Table 4.

Comparison of relative activation time between/within groups on shoulder abduction ($\overline{x}$ ± s, unit: ms).

		WBV group (n = 20)	Control group (n = 20)	WBV – Control (95% CI)	P‡ value
Right ES	Pre-test	184.8 ± 99.8	147.3 ± 159.9	37.5 (−47.8 to 122.8)	0.379
	Post-test	117.5 ± 115.4	178.0 ± 130.8	−60.4 (−139 to 18.5)	0.130
	P‡ value	0.001∗	0.052
Left ES	Pre-test	162.5 ± 108.8	158.0 ± 104.2	4.5 (−63.7 to 72.7)	0.894
	Post-test	57.7 ± 76.7	137.8 ± 77.5	−80.1 (−129.4 to −30.7)	0.002∗
	P‡ value	0.000∗	0.141
Right MF	Pre-test	237.5 ± 97.4	257.6 ± 100.2	−20.1 (−83.4 to 43.1)	0.524
	Post-test	144.1 ± 97.1	269.4 ± 196.9	−125.3 (−224.7 to −25.9)	0.015∗
	P‡ value	0.001∗	0.741
Left MF	Pre-test	157.3 ± 90.3	163.0 ± 76.3	−5.7 (−59.2 to 47.8)	0.830
	Post-test	105.4 ± 108.9	152.6 ± 81.2	−47.2 (−108.6 to 14.3)	0.129
	P‡ value	0.009∗	0.333
Right TrA/IO	Pre-test	165.7 ± 100.4	186.3 ± 122.5	−20.6 (−92.6 to 51.1)	0.564
	Post-test	69.4 ± 102.9	166.5 ± 94.4	−97.2 (−160.4 to −34.0)	0.004∗
	P‡ value	0.000∗	0.105
Let TrA/IO	Pre-test	160.7 ± 143.4	195.1 ± 108.6	−34.5 (−115.9 to 47.0)	0.397
	Post-test	124.6 ± 206.6	189.0 ± 100.4	−64.5 (−168.4 to 39.5)	0.217
	P‡ value	0.403	0.508
Right RA	Pre-test	231.3 ± 129.6	258.9 ± 123.1	−27.6 (−108.5 to 53.3)	0.494
	Post-test	128.0 ± 99.3	265.3 ± 117.9	−137.3 (−207.1 to −67.5)	0.000∗
	P‡ value	0.001∗	0.584
Left RA	Pre-test	108.8 ± 218.6	166.1 ± 181.9	−57.4 (−186.1 to 71.3)	0.373
	Post-test	70.6 ± 127.7	160.1 ± 176.6	−89.5 (−188.1 to 9.2)	0.074
	P‡ value	0.203	0.452

Relative activation time = muscle onset time-prime mover onset time (ms), a negative value indicated that the target muscle fired before the prime mover, and vice versa. WBV, whole-body vibration; ES, erector spinae; MF, multifidus; TrA/IO, transversus abdominus/internal oblique; RA, rectus abdominis; CI, confidence interval. Values are expressed as mean ± SD.^†Analyzed by the independent-samples t-test;^‡ analyzed by the paired-samples t-test;^∗ significant at P < 0.05.