EFFECTS OF TRAINING REGIMES AT DIFFERENT INTENSITIES ON PERFORMANCE AND OXIDATIVE STRESS IN MASTERS ATHLETES

Over the last decade, the participation of middle-aged and older (‘masters’) involved in sport activities at different levels has significantly increased, particularly in long-distance events. Master athletes are typically characterized as people who continue physical training throughout life and in this population, the incidence and risk of chronic and age-related diseases are reportedly lower, and self-rated health is better than in apparently healthy controls. However, regardless of training a decline in peak athletic performance in both endurance and sprint events and for all competitions/disciplines usually occurs with aging. In particular, declines in endurance exercise performance and its physiological determinants with ageing appear to be mediated in large part by a reduction in the exercise training ‘stimulus’, mainly as a result of increased work and family commitments, few masters still follow structured training programs, and the increased prevalence of exercise training-associated injuries that probably contributes to their reduced training intensity and volume. Furthermore, aging is accompanied by a progressive increase in free radical production (i.e., synthesis of reactive oxygen species) with a concomitant decrease in the enzymatic defence mechanisms, promoting the development of oxidative stress. The chronic repetition of exercise, i.e. exercise training, may have the capability to develop a compensation to oxidative stress in skeletal muscle fibres by means of an adaptation of the antioxidant and repair systems. This might result in a decreased resting level of oxidative damage and an increased resistance to oxidative stress. In general, the main types of training used to improve endurance exercise performance are: i) continuous training at moderate intensity (CON); and ii) discontinuous training at high intensity (DHIT). Different studies showed that even in sedentary or moderately trained individuals, DHIT might be an efficient strategy to induce adaptations in skeletal muscle and exercise performance that are comparable with conventional endurance training. The first part of the thesis is focus on master runners. First study aims to evaluate if an individualized training schedules characterized by an overall reduction of training volume is able to improve running performance. Moreover, the impact of CON and DHIT training programs on running performance and its main physiological factors in master runners has been evaluated. The second study aims to evaluate the effects of 8-week of DHIT and CON on resting level and time-course changes of several indexes of oxidative stress. The main findings of these studies show that despite a significant reduction of training volume, CON and DHIT, characterized by the same total volume, improve running economy and running performance. Furthermore, both CON and DHIT induced similar beneficial effects, reducing the resting levels of oxidative stress biomarkers in plasma and urine. The second part of the thesis is focused on master swimmers. The third study aims to compare the effects of two opposite training protocols (low-volume high-intensity vs high-volume low-intensity) in a group of trained master swimmers. The fourth study aims to examine the effects of low-volume high-intensity training on ROS production and on antioxidant capacity in master swimmers by applying electron paramagnetic resonance measurement. The results indicate that in master swimmers an increase of training volume may lead to an improvement of indexes of aerobic capacity and middle-long distance performance. A subsequent period of high-intensity low-volume training, besides maintaining previous improvements, may positively affect also short distance performance. Moreover, high intensity training improves antioxidant capacity and significantly decreases baseline ROS production.