Alternative strategies to improve the beneficial effects of exercise throughout life : dietary and physiological aspects

markdownabstractAbstract It is certain that the aging process leads to death, but decreasing the levels of pathology throughout life improves the quality of life and extends life span. Therefore, this dissertation focuses on alternative strategies that may contribute to improving the aging process and associated common pathologies. In particular, this work presents exercise as the foundation of healthy aging and discusses potential strategies to improve existing suboptimal interventions to improve the aging process. The introductory chapter defines the aging process and its main pathologies. The dissertation presents how non-invasive and more cost-effective interventions may ameliorate the aging process. Chapter 1 addresses the current controversy around the effects of dietary antioxidants in conjunction with endurance training. Based on some pre-clinical and clinical work, reduced formation of reactive oxygen species may blunt health benefits of endurance type of exercise training. However, the evidence is still not robust and number of reports do not show adverse effects of popular dietary antioxidants combined with endurance training. Additionally, it is possible that some dietary supplements (e.g. resveratrol) may improve effects of endurance training in subjects with e.g. vitamin deficiencies and cardiovascular dysfunction. Therefore, the lack of clarity warrants future studies on doses, types and combinations of dietary antioxidants and different exercise training modalities. Next to nutritional strategies, there is need for alternative interventions that will improve effects of exercise non-invasively and cost-effectively. Chapter 2 presents a validation study comparing 2 methods for the 2nd anaerobic threshold (AT2) during an incremental exercise test. AT2 assessment based on heart rate variability (HRVT) is a non-invasive and more cost-effective method than assessment based on the spiro-ergometry output or a lactate curve. Our results show that HRVT is sufficiently valid and accurate, but its application in rehabilitation patient groups still warrants separate validation studies. Nevertheless, our results indicate that it has potential application for individualized training design and monitoring. Chapter 3 and 4 describe a novel strategy to improve exercise tolerance by oxygen supplementation during exercise. Using a set up that can be easily applied in a clinical training center, chapter 4 shows that a 100% oxygen flow of 15 L.min-1 applied through a mask increased the arterial oxygen pressure to sufficient high levels in deconditioned type 2 diabetes patients. This feasibility study shows that higher oxygen availability may improve oxygen delivery to exercising muscles and improve exercise tolerance, if needed. The novel experimental method described in chapter 3 showed that recovery VO2 and muscle oxygenation kinetics following a submaximal bout of exercise under both hypoxic, normoxic and hyperoxic conditions may be useful to test whether supplemental oxygen is beneficial or not. Our results indicate that for submaximal exercise bouts healthy subjects will not benefit from supplementary oxygen. Nevertheless, performing acute exercise bouts under hyperoxic conditions may help detecting oxygen delivery limitations. Additionally, acute exercise tests under hyperoxic conditons will help establishing doses supplemental oxygen for better exercise training effects in deficient subjects e.g. older adults, CHF and COPD patients. Chapter 5 and 6 address the topics of increased sedentary time, physical activity level decline and its consequences (sarcopenia) in older adults. Chapter 6 shows higher likelihood for the metabolic syndrome and its components in most sedentary and inactive older adults. In aging populations at risk or with the metabolic syndrome (chapter 5) inactivity and sedentary behavior lead to its progression together with the muscle quality loss. In particular, low levels of muscle quality and high levels of adipose tissue are associated with a functional capacity decline and progression of the metabolic syndrome. Taken together, the lack of light, moderate-to-vigorous physical activity and resistance training increase the risk of chronic diseases (type 2 diabetes and cardiovascular disease) and disability at relatively younger age. Finally, in the general discussion we discuss our new insights and findings and make recommendations for future research and alternative strategies that may prevent aging related pathologies and improve the beneficial effects of exercise throughout life.