The relationship of testosterone and AR CAG repeat genotype with knee extensor muscle function of young and older men

► Free testosterone (FT) and AR genotype CAGn may be related to muscle strength. ► These relationships may be influenced or confounded by age. ► In older men FT was weakly associated with muscle strength and muscularity. ► Muscle strength was unrelated to AR genotype CAGn. ► There may be an increasing influence of FT on muscle function with age.