K562

PRICNCIPLES OF
EXERCISE PRESCRIPTION

 

 

Exercise prescription and exercise programming are similar activities in that they utilize pre-activity assessments to develop the recommendations given for success. Exercise programming and exercise prescription are different in the extent of the prior assessment. Exercise programming is used when the assessment is limited, whereas exercise prescription is used more in scenarios with a comprehensive assessment. The extent of the assessment often depends on the setting.

PRINCIPLES OF TRAINING

Physical activity is defined as any bodily movement produced by skeletal muscles that result in an increased energy expenditure. Exercise training is defined as planned, structured, and repetitive bodily movement done to improve or maintain one or more components of physical fitness. Cardiorespiratory endurance, along with muscle strength, muscle endurance, and flexibility, is one of the components of physical fitness. Cardiorespiratory endurance is the ability to perform large muscle, dynamic, moderate to high intensity exercise for prolonged periods of time. Exercise training improves cardiorespiratory endurance whereas both physical activity and cardiorespiratory endurance have been found to produce significant health benefits.

The principles of training apply to exercise training and exercise treatment more so than to physical activity.

  • Specificity of Training
  • Overload Principle

Specificity of Training refers to the type of exercise used to make specific changes in fitness. That is, resistance work (high load, few reps) improves muscle strength; stretching exercises improve flexibility; resistance work (light load, many reps) improves muscle endurance; and endurance exercises improve cardiorespiratory endurance. The specificity of exercise principle is so specific that if strength exercises are done with one arm, only that other arm will make improvements.

The Overload Principle: An overload is an intensity greater than encountered on a regularly daily basis. Physiological changes can only occur from exercise when an overload is applied. A small overload is required to move from sedentary to fit whereas an greater overload is needed to move to higher levels of fitness.

Each of these principles guides the design of an exercise program. In exercise training, the mode of exercise, as well as the frequency, duration and intensity of training are critical in achieving fitness, athletic, or health outcomes. The mode must be specific to the targeted component of fitness and the frequency, duration and intensity must be combined in a systematic overload that will result in physiologic adaptations.


THE EXERCISE PRESCRIPTION

Whether the purpose is athletic training or treatment of disease, the exercise program and prescription must include mode, frequency, duration, and intensity.

Mode, the type of exercise, utilizes the specificity of exercise principle to choose a type of exercise that will stimulate the desired outcome.

Frequency is number of sessions per week or the number of session per day.

Duration is the total time, measured in minutes, for each exercise session.

Intensity, measured as percent of capacity (VO2max), is the effort. Frequency, duration and intensity combine to produce an overload.

In exercise programming/prescription, the recommended frequency, duration, or intensity is called the target.

Additional aspects of the exercise prescription include progression, precautions, and recommendations when appropriate. Guidelines for the progression of exercise become a factor in the success of individuals who are beginning an exercise program or who are engaging in specific types of exercise programs.

Precautions for exercise are the modifications in the prescription or the additional concerns that must be addressed for each disease process, co-morbidity, or disability to make exercise safe. For example, individuals with diabetes who exercise will be given several precautions for the timing of meals, insulin injections, and glucose monitoring that will not be given to apparently healthy individuals without diabetes who exercise. Precautions given to individuals with angina will not be the same as those given to individuals with low back pain. Each chronic disease and disability will have a specific set of precautions.

Recommendations are additional life-style changes appropriate to the client or patient. For the most part, these recommendations include

          • Diet
            • Target Weights
          • Smoking Cessation
          • Stress Management
DETERMINING THE MODE

Cardiorespiratory exercise should be used to improve cardiorespiratory endurance. Cardiorespiratory exercises are continuous, dynamic exercise, which utilizes large muscle masses, requiring aerobic metabolic pathways to sustain the activity. Cardiorespiratory exercise can improve cardiorespiratory endurance as well as prevent and treat modern chronic disease. Even though physical activity has a similar effect on the prevention of disease, the role of physical activity in the treatment of modern chronic disease has yet to be established. When physical activity is programmed for health, activities that produce an energy expenditure beyond the intensity of activities of daily living (i.e. greater than 2.5 METs) should be recommended.

Examples of physical activities can be found listed below

Household Activities

  • Cleaning the house
  • Ironing clothes
  • Home repair

Leisure Activities

  • Carpentry
  • Washing the car
  • Walking the dog

Outdoor Activities

  • Gardening
  • Splitting wood

Work Activities

  • Construction
  • Lifting and carrying

Examples of cardiorespiratory exercise are listed below.

 

  • Cycling
  • Upright
  • Recumbent
  • Swimming
  • Jogging or Running
  • Walking
  • Cross Country Skiing
  • Hiking
  • Skating
  • Roller Blading
  • Skipping Rope
  • Dancing
  • Aerobic Games

Cardiorespiratory activities can be classified different ways. One way is to classify by skill and energy expenditure and another is to classify by the dependence of body weight. Categories for skill and energy expenditure groupings are listed below.


Group
Group 1
Group 2
Group 3
Definition
  • Ease of maintaining constant intensity
  • Low interindividual variation in energy expenditure
  • Ease of maintaining constant intensity
  • Energy expenditure is related to skill
  • Skill highly variable
  • Energy expenditure highly variable
Use

Desirable for more precise control of exercise intensity:

  • Beginning an exercise program
  • Rehabilitation
 Not contraindicated for the early stages of conditioning, but skill must be considered.

 Good for group interactions, but caution must be taken for

  • High risk-low fit
  • Symptomatic patients
Examples
Treadmill Walking
Cycle Ergometry
 Swimming
Cross-Country Skiing
Racquet Sports
Basketball
Soccer

Group 1 activities are recommended for exercise programs/prescriptions where the intensity is important to regulate and maintain. For example, control of exercise intensity to prevent overuse injuries in the novice exerciser who is overweight may limit the mode of exercise to those in Group 1. Similarly, more Group 1 exercises are utilized in rehabilitation programs where the control of exercise intensity is vital to the safety of the exercise program. However, as individual advances to higher fitness progression to exercises from Groups 2 and 3 may provide more variation in the types of activities.

Classifying cardiovascular exercise by body weight dependency is a different classification system than by skill and energy expenditure. Weight dependent exercises, or weight bearing activities, are those in which the body weight is moved throughout the exercise. Examples of weight bearing exercise are walking, jogging, running, and hiking.

On the other hand, in weight independent exercise, or non-weight bearing activity, the body weight is supported by the implement or media and does not contribute to the energy expenditure. Examples of non-weight bearing exercise are cycling and swimming. Non-weight bearing exercise may be more effective in preventing lower limb overuse injuries associated with exercise.

The mode of exercise that is effective in producing the desired outcome must be the first consideration in choosing the mode of exercise. However, modifications and variations can be made in mode to promote adherence as needed. Varying the mode of exercise among the weekly workouts and substituting recreational activities may be strategies that promote a higher adherence to the exercise.


EXERCISE FREQUENCY

Frequency is prescribed in sessions per day and in days per week. To improve cardiorespiratory fitness for the apparently healthy adult, the range of frequency is between 3 to 5 days per week. For a sedentary individual, the minimum overload is the 3 days per week whereas, for the higher fit individual the overload must be increased to 4 to 5 days per week.

In some chronic disease such as obesity or hypertension the most effective frequency may be a higher frequency per week. In these cases, the initial exercise prescription for a sedentary individual with obesity or hypertension may have higher frequencies than the apparently healthy adult.

Recommendations for exercise progression are essential for injury prevention when high frequency prescriptions are given to sedentary individuals. In the in-patient setting frequency will be prescribed in sessions per day for 3 to 5 days per week. These sessions may be as high as 3 to 5 per day. When programming for physical activity, most, if not all days of the week should be recommended.


EXERCISE DURATION

Exercise durations range from 5 min to 60 min. Rarely will prescribed exercise duration exceed 60 minutes. The law of diminishing returns begins at duration of 60 minutes. That is, the average individual will not receive significantly more benefit by working more than 60 minutes. In fact, the risk of overuse injury increases the risk:benefit ratio of exceeding 60 minutes of cardiorespiratory exercise for the apparently healthy adult.

The lower exercise duration, between 5 to 10 minutes, will be used in the clinical setting for chronic disease and disabilities.

The minimum duration to achieve an improvement in cardiorespiratory fitness is 20 minutes; the range is 20 to 60 minutes.

The minimum duration to maintain fitness is 20 minutes.

The range of prescribed duration, like frequency, is broad. Similar to the principles of prescribing frequency, duration will be prescribed in shorter 10 to 20 minute ranges depending on the fitness and health of the individual.

For apparently healthy individuals who are sedentary, the shorter durations from 20 to 30 or 30 to 40 minutes are adequate to improve cardiorespiratory fitness. For more fit individuals, 40 to 60 minutes may be the required overload to achieve further improvements in cardiorespiratory fitness. When programming for physical activity, duration of at least 30 minutes should be recommended.


The combination of exercise frequency and duration should be viewed with caution. Pollock, in a 1977 classic study, exercised six groups of men within the range frequency and duration for the exercise prescription for apparently healthy adults to improve cardiorespiratory fitness. Intensity was the same for all groups of men. Three groups exercised for 15 min, 30 min and 45 min for three days a week. Three other groups of men exercised 1 per week, 3 per week and 5 per week for 30 minutes.

The results of this study are illustrated in the figure to the right. As expected, the improvements in fitness were related to the overload.

However, the higher overloads were also related to higher injury rates. The highest duration and the highest frequency resulted in the highest injury rates.

Therefore, caution should be taken in determining the optimal duration and frequency to improve fitness without causing overuse injuries.

EXERCISE INTENSITY

Intensity of cardiorespiratory exercise is measured as percent of maximal capacity, more specifically, as a percent of VO2max.

 

Intensity
Percent VO2max
Very Light
Light
Moderate
Hard
Very Hard
Maximal
<20%
20-39%
40-59%
60-84%
>85%
100%
The box to the left summarizes the ACSM classification system for exercise intensity.

There are three primary steps in prescribing exercise intensity; and there are three sub-steps to the first two:

  • Determine the target intensity
    • Sliding scale based on existing fitness
    • 10% below the end point of the exercise test
    • 10% below the intensity that elicits an abnormal response
  • Provide the client/patient with a means of monitoring intensity
    • Heart Rate
    • RPE
    • METs
  • Translate the prescribed intensity to actual work rates for the exercise session

Determining the Target Intensity

There are three basic ways to determine the intensity of cardiorespiratory exercise. The first is based on the existing fitness; the second is modified for submaximal testing; and the third is based on an abnormal response to exercise. These are:

When prescribing exercise intensity, a range of intensities is recommended rather than a single intensity. A range of exercise intensities can be effective for most health or fitness outcomes. These ranges are often quite broad. An example is the 60-85% intensity range for improving fitness. Even though the range spans 25%, it will be easier for the client/patient to use a 10% range somewhere within the 25% range.

The Sliding Scale Based on Existing Fitness:

Individuals with lower cardiorespiratory fitness can improve fitness with lower exercise intensities, whereas individuals with higher cardiorespiratory fitness require higher exercise intensities to make improvements. Karvonen {Karvonen, 1957 #302} reported the minimal exercise intensity required to improve fitness in the apparently health population was 60% of capacity or VO2max. The sliding scale was developed to estimate effective exercise intensity for low and high fit individuals.

Target Intensity = [60 + Max METs]/100

This formula estimated higher exercise intensities for individuals with higher exercise capacities and lower exercise intensities for individuals with lower exercise capacities. For example, according to the sliding scale, an individual who exhibits a 5 MET capacity should exercise at 65% of capacity:

Target Intensity = [60 + 5]/100 = 65%

Whereas an individual who exhibits a 12 MET capacity should exercise at 72% of capacity.

Target Intensity = [60 + 12]/100 = 72%

Target intensities are given in range, usually 10% wide. The target intensity determined by the sliding scale can be used as the bottom, top or middle point of the prescribed intensity range. See the discussion below on choosing the prescriptive range of exercise intensity.

10% Below the End Point:

Whether it is a 12 minute walk or a maximal graded exercise test, an assessment of exercise capacity is given prior to exercise programming and prescription. For safety, exercise intensity should not be prescribed above the intensity used in the exercise assessment. According to the work of Cumming and colleagues, 50% of the individuals who exhibited a positive electrocardiographic response to maximal graded exercise testing would have been missed had the test terminated at 80% of heart rate max. Had these individuals been tested to 80% heart rate max, yet prescribed exercise intensity above the 80%, they may have been in danger of an adverse event during exercise. It is safer to prescribe exercise intensity below the intensity of exercise that has been evaluated. Prescribing the intensity 10% below the end point assures a more normal heart rate, ECG, and blood pressure response during training.
If submaximal graded exercise is utilized for the exercise testing, choosing the stage below the end point would assure a margin of error between the prescribed intensity and the end point intensity. If the exercise assessment involves 12 or 15 minute walk/run, choose a speed below the average speed or a heart rate below the highest heart rate exhibited during the assessment. When using the 10% below the end point to determine target heart rates, knowledge of the corresponding exercise intensity is not possible. It can only be estimated.

10% Below an Abnormal Response:

Abnormal cardiovascular responses to exercise are often reproducible. That is, an ischemic response to exercise will occur at the same double product for patients who exhibit stable angina. An ischemic response can be exhibited as a drop in blood pressure, dysrhythmia, and/or angina. Prescribing the exercise intensity below the ischemic response decreases the incidence of an abnormal response compromising the exercise or resulting in an adverse event. When using the 10% below the abnormality to determine target heart rates, knowledge of the corresponding exercise intensity is not possible. It can only be estimated.


Providing the client/patient with a means of monitoring intensity

The duration of exercise is measured by minutes and the frequency of exercise is measured by days. Minutes and days are easy for the client/patient to monitor. Intensity of exercise, on the other hand, is measured by percent of VO2max and is much harder for the client/patient to monitor. If a client is instructed to exercise between 60 to 70% of VO2max, it may be difficult for them to figure out how hard to work. Therefore, other variables that reflect the intensity of exercise must be monitored to estimate the intensity of exercise. These variables must exhibit a linear relationship with exercise intensity and be simple for the client/patient to monitor. The three most common linear variables used to monitor intensity are


As exercise intensity increases, so does heart rate, perceived exertion, and energy expenditure (METs or VO2). These variables can be used alone or in combination. Heart rates and RPE are most often used in the health and fitness setting whereas all three are more often used in exercise treatment.


Using Heart Rate to Guide Exercise Intensity.

There are several ways to choose target heart rates to guide exercise intensity. The three primary target heart rate methods are:

Before using heart rate to guide exercise intensity, there are some principles to remember regarding the heart rate VO2 relationship. To explore these relationships go to the K561 web site.

  1. Heart rate has a liner relationship with VO2. This relationship varies with
    1. Mode of exercise
    2. Calculation of target heart rates
  2. The linear relationship between heart rate and VO2 is best in cardiorespiratory exercise for guiding exercise intensity.
  3. Within the spectrum of cardiorespiratory exercise, the more muscle mass involved in the exercise, the better target heart rates reflect exercise intensity.
  4. A target heart rate calculated from one test mode may not be as accurate for other modes of exercise.
  5. If a heart rate:VO2 graph can be created for each mode of cardiorespiratory exercise, target heart rates will better reflect target intensities.
The two most common calculations for target heart rate are Percent Heart Rate max (%HRmax) and Heart Rate Reserve (HRR). The Figure to the right illustrates the %HRmax and %VO2max relationship. These two formulas show different relationships. As the intensity approaches maximal capacity, the two formulas appear to predict exercise intensity similarly. However at the lower intensities found in most health and fitness exercise prescriptions, there is a larger discrepancy between the two methods. Without corrections, 60% of %HRmax appears to be comparable to a significantly lower percentage of VO2max. Thus, %HRmax overestimates exercise intensity. The difference is between 10-15% in the light and moderate exercise intensities.

If %HRmax is to be used, 10-15% higher than target percentages should be calculated for the target heart rate. For example, for a target intensity 50-60%, a target heart rate between 65-75% of heart rate max should be calculated.

Target Heart Rate = HRmax x (%Intensity +15%)

Heart Rate Reserve

Heart rate reserve more accurately estimates energy expenditure because the range of the working heart rate (rest to max) is considered in the calculation. In the %HRmax formula it is assumed that heart rate goes down to zero. This is not true. Resting heart rate is significantly different than zero. The heart rate reserve formula considers the true resting and maximal heart rates.

Target Heart Rate = [(HRmax – HRrest) x %Intensity] + HR rest

Caution should be taken when using equations to estimate maximal heart rate. These formulas have large standard deviations; some formulas can be off +12 to 15 beats per minute. If the formula, 220-age were used to estimate maximal heart rate, the range of variation for the target heart rates for 60% intensity can exhibit a significant variation. For example: What is the target heart rate at 60% intensity for a 50 year old man with a resting heart rate of 70 beats per minute. To estimated his HRmax:

Estimated HRmax = 220 – age
= 220 – 50
= 170 beats per minute

If the standard deviation for this equation is +15 beats per minute, his maximal heart rate can be anywhere between 155 to 185 beats per minute. The resultant target heart rate at 60% can range between 121 and 139 beats per minute.

Thus, caution should be taken when estimating maximal heart rates to calculate target heart rates. The client/patient may find it too easy or too difficult to achieve the target heart rates. If so, the target heart rates should be modified in the field, according to the response of the client/patient. RPE is a good adjunct to help modify target heart rates calculated from estimated maximal heart rates.

The Direct Determination of Target Heart Rates.

The direct method of determining target heart rates does not need target heart rate formulas or calculations. Exercise test data is required for the direct method. The direct method is used more often in cases when the intensity is chosen as 10% below the end point or 10% below the abnormality. The direct determination of target heart rates can be accomplished several ways.

One way is to choose the heart rates that correspond to the stage of the exercise test that is at the target intensity.

A second way, illustrated to the left, is to graph the heart rate:VO2 response and draw a line from the target intensity to the heart rate.

Another way is to choose the heart rates of the stage below the end point of a submaximal graded exercise test. Or, in the case of an abnormal test, choose the heart rates of the stage below the presentation of the abnormality.

If a 12 minute walk/run is used for assessment, choose a heart rate below the highest heart rates taken during the walk/run. When using the direct determination of target heart rates, knowledge of the exact exercise intensity is not possible. It can only be estimated.

Using Rated Perceived Exertion to guide Exercise Intensity

Rating of perceived exertion (RPE) is a subjective rating system for exercise intensity based on general fatigue. RPE can be used in conjunction with target heart rates. RPE is often used as a substitute for target heart rates when

  • The ability to monitor heart rate is compromised
  • No exercise test heart rates exist
  • Applying effort to physical activities other than cardiorespiratory endurance (i.e. playing tennis or gardening)
  • The heart rate-VO2 relationship has been modified and new target heart rates cannot be calculated. For example, medications such as Beta-Blockers alter the heart rate – oxygen consumption. Target heart rates calculated in the non Beta-Blockade condition cannot be used when taking Beta-Blockers.

RPE is more often used in the clinical setting than in the health and fitness setting.
Two scales of RPE now exist. Both scales are illustrated below.

Category Scale Category-Ratio Scale
6
7     Very, very light
8
9     Very light
10
11     Fairly light
12
13     Somewhat hard
14
15     Hard
16
17     Very Hard
18
19     Very, very hard
20
0         Nothing at all             “No, Intensity”
0.3
0.5     Extremely weak         “Just noticeable”
0.7
1         Very weak
1.5
2         Weak                         “Light”
2.5
3         Moderate
4
5         Strong                         “Heavy”
6
7         Very strong
8
9
10      Extremely strong          “Strongest Intensity”

The first is called a Category Scale which has a linear relationship with cardiorespiratory exercise intensity. In fact, the scale, which ranges from 6 to 20, was developed to estimate exercise heart rates by multiplying the RPE by 10. Word description anchors every odd number on the scale.

The Category-Ratio Scale has a non-linear relationship which mimics the blood lactate or minute ventilation response to increasing exercise intensities. The word anchors were improved for better understanding with more common phrases used to describe exercise. Onset of blood lactate is between 4 and 5 on the Category-Ration Scale and represents 12 to 16 on the Category Scale.

The target RPE can be chosen in a similar manor as the direct method to determine target heart rates. If both target heart rates and RPE are to be used to guide intensity, take the RPE from the exercise test that corresponds to the target heart rate.

The instructions for RPE are important to guide the individual to focus on general fatigue:

During the exercise test we want you to pay close attention to how hard you feel the exercise work rate is. This feeling should reflect your total amount of exertion and fatigue, combining all sensations and feelings of your physical stress, effort and fatigue. Don’t concern yourself with any one factor such as leg pain, shortness of breath, or exercise intensity, but try to concentrate on your total inner feelings of exertion. Try not to underestimate or overestimate your feelings of exertion; be as accurate as you can.”

These instructions should be given before the exercise test as well as when giving the exercise prescription. Additional orientation to the RPE scale during exercise helps the individual focus on the feelings of exertion. After an exercise prescription is given and before the individual begins to exercise have the individual walk on a treadmill or ride a cycle ergometer at the target exercise intensity. This intensity should also elicit the target RPE. Instruct the individual to remember that this effort is the target RPE. Occasional orientations ensure proper use of the RPE to monitor exercise intensity


Using METs to guide Exercise Intensity

Prescribing exercise intensity with METs is the truest method to guide intensity. METs and VO2 are both measures of energy expenditure and can be converted to the other, using the following relationships.

1 MET = 3.5 ml/min kg
1 MET = 1.05 kcal/kg hr

METs are often easier for the individual and non-exercise physiology clinician to understand because the energy the expenditure is measured in multiples of one MET. For example, an exercise that is 10 METs has an energy expenditure 10 times greater than that of rest. Exercise intensities are easier to understand based on METs.

Keep in mind the principle of specificity of exercise. The desired outcome of the cardiorespiratory exercise program is an increase in cardiorespiratory energy. METs are energy expenditure. There is no purer form of estimating energy expenditure. Therefore the formula to determine target METs is:

Target METs = max METs x % Intensity

The energy expenditure of physical activities, exercise, occupational activities, leisure activities and sports has been determined. Choose those activities in which the energy expenditure is within the target MET range.



TRANSLATING EXERCISE INTENSITY FROM THE PRESCRIPTION TO THE WORKOUT

Whether you are prescribing exercise intensity by METs or suggesting a workrate for your client to exercise, the exercise intensity needs to be translated from percent intensity, heart rates, perceived exertions, and METs to actual work rates for each activity. The ACSM metabolic equations can be used to estimate the work rate for Group 1 activities recommended in the exercise prescription. Using the prescribed intensity, calculate the VO2. Calculate approximate work rates for the individual to try on the treadmill, cycle ergometer, arm crank, and/or stepper.

 


EXERCISE PRESCRIPTIONS FOR VARIOUS HEALTHY SCENARIOS

The general exercise prescription principles for the range of improving health to treating disease conditions is summarized below.

Physical Activity & Health
Physical Work Capacity
Exercise Treatment
Mode
Any physical activity >2.5 METs
Cardiorespiratory Endurance
Groups 1 -3
Cardiorespiratory Endurance,
Primarily Group 1 & non-weight bearing or walking
Frequency
Most, if not all days of the week
3 -5 per week
3-5 per day
3-5 per week
Duration
>30 min
30-60 min
5-10 min in-patient
20-60 min
Intensity
Moderate (40-60% VO2max)
Vigorous (60-80% VO2max)
Recommended per disease or disability
Precautions
None required
Specific to disease or disability
Specific to disease or disability
Recommendations
Specific to diet, stress, or smoking cessation
Specific to diet, stress, or smoking cessation
Specific to diet, stress, or smoking cessation

More specific exercise prescriptions for improving and maintaining physical work capacity are summarized below

Improve Physical Work Capacity for Sedentary
Maintain Physical Work Capacity
Improve Physical Work Capacity for Active
Mode
Cardiorespiratory Endurance
Groups 1 -3
Cardiorespiratory Endurance
Groups 1 -3
Cardiorespiratory Endurance
Groups 1 -3
Frequency
3-4 per week
2-3 per week
add 1-2 per week
Duration
30-40 min
20-30 min
add 10-20 min
not to exceed 60 min
Intensity
The lower range of
(60 + maxMETs)/100
same intensity
The upper range of
(60 + maxMETs)/100
Precautions
None required
Specific to disease or disability
Specific to disease or disability
Recommendations
Specific to diet, stress, or smoking cessation
Specific to diet, stress, or smoking cessation
Specific to diet, stress, or smoking cessation

If an active client presents with a high fitness you may not need to change their exercise prescription.

Exercise prescriptions are different for each disease process. See each disease


This page was last updated 17-Jan-2011
URL: http://www.indiana.edu/~k562
Webmaster: Janet P. Wallace, PhD, FACSM
Contact:wallacej@indiana.edu
Copyright 1998, The Trustees of Indiana University