It’s interesting how we take health information for granted. Anecdotes are everywhere, most with little to no science backing them. Take water consumption for example; the long-standing recommendation is 8 eight-ounce glasses per day. Many, including some health practitioners, believe this recommendation is totally accurate. While I am sure it is/was well intended, the daily eight is anecdotal; handed down from who knows where. Currently, the Institute of Medicine (IOM) and the only institution with an actual dietary recommendation for water suggest that men consume the equivalent of 13 eight-ounce glasses a day, or roughly 40% more than the daily eight. For women, the IOM suggests the equivalent of 9 glasses or 15% more than the old standard. And while this article is not about water consumption, the above example does illustrate how health myths can become public fact.
I think the everyday exercise recommendation, classically described as thirty minutes, five days a week, is a lot like the water recommendation concerning its presence in everyday life. It’s the “go to” for CNN’s chief medical correspondent Sanjay Gupta, first lady Michelle Obama, and others who try to promote exercise as part of a healthy lifestyle. But where does it come from, and why does it exist in the first place? And is it, like the old “Daily Eight,” based on nothing? Fortunately for us, the past and current exercise recommendation is based on six decades of observation and research, rather than anecdote.
To go back a bit, the first serious notions of exercise for health in America began in the late 19th and early 20th centuries, when it was a topic of conversation among physicians and health educators. During the early nineteen hundreds, physical hygiene, as it was called at the time, was promoted for performance in prestigious University settings and the military, with no regard to health or the public’s welfare. But Later, in a 1952 landmark study, researchers (Morris et al) showed that when male workers become more sedentary, their risks of heart disease and death increased in a predictable way. From that point the scientific evidence began to emerge, indicating that exercise and fitness had much more to offer than performance.
However, there were some problems associated with telling everyone to exercise in the late 1950’s and 1960’s. Despite emerging benefits, many physicians worried that physical exertion above the normal daily activities may make those with heart disease worse, so they often advised rest rather than exercise. What’s more, cardiovascular disease was still on the rise during the middle of the 20th century, and many health professionals felt that formal exercise may actually cause heart attacks in men above the age of 45. But, at that time there was an incomplete picture of what causes heart disease, as well as a lack of consensus on the finer points of the exercise prescription, namely how difficult an exercise should feel while it’s being performed.
In the early seventies studies began to show that structured exercise programs lead to better outcomes in many patient groups, primarily those with a history of heart disease. Since that time thirty plus health and fitness related recommendations have been issued. Most of them issued by organizations like the American Heart Association, the American College of Sports Medicine, and the YMCA. Surprisingly, today’s recommendation has not changed all that much from earlier editions, and for good reason. Put simply, as an individual goes from being sedentary to active the risk of death and disease drop in a predictable manner. Remember 1952?
The graph to the right represents why the physical activity recommendation came into existence, and why it really hasn’t changed too much in the last 50 years. Looking closely, you will see that as minutes of moderate physical activity increase (walking at three to four miles per hour), health risks, namely death and disease decrease.
So, in a world of advertisements, expert opinion, vitamins and supplements, you can rest assured that not everything you hear is taken from anecdote. Being physically active 30 minutes a day, five days a week at a pace that makes you breath harder, has been shown time and again to prolong life and reduce disease. And the best part; it does not have to cost anything.
Mike Clark is an Exercise Physiologist and Personal Trainer at Duke Center For Living’s Health and Fitness Center. He received his BA in Exercise and Sports Science from UNC.