Fig. 5

Intra-cluster similarity in the trunk muscle synergies (W1 to W5) between the non-CLBP and CLBP groups. The intra-cluster similarity of the muscle weighting components in W2 and W3 were significantly higher in the CLBP group than in the non-CLBP group (W2: p = 0.00006, d = 0.89; W3: p = 0.0012, d = 0.53). The similarity in W4 was significantly lower in the CLBP group than in the non-CLBP group (p = 0.0021, d = 0.57). There was no significant difference in W1 and W5 between the groups (W1: p = 0.241, W5: p = 0.599)