The impact of resistance training volume and intensity: Exploring the role of repetitions and sets in regulating irisin secretion and its anabolic and metabolic benefits in bodybuilders

Irisin, a myokine cleaved from the membrane protein Fibronectin type III domain-containing protein 5 (FNDC5), has emerged as a critical exercise-induced hormone. It is implicated in the browning of white adipose tissue, enhanced metabolic rate, and potential anabolic processes. In bodybuilding, where precise manipulation of training variables—specifically repetitions (reps) and sets—is paramount, understanding how these variables influence irisin secretion could optimize both physique and health outcomes. This narrative review aims to synthesize current evidence on the effects of resistance training protocols, with a focus on reps and sets, on irisin secretion. Furthermore, it explores the potential subsequent benefits of elevated irisin levels for bodybuilders, including its putative roles in fat metabolism, muscle remodeling, and overall metabolic health. Evidence suggests that high-volume resistance training protocols, characterized by multiple sets (≥3) and moderate repetitions (8-12 reps), may be potent stimulators of irisin release. This secretion is hypothesized to be mediated by muscle contraction-induced PGC-1α expression. Elevated irisin levels are often correlated with improved lipid oxidation, which could aid in cutting phases by promoting a leaner physique. Additionally, preclinical and some human studies suggest irisin may support muscle hypertrophy through enhanced nutrient partitioning and autocrine/paracrine signaling, though this mechanism requires further elucidation. Strategic manipulation of resistance training volume and intensity may represent a viable method for modulating irisin secretion. Incorporating protocols that could elevate this myokine might provide bodybuilders with a dual advantage: enhancing metabolic efficiency to reduce adipose tissue and potentially supporting muscle growth and recovery. However, the current evidence is not yet definitive, and more research is needed to confirm these links.