TABLE 5.

Piece-wise linear regression analysis for the relationship between anthropometrical characteristics and Δirisin levels.

Variables	Δirisin adjusted#
	β (95%CI)	P-value
BMI
Δirisin < −10.93 ng/ml	−0.05 (−0.07, −0.02)	0.0003***
Δirisin > −10.93 ng/ml	0.07 (0.01, 0.12)	0.0175*
FM
Δirisin < −8.3 ng/ml	−0.10 (−0.15, −0.06)	< 0.0001***
Δirisin > −8.3 ng/ml	0.21 (0.10, 0.32)	0.0003***
FM%
Δirisin < −8.46 ng/ml	−0.10 (−0.14, −0.06)	< 0.0001***
Δirisin > −8.46 ng/ml	0.21 (0.11, 0.30)	0.0001***
VFA
Δirisin < −8.3 ng/ml	−0.47 (−0.71, −0.23)	0.0002***
Δirisin > −8.3 ng/ml	1.06 (0.46, 1.66)	0.0009***
WHR
Δirisin < −8.46 ng/ml	−0.00 (−0.00, −0.00)	0.0168*
Δirisin > −8.46 ng/ml	0.00 (0.00, 0.00)	0.0045**
LTF
Δirisin < −8.3 ng/ml	0.01 (0.01, 0.02)	< 0.0001***
Δirisin > −8.3 ng/ml	−0.03 (−0.04, −0.01)	0.0006***
SVR
Δirisin < −8.3 ng/ml	0.00 (0.00, 0.00)	0.0003***
Δirisin > −8.3 ng/ml	−0.00 (−0.01, −0.00)	0.0041**
InBody score
Δirisin < −8.3 ng/ml	0.09 (0.04, 0.13)	0.0004***
Δirisin > −8.3 ng/ml	−0.23 (−0.34, −0.11)	0.0002***

Δirisin, the circulating irisin changes responses to ice swimming; #, indicates adjusted for age, gender age, gender, smoke, alcohol drinking, diabetes, distance swum per session, the frequency of ice swimming every week, and the total years of ice swimming.

Abbreviations: β, regression coefficient; CI, confidence interval; BMI, body mass index; FM, fat mass; FM%, percent body fat; VFA, visceral fat area; WHR, waist to hip ratio; LTF, lean-to-fat ratio; and SVR, skeletal muscle mass to visceral fat area ratio.

*P < 0.05; **P < 0.01; and ***P < 0.001.