CNTF genotype is associated with muscular strength and quality in humans across the adult age span

The relationship between ciliary neurotrophic factor (CNTF) genotype and mu scle strength was examined in 494 healthy men and women across the entire a dult age span (20-90 yr). Concentric (Con) and eccentric (Ecc) peak torque were assessed using a Kin-Corn isokinetic dynamometer for the knee extensor s (KE) and knee flexors (KF) at slow (0.52 rad/s) and faster (3.14 rad/s) v elocities. The results were covaried for age, gender, and body mass or fat- free mass (FFM). Individuals heterozygous for the CNTF null (A allele) muta tion (G/A) exhibited significantly higher Con peak torque of the KE and KF at 3.14 rad/s than G/G homozygotes when age, gender, and body mass were cov aried (P < 0.05). When the dominant leg FFM (estimated muscle mass) was use d in place of body mass as a covariate, Con peak torque of the KE at 3.14 r ad/s was also significantly greater in the G/A individuals (P < 0.05). In a ddition, muscle quality of the KE (peak torque at 3.14 rad(.)s(-1.)leg musc le mass(-1)) was significantly greater in the G/A heterozygotes (P < 0.05). Similar results were seen in a subanalysis of subjects 60 yr and older, as well as in Caucasian subjects. In contrast, A/A homozygotes demonstrated s ignificantly lower Ece peak torque at 0.52 rad/s for both KE and KF compare d with G/G and G/A groups (P < 0.05). No significant relation ships were ob served at 0.52 rad/s between genotype and Con peak torque. These data indic ate that individuals exhibiting the G/A genotype possess significantly grea ter muscular strength and muscle quality at relatively fast contraction spe eds than do G/G individuals. Because of high positive correlations between fast-velocity peak torque and muscular power, these findings suggest that f urther investigations should address the relationship between CNTF genotype and muscular power.