Chapter 5. Fitness Assessment

Transcription

1 Chapter 5 Fitness Assessment Table 5-5. Criteria for Waist Circumference in Adults Waist Circumference cm (in) Risk category Females Males Very low < 70 cm (< 28.5 in.) < 80 cm (31.5 in.) Low ( ) ( ) High ( ) ( ) Very High > 110 (> 43.5) > 120 (47.0) (Bray, Reproduced with permission by the American Journal of Clinical Nutrition. Am J Clin Nutr. American Society for Clinical Nutrition.) Step 3: Assess cardiorespiratory fitness Cardiorespiratory endurance, or aerobic capacity, is one of the most important components of fitness. Low levels of cardiorespiratory endurance have been associated with increased risk of premature death from all causes, most specifically from cardiovascular disease. In addition, greater aerobic fitness usually means that an individual is regularly active, and this has been linked with many health benefits (Blair, Kohl, Barlow, Paffenberger, Gibbons, & Macera, 1995); Sesso, Paffenberger, & Lee, 2000). You will find a list of these benefits in Chapter 6 ( Cardiorespiratory Programming ). Aerobic or cardiorespiratory fitness is defined as the ability to perform repetitive, moderate- to high-intensity, large-muscle movement for a prolonged period of time. (See Chapter 2, Exercise Physiology, for more information). Cardiorespiratory fitness can be evaluated with either maximal or submaximal exercise tests, and can be assessed either directly (with oxygen consumption equipment) or estimated (no oxygen consumption equipment is used). Maximal exercise tests These fall generally into two categories: diagnostic and functional. The purpose of a diagnostic exercise test (sometimes called a stress test or GXT) is to diagnose the presence and/or the extent of CHD in addition to evaluating ability to perform work (this is the type of test that a physician may recommend be performed on higher risk clients). The subject will be continuously monitored during exercise via a multi-lead ECG (electrocardiogram), and may or may not be using oxygen consumption equipment. This test usually takes place on a treadmill or cycle ergometer, and the patient is pushed to achieve maximum work effort. By evaluating the ECG (especially at higher intensities), the physician or technologist can discern heart function abnormalities as well as cardiorespiratory endurance. Obviously, this kind of test should only be administered by a licensed health care provider, authorized to perform such tests, in a clinical setting and only for medical or diagnostic purposes. The purpose of a functional maximal exercise test is simply to assess cardiorespiratory fitness. It is often used to evaluate athletes and is important in research. VO2max is usually directly measured with oxygen consumption equipment as the subject exercises to exhaustion, most commonly on a treadmill or cycle. 94 Aerobics and Fitness Association of America

2 Fitness Assessment Chapter 5 The advantages of max tests include the following. The large amount of information gathered, including the actual measurement of a person s ability at high levels (however, there is still about a 2% range of error due to equipment and other factors) versus the estimated level obtained in submaximal testing. Specific cardiorespiratory responses to stress and high intensity enable the diagnosis of heart disease. The disadvantages of max tests include the following. The need for special, expensive equipment and highly trained test administrators. It is recommended that a physician be present. Maximal testing is riskier than submaximal testing due to the potential for heart wave abnormalities at higher workloads. A high level of motivation on the part of the subject is necessary for exercise to exhaustion. All forms of testing are affected by the principle of specificity. Your clients will usually achieve higher test results when they are assessed performing an exercise with which they are familiar. For example, a cyclist will perform better on a cycle ergometer test than a client who never cycles, even though they may both be aerobically fit. However, on any piece of equipment it is still possible to assess a person s progress over time. Another type of test requiring a maximal effort is the field test. The 1.5-mile run and the 12-minute run tests are widely used in college-type settings where it is necessary to test large groups of young athletes all at once. Although inexpensive and easy to administer, these tests are higher risk due to their less supervised nature, and are not recommended for general population assessment. Norms are available (see Pollock & Wilmore, 1990). Submaximal exercise tests There are many types of submaximal tests. Here the purpose is not to diagnose heart disease (ECGs are rarely used), but to assess the client s functional aerobic fitness, show improvement of that fitness level over time, and to help you develop an appropriate level of exercise intensity. Submaximal tests may be used to predict or estimate VO2max, but the tests are concluded when a predetermined submaximal level has been reached (usually 85% of the estimated maximum heart rate), or when the subject has exercised for a specified time period (e.g., 3-Minute Step Test). The premise underlying submaximal testing is that the more fit an individual is, the lower his/her heart rate will be at any given level of intensity or workload. The advantages of submaximal testing (as compared with maximal testing) include the following. Submaximal testing is less expensive. Submaximal testing is less risky since the test ends at or before 85% of maximum heart rate or 70% of heart rate reserve. Less specialized equipment is required. Testing personnel does not have to be as highly trained or qualified. Personal Fitness Training: Theory & Practice 95

3 Chapter 5 Fitness Assessment The major disadvantages of submaximal testing include the following. Less information is obtained. Since maximum is only estimated and not actually achieved, submaximal testing is less accurate if the purpose is to measure VO2max. There are two basic types of submaximal tests: multi-stage (graded) and single stage (fixed load). A multi-stage, or graded, submaximal exercise test is based on three assumptions: (1) there is a linear relationship between VO 2, heart rate, and workload; (2) that mechanical efficiency (the amount of oxygen utilized at a given workload) is the same for everyone; and (3) that max heart rate can be predicted from the formula age = max heart rate. (In fact, this commonly used formula is accurate for only about 75% of the population. In the remaining 25%, max heart rate can vary from the formula by as much as bpm, resulting in either an under or over prediction of max heart rate (McArdle, Katch, & Katch, 1990). Even with these limitations, a multi-stage submaximal test will provide you with valuable information about the client s cardiorespiratory responses and ability to perform work at various intensities, and therefore enable you to recommend appropriate and accurate workloads during exercise sessions. Also, during follow-up re-tests, heart rate, rate of perceived exertion (RPE), and blood pressure responses to various workloads can be compared, allowing clients to see measured change in their cardiorespiratory fitness from the recommended program. Multi-stage tests can be performed on treadmills, cycle ergometers, or steps, and there are a variety of different protocols (testing formats) available. At many commercial and corporate fitness facilities, the submaximal cycle ergometer test is the preferred form of aerobic fitness assessment. Advantages of the test are that the ergometer is easy to calibrate, relatively inexpensive and portable (as compared to a treadmill), non-intimidating to clients, and that heart rate and blood pressure are easier to assess during cycling exercise than during walking or running exercise. Also, in a multi-stage test, more information can be obtained than during a single-stage test. Disadvantages are that it may be difficult to maintain a constant speed or workload, and localized muscle fatigue may limit performance. Advantages of treadmill testing include the fact that more muscle mass is involved, resulting in potentially higher estimated VO2max values; additionally, walking is an activity that is familiar to almost everyone. A multi-stage submaximal test typically involves the following scenario. Warm-up Stage 1: 3 minutes at a workload eliciting ~65% HRR Stage 2: 3 minutes at a workload eliciting ~75% HRR Stage 3: 3 minutes at a workload eliciting ~85% HRR Cool-down 96 Aerobics and Fitness Association of America

4 Fitness Assessment Chapter 5 Heart rates are taken at the end of each minute; blood pressure and RPE are taken at the end of each 3-minute stage. As you can see, considerably more data is collected, allowing for a more accurate estimation of VO2max as well as more points for comparison in future reassessments. Note that special training is required to administer multi-stage tests. This can be obtained through university courses or through certification programs such as those offered by the ACSM (Health Fitness Instructor Certification) or the YMCA. An alternative to the multi-stage test is the single-stage (fixed load) test. This test usually takes even less training to administer and requires less equipment. However, since there is only one stage, or workload, less information is obtained about your client. Heart rate, blood pressure, and RPE are usually not monitored during the actual exercise, which makes the test less useful for exercise prescription. Two popular types of submaximal fixed-load tests are the 3-Minute Step Test and the Rockport 1-Mile Walking Test. The 3-Minute YMCA Step Test The premise underlying the step test is that if a client has a low-recovery heart rate 1 minute after stepping, he/she is in better physical condition and therefore has a higher VO2max and a higher level of aerobic fitness. Advantages of the step test are that it requires inexpensive pieces of equipment (step, metronome, and watch), the client does not have to be skilled, the test is short, and large numbers of people can be tested at once. Major disadvantages of the step test are that it can be relatively strenuous for deconditioned clients, and may be harmful or dangerous for those with bad knees or balance problems. The protocol for administering the 3- Minute Step Test, after the informed consent process has been completed, is as follows. 1. Explain the purpose of the test to your client and describe the procedure. It is a good idea to suggest that clients refrain from conversation since talking, laughing, etc. may elevate their heart rate (although they must be encouraged to report any pain or discomfort). Static stretching of the gastrocnemius, hamstring, and iliopsoas muscles may be advised; and a short practice session is allowed (two- or three-step cycles). Make certain to tell your client that he/she may stop the test at any time if he/she feels pain or discomfort. There is no active warmup. 2. Set the metronome at 96 bpm (24-step cycles per minute), and when the client begins stepping, start your timer or stopwatch. For this test, stepping must be performed on a 12-inch (30.5 cm) bench with a basic step pattern of up, up, down, down. The lead foot may change if necessary during the test (no continuous alternating lead). Have your client step for 3 full minutes, and let him/her know when 1 minute has passed, 2 minutes have Photo Minute Step Test passed, and when 10 seconds are remaining. Personal Fitness Training: Theory & Practice 97

5 Chapter 5 Fitness Assessment 3. When the 3 minutes are up, remind the client to sit down immediately; within 5 seconds palpate the recovery heart rate (preferably on the radial artery at the wrist). Count the recovery heart rate for 1 full minute. 4. Use the minute value for the recovery heart rate and consult the norms appropriate for the client s age and sex in Appendix C. (Norms are also available that estimate VO2max based on recovery heart rate [Golding, 1989]). Note that the ACSM currently recommends that an ECG, heart rate monitor, or stethoscope be used to assure the most accurate heart rate measurement (American College of Sports Medicine, 2006). The Rockport Walking Test In 1986, the Rockport Walking Institute developed a test appropriate for the general population, including older and/or sedentary clients. The protocol for the test, after the informed consent process has been completed, is as follows. 1. Precede the test with a light warm-up consisting of rhythmic limbering and static stretching. Advise your client to stop at any time if he/she feels pain or discomfort, but that this test requires the most vigorous walk he/she can maintain for 1 mile. 2. The walking course needs to be smooth and flat, ideally a 1 4- mile track. As your client walks, announce the distance remaining with each lap. 3. After a mile has been completed, immediately palpate the pulse for 10 seconds (preferably on the radial artery). Allow your client to cool down. 4. Multiply the 10-second count by 6 and consult the norms for the client s age and sex in Appendix C (use both heart rate and completion time). Note that these norms are for men weighing 170 pounds and for women weighing 125 pounds. If your client weighs significantly more, then his/her aerobic fitness will be over-predicted; if he/she weighs significantly less, aerobic fitness will be under-predicted. Other factors that can influence the results are the client s level of motivation, ability to set a consistent pace, and level of body fat. VO2max may be estimated using a generalized equation (Kline et al., 1987). When consulting clients about the results of cardiorespiratory testing, remember that, for them, VO2max numbers may have little meaning. They may be more interested in their increased stamina and enhanced ability to perform daily activities. Help them to see tangible proof of their improvement over time. The Rockport Walking Treadmill Test This test is very similar to the one outlined above. The testing protocol is as follows. 1. Precede the test with a warm-up consisting of static stretching and walking on the treadmill. Find the exact pace at which the client can walk vigorously for 1 mile. 2. Have the client walk at the established pace for 1 mile. Record the time. 3. Immediately palpate the pulse for 10 seconds and then allow the client to cool down. 98 Aerobics and Fitness Association of America

6 Fitness Assessment Chapter 5 4. Multiply the 10-second count by 6 and consult the norms for age and sex in Appendix C. NOTE: All of the foregoing testing procedures must be preceded by the informed consent process, documented in writing, signed by the client, and disclosing risks/benefits associated with such procedures. These testing procedures should never be performed by personal fitness trainers for diagnostic-type purposes, but rather, only for fitness assessment. Step 4: Assess muscular fitness Muscle strength (the ability of a muscle or muscle group to exert maximal force for one repetition) and muscle endurance (the ability of a muscle or muscle group to exert submaximal force for several repetitions, or to hold a contraction for a sustained length of time) are both important components of fitness for your client s physical well-being. Without adequate muscle strength and endurance, clients are more likely to suffer from low-back pain and/or poor posture, as well as other musculoskeletal problems. Performing weight-bearing exercises that promote muscular fitness is a primary way to enhance or maintain bone mass, helping to prevent osteoporosis. The development of muscle strength and endurance leads to an increase in lean body mass and an improvement in body composition, which in turn causes an elevation in resting metabolic rate. In addition, maintaining muscle strength and endurance is an important factor (especially for elderly clients) in performing everyday essential tasks adequately and without undue risk of injury. Assessing muscular strength Muscle strength can be assessed either statically (isometrically) or dynamically (isotonically). Note that no one test can assess total body muscle strength or muscle endurance; all muscle fitness tests are specific to the muscle group being tested. For example, a bench press test is specific to the upper body, in particular the pectoralis major, anterior deltoids, and triceps. Static strength tests are most often performed on dynamometers. Dynamometers are available to assess hand grip strength and back and leg extensor strength, with the hand grip dynamometer being most widely used (keep in mind, this test does not measure a major muscle group and is therefore of limited predictive value). The procedure is simple after adjusting the handgrip size for your client, have the client stand, holding the dynamometer in one hand with the elbow flexed. Instruct him/her to exhale while squeezing as hard as possible (maximal voluntary contraction) for 2 3 seconds. Allow three trials for each hand and compare to the published norms (Canadian Society for Exercise Physiology, 2003). Keep in mind that static strength tests are specific to the muscle group being tested and measure strength only at the particular angle at which the test is performed. Also, since clients tend to hold their breath and bear down (Valsalva maneuver) during isometric contractions, they must be instructed to exhale during exertion in order to prevent possible cardiovascular problems. Muscular strength can also be assessed dynamically by the one-repetition maximum (1RM) test. Frequently performed 1RM tests are the bench press, which assesses the strength of the pectoralis major, anterior Personal Fitness Training: Theory & Practice 99