Pity the poor runner he'll have arthritis when he's older. Or will he?
Is it true that running is hard on the knees, hips, and feet? Runners still hear about that supposed connection, and there seems to be a kernel of truth in the supposition. After all, running is the kind of sport which produces 'wear-and-tear' injuries, not traumatic ones, and one key form of arthritis - osteoarthritis - is a wear-and-tear disease, in which the cartilage inside joints is gradually eroded over time. But what does the scientific literature really say? Do the relentless impact forces of running (a force greater than two and one-half times body weight is transmitted through the leg with each footstep, 1700 times per mile) eventually cause the cartilaginous structures in the knees and hips to deteriorate into the inflamed, arthritic state'?
The most comprehensive study concerning running and disability was begun in 1984 at the Stanford Arthritis Center in the US. Initially, 863 people (632 males and 231 females) ranging in age from 50 to 72 took part in the research. 498 individuals were long-distance runners, while 365 subjects did not run at all. The runners averaged about 210 minutes (27 miles) of running per week, had been running for an average of 12 years, and weighed considerably less than their sedentary counterparts ( 147 versus 161 pounds). Some of the runners had logged as many as 17,000 total miles during the 12 years leading up to the study.
The first five years
Over an initial five-year period, the benchmark Stanford study found that runners did NOT experience higher rates of arthritis, compared to 'average' individuals in the overall population. In fact, runners actually had a lower risk of disability in their muscular and skeletal systems, despite all of the aches and pains which are usually associated with a regular running programme. Runners made fewer visits to the doctor, spent about 33 per cent less time in the hospital, missed half as many work days, and - as expected - had lower blood pressures and resting heart rates, compared to non-runners. In addition, runners gave themselves higher perceived health ratings. To put it simply, runners FELT healthier than non-runners, and in fact they were.
What about the notion that knees and legs are damaged by the miles and miles of hard pounding associated with running? Well, disabling problems in the legs were actually five times as likely to occur in sedentary individuals, compared to runners. Running was also linked with fitter upper bodies: disabling conditions in the arms and shoulders were 20 times as likely to develop in non-runners !
Although it was true that about 40 per cent of the runners experienced a running-related injury over a one-year time span, most of the injuries were slight, and the damaged runners recovered rapidly. In fact, just eight out of 498 injured runners had to STOP running completely because of injury. In spite of their greater need to seek medical treatment for running-induced injuries, runners actually used fewer medications than lethargic individuals and, overall, spent significantly less money on health care.
Then the critics pounced
At first glance, the Stanford study seemed to represent great news. After all, joint, bone, and muscular disabilities developed at a lower rate in the running population, compared to sedentary folk. There wasn't a shred of evidence to support the idea that running predisposed people to a higher risk of musculoskeletal disability; in fact, the reverse was true. Being sedentary was a big risk!
However, the Stanford study quickly encountered a barrage of heavy-duty criticism. Critics contended (correctly) that people who quit running because of the development of osteoarthritis were unlikely to be included in the Stanford research, or in other similar research projects, because scientific investigators try to avoid using people who are already ill. Thus the incidence of arthritis among runners would likely be underestimated, since all the unfortunates who were hobbled by running would be excluded.
Partly in order to remedy that weakness, the Stanford scientists continued their study for an additional three years (to create an eight-year analysis) and also inspected their data in a novel way by dividing their subjects into two new groups. Whereas previously the Stanford white-coats had looked at 'runners' or 'non-runners,' according to who was CURRENTLY involved in a running programme, the investigators now divided their horde into those who had run for at least one month at some time in their lives (the 'ever' group) and those who had never run (the 'never' group). The plan behind creating the 'ever' group was to 'catch' some of the individuals who had tried running, sustained some musculoskeletal difficulties, and then dropped out of the sport. This might take away some of the glow from running, since even individuals who had only run for two months in their entire lifetimes would be considered 'runners.'
After three more years
Fortunately for running advocates, it didn't work that way: Differences in disability between the 'ever' and 'never' groups were still quite considerable - and sometimes even larger than the gap between current runners and non-runners. The extension of the Stanford study to eight years produced some other interesting results. One difference had to do with an event most of us are concerned about - death. Although both groups were similar in age, only eight of the runners died during the study period, while 30 sedentary individuals passed away. Significantly, 10 of the non-runners died from cardiovascular disease; only one runner met the same fate. Overall, 7 per cent of non-runners died during the study period, versus just 1.5 per cent of runners.
During the eight-year period, there was only one negative splotch on the runners' records: they did experience more bone fractures, mainly because of sports-related falls. However, breaks of the spine, wrist, and hip were significantly more common among non-runners, as were joint swelling and chronic joint pain.
Even better for women
Overall, male runners accrued musculoskeletal difficulties at rates which were 40 per cent lower than male non-runners. Running was even more important for ageing females: female runners accumulated problems at rates which were 89 per cent lower, compared to female non-runners. This may reflect the fact that sedentary females may be considerably more immobile than sedentary males. The more sedentary the lifestyle, the higher the risk of disability.
There did appear to be a 'dose effect' at work, with runners who ran very little experiencing almost three times as much disability as runners who ran more extensively. The threshold for achieving lower disability rates was quite modest, however. Running just 15 miles per week or so cut disability rates by 60 per cent, compared to running five or fewer weekly miles. Running more than 25 miles per week did not cut disability rates significantly.
Differences between the two groups became even greater as participants aged. In fact, the biggest chasm between disability rates occurred in the 75-to-79 age category, when musculoskeletal problems tended to skyrocket in the non-running group but stayed fairly steady among runners and others participating in regular aerobic exercise (cycling, swimming, etc.).
However, another kind of bias might have crept into the Stanford research. This potential prejudice could enter the investigation in the following way: people who are basically healthy often feel well enough to embark on a running programme. Their superior overall health might enable them to negotiate years of running without major problems. Meanwhile, people with niggling aches and pains and modest overall health would be less inclined to exercise and would eschew running. As the years rolled by, their nattering throbbings might change into arthritic aches, and since their overall health was not so good, the aches might develop quickly into major arthritic disease. Scientists watching these people might think that running brightened the horizons of the former group and that a sedentary lifestyle brought dark clouds to the latter, but the truth would be much simpler - that good health allowed people to run, while poor health prevented people from lacing up their jogging shoes. Activity might be the result of good health, not the cause of it.
Eliminating other slants
That kind of bias is nearly impossible to avoid. One way around it would be to ask some of the non-running subjects to take up the sport, to see if their disability rates became more like those of the runners. This was not done in the Stanford study. However, the Stanford scientists were able to eliminate other 'slants' to their data. They were able to show that the two groups did not have different family histories of arthritis or other skeletal and muscle diseases, and they monitored 'drop-outs' carefully, to make sure that runners weren't leaving the project because of injuries.
Although the Stanford researchers didn't ask their sedentary subjects to give exercise a try, other , scientists have done so. Notably, in a recent research effort a group of 50- to 65-year-old individuals who were previously sedentary embarked on a vigorous exercise programme and achieved considerable improvements in their musculoskeletal health. The bottom line? At present, it seems relatively certain that running and other forms of exercise are linked with positive health outcomes, including the well-being of the muscles, connective tissues, and joints. ('Ageing, Long-Distance Running, and the Development of Musculoskeletal Disability, ' The American Journal of Medicine, vol. 82, pp. 772- 780, 1987; 'Running and the Development of
Disability with Age, ' Annals of Internal Medicine, vol. 121, pp. 502-509, 1994)
Owen Anderson