# Physical Activity and Redox Balance in the Elderly: Signal Transduction Mechanisms
## 3 Physical Activity and Redox Balance in the Adult and the Elderly  
Aging is associated with a decrease in the activity of anti-oxidant systems, while exercise reduces the levels of oxidative stress markers, thus activating the antioxidant enzymes [29], suggesting that the greater the physical exercise, the smaller the effects of aging. Although this hypothesis could be very intriguing, it is generally supposed that low-moderate physical activity induces adaptations that increase resistance to oxidative stress, since exercise training decreases the risk for several diseases associated with oxidative stress. Many studies have been published on this topic, but conflicting results have been reported, likely due to different parameters and measurement methods used: many groups have reported protective effects of exercise on antioxidant systems, while others have reported negative effects of training. What is commonly accepted is that markers of oxidative stress are significantly lower in trained subjects with respect to untrained ones, similar to the conditions observed in young people. For example, 8 weeks of walking does not induce oxidative stress in aged subjects [30]. In fact, Low-Density Lipoprotein (LDL) oxidation and nitration levels are not affected by walking. Instead, LDL nitration is modified by acute moderate activity. Thus, it seems important to practice intense exercise to stimulate antioxidant enzymes, rather than low-moderate activity. This condition appears also after acute oxidative challenge. In fact, fit aged subjects show lower oxidative stress than unfit age-matched subjects at baseline conditions and after an acute oxidative challenge such as forearm ischemia-reperfusion [29]. However, this is not due to lower levels of circulating antioxidant molecules. Moreover, reduced oxidative damage that has been shown in fit individuals cannot be attributed to physiological parameters like adiposity or High-Density Lipoprotein (HDL). Instead, it is likely related to differences in antioxidant enzyme activity. Thus, to be physically fit appears an effective strategy for fighting age-related oxidative damage [29]. In 2016, [PERSON] and [PERSON] [31] showed that sedentary middle-aged adults could increase their resistance to oxidative stress (forearm Ischemia Reperfusion (IR)) through whole-body aerobic training (45-min sessions three times per week, with an intensity of 70-85% maximal heart rate). In fact, the level of the oxidative marker F2-isoprostanes was significantly decreased after exercise, but not at the baseline pre-IR [31]. Age-related dysfunctions of redox balance also determine endothelial alterations that have been associated with cardiovascular disease. Ten days of treadmill training (1 h at 70% of VO\({}_{\text{2 max}}\)) significantly increase flow-mediated dilation of arteries and Vascular Endothelial Growth Factor Receptor-positive (KDR+) circulating cells, while not affecting the level of SOD mRNA, intracellular nitric oxide (NO), ROS, endothelial Nitric Oxide Synthase (eNOS), NADPH oxidase 2 and neutrophil cytosolic factor 1 in healthy older adult subjects. Thus, these data suggest that short-term aerobic training can reduce risk factors for cardiovascular disease [32]. As for young subjects, the effect of antioxidant molecules, alone or in combination with exercise, has been tested for muscle physiology and function. For muscle tissue, a good antioxidant has not been found yet, although the effect of plant extract and moleculeslike resveratrol and vitamins have been investigated [33; 34; 35; 36; 37]. For example, a waste-water polyphenic mixture (LACHI MIX HT) containing hydroxytirosol (HT), gallic acid and homovanillic acid induced functional amelioration in the skeletal muscles of 27-month-old rats [33]. Moreover, a decrease of oxidative stress marker levels was observed [33]. The resveratrol had been used, with positive effects, in 18-month-old mice in combination with exercise for 4 weeks [34].