VDR Gene Polymorphisms and Inter-Individual Variability in Response to Resistance Training

Background: Vitamin D receptor (VDR) gene polymorphisms are linked to muscle and bone physiology, yet their influence on individual differences in resistance training adaptations, especially between sexes, is not well understood. Methods: In total, 191 healthy Chinese Han adults (94 men, 97 women) completed a 12-week, twice-weekly resistance training program (squat and bench press). Key indicators of strength, power, body composition, and muscle morphology were assessed before and after the intervention. Participants were genotyped for VDR polymorphisms (rs731236/TaqI, rs7975232/ApaI, rs1544410/BsmI, rs2228570/FokI). Data were analyzed to compare responses across genotype groups. Results: Training induced significant improvements in multiple outcomes. Overall, the AG genotype of rs731236 and the CT genotype of rs1544410 were associated with greater gains in bone mineral content. Sex-specific analyses revealed distinct patterns: in women, the rs731236-AA genotype correlated with better strength and power gains, while the AG genotype linked to greater body composition improvements. In men, the rs1544410-CC genotype was associated with superior lower-limb muscle growth. The rs7975232 showed no significant overall effect, and rs2228570 deviated from Hardy–Weinberg equilibrium. Conclusions: VDR gene polymorphisms, particularly rs731236 and rs1544410, are associated with inter-individual variability in resistance training responses among Chinese Han adults, demonstrating clear sex and phenotype specificity. These findings offer preliminary support for genotype-informed personalized training.