Table 3.

MF between two groups pre- and post-intervention (Hz).

	Control group			Observation group
	Baseline	After	P1	Baseline	After	P1	P2
Erector spine muscle
Healthy side	78.44 ± 12.03	86.50 ± 11.25	t = -7.55 P = .00	79.22 ± 12.33	94.39 ± 12.01	t = -11.21 P = .00	t = -2.09 P = .04
Affected side	75.39 ± 12.27	85.83 ± 11.01	t = -11.08 P = .00	75.39 ± 12.61	92.06 ± 13.44	t = -13.77 P = .00	t = -1.56 P = .13
Polyfidus muscle
Healthy side	84.23 ± 16.97	94.06 ± 9.33	t = -26.01 P = .00	90.22 ± 11.71	103.56 ± 10.41	t = -13.15 P = .00	t = -2.96 P = .01
Affected side	80.89 ± 8.48	89.28 ± 7.79	t = -8.52 P = .00	84.00 ± 15.34	101.74 ± 12.60	t = -21.91 P = .00	t = -3.67 P = .01

The MF of affected side of the erector muscle of spine and multifidus muscles in the observation group after 4 weeks intervention was significantly higher than those before treatment both in the observation and control group (P < .05, respectively). P1 = P value compared within group, P2 = P value compared between two groups after therapy.