Applied Physiology of Aging and the Master's Athlete
All living beings experience a period of growth and maturation followed by a period of decline, which is often accompanied by disease, and which culminates eventually in death. Although the aging process is hard-wired into our systems and cannot be stopped this does not mean that we are completely at its mercy. On the contrary, individuals can significantly, and sometimes dramatically, influence how quickly or how well they age. The foods they eat, activities in which they choose to engage, environmental toxins to which they are exposed, and numerous other factors have been shown to individuals can significantly, and sometimes dramatically, influence how quickly or how well they age. The foods they eat, activities in which they choose to engage, environmental toxins to which they are exposed, and numerous other factors have been shown to either “accelerate” or “slow” the aging process. Many of these changes can be minimized through regular exercise.
Master’s athletes are often considered to be as ideal a model for studying aging, and specifically quantifying primary aging, that we have available. These athletes have often lived pristine lives – eating well, exercising regularly, avoiding exposure to smoke, and having access to quality medical care. Yet despite doing almost everything right they still age. This is evidenced by the fact that performance records decrease with advancing age in virtually all individual competitive sports – such as track and field, running, bicycling, and swimming. The rates of decline are unique to each activity but generally decrease after the age of 40 with an accelerated rate of decline after the age of 70. The question is not IF they will age but HOW they will age. Master’s athletes tend to live longer, have fewer diseases, and possess higher levels of function than their less active peer counterparts demonstrating the power of lifestyle to minimize the effects of secondary aging.
Primary Aging: The innate process of maturation and subsequent decline which occurs in the body’s cells and physiological systems throughout the life span that makes the organism more susceptible to disease, injury, and death. These are “hard-wired” into our genetic code and cannot be altered.
Secondary Aging: Age-related deterioration's that result from lifestyle behaviors (physical activity, nutrition, tobacco, alcohol), disease processes (diabetes, cancer, cardiovascular disease), environment (exposure to toxins, air pollution, UV radiation), injury and illness. These factors are highly variable
and can be significantly controlled by the individual to delay some age-related processes.
Chronological Aging: The number of years a person has been alive, their chronological age, has long been used to categorize, and sometimes discriminate against, an individual. Chronological age, however, is a very crude and often inaccurate means of determining how “old” an individual is from the biological or physiological perspective. The mature adult population is diverse and therefore an individual who is older chronologically may be healthier, fitter and more functional than their younger counterparts.
Usual Aging: Describes how most individuals today “usually” or “typically” age. The typical older adult can function independently but has an increased risk of disease or disability. The disability risks are due, in large part, to the reduced functional reserve capacity of the individual and their downward aging trajectory. That is, they have a reduced capacity for performing more intense activities.
Successful Aging: Based on the research by Rowe and Kahn this is defined by the ability to maintain a low risk of disease and disease-related disability; high mental and physical function; and active engagement with life. It recognizes the importance of each of the seven dimensions of wellness – physical, intellectual, emotional, spiritual, environmental, vocational, social – to the overall well-being of an aging individual.
Lessons from Master’s Athletes
Participation in competition by master’s athletes has risen steadily over the past few decades. In 1987 only 500 participants competed in the annual Huntsman World Senior Games which offers a variety of sports competitions such as basketball, biking, swimming, volleyball, and tennis and is open to all athletes age 50 and older. By contrast 9,000 master’s athletes competed in the 2007 competition. In 2005, 9,000 competitors participated in events held across the U.S. as part of the National Senior Olympic Games competition hosted by the National Senior Games Association (NSGA). In 2007 the NSGA reached a milestone by hosting over 12,000 competitors and creating a new age division of 80+ for basketball. The NSGA anticipates participation swelling to 15,000 for the 2011 competition (www.nsga.com).
These athletes represent a growing hodgepodge of individuals with varying abilities, interests and sporting experience that are part of the global aging boom. The Administration on Aging estimates that in the U.S. alone almost 8,000 adults will turn 60 every day (www.aoa.gov) and many other countries are experiencing similar senior explosions. Some of these master’s athletes are ex-competitive athletes still eager to stay at the top of their game but a growing number were never competitive in their younger years and have just “aged into it”.
There are a growing number of others who have picked up their sport late in life. Athletes such as Helen Beauchamp who earned five gold medals and set one national record at the 2007 National Senior Games although she did not enter her first track and field event until the spry age of 64. Although different sports have their specific definitions of what constitutes a master’s athlete, I will be using it to mean athletes over the age of 50. The growing interest by the baby boomers, who began turning 60 in 2006, in health, wellness and anti-aging along with a high amount of discretionary income certainly helps create an environment conducive producing large number of master’s athletes. The Senior Olympians are perhaps the models of successful aging as they exhibit high levels of functional capabilities, less chronic disease conditions, a high quality of life and report higher levels of physical and mental health on subjective surveys (Wright and Perricelli 2008). The most reported conditions are low back pain (25.3%), hypertension (22.9%) and knee osteoarthritis (15.3%), all at lower prevalence rates than their peers in the general population (Wright and Perricelli 2008). This is consistent with a large volume of data showing that physically active adults at all ages are at lower risk of and have lower prevalence rates of many chronic diseases, such as cardiovascular disease, diabetes and some cancers (Tanaka and Seals 2003). As the boomers continue to age and as numerous organizations continue to extol the benefits of regular exercise it is likely that the number of master’s athletes will increase exponentially.
Lessons on Health and Function from Master’s Athletes
Because of their exemplary physical and mental condition master’s athletes represent a great model for the study of successful or optimal aging. The changes observed with advancing age in this group are the results of primary (physiological) aging rather than the effects of secondary (lifestyle) aging (Tanaka and Seals 2003). It has been well-established that negative lifestyle behaviors such as smoking, poor diet, weight gain and sedentary living contribute significantly to a loss of physical function by the age of 60-70. Because of their avoidance of these negative behaviors along with the adoption of many positive behaviors physical performance capability is well maintained to the 7th decade of life suggesting that most adults should also be able to sustain their physiological reserves until then (Tanaka and Seals 2003).
The Effects of Aging on Sports Performance
In the most recent review of the literature regarding age-associated changes in endurance exercise performance Tanaka and Seals (2008) state that “Older athletes strive to maintain or even improve upon the performance they achieved at younger ages, but declines in athletic performance are inevitable with ageing.” Both running and swimming performance appear to decline in a curvilinear fashion with advancing age although the patterns are not identical, and gender is an important factor. In general swimming performance declines to a lesser degree and drops off later than running.
Specifically, running performance is well maintained until around the age of 35 with modest declines in performance until the age of 50-60 with a progressively steeper increase in running times thereafter (Tanaka and Seals 2003). The rate of decline in endurance performance is faster in women especially after the age of 60 and has been shown to be up to threefold greater. Swimming performance, by contrast, does not appear to reach an exponential rate of decline until around the age of 70, a full 10 years later than running performance. In addition, the magnitude of decline is as much as 30% smaller in swimming compared to running. The increased magnitude of decline in running performance with age has been at least partially attributed to an increased incidence of orthopedic injuries compared to swimming which inhibits adequate training volume. Distant-dependent sex differences are observed in swimming with shorter events showing the greatest disparity. The differences declined with increasing distance and disappear altogether in the longest distance events (Tanaka and Seals 2003).
Strength and power performance are similarly affected. The typical aging adult will lose around 30% of their muscle mass and maximal strength from the time they peak in their 30’s to the age of 70 where the decline appears to increase in an accelerated fashion (Jones 2006). Strength training athletes appear to exhibit similar rates of decline although they remain much stronger than their more sedentary peers because their baseline started out much higher. Even in Olympic weightlifters’ maximal performance
levels decline rather linearly until around the age of 70 where the rates of decline accelerate significantly (Tanaka and Seals 2003). However, even nonagenarians retain the capacity for increasing muscular size, strength, and power with adequate resistance training. Therefore, athletes that have not participated in a regular program of weightlifting should be highly encouraged to do so.
Physiological Mechanisms Explaining the Declines in Performance. There are three primary determinants of maximal aerobic capacity that have been identified as contributing to the age-related reductions in endurance performance - VO2max, lactate threshold and exercise economy. It has been well-established
that VO2max is the primary determinant of endurance exercise performance in adults. An inverse relationship has been observed between VO2max and age in trained distance runners. Lactate threshold, defined as “the exercise intensity at which blood lactate levels increase significantly above baseline” (Tanaka and Seals 2003), also contributes to the age-related declines in endurance performance. However, the reduction in lactate threshold impacts endurance performance more in young adulthood
to early middle-age while reductions in VO2max affects performance more beyond middle-age. Although exercise economy, which is the oxygen cost to exercise at a given velocity, is an important determinant of endurance performance it does not appear to be altered with advancing age and thus contributes little to age-associated declines.
There are numerous physiological factors that contribute to the decline in VO-2max with advancing age. Oxygen consumption is determined by central and peripheral factors. The Fick equation states that VO2max = maximal cardiac output (CO) x maximal arterio-venous O2 difference (a-v O2). Maximal cardiac output is determined by multiplying maximal heart rate (HRmax) by maximal stroke volume (SVmax). HRmax declines about 0.7 beats per year, SVmax declines by 10-20% and peripheral oxygen extraction declines by 5-10% thus reducing VO2max in older master’s athletes compared to younger athletes.
However, another important consideration is training stimulus. While athletes may have great intentions of continuing their training routine it has been established that neither exercise training intensity nor volume can be maintained for long periods at older ages (Tanaka and Seals 2008). According to Tanaka and Seals (2008), numerous factors may be responsible. First, an increase in family or job responsibilities may reduce both the time and energy available for intense training. Second, there is an increased incidence of orthopedic injuries among master’s athletes. Third, bio behavioral changes may be at work. The motivation to train may be reduced as the athlete ages as well as the goals underlying the motivation may shift away from being focused on individual performance to health benefits. Lastly, the ‘intrinsic drive’ to exercise may decline with aging as demonstrated in animal studies. Regardless of the reasons or combination of factors an inability to maintain the training stimulus contributes to the rate of decline in VO2max and endurance exercise performance.