Frailty as a phenotypic manifestation of underlying oxidative stress.

Oxidative stress plays a key role in the aging process. Lifestyle behaviours including low physical activity and inadequate nutritional habits in addition to genetic susceptibility and some chronic diseases compromise physiological response to free radicals and promote oxidative damage. Reduced resilience (referred to the ability to respond to stressors or adverse conditions) or functional reserve in isolated organs or systems determines clinical manifestations as the age-related chronic diseases while multisystemic dysfunction results in the frailty phenotype. In older adults, frailty, but not age, is associated with elevation of oxidative stress markers and reduction of antioxidant parameters. Mitochondrial dysfunction related to oxidative stress plays a prominent role in this process affecting not only skeletal muscle but also other potential tissues and organs. Increasing endogenous antioxidant capacity in different systems by exercise outstand among therapeutic interventions with potential ability to prevent or delay frailty phenotype and to promote healthy aging.