Table 2.

Calculated effect sizes (standardized mean differences) of included studies and their designated magnitudes.

Study	Effect size	95% CI	Magnitude+
Yang et al. (2012)	−0.13	(−1.12, 0.85)	Small
Kim et al. (2011)HIGH FREQ	−0.09	(−0.96, 0.79)	Small
Michou et al. (2014)	−0.03	(−1.17, 1.10)	Small
Park et al. (2013)	0.55	(−0.39, 1.50)	Moderate
Shigematsu et al. (2013)	0.84	(−0.08, 1.77)	Large
Kumar et al. (2011)	0.86	(−0.25, 1.97)	Large
Kim et al. (2011)LOW FREQ	1.09*	(0.13, 2.04)	Large
Khedr et al. (2009)	1.15*	(0.31, 1.99)	Large
	Pooled = 0.55	(0.17, 0.93)

⁺Higgins and Green, 2008; CI, confidence interval; SMD, standardized mean difference.

^*These two studies were the only significant effect sizes, as their confidence intervals did not include zero.