Table 6 Multiple regression analysis for safe depths of 23 upper back acupoints

GV9

−0.06 (−0.38–0.26) 0.716

0.33 (0.22–0.43) <0.001*

0.08 (−0.16–0.32) 0.527

−0.60 (−2.15–0.95) 0.446

GV10

−0.01 (−0.31–0.28) 0.927

0.28 (0.18–0.38) <0.001*

0.23 (0.01–0.45) 0.038*

−0.85 (−2.27–0.57) 0.241

GV11

−0.25 (−0.55–0.05) 0.100

0.31 (0.22–0.41) <0.001*

0.19 (−0.04–0.41) 0.098

−1.05 (−2.49–0.39) 0.152

GV12

−0.14 (−0.48–0.20) 0.412

0.34 (0.23–0.45) <0.001*

0.21 (−0.04–0.47) 0.101

−1.41 (−3.06–0.24) 0.093

GV13

0.27 (−0.07–0.60) 0.114

0.27 (0.16–0.38) <0.001*

0.27 (0.02–0.52) 0.035*

−0.82 (−2.45–0.81) 0.324

GV14

0.46 (0.05–0.86) 0.027*

0.26 (0.13–0.39) <0.001*

0.17 (−0.13–0.48) 0.261

−0.61 (−2.58–1.36) 0.544

BL11

−0.07 (−0.50–0.37) 0.757

0.29 (0.15–0.44) <0.001*

0.10 (−0.22–0.43) 0.531

1.34 (−0.78–3.46) 0.213

BL12

0.18 (−0.24–0.60) 0.395

0.19 (0.06–0.33) 0.005*

0.02(−0.30–0.33) 0.927

1.06 (−0.97–3.09) 0.304

BL13

−0.51 (−0.78–-0.24) <0.001*

0.31 (0.22–0.40) <0.001*

0.04 (−0.16–0.24) 0.700

−0.52 (−1.83–0.80) 0.442

BL14

−0.32 (−0.62– −0.01) 0.044*

0.32 (0.22–0.42) <0.001*

0.037 (−0.19–0.27) 0.755

−0.82 (−2.31–0.68) 0.284

BL15

−0.33 (−0.58– −0.09) 0.008*

0.25 (0.17–0.33) <0.001*

0.20 (0.01–0.38) 0.035*

−0.77 (−1.96–0.42) 0.201

BL16

−0.16 (−0.44–0.12) 0.253

0.24 (0.15–0.33) <0.001*

0.20 (−0.01–0.40) 0.065

−0.142 (−1.48–1.20) 0.835

BL17

−0.22 (−0.47–0.03) 0.078

0.29 (0.21–0.37) <0.001*

0.05 (−0.14–0.23) 0.609

−1.16 (−2.36–0.04) 0.057

BL41

−0.51 (−0.86– −0.16) 0.005*

0.43 (0.31–0.54) <0.001*

−0.08 (−0.35–0.19) 0.553

−1.14 (−2.86–0.57) 0.191

BL42

−0.32 (−0.64– −0.01) 0.046*

0.33 (0.23–0.44) <0.001*

0.06 (−0.17–0.30) 0.598

−1.69 (−3.23– −0.14) 0.032*

BL43

−0.32 (−0.62– −0.02) 0.036*

0.28 (0.19–0.38) <0.001*

0.13 (−0.09–0.36) 0.242

−0.97 (−2.42–0.47) 0.186

BL44

−0.36 (−0.68– −0.04) 0.026*

0.29 (0.18–0.39) <0.001*

0.138 (−0.10–0.38) 0.256

−1.62 (−3.17– −0.07) 0.040*

BL45

−0.40 (−0.67– −0.14) 0.003*

0.34 (0.25–0.42) <0.001*

0.00 (−0.20–0.20) 1.000

−2.25 (−3.53– −0.98) 0.001*

BL46

−0.31 (−0.55– −0.07) 0.012*

0.31 (0.23–0.38) <0.001*

−0.01 (−0.19–0.18) 0.938

−1.66 (−2.84– −0.47) 0.006*

SI14

−0.10 (−0.56–0.36) 0.674

0.41 (0.26–0.56) <0.001*

0.13 (−0.22–0.47) 0.473

0.03 (−2.21–2.27) 0.978

SI15

0.20 (−0.26–0.66) 0.383

0.34 (0.20–0.49) <0.001*

0.18 (−0.16–0.53) 0.300

−0.22 (−2.45–2.00) 0.846

GB21

−0.26 (−0.64–0.13) 0.189

0.39 (0.26–0.51) <0.001*

−0.17 (−0.46–0.12) 0.249

−2.12 (−3.99– −0.25) 0.026*

SP21

−0.04 (−0.24–0.16) 0.695

0.14 (0.08–0.21) <0.001*

−0.07 (−0.22–0.09) 0.389

−0.57 (−1.55–0.41) 0.254