There’s no doubt that there is a loss of athletic performance with aging. We will never see a 70-year-old athlete take gold in the Olympic Games marathon. Sports scientists have offered several reasons why age robs us of the ability to compete with young endurance athletes at the highest level. In my last post I described a couple of studies examining the loss of muscle mass as this is one of the commonly accepted reasons for slowing down as we get older.
What’s not fully understood is why muscles atrophy. We know that muscle fibers get smaller and even seem to disappear later in life. It has to do with some combination of the well-documented physiology of aging and the less understood changes that typically occur in lifestyle resulting in our being less active as we get older. How much of the loss of performance can be attributed to these two variables – physiology and lifestyle – is open to speculation. Which causes the greater drop in performance over the years? The research I described here on muscle and aging still leaves the question unanswered.
But many scientists have come to conclusion that the major contributor to the decline is not really age, but rather lifestyle, especially a reduction in strenuous activity. They believe the physiology-lifestyle balance is around 30-70. In other words, 70% of our lowered performance may be explained by changes in lifestyle (training) with the changes due to aging accounting for only 30%.
Besides muscle wasting, there are other physical changes that science tells us to expect as we get older. Perhaps we can find an answer as to what the balance is between physiology and lifestyle as the root causes in one of them.
One other such critical marker of aging is aerobic capacity (VO2max). This is one of the most studied markers of endurance performance. Perhaps we’ll find the answer here.
But before getting into that, let’s review the big picture of what accounts for our performance in endurance sports. Science tells us there are three physiological predictors of your endurance performance regardless of age:
* Aerobic capacity has to do with how much oxygen you use per minute relative to your body weight when at a sustained, maximal workload. This intensity can be maintained for only a handful of minutes by highly fit athletes. The greater the aerobic capacity, the greater the likelihood you can produce a high level of performance.
* Lactate threshold is the percentage of aerobic capacity at which you begin to “redline” meaning that you start to experience an increase in the acidity of muscles and body fluids. Highly fit athletes can maintain this intensity for about an hour.
* Economy measures how efficiently you use oxygen to produce a given output (pace, speed, power). The greater the economy, the less wasted oxygen (and energy) and therefore the better your performance.
Of these three, science tells us that the best marker of age-related performance decline is aerobic capacity and secondarily lactate threshold while economy is a distant third and seems to remain stable (Tanaka, Tanaka, Wiswell). That economy would not be a good age-related performance predictor makes sense since after decades of training and racing the movement patterns of older athletes have become well-honed. So it’s aerobic capacity that we need to examine closely to see what might be expected as the candles on the birthday cake increase.
Aerobic capacity is largely dependent on how much oxygen-carrying blood your cardiovascular system can deliver to the muscles. So the starting point is your heart’s stroke volume (how much blood is pumped per beat). Among the many other aerobic capacity determiners are aerobic enzymes found in the muscles. Both of these and a bunch of other aerobic capacity determiners – such as how elastic your blood vessels are and how much red blood cell-building, natural levels of EPO you produce – have been shown to decline with age.
Ok, so aerobic capacity decreases as we get older. I can accept that. But by how much, and more importantly, why? Let’s go back to the research to look for answers.
There is quite a bit of research on age and aerobic capacity. How come? I suppose it’s because aerobic capacity is so easily measured in the lab (it’s been a common procedure since the 1920s) and it doesn’t require invasive techniques such as taking muscle biopsies or pricking the skin to draw blood (ouch!).
Since VO2max testing has been so common for so long we now finally have some longitudinal studies in which athletes are tested over several years to see how their aerobic capacities change. This offers hope of finding the affect of lifestyle on performance as distinct from the aging process. Let’s look at a few such studies.
Research tells us that the decline has a lot to do with how active we are as we get older. For example, a paper released in 2000 examined the combined affects of age and activity level over time (Wilson). The researchers reviewed 242 studies on aging and VO2max involving 13,828 male subjects. Each of the subjects was assigned to one of three groups based on how active they were: sedentary, moderately active exercisers and endurance-trained runners. Aerobic capacity was highest in the runners and lowest in the sedentary. No surprises there. The aerobic capacity changes per decade of life were sedentary -8.7%, active -7.3% and runners -6.8%. So if at age 30 a man had a VO2max of 60 and for the next 30 years didn’t exercise and lived a “normal” life (sedentary) he could expect his aerobic capacity at age 60 to be around 46. If moderately active it would be about 48. And if he trained it would be in the neighborhood of 49. Those are not significant changes.
But the study further reports that the subjects who were “endurance-trained runners” significantly decreased their volume (miles/kilometers run per week) and training intensity as they got older. I’ve found that as a common practice with aging athletes. There could be many reasons for this (which I’ll address in the following post). So maybe it’s not simply working out that maintains aerobic capacity and therefore, in part, race performances, but rather how much training you do and how intensely you do it. This is an important lesson
That aerobic capacity declines with aging and reduced training is not surprising. I’ve mentioned “use it or lose it” several times in this on-going discussion. This brings us back to the question of what the balance between age and lifestyle is when it comes to performance.
Three other reviews of the literature in the last decade or so examined the relationship between aging and training status to figure out the relative contributions of both (Hawkins, Wiswell, Young). They confirm that reductions in training volume and intensity are primary contributors to the loss of aerobic capacity with advancing age.
Let’s dig a little deeper to find which is more important to the maintenance of aerobic capacity with aging from a strictly training perspective – volume or intensity. The answer may provide some insights into how to train as age sneaks up on you – assuming you want to maintain, or at least slow, the drop in performance which probably first becomes apparent in your 50s and greatly accelerates somewhere beyond 70.
In the 1970s a team of researchers at the University of Illinois measured the aerobic capacities of 24 masters track runners who were 40 to 72 years old at the time (Pollock). Ten years later they were retested. Over the decade all continued to train but only 11 were still highly competitive. The other 13 quit racing and decreased their training intensity. The competitive athletes maintained their training intensities and, consequently, their aerobic capacities. There was no significant change. The non-competitive, low-intensity group lost about 12% of their aerobic capacities over 10 years.
So what’s the bottom line here? The research team led by Wilson showed us that the changes in aerobic capacity with aging are not too different between sedentary subjects and runners who reduce their training. Several other studies also showed us that decreases in training workload have a significant impact on aerobic capacity with the key being intensity, according to the Pollock paper. When training intensity was maintained by master runners over a 10-year period, aerobic capacity remained unchanged. When training volume remained about the same but intensity decreased, aerobic capacity dropped by an average of 1% per year.
That’s a clear message. It isn’t just exercising slowly for long periods of time that keeps our performance, at least in terms of aerobic capacity, from dropping rapidly; it’s primarily the intensity of the exercise that matters. That raises new issues (problems?) that I’ll address in my next post.
Hawkins S, Wiswell R. 2003. Rate and mechanism of maximal oxygen consumption decline with aging: implications for exercise training. Sports Med 33(12):877-88.
Pollock ML, Foster C, Knapp D, et al. 1987. Effect of age and training on aerobic capacity and body composition of master athletes. J Appl Physiol 62(2):725-31.
Tanaka H, Seals DR. 2003. Invited review: Dynamic exercise performance in masters athletes: insight into the effects of primary human aging on physiological functional capacity. J Appl Physiol 95(5):2152-62.
Tanaka H, Seals DR. 2008. Endurance exercise performance in masters athletes: age-associated changes and underlying physiological mechanisms. J Physiol 586(1):55-63.
Wilson TM, Tanaka H. 2000. Meta-analysis of the age-associated decline in maximal aerobic capacity in men: relation to training status. Am J Physiol Heart Cric Physiol 278(3):H829-34.
Wiswell RA, Jaque V, Marcell TJ, et al. 2000. Maximal aerobic power, lactate threshold, and running performance in master athletes. Med Sci Sports Exerc 32:1165-70.
Young BW, Medic N, Weir PL, Starkes JL. 2008. Explaining performance in elite middle-aged runners: contributions from age and from ongoing and past training factors. J Sport Exerc Psychol 30(6):737-54.