Table 2.

The PSI values of the three groups with 3 different times. Data is represented as mean ± SD (unit is g, gravitation).

	Group I	Group II	Group III	p-Value
0~10 min (Phase I)	0.013 ± 0.018	0.004 ± 0.008	0.001 ± 0.001	0.001 **
10~20 min (Phase II)	0.031 ± 0.042	0.005 ± 0.008	0.001 ± 0.0005	<0.001 ***
20~30 min (Phase III)	0.123 ± 0.155	0.012 ± 0.013	0.001 ± 0.0003	<0.001 ***

** p < 0.01, *** p < 0.001 (Group I is the inexperienced group, Group II is the beginners group, Group III is the advanced group).