Exercise-induced oxidative stress in older adults as a function of habitual activity level

OBJECTIVES: It has been suggested that regular physical activity might maintain and promote the antioxidant defense capacity against oxidative stress. Therefore, we assessed exercise-induced oxidative stress in relation to habitual physical activity level (PAL) in older adults. DESIGN: The study included a 2-week observation period for the measurement of average daily metabolic rate (ADMR) and PAL. Exercise-induced oxidative stress was measured during a 45-minute cycling test at submaximal intensity. SETTING: A university medical research center. PARTICIPANTS: Twenty-six subjects volunteered for the study (n = 26; mean age ± standard deviation 60 ± 1; body mass index 27 ± 1 kg/m²). MEASUREMENTS: PAL was determined as ADMR combined with a measurement of basal metabolic rate (BMR): PAL = ADMR/BMR. ADMR was measured over 2 weeks with the doubly labeled water method, preceded by a BMR measurement with a ventilated hood. Antipyrine oxidation was used as marker for oxidative stress in vivo. Reaction of antipyrine with hydroxyl radicals results in the formation of para-hydroxyantipyrine (p-APOH) and ortho-hydroxyantipyrine (o-APOH), where o-APOH is not formed through alternative oxygenetic pathways. RESULTS: PAL was inversely related to the exercise-induced increase in the ratio of o-APOH to native antipyrine (r = -0.49, P = .010). The relationship between PAL and exercise-induced increase in the ratio of p-APOH (r = -0.30, P = .140) or thiobarbituric acid reactive species (r = -0.31, P = .130) did not reach the level of significance. CONCLUSION: Physically active older adults have a reduced exercise-induced oxidative stress than older adults with a lower level of physical activity. It seems that regular physical activity improves the antioxidant defense capacity.