The term activity is used throughout this document when referring to both exercise and physical activity which can have different meanings. This web site has been prepared as support information for The MHE System Programming Systemsm. The System sets aerobic fitness guidelines from research validated activity questions.
The health-related fitness components are cardiorespiratory endurance, body composition, muscular endurance,muscular strength, andflexibility. Exercise often implies that vigorous conditioningroutines are needed to achieve fitness and health benefits. More recent public health recommendations depart from this idea and advance the notion that previously inactive (sedentary) adults will not follow vigorous conditioning routines, but are more apt to seek the safety of lower-intensity activity that is less structured (1). Current physical activity models advance the idea that a person does not need to exercise as strenuously for at least 20 minutes, as advocated in 1990 by the American College of Sports Medicine (ACSM), to reduce the risk of chronic diseases(2,3). More recent recommendations support both moderate and vigorous-intense activity for 30 minutes daily or longer and the total amount of activity can also be accumulated with intemittent bouts for at least 10 minutes throughout each day (2,4-6). The activity guidelines are largely based on research findings which demonstrate that regular moderate-intense exercise, which is more structured than physical activity, can protect against the development of cardiovascular disease by reducing several coronary heart disease risk factors (7-9). Three important health benefits that reduce the risk of coronary heart disease include: a lowering of diagnosed high blood pressure (hypertension), an increase in high density lipoprotein (HDL) cholesterol (the good form), and increased glucose tolerance (improved insulin sensitivity).
Activity and Health
There is general consensus within the public health community and among other scientists that the amount of activity should increase to improve national health. In the US only 22 percent of adults are active for health in light to moderate-intense activity (i.e., 30 minutes five or more times per week), and 24 percent or more are sedentary (i.e., reporting no leisure time physical activity in the past month) (10). It has also been estimated that 12% of the annual deaths in the US can be attributed to physical inactivity (11-13). Review the CDC's Physical Activity and Health Summary.
The benefits of regular physical activity are summarized in the 1996 Surgeon General's report on physical activity and health (5) Physical activity has been found to be beneficial for reducing the risk of several chronic diseases including coronary heart disease, high blood pressure, non-insulin dependent diabetes mellitus, osteoporosis, colon cancer, anxiety, and depression (2). (link to Physical Activity and Health: A Report of The Surgeon General At-A-Glance).
Adults who participate daily in physical activity for as little as 30 minutes in moderate-intense activities like golf, tennis, walking, dancing, swimming, gardening, and actively playing with children can expect better health. Even intermittent activity throughout the day like walking up the stairs rather than taking the escalator or elevator, walking instead of driving short distances, doing calisthenics, or pedaling a stationary cycle while watching television can benefit health.
The minimal amount of physical activity required for health benefits can be achieved by expending as little as 1,000 activity kilocalories (Calories) per week. More vigorous activity means less time and number of days weekly and the activity accumulation can be unstructured, enjoyable, and fit into personal patterns of daily living (14). The evidence supports the following joint physical activity recommendations from the National Centers for Chronic Disease Prevention and Health Promotion and the ACSM (2):
Every adult should accumulate 30 minutes or more of moderately intense physical activity on most, preferably all days of the week. The activity progression should be gradual and the accumulation can be intermittent throughout the day in relatively short bouts for as little as 10 minutes at a time. The recommendation emphasizes physical activity at a daily energy expenditure of approximately 200 kilocalories (Calories) which is equivalent to walking 2 miles per day (3-4 mph) 5 times per week, or 150 Calories each day (based on 7 days per week). A very good web site that calculates calories burned during various activities or during the day is www.nat.crgq.com/energy/advanced.html. Another good site that equates calories expended to food intake is www.caloriesperhour.com/.
Since 60 percent of US adults are physically inactive, the emphasis is on progressing gradually at a moderate-intense rate for 5 or more days per week. The pattern of physical activity should be regular (i.e., most days of the week and preferably daily). The general recommendation is for 5 or more days of the week if moderate-intense activities are chosen, and 3 or more days weekly if the selected activities are more vigorous.
Since the recommendations are based on the total amount of activity accumulated weekly, a person can choose activities that are enjoyable and fit into a daily routine. The 1996 Surgeon Genaral's reoport also recommends that people include resistance training for muscular fitness twice weekly by exercising against an opposing resistance such as a weight.
Theory and Practice
The Surgeon General's report is controversial among research scientists. Some researchers advance the notion that people can obtain health benefits by becoming more active throughout the day; while others feel it is important to exercise regularly and improve physical fitness. There may be truth in both of these positions since regular moderate-intense activity can improve health and help protect against the onset of many chronic diseases.
Howley and Franks summarize some favorable changes that can occur by selecting the proper type and amount of activity (15).
improving fitness, primarily cardiovascular fitness and thereby improving health.
improving fitness and health at the same time and separately.
improving fitness without a particular health outcome.
improving some specific health outcome but not fitness.
The authors advance the idea that improvements in many health-related matters do not always depend on increasing cardiovascular fitness (see term definitions:aerobic capacity and aerobic fitness) but the appropriate activity dose (i.e, intensity, frequency, and length of time) needed to bring about the specific health outcomes. They then conclude that health outcomes and gains may act through some other means rather than just improving aerobic capacity. This idea advances the notion that the total amount of Calories expended, rather than higher activity intensity, is the most important consideration when planning a program for health. Yet other research findings demonstrate that more intense activity lowers the death rate (mortality) from all causes, and the mortality reduction could be related to improved aerobic capacity (16,17). Powell and Blair estimate that 35 percent of the coronary heart disease related deaths in the US could be prevented if every person was vigorously active (18).
Program Planning(19-21)
One important consideration in planning an exercise program is that conditioning will occur only with regular exercise. This principal is referred to as the principle of adaptation which means that only regular exercise produces physical gains. Adaptation depends on challenging the physical capability beyond a minimum threshold level. If the appropriate type and amount of activity is in excess of this threshold level, a training overload is incurred and physiological gain usually occurs. Regular overloading can lead to increased function an the training workload needs to be increased to maintain overload and progress when the fitness level improves.
The progression rate at the beginning of an exercise program needs to be gradual to best ensure fitness benefits. Fitness should improve only when the appropriate amount of overload is progressively increased. This principle is referred to as the principle of progressive overload. When exercise stops the physical gains can regress to pre-training levels (regression). Retrogression refers to an excessive training overload with a reduction in physiological gain. Retrogression can occur with highly intense single exercise bouts (acute overload) over extended time periods. Excessive overload over time is commonnly referred to as chronic overload.
A final important concept in exercise planning is specificity. Activities need to be selected that target specific fitness components if physiologic outcomes are to occur. Weight training, for example, develops muscular fitness (strength and muscular endurance) not cardiorespiratory endurance or joint range of motion (flexibility). A well-planned exercise program needs to include exercises that are specific to each physical fitness component and body part.
Aerobic Conditioning
Aerobic fitness is improved only when the circulatory and respiratory systems respond to the increased demand to supply oxygen and fuel to the working muscles and eliminate metabolic by-products. Regular exercise in aerobic activities like walking, jogging, swimming, and rowing increases the transport of oxygen to the muscles and oxygen utilization by the exercising muscles.
For additional basic and general aerobic conditioning information, click-onAerobic Exercise Principles and also go to the Aerobic Exercise Main Page at Georgia State University. The purpose of aerobic conditioning is to improve cardiorespiratory fitness. Aerobic conditioning requires a commitment to regular exercise in rhythmic activities that use the larger muscle groups like walking, cycling, and swimming. Improving cardiorespiratory fitness depends upon exercising at an intensity that significantly increases the heart rate and leaves you at least a little short of breath.Conditioning is most apparent at exercise intensities exceeding 50% of aerobic capacity, 3 to 5 days weekly for 30 to 60 minutes per workout. The total activity time can also include shorter periods (8 to 10 minutes) of more intense activities at 60 to 75 percent of aerobic capacity. The total exercise time does not need to exceed 30 minutes on most days when the work intensity is higher (1,2,4).
Metabolism and Exercise
Metabolism is the chemical reactions that produce energy in the body. The immediate source of energy for biological work is ATP (adenosine triphosphate), a high energy chemical (phosphate) compound. Energy is rapidly produced when ATP is broken down to ADP (adenosine diphosphate) and inorganic phosphate (iP). A small amount of ATP can be produced anaerobically from ATP muscle stores and another high-energy phosphate compound, CP (phosphocreatine) or creatine phosphate, and ADP. Muscle ATP and CP stores are limited, and can be depleted in only 5-7 seconds in activities like sprint running.
Another anaerobic system (anaerobic glycolysis) can produce a limited amount of ATP. This energy producing system is primary in athletic events like 200 to 800 meter runs and 50 to 200 meter swims. In these kinds of activities, muscle and blood lactate (lactic acid) significantly increases, and a considerable oxygen deficit is incurred. Stored muscle glycogen (carbohydrate) is the primary fuel for anaerobic glycolysis. It eventually becomes necessary to consume oxygen for energy production during prolonged exercise. Physical training improves the ability to provide ATP during activity (metabolic fitness).
The contribution of fats, carbohydrates, and protein (to a lesser extent) to the total energy output during exercise can vary significantly depending on the intensity (effort) needed to meet activity demands. The higher the relative (in realtion to aerobic capacity) activity intensity the more the muscles depend on stored carbohydrates as a fuel source since carbohydrates can be used both aerobically and anaerobically. The lower the relative intensity (lesser effort) of an activity the more the body depends on fat for energy production, since fat can only be used by using oxygen. When the intensity of exercise is too heavy, blood lactic acid increases. It is at this point that the anaerobic or lactate thresholdis reached and the rate and depth of breathing significantly increases. Fatigue and reduced energy output occur when exercising muscle glycogen is depleted. For a good introduction to muscle physiology, go to The University of California, San Diego's Muscle Physiology Home Page.
Exercise Readiness
A pre-exercise readiness questionnaire has been developed in this document for individuals who are planning to maintain or increase their activity level. It is recognized that no single set of questions can cover all situations, and specific program practices can vary. The questionnaire is for guiding individuals who should have a medical examination and exercise test before participating in a moderate or vigorous exercise program.
Individuals with known or suspected cardiovascular, pulmonary, metabolic, orthopedic, or neurological disorders should consult with a physician before increasing the level of activity (21). In the National Institutes of Health Consensus Statement on Physical Activity and Cardiovascular Health it was stated that "most adults do not need medical consultation or pretesting before starting a moderate-intensity physical activity program. However, those with known cardiovasular disease and men over age 40 and women over 50 with multiple cardiovascular disease risk factors who contemplate a program of vigorous activity should have a medical evaluation prior to initiating such a program" (13).
In 1995 the ACSM recommended a medical exam within the past year for all exercising adults (22). The ACSM also recommended a pre-exercise medical exam including an exercise test for patients with diagnosed cardiac, pulmonary or metabolic disease, and for individuals with symptoms of cardiac or pulmonary disease. An exercise (stress) test was recommended for men over age 40 and women over 50 before participating in vigorous exercise (greater than 60 percent of aerobic capacity).
Younger individuals (i.e., women under 55 years of age and men under 45 years of age) were classified as low risk if there was no more than one coronary artery disease (CAD) risk factor and there were no signs or symptoms of cardiovascular, pulmonary, or metabolic disease. The ACSM continues to classify any adult regardless of age as high risk for exercise when there are major signs/symptoms or other clinical findings suggestive or supportive of cardiovascular, pulmonary or metabolic disease. Adults are considered to be at moderate exercise risk when there are two or more CAD risk factors. Older individuals (i.e., women greater than or equal to 55 years of age and men greater than or equal to 45 years of age) are classified as moderate risk for exercise in the absence of CAD risk factors.
ACSM guidance also includes the type and amount of activity and and the perception of effort during exercise. For low and moderate-risk individuals, an exercise test isn't necessary although not inappropriate. Moderately-intense activity "may be alternately defined as an intensity well within the individuals capacity, one which can be comfortably sustained for a prolonged period of time (~45 min), which has a gradual initiation and progression, and is generally noncompetetive"(23),p 27).
If exercise capacity is known, moderate-intensity exercise may be defined between 40-60% of aerobic capacity. Otherwise, exercising between 3-6 METs (equivalent to brisk walking at 3-4 mph) may be appropriate for most healthy adults unless a person has limited exercise tolerance (i.e., considers the activity to be hard to very hard). For persons participating in moderate-intensity exercise or organized exercise programs, go to the AHA's website and enter exercise cardiovascular screening for your advanced search. Then select Recommendations for Cardiovascular Screening--Tables.
The following questionnaire has been developed primarily from ACSM, American Heart Association, and the Canadian Society for Exercise Physiology resources (22,23,24). Disclaimer: The questionnaire is not intended to render medical advice or prescribe medical treatment for specific conditions for individuals nor substitute for such advice for treatment. Persons with pre-existing medical conditions or who are under a physician’s care and persons concerned about their readiness for exercise should consult with a physician before beginning. Always ask your physician for advice if you have questions and concerns about your physical activity readiness.By responding to the questions below, you can get a general idea as to whether exercise could be harmful to you.
Diagnosedcardiopulmonary and metabolic diseases:-- Do not begin without physician approval!
Have you ever been told by a physician that you have a heart problem and recommended only medically supervised physical activity?
Do you have cardiac, peripheral vascular, or cerebrovascular disease?
Do you have chronic obstructive pulmonary disease, asthma, cystic fibrosis, or other diagnosed lung disease?
Do you have kidney, liver, or thyroid disease?
Do you have diabetes mellitus (either type 1 or 2)?
Signs or symptoms suggestive of cardiopulmonary Disease: -- See your doctor for discussion or clarification if any should apply!
Do you experience pain, tightness or pressure in the chest, neck, jaw, arms, or other areas that may be due to insufficient blood flow?
Are you short of breath at rest or with mild exertion?
Have you had problems with dizziness or fainting?
When you stand up or during the night, do you have difficulty breathing?
Do you have an abnormally fast heart beat or fluttering?
Do you experience severe pain in the leg muscles while walking?
Do you suffer from ankle swelling because of fluid accumulation?
Has a doctor told you that you have a heart murmur?
Do you experience unusual fatigue or breathlessness with usual activities?.
Other: --- Do not exercise before you see a physician!
Are you over age 65 and not accustomed to regular exercise?
Do you have any physical condition, impairment, or disability including any joint or muscle problem that could be made worse by a change in physical activity?
Has your doctor informed you or do you know of any medical or physical reason why you should not exercise?
Coronary Artery Disease Risk Factors: --See your doctor before exercising if you select at least 2 from the list below. The last question is a bonus (subtract 1 point from your total score).
Cigarette smoking: Do you presently smoke cigarettes or have you quit within the previous 6 months?
Cholesterol: Is your total blood cholesterol level greater than (>)200 mg/dl or is your HDL (good form) less than (<) 35 mg/dl. If low-density lipoprotein cholesterol is known, use >130 mg/dl rather than total cholesterol of >200 mg/dl)? Are you on lipid-lowering medication?
Hypertension: Is your systolic (upper reading) blood pressure greater than or equal to 140 mm Hg and/or diastolic (lower reading) greater than or equal to 90 mm Hg on two separate occasions or are you taking medication to lower your blood pressure?
Family history: Has any of your first-degree relatives had a heart attack, coronary revascularization, or sudden death (i.e., father, brother or son before 55 years of age or mother, sister or daughter before 65 years of age)?
Impaired fasting glucose: Is your fasting blood glucose greater than or equal to 110 mg/dl confirmed by measurements on at least 2 separate occasions?
Obesity: Is your body mass index (BMI) greater than or equal to 30 or waist girth >100 cm?
Sedentary lifestyle: Do you participate in a regular exercise program or meet the minimal physical activity recommendations from the US Surgeon General's report?
Bonus: Do you have a serum HDL cholesterol greater than 60 mg/dl? If yes, subtract one risk factor from the above risk factors since high serum HDL decreases coronary artery disease risk.
An over-aggressive approach to exercise should be avoided. Probably the greatest sources of problems for beginning exercisers are over-stressed muscles, tendon and joint problems, shin splints, stress fractures to bones, muscle soreness, joint discomfort, and lower back pain. You should contact your doctor as soon as possible if you experience extreme breathlessness during or after mild exertion or exercise induced nausea, pain or pressure in the chest or pain in the arms, neck or jaw, dizziness, or confusion.
Fitness Programming
The MHE Fitness Programming SystemSMsupports the idea that there is a basic amount of activity that should become a regular part of a personal health and fitness plan. The System sets personal aerobic conditioning guidelines from an easy to complete activity questionnaire (click to access). If you have questions about the results, carefully re-read the questions and enter your activity information again. The resulting exercise program guidelines are intended for review by a physician or qualified fitness professional.
Training intensity and METs. The System sets a training-intensity range in METs, where one MET is the amount of energy expended while sitting quietly at rest. By grading activity intensity in MET units, it is possible to classify average intensities for a wide range of physical activities where a higher MET value is more intense than a lower value. For example, moderate-intense activities like pleasure walking, walking the dog, or walking during a break from work at 3 to 4.5 mph would require an intensity range between 3 to 6 METs; while the level of intensity for most competetive sports are greater than 6 METs. You can go to: General Activities defined by level of Intensityfor an expanded list of moderate and vigorous physical activities defined by level of intensity in accordance with CDC and ACSM guidelines. You can also obtain a more extensive list of activity-MET units for record keeping by clicking "MET Values" on the left list (modified from reference 24, pp 657-665). All the activities are moderately intense at 3 METs and higher. The Table below is for general illustration.
3-4 METs Archery Bowling Golf, pulling a cart Sailing a small boat
Slow walking (2-3 mph)
6-7 METs Cycling (11 mph) Folk and square dancing Hiking cross country Splitting wood (hand ax or saw)
Walking (very, very fast)
4-5 METs Carpentry Cycling (8 mph) Dancing Gardening and lawn work Golf (carrying the clubs)
A worthwhile goal is to select physical activities at an intensity that can improve health. Fortunately, health promoting activities are moderately intense. In fact, there is a general consensus within the public health community that an energy expenditure within 700 to 2000 Calories or more per week within a 3-6 MET range can improve health and reduce death rate in middle-aged and older populations (6,17).
Training intensity and effort. Since activity effort is related to both individual aerobic capacityand exercise involvement, it is important to tailor exercise program guidelines to a person's relative capability which means that exercise guidelines are set at a percentage of aerobic capacity. The American College of Sports Medicine defines moderate-intense exercise between 40 to 60 percent of aerobic capacity and vigorous exercise above 60 percent (click to access)(24). The ACSM also defines moderate-intense physical activity at a level that can be sustained comfortably for as long as 60 minutes, if workouts are generally non-competitive and include a gradual progression, and describes vigorous exercise as activity that significantly challenges the cardiorespiratory system resulting in fatigue within 20 minutes.
METs, aerobic activities and weight management. An aerobic-conditioning session should range from 12 to 60 minutes. If the goal is fat reduction and a person is not accustomed to regular exercise, the total activity accumulation throughout the day (within the 3-6 MET range) should be longer. Moderate-intense daily physical activity can help reduce body fat if the added amount of large muscle group activity is consistently higher. Since the energy contained in a pound of fat is 3,500 Calories it is possible to estimate the time needed to lose fat weight. For example, a 155 pound person who walks for 45 minutes per day at 4-5 METs could expend up to 200 extra Calories per workout day or 1,000 extra calories each week (frequency = 5 days per week). In one year approximately 15 pounds of fat could be lost provided there was no increase in caloric intake. Combine the exercise with a 200 Calorie food deficit plan each day and 35 pounds could be lost over the same period. For good nutrition and weight control information, go to the NHLBI's website Healthy Weight. Also review the Department of Health and Human Services (HHS) and the Department of Agriculture (USDA) publication: Dietary Guidelines for Americans 2005.
Monitoring Exerise Intensity
Heart rate and exercise intensity. Monitoring the heart rate response to exercise is one method for assessing workout intensity. By using an age-adjusted or known maximal heart rate (MHR), a heart rate exercise benefit range (EBR) can be set within a high and low heart rate in relation to the MHR. When MHR is unknown, the value is commonly estimated by subtracting the age from 220 beats per minute (bpm). Unfortunately, this method for estimating MHR can be problematic since the result can vary for 68 percent of the population within 10-12 bpm above or below the average estimated value. Also, certain medications can invalidate the usefulness of a predicted MHR for setting a heart rate benefit range for aerobic conditoning. Using the MHR obtained at maximal oxygen intake (see aerobic capacity) or from maximal exercise testing is the best method for ssetting the EBR for aerobic conditioning. Only highly trained athletes in sports like bicycling, rowing, running, or swimming should push themselves to the upper limit needed to attain MHR. Most individuals should ask a qualified fitness professional or physician about using an estimated MHR as a reliable indicator for setting an EBR for conditioning.
Pulse counting procedure. Because it is difficult to obtain the heart rate during exercise (unless you have a heart rate monitor), the pulse taken immediately after you stop exercising. Correct procedure depends on beginning the first pulse count within 5 seconds after you stop exercising and completing the count within 15 seconds. The following is a description of the procedure:
Find your pulse immediately after exercise by placing your first two fingers (not your thumb) over the radial artery on the thumb side of the wrist (inside the wrist bone) or lightly on the carotid artery in the groove in the neck on the side of the voice box below the angle of the jaw. Press lightly and do not press on both carotid arteries at the same time. Begin counting and count the number of pulses in a 10-second period. The first pulse that begins the 10-second interval should be "0" and you should continue counting throughout the 10-second period (i.e., 0…1…2…3…4…etc.). Then multiply the 10-second count times 6 to convert the pulse rate to beats per minute.
The benefit range for aerobic conditioning can vary between 55 to 90 percent of MHR, or 40 to 85 percent of aerobic capacity (same as heart rate reserve) (29). For an example of how to use the heart-rate reserve method, see the Karvonen formula below. When using the Karvonen formula to set the EBR, the training heart rate range can be as low as 40 to 49 percent of heart rate reserve for individuals who are unfit.
From the Table below, for a person who is 45 years of age, the EBR can be set between 96 to 157 bpm at 55 to 90 percent of MHR (based on a predicted MHR = 220 bpm minus the age). The table is for illustration purposes and is intended to show the wide exercise benefit ranges for various age groups.
Age in Years 20-30 31-40 41-50 51-60
61+
EBR in bpm 107-175 101-166 96-157 91-148
85-139
MHR in bpm 195 185 175 165
155
If you are unfit and just beginning to exercise, it is a good idea to stay at the low end of your EBR. The progression should be gradual and you should not reach the high end until after 6 months. For those who are highly fit or training for competitive sports, exercise heart rate may be at the high end or even exceed the highest value of the EBR.
Karvonen formula. Another method commonly used for determining an exercise heart rate range for aerobic training is to estimate the heart rate response at a given percent of aerobic capacity by using the Karvonen formula. To use this method, you will need to know your resting and estimated (or known) maximal heart rate in beats per minute. First count the number of pulses for 30 seconds while standing at rest and multiply the value by 2 to obtain the resting heart rate in beats per minute. The calculation is as follows for a 45 year old person exercising at 60 percent of aerobic capacity with a resting heart rate = 75 bpm:
As aerobic fitness improves, your exercise heart rate may be lower for the same workout intensity in METs. The lower heart rate at the same work intensity means that the amount of blood ejected by the heart with each beat (stroke volume) has increased and the cardiac output (heart rate in bpm x stroke volume) can stay at the same level with fewer heart beats. Before increasing exercise intensity, it is a good idea to ask whether the increased effort is necessary for health benefits and general conditioning. Remember to always assess how you feel and reduce effort if you are exercising too hard.
Using the exercise heart rate alone is not a precise method for monitoring training intensity (24). In fact, a number of external factors can cause the heart rate to vary independently of workout intensity (metabolic demand) (27). Some of these factors include time of previous meal, environmental termperature, and airflow/ humidity which can influence heat dissipation. Also the degree of rest, overtraining, illness, and certain cardiovascular medications can often invalidate the use of exercise heart rate as an indicator of metabolic demand. However, an abnormal heart rate response to exercise like rapid and irregular heart beats or a failure of the heart rate to rise with an increase in metabolic demand are important signs that warrant physician attention.
Perceived exertion and intensity. Another method for monitoring physical effort is to assess how you feel using a perceived exertion rating (RPE) scale. The procedure is best used for nonstop activities like walking, jogging, bench stepping, swimming, or cycling. Monitoring exercise effort by using the RPE scale can provide a method for checking your training heart rate range as an indicator of intensity, and can also be used during exercise without stopping to obtain a pulse.
Rating perceived exertion can help you sense effort by listening to your body. The proper rating of perceived effort depends on input from the muscles, joints, breathing rate, and energy demand. By using an RPE scale, you can learn to evaluate your internal comfort zone and sense excessive discomfort. The following is a description of one commonly used procedure (28-30):
Estimate your exertion by using the exercise intensity scale below. The scale begins with 0 (nothing at all) and increases to extremely heavy (maximum). For example, 10 is the exertion you feel when the exhaustion is beyond anything you have ever experienced and the exercise is so difficult that you almost can’t make it. If the exertion is fairly light, you should answer 2 or 3 and so on. Feel free to use any number on the scale that you wish, as well as half values (e.g., 1.5) or decimals (e.g., 0.7, 4.6, etc.). It is important to select a number that best describes how you feel while exercising and not after you stop. Rate yourself as honestly as possible and try not to overestimate or underestimate your numerical value. Do not rate kind of work you are doing like comparing running to cycling or swimming. If you are exercising with another person or in a group do not compare your rating to others who might influence the number.
0
Nothing at all
0.5
Extremely light
Just noticeable
1
Very light
Like slow continuous walking
2
Light
Weak
3
Moderate
Can continue without difficulty
4
Somewhat heavy
5
Heavy (strong)
Can continue without excessive fatigue
6
7
Very Heavy
Very tired and strenuous
8
9
10
Extremely heavy
Maximum
The breathing rate is a good indicator of perceived exertion. Therefore it is a good rule to use a conversation test to rate your effort. You are most likely working too hard if you need to stop and catch your breath. If you can talk and exercise at the same time, you are not working too hard. However, aerobic exercise should leave you at least a little short of breath. With practice, you should be able to use the RPE scale and eventually reduce the number of times needed for pulse counting. The intensity for beginning an aerobic conditioning program should be at the low end of your MET-intensity range and you should gradually increase workout intensity only after assessing both exercise heart rate and RPE. The RPE range for most individuals is between 3 (moderate) and 5 (strong). For those who are unfit, the RPE should remain at 3.
The perception of effort during exercise is related to activity tolerance and can vary considerably throughout the population. Since physical activity intensity is classified for public health considerations in both absolute and relative (i.e., in relation to aerobic capacity) terms, it is often convenient to use brisk walking at 3-4 mph as an example of a moderate-intense activity. This example can be misleading for some individuals with reduced acivity tolerance. For those individuals, walking at 3-4 mph exercise can be vigorous. Yet for others with a high level of exercise capability, walking at 3-4 mph walk may require a relatively low level of effort.
Frequency and Duration
Frequency.The minimum number of workouts for cardiorespiratory conditioning is 3 times weekly with no more than two days between exercise sessions. You should gradually progress to 5 days per week only if your fitness level improves and you can effectively manage the additional load. The benefits of exercising beyond 5 days per week may be outweighed by an increased injury risk. If you should exercise five days per week, it is important to lower exercise intensity. Avoid exercising if you are ill, especially if you have a fever or are recovering from an infection. Plan your workouts to avoid strenuous exercise during hot and/or humid days or immediately after a meal. However, light or moderate activity (like walking) may be beneficial after eating, especially if you are trying to lose weight. Whatever your schedule, plan to exercise at a time that is free from interruptions.
Duration. The length of time for an aerobic workout can vary between 8 to 60 minutes and there is an inverse relationship between duration and workout intensity. You should gradually progress from 10-15 minutes of continuous exercise to 30-60 minutes (longer duration for moderately intense exercise and weight management). Intense conditioning on consecutive days can lead to general fatigue and increase injury risk. Depending on your fitness level, it is a good idea to reduce your average workout duration if intensity and/or frequency are consistently high. You should exercise within the DURATIONrange given in your exercise program guidelines. If you have been physically inactive, select light to moderate-intense aerobic activities within the 3-6 MET range, and/or stay at the low end of your duration range and gradually increase the length of the workouts.
Less-intense activities like walking can be maintained for longer periods since exercise duration depends on activity intensity. You can also improve aerobic fitness by varying your effort during a single workout (e.g., by alternating slow jogging and walking with brief rest pauses). This approach is also useful for extending workout duration and expending extra calories.
Activity Selection
When considering the kinds of activities for improving cardiorespiratory fitness, it is important to select activities that permit you to closely monitor exercise intensity while minimizing injury risk. If your goal is to improve aerobic capacity, training intensity should remain between 60% to 80% of your aerobic capacity (73-87% of HR max). This intensity range, however, could be lower depending on your previous exercise status (i.e., inactive). If your goal is to improve CR fitness and manage body compostion, you will need to select activities that meet the optimal frequency and duration recommendations by the ACSM based on your present activity status (i.e., 3-4 days per week and eventually 20 to 60 minutes per exercise session).
Sample aerobic fitness activities within your training intensity range in METs are given on the SAMPLE ACTIVITY LIST of your Exercise Program Guidelines. you can also obtain an updated list of activity-MET values by clicking on the left list (Met Values).
There are many activities that can meet your conditioning needs and as your fitness level improves the activity options can increase. Initially, your activity choices should include activities where the intensity can be carefully controlled and closely monitored. The kinds of activities can slso include running, cycling, swimming, aerobic dance exercise, rowing, or cross-country skiing. Other options could include the use of aerobic conditioning equipment like ski machines, stair climbers, rowing machines, stationary bicycles, and other aerobic conditoning equipment. For individuals who are overweight or tend to be injury prone, it is important to choose low-impact over high-impact exerscises. Activities like cycling, swimming, rowing, and water aerobics reduce the impact of the body against the ground which can reduce injury risk. Other important guidelines for preventing injuries include: regular conditioning, a gradual increase in workout intensity and duration, and getting adequate rest between exercise sessions. You should also warm-up and cool-down with before and after every exercise session.
Beyond formal exercise, it is also important to increase supplemental moving about activities which incorporate activity throughout the day. Examples include: lawn and garden work, active play, home maintenance, using stairs, and walking a longer distance from a parked car to the destination.
Warm-up. The major purpose of the warm-up is to elevate heart rate and body temperature, and increase blood flow to the muscles. The warm-up period should be gradual (5-15 minutes) consisting of low-intense exercise and stretching. The Stretching exercises should be included as part of the warm-up and cool-down periods after muscle temperature is increased.
Cool-down. The conditioning session should end with 5-15 minutes of light exercises and stretching. The cool-down promotes blood return to the heart and prevents blood pooling in the legs. The cool-down may also stabilize heart action and decrease the amount of muscle soreness following exercise. A beneficial cool-down should consist of light exercise such as walking and calisthenics for at least 5 minutes followed by flexibility exercises. The flexibility exercises should primarily focus on the muscles used during the exercise session.
Endurance training techniques. Cross training refers to a training procedure that includes different kinds of activities selected to improve the same physical fitness component (e.g., cardiorespiratory fitness). A cross training routine could include running on one day, cycling on another, and swimming on another. one major intent of this conditioning method is to reduce injury risk by avoiding overuse of the same body parts. It is important to make certain that the choice of activities complement one another and are specific to your training goals when incorporating cross training into your routine,.
One popular cardiorespiratory training techniques is to incorporate lower-intensity training over a longer period of time without increasing exercise intensity. By exercising continuously at a moderately intense level, you can reduce injury risk and extend exercise duration to 40 to 60 minutes per session. This type of conditioning can also be enjoyable because exercise intensity is lowered.
Interval training uses repeated bouts of shorter and more intense exercise. This procedure is more popular among athletes who need to attain higher fitness levels over a shorter time period. The duration of the repeated exercise periods can range between 10 seconds to 5 minutes followed by intermittent rest periods. The rest and exercise periods can vary depending on the training intent.
Progression Rate
A properly designed aerobic conditioning program should increase exercise tolerance as your fitness level improves. By keeping a record of your heart rate after at least 10 minutes of nonstop aerobic exercise, you may find that you are able to increase your training intensity in METs and still stay within your training heart rate range. This increase in energy output may be the result of improved aerobic capacity. The conditioning effects during the first six to eight weeks can improve aerobic capacity as much as 3% per week during the first month, 2% each week for the second month, and 1% per week or less thereafter. The rate of improvement depends on age, initial fitness level, extent of determination, and health status. Older individuals do not improve as much as younger persons with similar entry fitness levels. There are generally three progression stages in an aerobic exercise program (24).
Initial conditioning stage. Objectives during this conditioning phase are to avoid discouragement by not exercising too hard, progress gradually, avoid soreness and injury, and permit the body to adapt slowly. This four to six week stage should include light muscular endurance activities and low-to moderate-intense aerobic activities. Your Exercise Program Guidelines have been adjusted to your exercise experience and present activity status. If you have been physically inactive, stay at the low ends of your INTENSITY, DURATION, and PULSE ranges. The length of the exercise session should begin with 12 to 15 minutes and progress to 20 minutes. After the first week, begin adding additional minutes of continuous exercise to your workouts until you can comfortably attain the MAXIMUM DURATION for your selected activities (longer duration for less-intense activities). You should limit exercise FREQUENCY to 3 times weekly on non-consecutive days. Your workouts should make you feel warm, cause some sweating, and leave you a little short of breath. During this stage of conditioning, it is a good idea to seek-out the guidance of an exercise professional. The following is a sample progression rate for an apparently healthy individual:
Week
Exercise
Exercise
Frequency
Exercise
Duration
Days/Wk
Intensity
(minutes)
1
3
Light
12
2
3
Light to moderate
14
3
3
Moderate
16
4
3
Moderate
18
5
3
Moderate
20
Improvement conditioning stage. This slow progression stage usually lasts from 12 to 20 weeks with a gradual increase in exercise intensity and incremental changes in exercise duration every two to three weeks depending on your fitness goals. A general goal during this stage is to exercise 3 to 4 days per week and to eventually increase duration to 30 minutes per session. The exercise intensity during this phase should be at the mid-to upper-level of your training heart rate range (between 70% and 80% of your HR reserve) which represents a moderate to somewhat heavy effort. It is a good idea to age-adjust your progression rate by allowing one additional week for conditioning changes to occur for each 10 years after age 30.
Maintenance conditioning stage. This stage usually begins after 16-28 weeks of training after you have attained your fitness goal. The major objective is to maintain your physical fitness level. You most likely will be able to retain your present fitness level if the exercise intensity and duration are maintained at the same level as during the final weeks of the slow progression phase. However, frequency can be reduced to twice weekly without reducing physical fitness. If you choose to maintain frequency at 3 to 4 days per week, you should be able to reduce duration to 20 to 25 minutes per workout day. It is important, however, to increase exercise intensity during this phase if you wish to maintain your present level of CF.
Muscular Fitness
For a good introduction to this topic click-on the Strength Training Main Pageat Georgia State University. The ACSM recommends that "strength training of a moderate intensity, sufficient to develop and maintain fat-free weight, should be an integral part of an adult fitness program. One set of 8-12 repetitions of eight to ten exercises that condition the major muscle groups at least 2 days a week is the recommended minumum"(24). The ACSM adapts the recommendiation for older and/or less fit individuals (approximately 50-60 years of age and above), to 10-15 repetitions using lighter weights and the use of multiple-set routines if time permits. Persons under age 50 should try to perform 10 repetitions with an increase in resistance (load) when a near-maximum effort is needed to perform 8-10 repetitions. For persons over age 50, resistance should be increased when 15 or more repetitions can be achieved. It is also important to incorporate less-structured resistance training into daily activities by becoming more aware of (and adding) proper lifting, carrying, pushing, and pulling procedures. For more complete muscular fitness informaton, go to the ACSM's webite and enter resistance training for your search topic.
Flexibility
The ACSM also recommends that stretching be performed for the major muscle groups at a minimum of 2-3 days per week and at least four repetitions, held for 10-30 seconds per stretch (24). The web site at Georgia State University is a good source for general flexibility information.
Recommendations
The ACSM recommendations and general recommendation for improving health and physical fitness are as follows:
For health benefits, attempt to perform at least 30-minutes of moderate-or high-intensity activity on most, preferably all, days of the week. Remember that the total amount of activity can be accumulated by performing multiple bouts (each lasting 8-12 minutes) throughout the day.
Spend 65 to75 percent of your time doing large-muscle group endurance activities and the rest of the time performing strength-developing and flexibility exercises (at least twice weekly for a total of 60 minutes). Stretching exercises need to be included to maintain or improve joint range of motion.
The cardiorespiratory endurance exercise portion of your program should be moderate-to high-intensity based on your goals and interests. Remember that progression rate can vary individually for the conditioning stages.
Select a variety of aerobic exercises that fit personal needs, interests, and capabilities. If you are not accustomed to exercise, have orthopedic limitations, or at risk for over-use injuries ask a physician or certified exercise trainer for advice.
Persons with cardiovascular, respiratory, metabolic, or musculo-skeletal problems should be evaluated by a physician and given an exercise program suited to their health needs according to the guidelines established by the Centers for Disease Control and the the American College of Sports Medicine (2,24,31).Exercise sessions may need medical supervision for some individuals (21).
