To develop a global view of muscle transcriptional differences between older men and women and sex-specific aging, we obtained muscle biopsies from the biceps brachii of young and older men and women and profiled the whole-genome gene expression using microarray. A logistic regression-based method in combination with an intensity-based Bayesian moderated t test was used to identify significant sex- and aging-related gene functional groups. Our analysis revealed extensive sex differences in the muscle transcriptome of older individuals and different patterns of transcriptional changes with aging in men and women. In older women, we observed a coordinated transcriptional upregulation of immune activation, extracellular matrix remodeling, and lipids storage; and a downregulation of mitochondrial biogenesis and function and muscle regeneration. The effect of aging results in sexual dimorphic alterations in the skeletal muscle transcriptome, which may modify the risk for developing musculoskeletal and metabolic diseases in men and women.

Purpose: To assess strength, size, and muscle quality differences between younger and older males and females in response to training. Methods:The bicep and tricep of the non-dominant arm were trained for twelve weeks in younger and older males and females (n = 41). The bicep of both arms were assessed pre and post for muscle strength using one-repetition maximum (1 RM) testing, and size using magnetic resonance imaging (MRI).Results: Strength (p Ͻ 0.05), mCSA (p Ͻ 0.05), and 1 RM MQ (p Ͻ 0.00) increased in response to training in all subjects regardless of age or gender. Younger and older subjects had similar increases in strength (45.49 ± 15.30% vs. 42.67 ± 26.67% respectively), mCSA (16.22 ± 7.98% vs. 19.17 ± 6.19% respectively), and 1RM MQ (25.73 ± 15.76 vs. 19.67 ± 20.66 respectively). Women increased their strength (55.59 ± 19.45% vs. 32.87 ± 15.66% p Ͻ 0.00 respectively), size (20.36 ± 6.29% vs. 14.72 ± 7.28% p Ͻ 0.02 respectively), and 1 RM MQ (29.74 ± 18.33% vs. 16.30 ± 15.59% p Ͻ.02) more than men. In comparing age and gender, younger females increased their strength more than older males (56.42 ± 12.92% vs. 29.17 ± 21.8% p Ͻ.02 respectively). Older females also increased their strength more than older males (54.68 ± 25.73 vs. 29.17 ± 21.80% respectively). Younger females increased their 1 RM MQ more than older males (.18 ± .08 kg/cm vs. .06 ± .08 kg/cm p Ͻ.02 respectively). Conclusion:Strength and mCSA increases similarly in older and younger subjects. However, the overall strength and quality of the muscle seems to improve more in women than in men.