Abstract
Background:
Exercise-induced release of irisin is associated with various improved health outcomes. However, the most effective exercise mode(s) to stimulate irisin release remain unclear. In this systematic review, we separately examine potential differences in (i) resting irisin concentrations (chronic change) after resistance (RT) and endurance training (ET) and (ii) the concentrations of irisin after a single bout (acute change) of resistance (RE) and endurance exercise (EE).
Methods:
Searching was completed February 2022 in PubMed, CINAHL, Web of Science, Cochrane Library, SCOPUS, and SportDiscus. Studies were included by consensus of 2 reviewers, if they were randomized controlled trials (RCTs) or comparison studies with adults over 18 years and compared chronic change after RT and ET for any intervention duration or acute change after RE and EE. Risk of bias and quality of findings were independently assessed using PEDRo and GRADE, respectively. Irisin post means and standard deviations were extracted to calculate standardized mean differences (SMDs) and 95% confidence intervals using a random effect model.
Results:
Of 174 studies screened, 8 chronic and 4 acute studies were included in the analysis, comprising a total of 332 participants. No difference between RT or ET for chronic irisin response was found (P = 0.380, SMD = 0.17, n = 248); however, there tended to be greater acute increases in circulating irisin after RE than EE (P < 0.001, SMD = 0.93, n = 56).
Conclusions:
A greater effect of RE on irisin concentrations than EE was found in acute studies. Future research requires larger sample sizes and matched intensities.