Age is less kind to some of us than others. High school reunions often dramatically illustrate this point. Among runners, declines in performance plague some runners in their early thirties, while others (notably Carlos Lopes who won the 1984 Olympic Marathon at age 37, and then ran 2:07:12 at age 38) remain at their best much longer.
Father time, however, eventually catches up with everyone. In a 1993 review of top U.S. distance running performances, Dr. Michael Joyner found that from age 35 until age 55, race times increase by about 6% per decade for men and 9% per decade for women. The difference between the genders is probably related to cultural factors, including the smaller number of competitive women runners over age 40, and the restricted exercise opportunities for women prior to Title IX.
Dr. Joyner found that race times increase more quickly after age 55. Why? Once again, we do not know what portion is due to physiology and what portion is related to cultural factors. Fewer older runners have trained continuously from younger ages, and fewer older athletes are training at the same intensity and duration as elite younger runners. In addition, older runners have had more time for the cumulative effects of injuries to take their toll. A portion of the slow down in top performances among more senior runners, therefore, is likely due to a smaller talent pool. As more runners continue to train and race into their 60's and 70's, performances at these ages may correspondingly improve, revealing the effects of physiology.
The three physiological variables that best predict distance running performance are VO2 max, running economy, and the lactate threshold. Among sedentary folks, VO2 max declines about 10% per decade. Possible reasons for this decline include decreases in maximal heart rate, less blood pumped with each contraction, reduced muscle mass, and reduced ability of the muscles to use oxygen. Each of these factors, however, may be more related to inactivity than to genetic programming.
Studies with runners have found much smaller decreases in VO2 max with age. Dr. M.L. Pollock found that senior track athletes who maintained the intensity of training did not have a significant decrease in VO2 max over a 10 year period. Prior to the 1968 Olympics, Jack Daniels, Ph.D., and colleagues tested 26 of the best distance runners in the U.S. Those runners were then brought back to the lab for a 25-year follow-up to see how their physiology had changed. Absolute VO2 max had declined by 14% in those athletes who were still running, compared to 24% in those who stopped training. When analyzed relative to bodyweight, the difference between those who remained fit and those who quit was even greater. These results suggest that a large portion of the decline in VO2 max typically seen with age is related to inactivity.
Surprisingly, maximum heart rate in those subjects declined by only 2 beats per minute over 25 years. These results run counter to the formulas commonly used to estimate maximum heart rate based on age, and suggest that declines in maximum heart rate with age may be related to lifestyle.
Older runners may actually have some advantages over the younger crowd due to our longer training histories. According to Don Morgan, Ph.D., who has conducted a large number of studies on running economy, the most important factor for improving economy may be the number of years that you have been running, rather than the specific types of workouts that you run. Another plus is that the more years of endurance training you have under your belt, the closer your lactate threshold tends to get to your VO2 max. That's because training adaptations in the working muscles, such as more capillaries and mitochondria, continue to occur for many years. Pity the poor 20 year olds who have only been training for a few years!
Lifestyle and Scar Tissue
As runners approach 40, factors such as spouses, children, mortgages, and careers tend to impinge on the running lifestyle. Since joining the Masters ranks, I find that training has gradually slipped down my list of priorities. A portion of the observed slowing with age, therefore, is no doubt due to an inability to focus one's energies on training and competition. Although you may be training as hard as you can, that is in the context of everything else going on in your life.
In addition, although the mind may still be willing and the heart and lungs able, after years of abuse our muscles and tendons can no longer withstand the wear and tear of high level training. In the long run, scar tissue gets the best of many runners. In the 1980's, New Zealand's John Campbell ran a series of outstanding races between ages 38 and 42, including a 2:11:04 marathon at age 41. A close look at John's running career sheds an interesting light on his performances. After a promising start as a young runner, John took about 13 years off before making a comeback at age 36. At age 40, therefore, John's legs had the cumulative running wear and tear of a much younger man.
Will you race slower at age 70 than at age 30? Undoubtedly. But the timing and rate at which you slow down are not entirely genetically based. We do not know the degree to which declines in running performance are due to physiological changes with age relative to changing priorities, a smaller population of athletes, and the cumulative effect of injuries. Evidence is accumulating, however, that many of the reductions in physiological function associated with aging can be substantially reduced through training.
(This column originally appeared in Running Times Magazine.)