Glucocorticoid Receptor (NR3C1) Variants Associate with the Muscle Strength and Size Response to Resistance Training

Glucocorticoid receptor (NR3C1) polymorphisms associate with obesity, muscle strength,
and cortisol sensitivity. We examined associations among four NR3C1 polymorphisms
and the muscle response to resistance training (RT). European-American adults (n = 602,
23.8±0.4yr) completed a 12 week unilateral arm RT program. Maximum voluntary contraction
(MVC) assessed isometric strength (kg) and MRI assessed biceps size (cm^2) preand
post-resistance training. Subjects were genotyped for NR3C1 -2722G>A, -1887G>A,
-1017T>C, and +363A>G. Men carrying the -2722G allele gained less relative MVC (17.3
±1.2vs33.5±6.1%) (p = 0.010) than AA homozygotes; men with -1887GG gained greater
relative MVC than A allele carriers (19.6±1.4vs13.2±2.3%) (p = 0.016). Women carrying
the -1017T allele gained greater relative size (18.7±0.5vs16.1±0.9%) (p = 0.016) than CC
homozygotes.We found sex-specific NR3C1 associations with the muscle strength and
size response to RT. Future studies should investigate whether these associations are
partially explained by cortisol’s actions in muscle tissue as they interact with sex differences
in cortisol production.