Acute effects of high-intensity interval training on adiponectin isoforms in inactive young adults: a quasi-experimental study

Background: Physical inactivity is a key risk factor for metabolic disorders. High-intensity interval training (HIIT) has been recognized for its metabolic benefits, but its acute effects on adiponectin isoforms remain unclear. This study examines the impact of a single HIIT session on circulating adiponectin (high-molecular weight; HMW, medium-molecular-weight; MMW, and low-molecular weight; LMW) isoforms and metabolic outcomes in insufficiently active young adults. Methods: A quasi-experimental study was conducted with 21 physically inactive adults (11 women, 10 men, mean age 22.7 ± 1.5 years). Participants performed a HIIT session consisting of six bouts at 80% heart rate reserve (HRR). Pre- and post-exercise blood samples were ana-lyzed for adiponectin isoforms via Western blotting, and metabolic markers were assessed. Statistical analyses included Wilcoxon tests. Results: MMW adiponectin significantly increased (~ 19%; effect size [95%CI]: 0.49 [-0.02-1.00] p < 0.05), while LMW and HMW adiponectin remained unchanged. The HMW/MMW ratio decreased (-16%; effect size [95%CI]: -0.49 [-0.99-0.00] p < 0.05). Additionally, non-HDL cholesterol (effect size [95%CI]: 0.464 [-0.03-0.958]) and lactate levels (effect size [95%CI]: 1.164 [0.568–1.759]) increased post-exercise (both p < 0.05). Conclusions: A single HIIT session acutely increases MMW adiponectin in insufficiently active young adults. Further research is needed to determine the long-term metabolic implications of repeated HIIT sessions on adiponectin isoform dynamics. Trial registration: retrospectively registered in ClinicalTrials.gov (NCT07146867) on August 21st, 2025.