“I put a humidifier and a dehumidifier in the same room; I let ‘em fight it out to see who wins.” [Comedian Steven Wright]
I would like to think that the majority of runners participate in the sport simply because they enjoy it. Realistically, I know that a certain percentage does so for other reasons: weight-control, social connections, competitive drive, or health-related benefits. Even if that last category is not the #1 motivation for all runners, I’m sure that all do see it as a positive payback for all the hours and effort expended on the roads or track.
The fact that runners believe they are reaping some health rewards should come as no surprise; most everyone has been inundated over the past few decades with information on the upsides of exercise and the downsides of a sedentary lifestyle. Most of this refers to the effects of activity/non-activity on the cardiovascular system and the attendant risks for disease processes such as heart attack and stroke, though there have also been numerous studies that address other health issues, including the risks for developing various cancers.
Some of the claims regarding the benefits of running have at times overstated the case; back in the 1970s, for example, a widely-quoted “fact” published by the American Medical Joggers Association was that marathon running provided immunity against coronary artery disease and heart attacks. Within a decade, however, evidence began to accumulate that this was not the case at all.
Nonetheless, research continued to indicate that the risks for such events were significantly lower in those individuals who regularly engaged in at least moderate to vigorous exercise activities (such as running) and conversely increased in those who do not. And from that information, it became an assumed corollary that those who spend their day in an essentially sedentary occupation (i.e., desk job) or avocation (i.e., couch potato) can effectively mitigate the negative effects of those 23 hours of inactivity by spending the remaining hour exercising. Not a bad deal!
Unfortunately, it now appears that things are not so simple. Over the past few years, new studies have been published that strongly contradict this assumption. To wit:
- A study in the Journal of the American College of Cardiology (2011) found a relationship between prolonged sitting (as reflected by television or computer screen viewing time) and increased mortality and cardiovascular disease events. This relationship was not affected in a significant way by levels of physical exercise activities.
- A 2009 editorial in the British Journal of Sports Medicine noted the increase over the past few decades in the amount of time the average adult spends being sedentary (now over 9 hours/day!) and the detrimental effects of this development on a variety of health parameters such as increased obesity, development of diabetes, heart disease, and more. Again, the effect of physical activity in lessening this problem is negligible.
- An overview of this topic that appeared in Exercise and Sports Science Reviews (2010) reported that uninterrupted, prolonged sitting actually causes cellular changes in muscles that are associated with increased risk for heart disease, diabetes, and other diseases.
- A 2010 study (Medicine and Science in Sports and Exercise) examined the relationship between two sedentary behaviors (riding in a car and watching TV) and cardiovascular disease mortality in 7744 men over a period of 21 years. Men who spent more than 23 hours a week watching TV and sitting in their cars (as passengers or as drivers) had a 64 percent greater chance of dying from heart disease than those who sat for 11 hours a week or less. Many of the men who sat long hours and developed heart problems also exercised. The study’s lead author noted in an interview that, while increased physical activity does have some beneficial effect on reducing CVD risk, “One does not undo the other.”
- Another study, published in the journal Circulation in 2009, looked at nearly 9,000 Australians and found that for each additional hour of television a person sat and watched per day, the risk of dying rose by 11 percent, regardless of the amount of participation in leisure-time physical activity.
A previous column (Article #88) outlined the detrimental effects of prolonged sitting on muscle balance, which could lead to injuries; now we see that it can have more serious, far-reaching consequences. These findings do not mean that those with desk jobs need to quit and become farmers. There are indications that simply interrupting the long hours of sitting, by taking short stand-up or walking breaks for a minute or two, can result in significant benefits in reducing these adverse findings.
The bottom line is, keep on running, but also reduce your uninterrupted sitting time.