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.

References

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.

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