Table 3.

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

		WBV group (n = 20)	Control group (n = 20)	WBV – Control (95% CI)	P† value
Right ES	Pre-test	41.5 ± 156.5	61.8 ± 125.5	−20.3 (−111.1 to 70.5)	0.653
	Post-test	46.5 ± 139.8	71.5 ± 94.6	−25.1 (−101.4 to 51.3)	0.511
	P‡ value	0.875	0.564
Left ES	Pre-test	34.0 ± 94.5	21.7 ± 95.2	12.2 (−48.5 to 72.9)	0.686
	Post-test	5.6 ± 71.9	−1.6 ± 68.7	7.2 (−37.8 to 52.2)	0.748
	P‡ value	0.089	0.083
Right MF	Pre-test	85.2 ± 94.4	54.6 ± 103.7	30.6 (−32.9 to 94.1)	0.335
	Post-test	48.6 ± 78.7	71.1 ± 98.2	−23.1 (−80.0 to 33.9)	0.418
	P‡ value	0.014∗	0.281
Left MF	Pre-test	68.3 ± 81.9	52.3 ± 99.0	16.0 (−42.1 to 74.2)	0.580
	Post-test	30.2 ± 81.1	56.9 ± 95.1	−26.7 (−83.3 to 29.9)	0.346
	P‡ value	0.011∗	0.710
Right TrA/IO	Pre-test	147.2 ± 79.9	202.2 ± 94.0	−55.1 (−110.9 to 0.8)	0.053
	Post-test	103.4 ± 96.4	205.9 ± 125.1	−102.5 (−174.0 to −31.0)	0.006∗
	P‡ value	0.008∗	0.860
Left TrA/IO	Pre-test	160.3 ± 119.3	222.8 ± 168.2	−62.5 (−155.9 to 30.8)	0.183
	Post-test	97.2 ± 159.0	195.2 ± 147.9	−98.0 (−196.3 to 0.3)	0.051
	P‡ value	0.026∗	0.167
Right RA	Pre-test	259.4 ± 137.1	236.1 ± 162.2	23.3 (−72.9 to 119.4)	0.627
	Post-test	234.0 ± 118.1	218.2 ± 156.7	15.8 (−73.0 to 104.6)	0.721
	P‡ value	0.337	0.346
Left RA	Pre-test	231.4 ± 155.0	267.7 ± 132.3	−36.4 (−128.6 to 55.9)	0.430
	Post-test	174.3 ± 147.8	272.0 ± 141.7	−97.8 (−190.4 to −5.1)	0.039∗
	P‡ value	0.062	0.772

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.