Relationships Between Circulating Irisin Response to Ice Swimming and Body Composition in People With Regular Exercise Experience

Severe cold exercise involves the irisin response, and may be related to body composition. We aimed to investigate changes in circulating irisin after ice swimming (IS), as well as to evaluate the correlation between body composition and the change in irisin caused by IS (Delta irisin). 81 ice swimmers were recruited to perform IS activities. Blood samples were drawn 30 min before and 30 min after IS, and the serum levels of irisin and the ice swimmers' body composition were measured. As results, circulating irisin declined significantly during the recovery period following IS exercise (P < 0.001). The afternoon baseline circulating irisin level and Delta irisin in response to IS were correlated with body fat characteristics rather than muscle parameters in ice swimmers. Delta irisin subgroup analyses showed that the Delta irisin ascending group (Delta irisin+) subjects had a higher fat composition and higher basal irisin levels than the Delta irisin descending group (Delta irisin-). Furthermore, the decrease in irisin was negatively correlated with fat components in Delta irisin- subjects, whereas no correlation was observed between the increase in irisin and body composition in Delta irisin + subjects. Finally, a non-linear association analysis suggested that body fat indicators had obvious curvilinear relationships with Delta irisin. In conclusion, IS caused a significant decrease in irisin. Statistical and curvilinear associations suggested that the correlation between fat tissue and Delta irisin caused by IS is dimorphic and the underlying mechanisms may be due to the different metabolic states of subjects.