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

<b>Background</b>: Vitamin D receptor (<i>VDR</i>) 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. <b>Methods</b>: 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 <i>VDR</i> polymorphisms (rs731236/<i>TaqI</i>, rs7975232/<i>ApaI</i>, rs1544410/<i>BsmI</i>, rs2228570/<i>FokI</i>). Data were analyzed to compare responses across genotype groups. <b>Results</b>: 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. <b>Conclusions</b>: <i>VDR</i> 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.