• Use It or Lose It
  Can We Slow the Effects of  Physical Decline as We Age?
  by Keith R. Williams, Phd
  
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Your long-distance running performances generally peak when you are somewhere between the early 20s and the mid-30s. After that, there is an inevitable decline in performance that starts well before middle age and continues throughout the rest of life. That’s the bad news.

The good news is that one of the beneficial consequences of a lifelong commitment to running is that over the years you’ll experience a slower rate of decline with age in the physiological functions related to performance than do your sedentary friends or those who train minimally. There appears to be wisdom in the saying “Use it or lose it.” Just how much can you expect performance to decline over the years? What causes this decline? Is the decline the same for men and women?
 
 

Confounding Factors

Before detailing some of the changes that occur in performance as we age, let’s briefly consider several factors that complicate the issue. The primary problem is that it is difficult to separate the effects on performance that are directly attributable to aging from those that are due to disease, disuse, or other factors. It is also difficult to identify how evolving social environments and scientific advances in training and equipment may have affected performance times across ages.

Bortz and Bortz (1996) propose that changes in athletic performance records with age may be a possible biomarker of aging, that is, a way of identifying changes due to the aging process, independent of the influences of disease or reduced activity. For example, an individual capable of setting a world record is in an elite group that is highly motivated, highly trained, and probably influenced minimally by factors other than aging. However, even using performance records as a method for isolating changes due to aging does not eliminate potentially confounding factors. World records have continued to improve over the decades, the result of advanced training methods, increased competitive opportunities, and improved equipment and facilities, and these factors may affect age-related records in inconsistent ways.

Another problem is that most of the data available is from a cross-section of the running population and not from longitudinal changes in individuals over time. Cross-sectional data may not be fully representative of how an individual’s performance will change.

It is also not possible to identify directly how injuries may influence decrements in performance with age. Koplan et al. (1995) surveyed more than 500 finishers of a 10K road race 10 years after the race and found that 56 percent of the entrants were still running, and 81 percent were still exercising regularly. Fifty-three percent reported at least one injury during the 10-year period, and 30 percent had had at least one injury requiring medical care. Of those who stopped running, 31 percent of the men and 17 percent of the women cited injury as the primary reason. It is likely that some amount of the decrease in performance with age is the result of injury, but data is not available to document the exact nature of any effect.

The possible confounding influence on performance data of the factors just mentioned suggests that we should consider with some caution the conclusions that follow, especially when generalizing the results to individual runners.
 
 

Changes in Performance with Age

As a general rule, distance-running performance times increase with age, and the rate of decline becomes greater somewhere in the age range of 55 to 65. Substantial individual variations exist in the rate of decline. Figures 1 and 2 illustrate the change in performance with age, showing the pattern of change in running times for the top male and top female finishers at each age in the 1997 Boston Marathon.

The curving gray lines are based on best-fit equations for the data, and the two straight, colored lines in each figure can approximate the pattern of change. Between ages 30 and 55, the change averaged 1.3 minutes per year (0.9 percent) for men, with an average decline in performance of 3.7 minutes per year (1.8 percent) between ages 55 and 75. For women, the performance time changes with age were slightly greater, averaging 2.7 minutes per year between ages 30 and 55 (1.5 percent) and 7.6 minutes per year between 55 and 64 (3.4 percent).

The number of women in the 55 to 64 age bracket was relatively small, and the changes cited here may not be representative of what would be found in a larger sample. The pattern of change with age is similar for this data to that found in most research studies, though the exact rate of change varies.

These marathon results are somewhat higher than the 0.5 percent decline described for age-group records by Bortz (1996) between ages 35 and 60. Between ages 55 and 75 their data show an average change of about 2 percent per year. Joyner (1993) cites several studies finding 6 to 9 percent decrements per decade (0.6 to 0.9 percent per year) until the mid-50s, with accelerated rates of decline in later years. In another study (Evans et al. 1994), the best 10K times by age in three road races were averaged over a five-year period, and performance times were found to change quadradically with age. Average changes between 30 and 55 were approximately 1.1 percent per year for men and 1.3 percent per year for women, and between 55 and 75 the changes were 2.1 percent per year for men and 3.3 percent per year for women.
Analysis of 50K to 200K running age-group world records shows similar, but slightly higher, results compared to those just presented for the marathon. Between ages 40 and 55 there is an average 1.5 percent decrement in performance per year for men, and from age 55 to 75 the decrement is 3.3 percent per year. For women, the decline is 2.3 percent per year from ages 40 to 55, and data beyond age 55 is so variable that no consistent trends can be identified.

These rates of change may be higher than those for shorter distances because of the increased demands ultradistance running puts on the structural and physiological systems in the body, which reduces the pool of runners attempting to run those distances and perhaps exaggerates the affects of aging.

From these various data we can conclude that those who remain fit and free of major injuries or disease can still expect a decline in performance that will average at least 0.5 percent per year between age 35 and 60. Those who train less intensely as years go by, or who are afflicted with periods of injury or disease, can probably expect faster decrements in performance, as high as 1 to 2 percent per year. After an approximate age of 60, the rate of decline is likely to increase. While the data cited here show slightly faster rates of decline for women compared to men, this may be an artifact influenced by the fewer number of women competing regularly in long-distance events over the past few decades compared to men.
 
 
 
 

Physiological Basis for Performance

The physiological factors that are generally thought to affect changes in performance with age are the same as those thought to be the major determinants of distance running performance: maximal oxygen uptake (VO2max), the percent of VO2max at race pace, the workload where lactate accumulation exceeds a designated level (“lactate threshold”), and running economy (VO2submax).

A more detailed discussion of these factors can be found in articles by Joyner (1993), Sjodin (1985), and Daniels (1985). VO2max is the maximum amount of oxygen that can be consumed during intense exercise, and considerable variability in VO2max can exist between runners. VO2max can be altered with training, but a variety of genetic factors also have an effect on the maximal level that any individual can attain.

Running economy is the rate of oxygen consumption at submaximal levels, and it can vary by as much as 30 percent between individuals (Daniels 1985). A lower VO2submax at a given speed would be an advantage in distance running. Economy is probably primarily important as it relates to VO2max during running at a given speed, though Sjodin (1985) cited studies that suggested that marathoners were more economical than runners concentrating on shorter distances.

Both running economy and VO2max affect the percentage of VO2max utilized at a given speed. High correlations have been found between performance time and the percent VO2max used when running at race pace. Depending on the length of the race, runners may sustain somewhere between 65 and 98 percent of VO2max over the course of the race, with longer races run at a lower percentage of VO2max and slower runners using a lower percentage of maximum aerobic capacity (Joyner 1993; Sjodin 1985).

As one’s running speed increases, changes occur in the energy sources utilized, and at some point a chemical substance called lactate begins to accumulate in the blood. The point at which this occurs has frequently, and sometimes controversially, been called the “lactate threshold.” The specific mechanism of these changes continues to be debated; but of practical importance is the fact that a well-trained runner can sustain a fraction of his VO2max that is slightly above the lactate threshold pace, and there seems to be a strong relationship between the threshold pace and performance (Sjodin 1985).
 
 

Changes in Physiological Factors with Age

As we age, our VO2max decreases, which seems to be closely linked with the decline seen in performance. Studies examining changes in VO2max with age have shown that it declines at the rate of 9 to 15 percent per decade in sedentary individuals, while those who continue active training show a change that is as little as half that much (Joyner 1993; Evan et al. 1995; Trappe et al. 1996).

Pollock (1987) examined 24 masters track athletes in a 10-year follow-up study and found only a nonsignificant 3 percent change in VO2max for a subgroup that had remained competitive over the 10-year period. Other runners who continued training but did not compete showed a greater decline. Runners who remained competitive in their 60s did show a greater decline at some point, leading the authors to conclude that within the age range of 60 to 65 some reduction in VO2max is inevitable. This greater change after age 60 is consistent with the increased rate of decline in performance at ages above 60 that we discussed earlier.

Trappe et al. (1996) studied 53 former elite male runners 22 years after initial tests and found a decrease averaging 6 percent per decade-or 0.6 percent per year-for a group who continued a high-level of training, a 10 percent decline for a group who ran for fitness, and a 15 percent decrease for a group not engaged in any regular physical activity. Evans et al. (1995) found an approximate 1-percent per year decrease in VO2max in highly trained women ranging in age from 23 to 56.

With sedentary individuals, the decrease in VO2max is due at least in part to a decrease in maximum heart rate and stroke volume. There is some data to suggest that stroke volume may be maintained or even increased in active runners (Pollock 1987). Other factors, such as a decline in peripheral oxygen extraction and a reduction in lean body mass or muscle mass, may also be involved (Joyner 1993; Fleg and Lakatta 1988). A decrease in heart rate with age seems certain to be associated with the age-related decrease in VO2max, but the exact nature of the effect of age on other factors affecting oxygen delivery to the muscles in trained runners is not as clear (Evans 1995; Pollock 1987; Rivera et al. 1989).

Joyner (1993) cited evidence suggesting that the lactate threshold remains at the same speed as one ages, and that by maintaining training, older individuals may prevent or eliminate the usual age-related decline in skeletal muscle oxidative capacity. In contrast, Evans et al. (1995) found the running speed associated with lactate threshold to decrease with age and concluded that the change in lactate threshold was an important factor in the decline in performance between the ages of approximately 20 and 65. Allen et al. (1985) matched eight masters runners (average age = 56) with younger runners (average age = 25) on the basis of 10K performance times. The older runners, despite a lower VO2max, were able to match the paces of the younger runners because they ran at race pace with higher lactate levels and at a higher percentage of VO2max. Though it is not clear whether the speed associated with lactate threshold changes with age, it appears that lactate levels are still important in determining performance levels in older individuals.

Joyner (1993) concluded that running economy does not change with age, based on available literature, with Allen et al. (1985) reporting a similar finding. Trappe et al. (1995) found similar results for active runners, but higher submaximal oxygen consumption in the group of former elite runners who were no longer physically active.

Evans et al. (1995) found significantly higher oxygen consumption in a group of older women (mean age = 52) compared to a younger group (mean age = 30), concluding that running economy did not play a major role in age-related declines in 10K performance. Overall, there does not appear to be evidence that changes in running economy are important in explaining the decline in performance with age, though little information is available for older subjects (60+) or those who run longer distances (50K+).

Physiological changes that might be specific to runners who engage in ultradistance running have not been examined in detail. It is likely that changes for this group will parallel those found for 10K and marathon runners, though it is also probable that muscle, bone, and soft tissue fatigue or failure will begin to have a greater influence on performance in the longer distances. While a great deal of research has been done to examine the influence of repetitive loads on body tissues, almost all of the studies have simulated conditions less extreme than those involved in ultradistance running. As a result, specific information is not available.
 
 

Summary

The reductions in performance for age-group records cited by Bortz (1996) suggest a minimum rate of decline in performance of 0.5 percent per year between ages 35 and 65. This rate of decrease is similar in magnitude to the 5 percent per decade decline in VO2max that appears to occur even for highly-trained individuals.

While a decline in performance averaging as low or lower than 0.5 percent per year is possible, for most runners the rate is probably higher, affected by changes in training intensity, motivation, injury, and other related factors.

Depending on the level of training continued over the years, the decline may range anywhere from 0.5 percent to 2 percent or more per year, and after age 60, the rate of decline will probably increase. It appears that these performance declines are directly related to changes in some of the physiological factors that are important to performance, most notably VO2max.

Continued training as one advances in years appears to have the beneficial effect of reducing the usual decline with age of some of the physiological functions that are important to performance. Additionally, continued training should bring with it additional health benefits that will help active runners maintain a better quality of life into their later years.
 
 

References

Allen, W.; Seals, D.; Hurley, B.F.; Ehasni, A.;  and Hagberg, J. 1985. Lactate threshold and distance-running performance in young and older endurance athletes. J. Appl. Physiol., 58(4):1281-1284.
Bortz, W. M. IV, and Bortz, W. M. II. 1996. How fast do we age? Exercise performance over time as a biomarker. Journal of Gerontology. Series A, Biological Sciences and Medical Sciences. 51(5):M223-225.
Daniels, J. T. 1985. A physiologist’s view of running economy. Med. Sci. Sprts. Exerc. 17(3):332-338.
Evans, S. L.; Davy, K. P.; Stevenson, E. T.; and Seals, D. R. 1995. Physiological determinants of 10-km performance in highly trained female runners of different ages. J. Appl. Physiol. 78(5):1931-1941.
Evans, S.; Stevenson, E.; Keith, H.; and Seals, D. 1994. Endurance running performance in women: influence of age in relation to men (Abstract). Med. Sci. Sprts. Exerc. 26(5):S137.
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Joyner, M. (1993). Physiological limiting factors and distance running: influence of gender and age on record performances. Exercise and Sport Science Reviews, 21:103-133.
Koplan, J.; Rothenberg, R.;  and Jones, E. 1995. The natural history of exercise: a 10-year follow-up of a cohort of runners. Med. Sci. Sprts. Exerc. 27(8):1180-1184.
Pollock, M.; Foster, C.; Knapp, D.; Rod, J.; and Schmidt, D. 1987. Effect of age and training on aerobic capacity and body composition of master athletes. J. Appl. Physiol. 62(2):725-731.
Rivera, A.; Pells III, A.; Sady, S.; Sady, M.; Cullinane, E.; and Thompson, P. 1989. Physiological factors associated with the lower maximal oxygen consumption of master runners. J. Appl. Physiol. 66(2):949-954.
Sjodin, B., and Svendenhag, J. 1985. Applied physiology of marathon running. Sprts. Med. 2:83-99.
Trappe, S. W.; Costill, D. L.; Fink. W. J.; and Pearson, D. R. 1995. Skeletal muscle characteristics among distance runners: a 20-year follow-up study. J. Appl. Physiol. 78(3):823-829.
Trappe, S. W.; Costill, D. L.; Vukovich, M. D.; Jones, J.; and Melham, T. 1996. Aging among elite distance runners: a 22-year longitudinal study. J. Appl. Physiol. 80(1):285-290.