Recent Research into the Interaction of Exercise and Aging
Today's open access papers touch on aspects of the interaction between exercise and the pace of aging. People age at somewhat different rates, and for the vast majority of us lifestyle is a far greater determinant of that rate than our genes. Until such time as the clinical deployment of rejuvenation therapies is well underway, and in regions of the world sufficiently wealthy to have tamed the majority of infectious disease, it remains the case that our choices regarding our health, such as calorie restriction and exercise, are the most reliable means of improving life expectancy. The size of the effect is not enormous in the grand scheme of things: three quarters of slim, fit, well-considered people die before reaching 90 years of age, after all. You cannot add decades to your life by making incrementally better lifestyle choices.
So why bother? Well, firstly because being increasingly sick for a span of decades at the end of life is a real drag, and exercise and calorie restriction do make a sizable difference to the odds of avoiding much of that fate. But more importantly this is an era of radical, accelerating progress in the life sciences. With every passing year we move closer towards the deployment of real, working rejuvenation therapies. Some of the the first of those, senolytic treatments to clear senescent cells, can already be used by the adventurous. The times are changing rapidly when it comes to medical science. A few years of life gained through exercise, or achieving an extra decade of being fit enough to travel to try new therapies via medical tourism, may well make the difference between considerable benefits and a longer life, or missing out on that chance.
If exercise was incredibly expensive, or if exercise to improve health was only possible at the end of a multi-billion investment in medical research and development, then it wouldn't be worth it. That is the same story as for many lines of development that aim to modestly slow the aging process, those based on replicating calorie restriction, for example. Such treatments will be expensive to create, and the past twenty years tells us that this process has a high rate of failure. It just isn't worth it when other lines of rejuvenation research have far greater expected outcomes in terms of health gained and years added. But exercise is here now, free, and highly reliable. Modest gains achieved at little cost, and that near always work as intended, are not to be ignored. It helps.
The Inherent Human Aging Process and the Facilitating Role of Exercise
Arguably the best available depictions of the global physiological changes produced by age are the profiles of world record performance times in swimming, athletics, and cycling, depicting the trajectory of decline in maximal integrated physiological performance capability. The curves suggest that the aging process produces a synchronized, controlled decrease in physiological performance over the human lifespan. The shape of the performance profile by age is essentially independent of discipline, distance, or phenotype. Importantly, the specific times of performance are not the driving force in the production of the shape of the declining performance profile.
We suggest that in these highly trained individuals the shape of the curve is generated by the aging process operating on a physiology optimized for any given age. We hypothesize that with adequate training this same profile and trajectory, but with lower performance times, would be generated by all individuals who engage in sufficient physical activity/exercise. Unlike performance, data obtained from examining individual physiological systems or tissues do not give information on the unceasing and changing global integrating functions of the aging process. However, these data do give valuable information about the integrity of physiological systems at a particular age and allow a direct comparison to be made between the effects of inactivity and physical activity/exercise.
Being physically active has been shown to have global protective effects on physiological systems and thus facilitates the aging process by maintaining physiological integrity. There is emerging evidence which suggests that physiological regulation of aging may be multi-compartmentalized. We do not advocate exercise as a panacea, but all the evidence indicates that being physically active and exercising is far superior to any other alternative for achieving optimal aging.
Immunosenescence is characterized by deterioration of the immune system caused by aging which induces changes to innate and adaptive immunity. Immunosenescence affects function and phenotype of immune cells, such as expression and function of receptors for immune cells which contributes to loss of immune function (chemotaxis, intracellular killing). Moreover, these alterations decrease the response to pathogens, which leads to several age-related diseases including cardiovascular disease, Alzheimer's disease, and diabetes in older individuals. Furthermore, increased risk of autoimmune disease and chronic infection is increased with an aging immune system, which is characterized by a pro-inflammatory environment, ultimately leading to accelerated biological aging.
During the last century, sedentarism rose dramatically, with a concomitant increase in certain type of cancers (such as breast cancer, colon, or prostate cancer), and autoimmune disease. Numerous studies on physical activity and immunity, with focus on special populations (i.e., people with diabetes, HIV patients) demonstrate that chronic exercise enhances immunity. However, the majority of previous work has focused on either a pathological population or healthy young adults whilst research in elderly populations is scarce. Research conducted to date has primarily focused on aerobic and resistance exercise training and its effect on immunity. This review focuses on the potential for exercise training to affect the aging immune system. The concept is that some lifestyle strategies such as high-intensity exercise training may prevent disease through the attenuation of immunosenescence.