Table 1. Comparison of the EO, IO, and RA muscle activities during the bridge exercise on an US and a SS according to the knee angle Unit (%).

Muscle	Surface	45°	90°	120°
EO	SS	4.3±2.57	4.1±3.4	4.9±5.1
	US	7.8±4.9††	6.1±6.1†	10.0±1.9††
IO	SS*	2.7±1.0	3.0±1.6	4.0±2.1
	US**	4.5±2.0††	4.1±2.4††	7.7±4.6††
RA	SS**	0.4±0.5	0.8±0.6	0.8±0.6
	US**	0.5±0.6†	0.9±0.7††	1.1±0.8††

EO: external oblique, IO: internal oblique, RA: rectus abdominis, SS: stable surface, US: unstable surface, *: repeated ANOVA, ^†: paired t-test, ^*;†: p<0.05, ^**;††: p<0.01