Background: Myonectin (CTRP15), a recently identified myokine, plays a crucial role in regulating glucose metabolism. Objectives: This study aimed to compare the effects of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on serum myonectin levels, using matched training volumes for both interventions. Methods: Twenty-four male Wistar rats, aged 18 to 20 weeks, were randomly assigned to three groups of eight: Control, MICT, and HIIT. The training groups participated in HIIT and MICT programs (three days per week) on a treadmill for eight weeks. Measurements included serum glucose, insulin, myonectin, and the homeostasis model assessment of insulin resistance (HOMA-IR). Additionally, the weight of the Flexor hallucis longus (FHL), gastrocnemius muscles, and epididymal and retroperitoneal fat pads was recorded. Results: Both HIIT and MICT significantly reduced weight gain and fat mass (epididymal and retroperitoneal) compared to the control group (P < 0.05). Eight weeks of HIIT significantly decreased serum insulin levels and HOMA-IR compared to both the control and MICT groups (P < 0.05). No significant differences in serum myonectin levels were observed between the groups. Conclusions: This study suggests that HIIT is more effective than MICT in improving metabolic status in rats, though it does not significantly affect serum myonectin levels.
