The purpose of this study was to investigated the effect of age – over or under life-expectancy (LE) – on six months resistance training alone or combined with a nutritional supplement, and cognitive training by analyzing markers for oxidative stress and antioxidant defense in institutionalized elderly, living in Vienna. Three groups (n = 117, age = 83.1 ± 6.1 years) – resistance training (RT), RT combined with protein and vitamin supplementation (RTS) or cognitive training (CT) – performed two guided training sessions per week for six months. Oxidative stress, antioxidant defense and DNA strand breaks were analyzed and transformed into an “antioxidant factor” to compare the total effect of the intervention. Physical fitness was assessed by the 6-min-walking, the chair-rise and the handgrip strength tests. We observed significant negative baseline correlations between 8-oxo-7.8-dihydroguanosine and handgrip strength (r = −0.350, p = 0.001), and between high sensitive troponin-T and the 6-min-walking test (r = −0.210, p = 0.035). RT and RTS groups, showed significant improvements in physical performance. Over LE, subjects of the RT group demonstrated a significant greater response in the “antioxidant factor” compared to RTS and CT (RT vs. RTS p = 0.033, RT vs. CT p = 0.028), whereas no difference was observed between the intervention groups under LE. Six months of elastic band resistance training lead to improvements in antioxidant defense, DNA stability and oxidative damage, summarized in the “antioxidant factor”, however mainly in subjects over their statistical LE. Consuming a supplement containing antioxidants might inhibit optimal cellular response to exercise. The study was approved by the ethics committee of the City of Vienna (EK-11–151–0811) and registered at ClinicalTrials.gov, NCT01775111.