Exercise and Healthy Aging

 Exercise is useful in the prevention and management of type 2 diabetes, hypertension, coronary heart disease, dementia and depression and helps in healthy aging. Regular exercise is also known to be of significant benefit in the prevention of colon and postmenopausal breast cancer. Exercise helps to preserve muscle mass, prevents osteoporosis and age-associated dementia and Alzheimer’s disease and thus, helps in healthy aging. The mechanism(s) responsible for the beneficial actions of exercise include: (a) a 100-fold increase in plasma interleukin-6 (IL-6) levels that triggers anti-oxidant defenses in the body, (b) increased production of brain-derived neurotrophic factor (BDNF), (c) increase in niacinamide that regulates insulin sensitivity, and promote glycemic control, (d) enhanced utilization of polyunsaturated fatty acids (PUFAs) and augmented formation of lipoxins, resolvins, protectins and nitrolipids, potent anti-inflammatory molecules, and (e) increase in the formation of endothelial nitric oxide (NO), a vasodilator and platelet anti-aggregator, that enhances the formation of mitochondria. Exercise is anti-inflammatory in nature and regular exercise has favourable effects on immune system that accounts for its ability to prevent adult diseases.

People who are physically inactive have a life span that is 5 years shorter than that of physically active people. Moreover, the expected lifetime without long-standing illness is reduced by approximately 8 years in physically inactive people (1). Physical inactivity increases the risk of type 2 diabetes, cardiovascular disease, colon cancer; postmenopausal breast cancer, dementia and depression Low-grade systemic inflammation is associated with physical inactivity independent of obesity (8) that, in turn, promotes development of insulin resistance, atherosclerosis, neurodegeneration and tumour growth.

EXERCISE DOES NOT ALWAYS EQUATE WITH MUSCLE CONTRACTION ALONE In majority of the instances, exercise is synonymous with contraction of a muscle or muscles. But, it should be understood that contraction of a muscle does not necessarily imply that the muscle shortens; it only means that tension has been generated. Muscles can contract in the following ways: Isometric contraction This is a contraction in which no movement takes place, because the load on the muscle exceeds the tension generated by the contracting muscle. This occurs when a muscle attempts to push or pull an immovable object. Isotonic contraction This is a contraction in which movement does take place, because the tension generated by the contracting muscle exceeds the load on the muscle. This occurs when one uses his/her muscles to successfully push or pull an object. Isotonic contractions are further divided into two types: - Concentric contraction This is a contraction in which the muscle decreases in length (shortens) against an opposing load, such as lifting a weight up. - Eccentric contraction This is a contraction in which the muscle increases in length (lengthens) as it resists a load, such as pushing something down. During a concentric contraction, the muscles that are shortening serve as the agonists and hence do all of the work. During an eccentric contraction the muscles that are lengthening serve as the agonists (and do all of the work). For all practical purposes exercise involves contraction and relaxation of various muscles of the body depending on the type of exercise performed. Hence, performance of exercise is almost synonymous with muscular contraction and release of myokines in the process.

 CONCLUSIONS Exercise has many benefits and some of the molecules that are involved in bringing about these beneficial actions appear to be IL-6, BDNF, irisin, lipoxins, resolvins, protectins, nitrolipids, PUFAs, NO, ROS (reactive oxygen species), TNF-α, and enhanced expression of follistatin, Nur77, PGC1-α, and decreased expression of myostatin and alterations in the expression of a plethora of genes (see Figures 1 and 2). It is likely that polymorphism in the genes that are altered by exercise may render some subjects resistant or beneficially susceptible to the positive effects of exercise.