We examined associations among myostatin (MSTN) 2379 A > G and 163 G > A and follistatin (FST) −5003 A > T and −833 G > T single nucleotide polymorphisms (SNP) on the muscle size and the strength response to resistance training (RT).Methods:
Subjects (n = 645, age = 24.1 ± 0.2 yr, body mass index [BMI] = 24.2 ± 0.2 kg·m−2) self-disclosed themselves as Caucasian (78.9%), African American (3.6%), Asian (8.4%), Hispanic (5.0%), or Other (4.2%). They were genotyped for MSTN 2379 A > G (n = 645), MSTN 163 G > A (n = 639), FST −5003 A > T (n = 580), and FST −833 G > T (n = 603). We assessed dynamic (one repetition maximum [1RM]) and isometric (maximum voluntary contraction [MVC]) muscle strength and size (cross-sectional area [CSA]) of the elbow flexors before and after 12 wk of unilateral upper-arm RT. Repeated-measures ANCOVA tested associations among genetic variants and muscle phenotypes with age and BMI as covariates.Results:
Baseline MVC was greater among African Americans who were carriers of the MSTN G2379 allele (AG/GG, n = 15) than the A2379A homozygotes (n = 8; 64.2 ± 6.8 vs 49.8 ± 8.7 kg). African Americans who were carriers of the FST T−5003 allele (n = 12) had greater baseline 1RM (11.9 ± 0.7 vs 8.8 ± 0.5 kg) and CSA (24.4 ± 1.3 vs 19.1 ± 1.2 cm2) than African Americans with the A-5003A genotype (n = 14; P < 0.05). No MSTN or FST genotype and muscle phenotype associations were found among the other ethnic groups (P ≥ 0.05).Conclusion:
MSTN 2379 A > G and FST −5003 A > T were associated with baseline muscle strength and size among African Americans only. These ethnic-specific associations are hypothesis generating and should be confirmed in a larger sample of African Americans.