No pain, no gain. Right? Wrong. That 1970s approach to exercise has been traded in for the new millennium’s favored philosophies: “no pain, much gain” and “train, don’t strain.”1 The take-home message is that physical activity should be part of daily life; it doesn’t have to be high intensity or inconvenient, and it should be fun!
Surveying the Hurdles
The promise of thinner versions of themselves may motivate most people to start exercising, but that’s not all that physical activity has to offer. Numerous research studies conclude that regular physical activity and exercise decreases mortality, improves cardiovascular and respiratory function, reduces coronary heart disease risk factors, lowers the risk of colon cancer, improves immune function, and enhances a sense of well-being.1-4 In addition to smoking cessation, becoming more physically active is the best thing you can do for your health.
Less than half (48%) of Americans meet the 2008 federal physical activity guidelines
for aerobic activity.5
Statistics reveal that more than 50% of Americans do not exercise regularly and the growing incidence in obesity and overweight may be related.3,5
Inactivity tends to increase with age and is more common among women than men. It is of concern that less than three in 10 high school students get at least 60 minutes of physical activity every day.5 Inactivity is more prevalent among those with lower income and less education and is also more common among black and Hispanic adults than whites.3 In addition, the growing trend of obesity among Americans has been largely linked to a sedentary lifestyle.
2008 Age-Adjusted Estimates of the Percentage of Adults Who Are Physically Inactive
Photo courtesy of the Centers for Disease Control and Prevention.
Although many people enthusiastically begin exercise programs at one time or another, only 50% sustain their participation for more than six months.6,7 It’s no wonder that people have trouble sticking to an exercise routine. Our high-tech society makes it convenient to remain sedentary but difficult to start and maintain physical activity.
Figuring out how to get Americans out of their seats and away from their TVs and computers poses a real challenge. However, all healthcare professionals can help drive a shift toward a more active lifestyle by spreading the word public health officials have been preaching — a kinder, gentler philosophy of getting into shape. In fact, government guidelines actually encourage healthcare professionals to routinely talk to patients about incorporating physical activity into their daily lives.1,7-9 In well-defined terms, healthcare professionals may assess physical activity habits, suggest basic lifestyle changes, and monitor patients’ responses to these changes.4,6,10
Several health agencies have released guidelines to promote more participation in physical activity and encourage long-term adherence.8,11,12 Current recommendations have evolved from a structured program of vigorous exercise for cardiovascular fitness to more moderate levels of physical activity for health benefits — disease prevention, longevity and quality of life.
To understand these guidelines, we need to understand the terms used in the exercise industry. Physical activity is any bodily movement produced by the contraction of the skeletal muscles that increases energy expenditure above a baseline level.13
Exercise — a subcategory of physical activity — is planned, structured and repetitive body movements performed to maintain or improve one or more components of physical fitness.4,8
Health-related aspects of physical fitness include cardiorespiratory endurance, muscular strength and endurance, flexibility, and body composition or percentage of body fat.4,8,12
In 1992, the American Heart Association
officially named physical inactivity — not lack of exercise — as a major independent risk factor for heart disease. This term was used because a broad array of health benefits accrue from regular intermittent physical activity as well as from regular continuous exercise.4,10
Men and women of all ages benefit from a moderate amount of physical activity. On October 7, 2008, the U.S. Department of Health and Human Services (HHS) released the 2008 Physical Activity Guidelines for Americans
.14 (Level C)
These guidelines are based on a report submitted by the Physical Activity Guidelines Advisory Committee, a group comprising 13 leading experts in the field of exercise science and public health. This committee conducted an extensive review of the scientific data relating physical activity to health published since the release of the 1996 Surgeon General’s Report on Physical Activity and Health. The guidelines are intended to be a primary source of information for physical educators, health providers, policy makers, and the public on the amount, types, and intensity of physical activity needed to achieve many health benefits for Americans across the life span. The At-A-Glance Fact Sheet for Professionals
is designed as a quick deskside reference to the 2008 Physical Activity Guidelines for Americans.
The good news is the guidelines were designed to be achievable and can be customized according to a person’s lifestyle, interests and goals. The content of these guidelines complements the Dietary Guidelines for Americans
, a joint effort of HHS and the U.S. Department of Agriculture. Together, the two documents provide guidance on the importance of being physically active and eating a healthy diet to promote good health and reduce the risk of chronic diseases. The 2008 Physical Activity Guidelines for Americans
are the first comprehensive guidelines on physical activity ever to be issued by the Federal government and are evidence based. The Physical Activity objectives established for Healthy People 2020 confirm the strong science supporting the health benefits of regular physical activity for both youth and adults.8
Knowing how much you should exercise depends on your current health status, initial level of fitness, available time, personal goals, equipment and facilities. Individual goals, such as enhancing vigor in daily life, improving cardiorespiratory fitness, or lowering blood pressure, also affect the required amount of exercise. Exercise guidelines and prescriptions are based on the FITT Formula and take into account the Frequency (how often), Intensity (how hard), Time (how long), and Type (mode) of exercise. Amount or volume of exercise is a function of these four variables and should be tailored to individual needs.5
A dose-response relationship exists between physical activity and health/fitness.4,8,15 (Level ML)
Additional benefit can be achieved by adding more time in moderate-intensity activity (a longer walk), substituting more vigorous activity (30 minutes of running), or stepping up the frequency of physical activity (using the stairs more frequently). For those whose goals extend beyond health benefits and include higher levels of cardiorespiratory fitness, the more familiar classic recommendation still applies. Namely, the minimum level of FITT factors recommended is 20 to 60 minutes of continuous aerobic exercise of moderate to vigorous intensity three to five days per week.4,16
Aerobic exercise is defined as physical activity requiring an increased need for oxygenation. Therefore, physical activity that causes you to breathe deeper or more rapidly is aerobic.
Total energy expended in exercise is usually expressed in kilocalories (kcal), and the minimum calorie expenditure for health is 150 kcal/day or 1,000 kcal/week.8,17
If you are aiming for maximum health benefit, you will require 30 to 60 minutes of purposeful moderate exercise five times a week, or 20 to 60 minutes of vigorous exercise at least three times a week. A combination of moderate and vigorous exercise can be substituted three to five times per week.15 (Level ML)
For even higher levels of fitness or weight loss, the upper end of the range is an expenditure of 300 kcal/day to 400 kcal/day in activity.12,17
Even though this is the template for caloric expenditure, age, gender and health status can influence the totals. Thirty minutes of moderate activity daily equals between 600 to 1,200 calories of energy expended each week. One pound of weight loss is achieved after 3,500 calories are expended.18
Other terms to define in exercise vocabulary include dynamic and static exercise. Dynamic exercise is movement of the muscles and joints, such as swimming, walking, skiing, bicycling, gardening and even house cleaning. Continuous movement with oxygen improves circulation, strength and endurance. Static exercise, also known as isometrics, uses muscle strength without involving the joints in the movement. Static exercise, such as some forms of weightlifting, strengthens muscles but also temporarily increases blood pressure. A Valsalva maneuver from bearing down and holding your breath, such as when pushing something heavy, can cause a dangerous increase in blood pressure and pelvic muscle strain and should be avoided, especially for diabetics and those with existing hypertension. Stretching exercises can be either dynamic or static, depending on how the stretch is done. Breathing during a sustained and steady stretch for 30 seconds has been shown to be the most effective for flexibility and to decrease muscle fatigue.
Benefits of Exercise
Research demonstrates that regular physical exercise:19-21
- Combats chronic diseases
- Improves mood, energy level and self-esteem
- Helps manage weight
- Strengthens the cardiovascular system
- Promotes better sleep
- Improves sexual relations
- Promotes relaxation and fun
- Increases exercise tolerance
- Increases insulin sensitivity
- Lowers stress levels
- Controls blood pressure and blood sugar
- Helps build healthy bones, muscles and joints
- Has an anti-aging effect at the cellular level
The term “aerobic” means “with oxygen” and includes activities that require the body to use oxygen to produce the energy needed to perform an activity. Also referred to as dynamic or endurance exercise, aerobic exercise consists of continuous rhythmic movements of large muscle groups that can be sustained for a period of time.22 Walking, jogging, cycling, stair climbing, rowing, dancing, martial arts and swimming all fall into this category. Aerobic activities improve cardiorespiratory fitness by increasing the heart and breathing rates and training the heart, lungs and skeletal muscles to use oxygen more efficiently, thereby increasing energy and capacity for work.
To help understand this concept, think of your circulatory system as water flowing through pipes in a house. For instance, if you have one faucet on in your house, the water moves fast; but if all the water outlets are turned on, the pressure will decrease and slow the flow rate. In your body this is called your VO2
max, which refers to the maximal amount of oxygen your body can obtain and use during cardiovascular training sessions. As you work out, your heart can only pump a certain amount of blood throughout your body. To help keep your blood pressure down, the heart will distribute blood to different parts of the body and not concentrate the flow to one area. The higher VO2
max, the more oxygen you can use and disperse to the needed muscles. To improve your VO2
max, which measures your cardiorespiratory fitness, you need to program your body, through cardiovascular exercise, to effectively use the oxygen available in the circulatory system.23 (Level A)
Numerous research studies now offer empirical evidence for the benefits of exercise. Improved exercise capacity offers cardiovascular, respiratory, hemodynamic, hormonal, metabolic, neurological and immunological benefits.9-12
Additionally, the risk factors for heart disease and stroke go down. Regular aerobic activity increases high-density lipoprotein, considered “good” cholesterol, and decreases triglycerides. It also lowers blood sugar and lessens the cell’s resistance to insulin. Exercise improves the cell’s sensitivity to endogenous insulin, which is a great benefit to diabetics. Because aerobic activity burns calories, it helps with weight loss and in maintaining desired weight, and it decreases intra-abdominal fat.12
By lowering both systolic and diastolic blood pressures by 8 mmHg to 10 mmHg, aerobic exercise fights atherosclerosis by reducing stress on arteries and preventing the vascular injury that low-density lipoprotein, considered “bad” cholesterol, causes in forming fatty plaques.1
A study in mice has indicated that at the cellular level, moderate but consistent aerobic exercise prevents cardiac tissue death by stabilizing telomere proteins.24 (Level A)
Endurance exercise also decreases the risk of a heart attack by preventing the blood-clotting mechanism from forming clots while decreasing the stickiness of platelets.6
Dynamic exercise improves cardiovascular function by strengthening the heart muscle so it can pump more blood with each beat.12
A fit heart pumps more effectively with each stroke volume
and can meet all the body’s needs for blood and oxygen even with a slower rate. Recent research has demonstrated that long-term physical activity has an anti-aging effect at the cellular level, suggesting that exercise may prevent aging of the cardiovascular system.20
In addition to physical benefits, aerobic exercise relieves symptoms of depression and anxiety and improves self-esteem and self-confidence, in most cases.6,12 Clearly, consistent exercise benefits all the systems of the body and prevents long-term chronic disease development.
Now That’s Intense!
Moderate-intensity aerobic activity raises your heart rate and gets the blood pumping without leaving you out of breath, exhausted and ready to collapse. While the rate and depth of breathing rise during exercise, you should never feel so breathless that you are unable to carry on a normal conversation.3,24 This simple measure is referred to as the “talk test” and is used to avoid overexertion. Use this only as a test and not as a continuous act, because carrying on a conversation during exercise will decrease your cardiovascular performance and inhibit your progress toward cardiorespiratory fitness.
Target heart rate (THR) and the Borg Rating of Perceived Exertion (RPE) scale also gauge exercise intensity. THR is a range that is considered safe for exercise and is affected by age, medication use, and fitness level. Using heart rate to estimate how hard you are working during exercise requires taking your pulse periodically and staying within 60% to 80% of your maximum heart rate.23,25
To find the target heart rate for your proper cardiovascular training zone, use the Karvonen Formula as a general rule of thumb.25
The simple mathematical formula to determine target heart rate training zone is THR (Target Heart Rate) = Max HR (Maximum Heart Rate) - resting HR x % intensity. For example, 220 minus your age x 60% to 80% for the lower and upper limits of desired target heart rate. For more information on target heart rate zone training go to http://www.pnc.edu/hr/Wellness/target_heart_rate_zone_training.htm
While THR is a helpful guide, this one-size-fits-all approach isn’t right for everyone due to a standard deviation of plus or minus 10 to 12 beats per minute.4,9,16 Due to individual variation, the RPE is still being used when monitoring the intensity of exercise. The Borg Scale tool is a subjective measure of exercise intensity that requires listening to your body.26 It is a 15-point scale ranging from 6 to 20 that individuals use to rate their perceived exertion. Healthcare professionals generally agree that a rate of 12 to 14 on the Borg Scale represents a moderate level of intensity, which is suggested. It measures how hard you feel you are working during physical activity; simply explained, light exercise feels light, and strenuous exercise feels strenuous.
Exercising Your Options
For those who dislike traditional exercise, can’t find the time, are embarrassed at taking part, or are unable to exercise vigorously, another option can supplement or replace formal exercise. An alternative is to focus on lifestyle activities to increase energy expenditure.4,18 This approach offers sedentary people a non-threatening starting point and encourages them to be more active throughout the day.
House cleaning activities, walking breaks at work, using stairs, gardening, active recreational pursuits such as dancing and golf, and playing with toddlers provide health benefits when performed daily at a moderate intensity. A brisk walk to the store or office, or housework, such as floor scrubbing, may be all that is necessary to meet the goals of some people. A level of physical activity necessary to achieve the majority of health benefits is less than that needed to attain a high level of cardiorespiratory fitness.4,16
If finding time is a problem, shorter sessions of physical activity can be accumulated over the course of the day.15 (Level ML)
Three 10-minute or two 15-minute bouts of exercise yield cardiorespiratory fitness gains comparable to those from one continuous 30-minute session of equal intensity.4,12
Intermittent physical activity allows for more flexibility and is also associated with greater adherence to a regular exercise program.1,4
This technique is for people with little or no available time, who are not in good cardiovascular shape, or who have health problems that limit their ability. However, the most efficient and effective method is 30 minutes of continuous cardiovascular exercise. For examples of moderate amounts of activity go to http://www.cdc.gov/nccdphp/sgr/ataglan.htm