 0.01) and of the functional assessment factor (r = 0.889, P < 0.01). For the individual items of the SSFS, other than supine postural assessment (r = 0.567, P < 0.01), prone press-up (r = 0.544, P < 0.01) and wall angel (r = 0.505, P < 0.01), other items resulted in good test-retest reliability (r > 0.6, P < 0.01). The reliability analysis determines the SSFS to have high reliability.

Ten domestic experts with professional and academic background in the field of sports medicine and sports rehabilitation were invited for this study, all of them have senior titles. The expert consultation form was distributed twice, and the response rate was 100% during both times, indicating high motivation towards the study; the coefficient of expert authority (Cr) was 0.9, representing high expert authority. All eight items of the scale were retained based on expert opinion.

Spearman correlation analysis was used to evaluate the correlation between each item and the total score. The results showed that the entries were significantly correlated with the total score; therefore, no item was deleted from SSFS.

Exploratory factor analysis was used to evaluate the structural validity of the scale. In this study, the KMO value was 0.779 and the Bartlett’s test of Sphericity resulted a value of 829.680, and p < 0.01, indicating that the source data was suitable for factor analysis. The two metric factors with eigenvalues > 1 were extracted, and the contribution rate of factor 1 was 30.900%, the contribution rate of factor 2 was 15.156%, and the cumulative contribution rate was 46.057%.

Confirmatory factor analysis was performed on the overall fitting of the two-factor model of the SSFS using AMOS 21.0. The initial model resulted in the following values: χ2/df (chi-squared over degree of freedom) = 2.440, RMSEA (root mean square error of approximation) = 0.04 < 0.05, GFI (goodness of fit index) = 0.945, AGFI (adjusted goodness of fit) = 0.920, CFI (comparative fit index) = 0.967, IFI (incremental fit index) = 0.951, TLI (Tucker-Lewis index) = 0.951. GFI, AGFI, CFI, IFI, and TLI were all > 0.90.