We are not meant to be sedentary. It is only starting in the 20th century, with the rise of automobiles and desk jobs, that it even became possible for anyone but the wealthiest to be “couch potatoes”. The physical activity of early European settlers in Australia, for example, was estimated to exceed that of their modern counterparts by the equivalent of 16 km of walking per day (10 miles) . Amish farmers in the Appalachian part of Ohio, who live a traditional non-mechanized lifestyle, walk the equivalent of at least 9 miles a day and on top of that do a lot more high intensity activity than non-Amish in the same region .
There are well-known detrimental health effects of a sedentary lifestyle, and the combination of inactivity and poor diet is especially harmful. Obesity is strongly correlated with physical inactivity . It can become a vicious circle, the more overweight you get, the less you feel like moving. Most adults in the Western world do not get enough physical activity, and only 10% of the people over age 60 exercise regularly. [Update 03/10/2019: It is the inactivity and poor diet that are harmful, not being overweight by itself[
A sedentary lifestyle is a major risk factor for conditions like heart disease, type II diabetes and arthritis. Most adults are not meeting minimum exercise guidelines, and activity levels decrease with age, so our health care and long-term care systems are very overburdened due to largely preventable diseases. And while the problem of our growing number of overweight and obese Americans (and now people around the world) is caused to a certain extent by bad (and supersized) diet, the other major contributor is inactivity.
Recently it has been recognized that many of what are normally thought of as effects of aging are in fact largely attributable to inactivity [4,5,6,7]. The biology of why staying active prevents the body’s “decay” is explained in Younger Next Year , and lots of books detail the health benefits of exercise, see for example Fitness and Health. It’s been clearly demonstrated that exercise adds life to your years as well as years to your life. To me the “adding life to your years” is the most important: It can be the difference between being vibrant right up to the end of life, or suffering a long debilitating decline.
Use it or lose it: There’s the famous “Wolfe’s law” in biology which states that bones will adapt to the loads that are placed upon them (so they get bigger and stronger if we load them often, or can get thinner and weaker if we don’t), but a similar thing happens for muscles and other important tissues in the body. One of the scariest statistics of aging is that if we are not active we can lose 3 to 5% of our muscle mass every decade as we age. If that statistic doesn’t frighten you, perhaps the picture above is worth a thousand words: These are scans of the cross-sections of men’s left and right thigh muscles. For the 40 year old and 70 year old triathletes, the thin white ring around the outside is fat, the small black circle surrounding the white circle in the middle is the thigh bone (femur), and the rest is muscle. For the 74 Year old sedentary man the large white outside is now fat. Even the femur is smaller so he’s lost bone as well as a lot of muscle. This is a single anecdotal result, but a recent controlled study confirmed it for a group of serious masters cyclists aged 55-79 who averaged over 100 miles per week. There was no significant age-related loss in the quad muscles with age . This contrasted sharply with a sedentary control group of similar age range. Immune system function in the masters cyclists was also significantly superior to that of the control group.
Ok, so we know it’s important, so how to get motivated to do it? That will be the subject of a post coming soon. Hint: In my opinion the most important thing is finding activities you enjoy so physical activity is fun, not “taking a pill”.
- Egger G, Vogels N, Westerterp K, “Estimating historical changes in physical activity levels.”, The Medical Journal of Australia, 2001
- Katz, M, et al, “Physical Activity Among Amish and Non-Amish Adults Living in Ohio Appalachia”, J Community Health, 2012
- Hill J, Wyatt H, “Role of physical activity in preventing and treating obesity.”, J Appl Physiol, 2005
- Deschenes, M, et al, “Exercise-Induced Hormonal Changes and Their Effects on Skeletal Muscle Tissue”, Sports Med, 1991
- Sharkey, Fitness and Health, 2001
- Shephard, R, Aging, Physical Activity, and Health, Human Kinetics, 1997
- Spiriduso, Physical Dimensions of Aging, Human Kinetics, 1995
- Crowley, Younger Next Year, Workman Publishing Company, 2007
- Pollock, R, et al, “Properties of the vastus lateralis muscle in relation to age and physiological function in master cyclists aged 55-79 years”, Aging Cell. 2018