What is Exercise and Why Do We Need It?

Exercise is a good thing for your body and your skin

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Please seek the advice of a qualified medical professional to see if you are healthy enough for physical activity before starting any exercise routines. 

Everyone has heard that exercise is a good thing. We all know we should do it, but what exactly does “exercise” mean? How much of it are we supposed to do? Does mowing the lawn count? 

In order to understand “exercise,” it may be helpful to understand the difference between “exercise,” “physical activity,” and “fitness.” In a public health forum in Washington D.C. in 1985, the authors describe physical activity as any movement we create with our muscles that results in energy (kilocalorie) expenditure.[1] 

Exercise can be thought of as a part of physical activity, in which physical activity is deliberate, organized, and repetitive with a purpose to improve or maintain health and fitness.[2] Therefore, physical activity may encompass any movement of daily life, while exercise is purposeful movement with the intention to improve fitness. 

This brings us to the last definition of “fitness,” which is described as a set of attributes including: (a) muscular endurance, (b) muscular strength, (c) cardiorespiratory endurance, (d) body composition, and (e) flexibility.[1] Someone who is fit is able to “carry out daily tasks with vigor and alertness, without undue fatigue and with ample energy to enjoy leisure-time pursuits and to meet unforeseen emergencies.”[3]

How much exercise is enough and why is it important? The 2008 Physical Activity Guidelines for Americans suggests adults get no less than 2.5 hours of moderate intensity aerobic activity each week.[4] However, depending on the individual, 2.5 hours may be more or less than what is necessary for different fitness goals. Exercise is highly customizable; it consists of many components including different modes, intensity levels, and duration. One study found that normal weight women required one hour per day of physical activity to maintain their weight, therefore some individuals may require more exercise each week to meet their goals.[5] 

Activity that causes a sustained increase in heart rate is termed “aerobic activity,” and has been deemed especially important to prevent cardiovascular disease.[6] Anaerobic exercise is typically higher intensity and shorter duration than aerobic exercise, and includes activities such as weight lifting and sprinting.[7] Adults have also been instructed to do muscular strength training two days per week, which could include weight training, resistance training, and many other options.[4] Studies show that weight training fights osteoporosis,[8] and can help older adults to maintain their functional tasks of daily living.[9] Flexibility training is an important component of physical fitness for all ages alike, and should also be integrated into your weekly exercises.  

Exercise is complex, widely variable, highly customizable, and an important aspect of overall wellness. A carefully designed exercise program will not only improve physical fitness, but can improve symptoms of depression,[10] improve skin appearance,[11] and can sharpen the mind.[12]


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1.    Caspersen CJ, Powell KE, Christenson GM. Physical activity, exercise, and physical fitness: definitions and distinctions for health-related research. Public Health Rep.1985;100(2):126-131; PMID: 3920711.

2.    Taylor HL. Physical activity: is it still a risk factor? Prev Med.1983;12(1):20-24; PMID: 6844306.

3.    President's Council on Physical Fitness and Sports: Physical Fitness Research Digest. Washington DC1971.

4.    Physical Activity Guidelines for Americans. 2008.

5.    Lee IM, Djousse L, Sesso HD, et al. Physical activity and weight gain prevention. Jama.2010;303(12):1173-1179; PMID: 20332403.

6.    Sesso HD, Paffenbarger RS, Jr., Lee IM. Physical activity and coronary heart disease in men: The Harvard Alumni Health Study. Circulation.2000;102(9):975-980; PMID: 10961960.

7.    Lukacs A, Barkai L. Effect of aerobic and anaerobic exercises on glycemic control in type 1 diabetic youths. World J Diabetes.2015;6(3):534-542; PMID: 25897363.

8.    Engelke K, Kemmler W, Lauber D, et al. Exercise maintains bone density at spine and hip EFOPS: a 3-year longitudinal study in early postmenopausal women. Osteoporos Int.2006;17(1):133-142; PMID: 16096715.

9.    Katzmarzyk PT, Craig CL. Musculoskeletal fitness and risk of mortality. Med Sci Sports Exerc.2002;34(5):740-744; PMID: 11984288.10.    Hoffman BM, Babyak MA, Craighead WE, et al. Exercise and pharmacotherapy in patients with major depression: one-year follow-up of the SMILE study. Psychosom Med.2011;73(2):127-133; PMID: 21148807.

11.    Jaret P. Exercise for Healthy Skin. webmd 2011; - 3. Accessed August 12, 2016.

12.    Larson EB, Wang L, Bowen JD, et al. Exercise is associated with reduced risk for incident dementia among persons 65 years of age and older. Ann Intern Med.2006;144(2):73-81; PMID: 16418406.