The following appeared in the editorial section of a health and fitness magazine.
"In a study of the effects of exercise on longevity, medical researchers tracked 500 middle-aged men over a 20-year period. The subjects represented a variety of occupations in several different parts of the country and responded to an annual survey in which they were asked: How often and how strenuously do you exercise? Of those who responded, the men who reported that they engaged in vigorous outdoor exercise nearly every day lived longer than the men who reported that they exercised mildly only once or twice a week. Given the clear link that this study establishes between longevity and exercise, doctors should not recommend moderate exercise to their patients but should instead encourage vigorous outdoor exercise on a daily basis."
It is natural to assume that exercise would have a positive effect on the length of life for middle-aged men given all of the medical literature that has been published in the past showing a positive correlation between exercise and longevity. In this particular argument, the writer puts forth a study purporting to track five hundred middle-aged men with different occupations in different parts of the country. The survey was apparently conducted on the basis of an annual survey asking how often and how strenuously these men exercised. The writer not only concludes that there is a clear link between longevity and exercise, but that doctors should not recommend moderate exercise, rather vigorous outdoor exercise on a daily basis to all their patients. This writer's argument fails to convince in a number of areas due to several lapses in logical thinking.
The first and most glaring error in logic lies in the fact that the results of only two types of exercising men are reported: those that exercise strenuously outdoors almost every day and those that only had mild exercise once or twice per week. There are no other results mentioned from the survey, such as the results of men who exercise vigorously indoors every day, or those that exercise moderately either indoors or outdoors three or four times per week. Additionally, it is likely that those men that are exercising outdoors vigorously and almost every day are already in better health than those men that only exercise mildly once or twice per week. Unhealthy men, either due to obesity, smoking or other health-related problems, would naturally be expected to exercise less and die sooner than those apparently healthy men who are physically able to exercise strenuously every day.
Furthermore, the writer indicates that the survey looked at men in different parts of the country with a variety of occupations. It would follow that men that can exercise vigorously outdoors almost every day must live in more favorable climates for such exercise. Milder weather that permits outdoor exercise would likely be healthier for any men rather than the harsher climates that may be present in other parts of the country. In addition, some occupations such as a policeman, firefighter or steelworker are naturally more dangerous than others, leading to a possibly reduced life span. The writer fails to take into account any possible disparity in longevity that may be caused by climatic differences where the men lived or due to their occupations, thus weakening the argument and its conclusion.
Finally, the argument suffers from a critical flaw in its conclusion when the writer states that doctors should not recommend moderate exercise for their patients, instead stating that they should only encourage vigorous outdoor exercise on a daily basis. This conclusion is supported by absolutely no evidence in the argument - indeed moderate exercise is not even mentioned until the end of the editorial. Additionally, the argument fails to take into account that the study only addresses men, not women or children that are also doctors' patients. Furthermore, for some men, women or children, outdoor vigorous exercise on a daily basis might actually be detrimental to their health, such as those at risk for a heart attack or living in harsh climates.
In summary, the writer fails to show that doctors should recommend vigorous daily outdoor exercise rather than moderate exercise whether it is for men, women or children. To strengthen the argument, evidence should be presented that directly links strenuous outdoor exercise on a daily basis for men as well as all doctors' patients before any such recommendation should be adopted. This weak argument might actually cause more damage to patients' health than it would prevent.