TABLE 1.
Baseline characteristics of participants (N = 81).
| Characteristic | Statistics | Range |
| Men, n (%) | 66 (81.5) | |
| Age, (years) | 58.3 ± 8.4 | 42.0–84.0 |
| Current smoker, n (%) | 20 (24.7) | |
| Alcohol consumption (≥30 g/day), n (%) | 42 (51.9) | |
| Diabetes, n (%) | 7 (8.6) | |
| Ice swimming distance per session, n (%), (meters) | 30–250 | |
| <80 m | 69 (85.2) | |
| ≥80 m | 12 (14.8) | |
| Ice swimming frequency per week, n (%) | 1.0–7.0 | |
| ≤3 t/w | 14 (17.3) | |
| 4–5 t/w | 25 (30.9) | |
| 6–7 t/w | 42 (51.9) | |
| Total Ice swimming years, n (%), (years) | 2–25 | |
| <5 years | 30 (37.0) | |
| 5–9 years | 24 (29.6) | |
| ≥10 years | 27 (33.3) | |
| BMR, (kcal) | 1536.8 ± 177.7 | 1074.0–1828.0 |
| BMI, (kg/m2) | 26.2 ± 2.7 | 21.2–33.8 |
| FM, (kg) | 20.7 ± 5.4 | 10.1–35.8 |
| FM% | 27.6 ± 5.9 | 15.8–46.2 |
| VFA, (cm2) | 93.4 ± 28.4 | 47.2–178.9 |
| WHR | 0.9 ± 0.1 | 0.8–1.0 |
| FFM, (kg) | 54.0 ± 8.2 | 32.6–67.5 |
| FFMI, (kg/m2) | 18.9 ± 1.8 | 14.1–22.5 |
| SLM, (kg) | 51.0 ± 7.8 | 30.7–63.7 |
| SMM, (kg) | 29.9 ± 5.5 | 8.3–38.4 |
| SMMI, (kg/m2) | 10.4 ± 1.4 | 3.0–12.9 |
| LTF | 2.8 ± 0.8 | 1.2–5.3 |
| SVR, (kg/cm2) | 0.3 ± 0.1 | 0.1–0.7 |
| Inbody score | 71.7 ± 5.7 | 58.0–84.0 |
| Irisin before, (ng/ml) | 104.4 ± 100.9 | 9.2–632.0 |
| Irisin after, (ng/ml) | 84.7 ± 94.6 | 1.8–647.3 |
| Δirisin, (ng/ml) | −19.7 ± 29.7 | −172.0–49.0 |
| Δirisin+, (ng/ml) | 14.3 ± 14.4 | 0.5–49.0 |
| Δ irisin−, (ng/ml) | −26.9 ± 27.1 | −172.0–−0.7 |
Continuous variables are represented by Mean ± standard deviation; Categorical variables are represented by numerical and percentage.
Abbreviations: BMR, basal metabolic rate; BMI, body mass index; FM, fat mass; FM%, percent body fat; VFA, visceral fat area; WHR, waist to hip ratio; FFM, fat free mass; FFMI, fat free mass index; SLM, soft lean mass; SMM, skeletal muscle mass; SMMI, skeletal muscle mass index; LTF, lean-to-fat ratio; and SVR, skeletal muscle mass to visceral fat area ratio. Irisin before, the circulating irisin levels before ice swimming (baseline irisin levels); Irisin after, the circulating irisin levels after ice swimming; Δirisin, the circulating irisin changes responses to ice swimming; Δirisin+, the Δirisin ascending group; and Δ irisin−, the Δirisin descending group.