EXERCISE PRESCRIPTION

EXERCISE PRESCRIPTION

 

Substantial data are available regarding the benefits of physical activity. 

For primary preventative benefits, physical activity patterns should begin in the early school years and continue throughout an individual's life.

Schools must specifically designate physical education programs with aerobic activities for children at early ages. Programs should include recreational sports (eg, running, dancing, and swimming).

Support at home for an active lifestyle for children helps to promote healthy physical activity patterns.

In the clinical setting, discuss physical activity and provide exercise prescriptions for patients and their families. In some instances, suggestions could be made about implementing physical activity recommendations at the work site.

Consider intensity, duration, frequency, mode, and progression in all types of physical activity programs. As children and adolescents become adults and discontinue the athletic endeavors of school and college, primary prevention must include a plan for a lifetime of appropriate physical activity.

Ideally, this activity should be performed for at least 30-60 minutes, 4-6 times weekly or 30 minutes on most days of the week. The frequency, duration, and intensity of activity should be individualized (exercise prescription) to personal satisfaction, mode, and progression.

Subjects may use individual end points of exercise, such as breathlessness and/or a fatigue level ranging from somewhat hard to hard on the Borg perceived exertion scale.

Standardized charts that designate heart rates may help by providing heart rate end points that can be measured immediately after exercise, but these are not necessary.

Exercise should include aerobic activities, such as bicycling (stationary or routine), walk-jog protocols, swimming, and other active recreational or leisure sports. Shoes and clothing should be appropriate for extremes of heat, cold, and humidity.

Resistive exercises using free weights or standard equipment should be performed 2-3 times per week. These exercises should include 8-10 exercise sets that consist of 10-15 repetitions per set (including arms, shoulders, chest, trunk, back, hips, and legs) and are performed at a moderate intensity.

Resistive exercises tend to complement aerobic exercise in that some training effect is realized. However, development of muscle tone and strengthening of body musculature is more important as adult’s age.

The long-term effect of any physical activity program is affected by compliance. In today's mobile society, an exercise plan must include activities for business trips and vacations.

Exercise facilities may not be convenient in such settings, which may mean improvising. For example, a walk-jogger should bring walking or running shoes and find a safe place to walk or run at a pace that approximates the usual activity level. Many hotels or motels have exercise facilities with a track or treadmill, exercise cycle, and weights, enabling travelers or others away from their usual routine to maintain an exercise program.

Physical activity measured in total time or kilocalories (kcal) or kilojoules (kJ) per week is appropriate and may be achieved with various combinations of scheduling, such as 10-15 minutes in the morning, at noon, and/or an afternoon/evening session. Many persons may schedule longer, less frequent periods of exercise.

As intensity decreases, frequency and duration should increase and vice versa. The dosage or total energy (calorie) expenditure per week must be individualized (exercise prescription).

Persons with influenza syndromes or respiratory illnesses should decrease or stop exercise until they have recovered. If the recovery time is greater than 2-3 weeks, activity should be resumed at a lower level to compensate for the slight loss in training level. 

Maintenance of the cardiovascular training effects of exercise has been shown to be more related to the exercise intensity than to exercise frequency or duration. In other words, if the intensity is maintained, even though the exercise sessions are less frequent or shorter in duration, transient reductions in conditioning from the decreased exercise appears to be minimized.

Various exercise testing measures of functional capacity should be used in special populations but are not necessary for primary prevention. Traditionally, many athletically inclined persons like to have periodic oxygen-uptake (VO2) measurements to assess their level of training.

However, recent technologic advances have not only made cardiopulmonary (CPX) or metabolic (CMET) testing more commonplace among medical practices, but they have also become increasingly popular as a part of a routine physical and stress test evaluation, especially for individuals who are considered at high risk for cardiovascular disease (eg, those with hypertension, shortness of breath, chest discomfort, or abnormal blood lipid levels).

A lifestyle of physical activity from childhood throughout the adult years fosters health and longevity. Even brisk walking as a physical activity/exercise habit promotes health benefits. This is the simplest program for most individuals and has clear benefits. This improved state of health is enhanced by weight control, restricted intake of saturated fat and cholesterol, abstinence from cigarette smoking, and control of high blood pressure and glucose intolerance.

BENEFITS OF EXERCISE

Routine exercise improves tissue VO2 affects the following:

Ø  Improves insulin sensitivity

Ø  Improves glycemic control in persons with type 2 diabetes (and, hence, decreases overall mortality)

Ø  Decreases blood pressure

Ø  Decreases low-density lipoprotein and triglyceride levels

Ø  Increases high-density lipoprotein levels

§  Considerable data also support evidence that exercise may decrease the prevalence of colon cancer and endometrial cancer. Exercise also helps with osteoarthritis and obesity, as well as reportedly benefits persons with migraine headaches  and fibromyalgia.

§  Middle-aged men and women who work in physically demanding jobs or perform moderate to strenuous recreational activities have fewer manifestations of coronary artery disease than their less active peers. Meta-analysis studies of clinical trials reveal that medically prescribed and supervised exercise can reduce mortality rates for persons with coronary artery disease.

§  Several studies suggest that relatively small amounts of physical activity show considerable reductions in mortality and improved health outcomes among participants when compared with sedentary control subjects. These findings imply that a minimal activity (ie, exercising once per week) may have positive health benefits even though fitness may not be measurably improved. Some authors have suggested that a threshold of physical activity may be necessary for maintaining optimal health and that future investigation should involve control subjects who participate in at least minimal activity levels rather than comparing exercise treatment groups to control subjects who are completely sedentary.

§  In addition to the physical benefits of exercise, both short- and long-term aerobic exercise training is associated with improvements in various indexes of psychologic functioning. Cross-sectional studies reveal that compared with sedentary individuals, active persons are more likely to be better adjusted, to perform better on tests of cognitive functioning, to exhibit reduced cardiovascular responses to stress, and to report fewer symptoms of anxiety and depression.

§  In one report, persons who increased their activity levels from 1965-1974 were at no greater risk for depression than those individuals who were active all along; however, persons who were active and became inactive were 1.5 times as likely to become depressed by 1983 compared with those who maintained an active lifestyle. Longitudinal studies have also documented significant improvement in psychologic functioning. Exercise training reduces depression in healthy older men and in persons with cardiac disease or major depression.

§  Exercise also improves self-confidence and self-esteem, attenuates cardiovascular and neurohumoral responses to mental stress, and reduces some type A behaviors. Although exercise training generally has not been found to improve cognitive performance, short bouts of exercise may have short-term facilitative effects.

§  Despite the positive physical and mental health benefits of exercise, long-term adherence to exercise programs remains problematic. Overall physical activity levels decrease with aging, in minority populations, in females, in disabled persons, and in those with chronic disease. Only an estimated 50% of all persons who initiate an exercise program continue the habit for more than 6 months. The issue of nonadherence is particularly important because exercise is only beneficial if it is maintained for extended periods. Thus, developing strategies to improve exercise initiation and adherence, especially for persons who are among the least active (eg, 75% of black women; less educated, obese, elderly persons), is important.

DIFFERENT TYPES OF EXERCISE

Exercise has been defined as an activity for the express purpose of improving fitness or health. Physical activity includes all forms of activity (eg, occupational, recreational, sports-related) that are performed without the specific purpose of fitness or health.

Different types of exercise are as follows:

GENERAL GUIDELINES

RESISTANCE AND REPETITIONS

TYPE OF EXERCISE (MODE)

ENERGY (CALORIC) EXPENDITURE

LIFETIME ACTIVITIES

SELECTING THE RIGHT PHYSICAL ACTIVITIES

EXERCISE PRESCRIPTION FOR SPECIAL POPULATIONS

ADVANCED AGE

Ø  Maximum ventilatory perfusion (VQ) drops 5-15% per decade in individuals aged 20-80 years. A lifetime of dynamic exercise maintains the individual's VQ at a level higher than that expected for any given age. The rate of decline in VQ is directly related to maintenance of the physical activity level, which emphasizes the importance of physical activity.

Ø  Developing and maintaining aerobic endurance, joint flexibility, and muscle strength is important in a comprehensive exercise program, especially as people age. Elderly women and men show comparable improvement in exercise training, and adherence to training in elderly individuals is high.

Ø  Resistance training exercise alone has only a modest effect on risk factors compared with aerobic endurance training, but resistance training does aid carbohydrate metabolism through the development or maintenance of muscle mass and effects on basal metabolism. Furthermore, resistance training is recommended by most health promotion organizations for its effects on maintenance of strength, muscle mass, bone mineral density, functional capacity, and prevention and/or rehabilitation of musculoskeletal problems (eg, low back pain).

Ø  In elderly individuals, resistance training is both safe and beneficial in improving flexibility and quality of life. Persons with cardiovascular disease are usually asked to refrain from heavy lifting and forceful isometric exercises, but moderate-intensity dynamic strength training is safe and beneficial in persons at low risk.

PULMONARY DISEASE

Ø  Individuals with pulmonary disease should engage in low workloads of short duration.

Ø  Patients should exercise in frequent intervals rather than a longer duration and fewer intervals.

Ø  Supplemental oxygen is needed.

DIABETES

Ø  Exercise should be of short duration with a gradual progression to longer durations, as tolerated.

Ø  Exercises include aquatic aerobics, swimming, walking, jogging, or bicycling, among others.

Ø  Monitor blood sugar because hypoglycemia or hyperglycemia can occur in diabetic persons during exercise.

o    Before exercise: Consume a meal 1-3 hours before exercising, administer insulin at least 1 hour before exercise, and, if the blood glucose level is greater than 250 mg/dL, check urine for ketones.

o    During exercise: Supplement energy (caloric) intake every 30 minutes and maintain adequate fluid replacement.

o    After exercise: Monitor the glucose level, increase energy (caloric) intake for 12-24 hours following activity, and expect postexercise hypoglycemia; thus, appropriately adjust insulin dosing.

OBESITY

Ø  Individuals who are morbidly obese should be cautious of orthopedic stresses.

Ø  They may start with non–weight-bearing exercises (eg, swimming, water aerobics, floor exercises).

Ø  These individuals should avoid high-impact aerobic activities.

Ø  Emphasize duration as tolerated and exercise frequency (sessions per week).

Ø  Emphasize premeal exercise, especially exercise in the morning before eating breakfast to mobilize fats (lipolysis).

MATERNITY

Ø  Research on exercise during pregnancy continues to demonstrate marked benefits for the mother and fetus. The type, intensity, frequency, and duration of the exercise seem to be important determinants of its beneficial effects.

Ø  Maternal benefits include improved cardiovascular function, limited weight gain and fat retention, easier and less complicated labor, quick recovery, and improved fitness.

Ø  Fetal benefits may include decreased growth of the fat organ, improved stress tolerance, and advanced neurobehavioral maturation.

Ø  Offspring are leaner at age 5 years and have a slightly better neurodevelopmental outcome. Post pubertal effects are still unknown.

Ø  In the absence of medical contraindications, women should be encouraged to maintain their prepregnancy activity level. In general, activity should be individualized (exercise prescription), depending on previous activity levels

Ø  Available outcome data suggest that a healthy woman may begin or maintain a regular exercise regimen during pregnancy, with benefit and without adversely affecting the course and outcome of the pregnancy. Data also suggest that the clear difference between theoretic concern and observed outcome is best explained by the hypothesis that the physiologic adaptations to exercise and to pregnancy are complementary and fetoprotective.

Ø  Although an upper level of safe performance is not established, otherwise healthy mothers-to-be appear to obtain the benefits of a regular exercise regimen without undue risk to the embryo and fetus. The exact regimen can be flexible and individualized (exercise prescription), provided that both the exercise and the pregnancy are monitored.

OSTEOPOROSIS

Ø  Exercise is an essential part of treatment for patients with osteoporosis. Just as regular workouts build muscle, these activities also maintain and may even increase bone strength. By strengthening the muscles and bones and improving balance, exercise can reduce the risk of falls and resulting fractures.

Ø  Exercise works well with medications that increase bone density and strength.

Ø  Exercise, medication, and proper diet, including an absorbable source of calcium, phosphorus, boron, and other bone-building minerals, are more effective in combating osteoporosis than any one treatment alone.

Ø  Weight-bearing exercises and resistance training benefit bones and muscles as well as help improve general health.

o    Weight-bearing exercise

§  For most people who have osteoporosis, brisk walking is ideal.

§  Walking can be performed anywhere, requires no special equipment, and carries minimal risk of injury.

§  If walking is too difficult or painful, workouts on a stationary exercise cycle are a good alternative.

o    Resistance training

§  Lifting weights or using strength-training machines strengthens bones, especially if one exercises all of the major muscle groups in the legs, arms, and trunk.

§  A qualified trainer, exercise specialist, or therapist is important for instructing and guiding resistance-training programs.

§  Joining a gym or fitness facility is a good way to begin because these facilities typically provide access to trainers who can advise on proper techniques.

§  Strength training is a slow process, so it should be started at a low level and should be gradually built up over several months. For each exercise, select weights or set the machine so the muscle being trained becomes fatigued after 10-15 repetitions. As muscles strengthen, gradually add more weight. The weight should not be increased more than 10% per week because larger increases can increase the risk of injury.

TIPS FOR TROUBLE-FREE EXERCISE

Ø  Lift and lower weights slowly to maximize muscle strength and to minimize the risk of injury.

Ø  Perform resistance workouts on any given muscle group every second or third day. This gives your body a chance to recover.

Ø  Avoid exercise that puts excessive stress on the bones, such as running or high-impact aerobics. Rowing is appropriate if proper form is used and the rowing machine provides a way to maintain continuous inertia with the use of a flywheel.

Ø  Stiffness is normal the morning after exercise. If pain continues for most of the following day, joints become swollen, or a limp develops, stop the program until comfortable again and reduce the weight and number of repetitions by 25-50%. If bone, joint, or muscle pain is severe, call the doctor.

Ø  If a particular area of the body feels sore right after exercise, apply ice for 10-15 minutes. Wrap ice in a towel or plastic bag or just hold a cold canned or bottled beverage on the spot.

Ø  Vary the routine to make it more interesting. For example, if the strength-building program involves 12 separate exercises, complete 6 in one session and the other 6 in the next session.

ADDITIONAL RESEARCH AND FUTURE ISSUES

The body of knowledge on exercise is large, but data on exercise and its effects on the cardiovascular system and long-term survival are still relatively limited. The responsibility for conducting research lies with government agencies, private health organizations, the insurance industry, employers, universities, and medical schools.

Basic knowledge of the anatomic, biochemical, and physiologic changes that result from various patterns of physical activity (short- and long-term, sustained and intermittent, isotonic and isometric, low and high intensity) in persons of different ages is needed, as is a determination of whether a certain minimum-intensity threshold of physical activity is required for benefit.

The biomedical and economic impact of participation in exercise programs on coronary artery disease, cerebrovascular and peripheral vascular disease, heart failure, and hypertension should also be evaluated. The psychosocial functioning of persons with coronary artery disease and the potential value of exercise in enhancing the quality of life for cardiac and other patients warrants further study. Future studies should include adequate numbers of women, ethnic groups, and elderly persons to better meet research objectives.

Furthermore, the presence and extent of coronary risk factors in disabled and disadvantaged individuals and in minority groups must be identified and better defined. Consequently, the effect of modifications (eg, increases in physical activity on members of these groups) should be explored. Large studies should also include a significant number of these persons.

Research should be continued to establish the cost-effectiveness of physical activity programs for the enhancement of cardiovascular health, with a focus on the type of promotional strategies required for initiating and maintaining physical activity (eg, insurance incentives, health personnel, public policy, media materials) and the social context of such activity (eg, industry and business, rural and urban settings, schools, churches, families).

Research should also involve issues such as how physical activity can prevent (or decrease the duration of) the hospitalization of patients with chronic disease.

More information is also needed to identify societal, cultural, ethnic, and personal factors that affect development or maintenance of lifelong patterns of physical activity and incorporation of these into exercise promotion strategies.

Research on better and more effective physical activity interventions that improve long-term compliance to a physically active lifestyle is urgently needed. Innovative nontraditional methods of increasing physical activity in the population must be developed, implemented, and evaluated.

In summary, future developments and studies should focus not only on the benefits of physical activity, but also on exercise adherence strategies and the methods used to facilitate dissemination of present and future knowledge to all members of society.

GLOSSARY OF TERMS

Exercise intensity is generally expressed as a percentage of either HR or VO2.

VO2:- By definition, VO2 is the oxygen uptake by an individual at rest or during exertion, expressed commonly in milliliters of oxygen consumed per kilogram body weight per minute (mL/kg/min)

HEART RATE RESERVE (HRR): is defined as the maximal heart rate (HRmax) observed during a symptom-limited exercise stress test minus the resting heart rate (HR rest). A percentage of the HRR range is added to the HR rest to determine a target heart rate (THR) range to be used during exercise.

This approach accounts for individual variability in the HR rest and better reflects the peak exercise oxygen consumption (VO2 max). VO2 max reflects the highest rate of oxygen consumption that one can achieve.

OXYGEN UPTAKE RESERVE (VO2 R): is the difference between resting and maximal VO2. Previous guidelines suggest exercise prescriptions should be based on the oxygen uptake reserve (VO2 R) rather than a direct percentage of the VO2 max. 

Exercise intensities based on VO2 R are approximately equal to the same percentage values for HRR; therefore, the use of HRR in determining appropriate exercise intensities is suitable in most cases.

However, certain exceptions to using this approach may include patients with poor Chronotropic responses, dysautonomia, pacemakers, or heart transplantation.

TARGET HEART RATE (THR): for exercise is generally recommended from 50% to 85% HRR (or VO2 R). For deconditioned individuals, 40-50% HRR may be more appropriate for beginning exercise, whereas physically active individuals may require higher intensities to achieve improvements in their conditioning. 

As an illustration in determining THR, the example below uses a resting HR (RHR) of 70 and a HRmax of 180 bpm.

The HRR is 180 – 70, or 110 bpm. Using an average intensity of 60-80% HRR, the THR ranges are calculated (Karvonen approach) as follows:

THR = (HRR × 60%) + RHR;

THR = (110 × 0.60) + 70 = 136 bpm

(110 × 0.80) + 70 = 158 bpm

So, a THR range would be 136 - 158 beats per min

Or

A pulse count of 22 - 26 beats per 10 seconds

METABOLIC EQUIVALENTS (METS) are useful units when recommending exercise.

By definition, 1 MET is the amount of oxygen consumed at rest or about 3.5 mL/kg/min. However, recent studies indicate that the average resting MET level in subjects with coronary heart disease is 23% to 36% lower than the 3.5 mL/kg/min standard value. 

Nevertheless, most people walking 2 mph require 2 METs, and 3 mph require 3-4 METs. Published MET tables describe many activities in terms of the estimated MET requirements. 

Example: If an individual has a VO2 max of 34 mL/kg/min, the VO2 R is 34 minus the resting VO2 of 3.5 mL/kg/min equals 30.5 mL/kg/min. dividing this result by 3.5 yields 8.7 METs. Using 60-80% VO2 R, the recommended range of exercise METs may be determined by the following:

(8.7 × 0.60) + 1.0 (resting) = 6.2 METs

(8.7 × 0.80) + 1.0 (resting) = 8 METs

When one consults a common MET table, an exercise intensity of 6.2-8.0 METs is equivalent to a slow walk-jog combination exercise, hiking with a backpack, hill climbing, and numerous other moderately vigorous activities.

Exercise intensity may be customized to the individual (exercise prescription) based upon their metabolic response to progressive exercise if the VO2 max and the anaerobic threshold (AT) or ventilatory threshold (VT) is determined. 

By definition, the VT may be described as the level of oxygen consumption (VO2) at which a significant increase in anaerobiosis occurs, as evidenced by an increase in blood lactate levels and respiratory responses to the increasing exercise workload. MET is a unit of energy or level of oxygen used at rest (1 MET = VO2 of 3.5 mL/kg/min).

Exertion below the VT can generally be sustained for long time periods; whereas, above the VT, the individual can only tolerate a limited amount of time such as several minutes. As a training principle, exercising at the VT may be optimal due to considerable stimulation with a minimal lactate accumulation.

Many recreational as well as high-caliber endurance athletes train above the VT but below the respiratory compensation (RC) point. The RC may be described as the point when the CO2 production is increased in relation to ventilation; typically when the individual no longer has voluntary control over the ventilation (ie, the ventilation is driven by metabolic factors).

MAXIMAL VOLUNTARY VENTILATION (MVV) is defined as the maximal amount of ventilation per minute, generally determined by a 12-second hyperventilation procedure to maximal ventilation capabilities.

RESPIRATORY EXCHANGE RATIO (R OR RER) or RESPIRATORY QUOTIENT (RQ): is the ratio of the VO2 to the carbon dioxide produced in the body. At rest, the RER reflects the substrate's use of fuel sources (eg, carbohydrates, fats, proteins).

The metabolism of fats or fatty acids yields a ratio of 0.7; of carbohydrates, 1; and of protein, 0.84. During exercise, the RER generally exceeds 1 because of the additional carbon dioxide produced as a byproduct of the bicarbonate system and because of lactate buffering.

BORG RATINGS OF PERCEIVED EXERTION

The RPE scale is used widely in exercise science and sports medicine to monitor or prescribe levels of exercise intensity. The 95%-limits-of-agreement technique has been advocated as a better means of assessing within-subject (trial-to-trial) agreement.

The perception of exertion is a monitoring behavior that uses all sources of information to govern actions that can benefit or preserve health and partake of adaptive pursuits. How a person feels about exertion moderates his or her response to exercise and effort.

The perception of what is happening in exercise, and its concomitant effect on physiologic function, must be known to further understand the nature of an exercise response. How a person feels modifies reactions to exercise stress and the mechanisms that underlie them.

Exercise is never a purely mechanistic physiologic reaction. The interpretation of the exercise experience governs the nature, quality, and extent of the exercise response. To fully understand and accurately assess the nature of an exercise behavior, measuring as many moderating variables as possible is necessary.

Physiologic measures can be used to grade the strain for each individual, but so can exertion estimates. In an exercise response, the underlying determining mechanism may not be the pure physiologic parameter being measured. Without knowledge of the psychologic moderator variables, the physiologic measurement alone is misleading; its value as a predictor variable is usually negligible.

The particular circumstances in which the physiologic measurement is taken may be more important for predicting or analyzing a response than the variable itself. To exercise only according to HR is dangerous.

The aches and strain that are felt may be very important indicators of the real degree of exertion. Rigid adherence to the objective measures of physiology may cause interpretive and prescriptive errors of great magnitude.

In many circumstances, the psychologic components of an exercise response are more reliable and relevant than the physiologic measures. This has been shown to be true in the assessment of long-term exercise strain for determining the early symptoms of overtraining or maladaptation.

Borg's original intention was to construct a category scale from 6-20 in which scale levels were roughly one tenth of the HR for equivalent scaled exercise levels.

A score of 6 (no exertion at all) should exhibit an HR somewhere in the vicinity of 60 bpm for a young to middle-aged, mildly fit individual.

This correspondence is generally reserved for middle-aged people exercising at moderate to high intensity levels. At best, this is a very rough estimation of the relationship; individual variability is significant. Also, the relationship between HR and RPE within an individual varies with different forms of activity. The RPE is best reserved for intraindividual comparisons for a specific form of exercise.

HRs are related linearly to the scale scores (r = 0.8-0.9). However, even with this relationship one cannot conclude that HR is a cause of the perceived exertion.

The perception of exertion integrates many more exercise factors than are considered with singular or isolated physiologic variables. This integration is a truer indication of an exercise response than is depicted by restricted variables such as HRs, lactate measurements, or blood measurements.

To understand a certain RPE value, knowing

1)     The age and other personal characteristics of the individual

2)     What type of activity was performed

3)     The environmental conditions that existed at the time are important

The instructions for using the scale are to "estimate how hard and strenuous you feel the work to be." The perception should be general, rather than focusing on specific parts of the body (eg, "tired arms"). The perception of exertion should include as many contributory sensations as possible.

Once the verbal description is determined, the individual should choose an exact number that corresponds to the verbal descriptor. When a subject is unable to complete the highest workload, the rating should be of the work at the time of the final interruption. With athletes, the major problem with using RPE is their common tendency to underestimate the exertion level.

Practice in using the scale is necessary. If the various categories can be aligned with other categories or levels of work response, an accurate level of discrimination can be developed between the categories.

The RPE yields important additional data beyond those available through isolated physiologic variables. In conscientious and reliable individuals, its value exceeds that of singular parameters of performance.

INSTRUCTIONS FOR USE:

                During the exercise you are to rate your perception of exertion.

Use this scale, where 6 mean no exertion at all, and 20 means a totally maximum effort.

The 13 on the scale is a somewhat heavy exercise but capable of being performed at steady state (ie, anaerobic threshold).

When at a level of 17, the effort level requires you to push yourself hard even though it is possible to continue for some time.

For many people, 19 are about as strenuous as exercise becomes because they often reserve a small amount of possible extra effort.

THE BORG SCALE IS AS FOLLOWS

6 – No exertion at all

7 - 8 – Extremely light (very, very light)

9 - 10 – Very light (A1 warm-up/recovery)

11 – Light (A2 aerobic threshold)

12 - 13 – Moderate (EN-1 anaerobic threshold)

14 - 15 – Hard (EN-2 VO2 max or 400-m swimming pace)

16 - 17 – Very hard (AN-1 peak lactate tolerance, 200-m swimming pace)

18 - 19 – Extremely hard (AN-2 anaerobic power, 25-50–m swimming pace)

20 – Maximum all-out effort, with absolutely nothing being held in reserve

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