Treadmill Laboratory (Aerobic and Anaerobic Tests) Laboratory Organization The lab group will be split into two groups of eight students for this lab. One group will go to the Environmental Physiology Unit (EPU, room K8615) and perform the treadmill protocols for the first 55 minutes. The second group will start these tests in the EPU after the first group is finished. The main lab will be open during the treadmill testing. Blood pressure and anthropometric equipment will be available for students to review these procedures (when they are not required to attend the treadmill lab). Treadmill Protocols The treadmill tests are described as laboratory tests, not field or field/lab tests, because of the bulk and expense of a treadmill capable of a 20% slope and the ability to monitor the subject closely during the test (with ECG, etc.). Additionally, the treadmill tests do not lend themselves to simultaneous testing of many people, due to obvious reasons. However, the physiological sophistication of these treadmill tests is as simple as most field-tests. Maximal Stress Tests Maximum oxygen consumption can be estimated from performance during standardised protocols on the treadmill, cycle ergometer, or arm ergometer. The protocol chosen often depends on the equipment available, the population being tested, and the primary purpose of the test. Usually tests starts with a low workload with 1- to 3-min stages, and an increase of no more than 3 METs (10.5 ml/kg/min) per stage is generally recommended. The test should be no longer than 15 to 20 min to avoid boredom and loss of motivation. When using a protocol to estimate VO2max. from performance, it is important to follow the protocol precisely. For example, Ragg et al. found that performance time on a graded exercise test with constant walking speed increased from 15 to 25 minutes when subjects were allowed to hold on to the handrail. Bruce Protocol As an exercise therapist you will have to refer people for a maximal stress test on occasion. It is therefore a good idea for you to take a fellow student through such a protocol. The Bruce protocol is the most frequently used diagnostic test for coronary heart disease and the best-validated test for estimating VO2max. from maximal performance. This Bruce test starts at a low work level, allowing time for warm-up and cardiovascular adaptation. The increases in workload are relatively large compared to some protocols (3-4 METs per stage); thus the test can be completed quickly. Bruce, Kusumi, and Hosmer developed predictive equations for VO2max. from performance time on the Bruce protocol. Stepwise multiple regression analysis was used to develop population-specific predictive equations for VO2max for healthy adults, active men, sedentary men, and cardiac men (N = 393). Correlation coefficients ranged from r = .0.86 to r = 0.92. Foster et al. developed generalised equations for estimating VO2max from the Bruce protocol using the Bruce protocol with concurrent measurement of VO2max. The sample (230 males) included patients with angina, coronary bypass surgery patients, cardiac rehabilitation patients, healthy adults, and athletes. Equipment needed: Motor-driven treadmill Stopwatch to time test duration. Electrocardiogram (ECG) (for diagnostic test). A Heart-rate monitor can be used for a straight VO2 max. estimate.. Protocol The Bruce protocol is summarised in the table below. Note that both speed and grade increase at each stage. In cardiac patients the test may be begun at 1.7 miles per hour at 0% grade for 3-minutes increasing to 5% for the next three minutes. These two stages are omitted in healthier subjects. Stage 1 2 3 4 5 6 7 Duration (min) 3 3 3 3 3 3 3 Speed (mph) 1.7 2.5 3.4 4.2 5.0 5.5 6.0 Grade (%) 10 12 14 16 18 20 22 Electrocardiogram (ECG) We will use a 3 lead ECG configuration (CM5 position) to monitor our subject. The CM5 position has the following placements of the three leads. Left Arm (lead LA) Right Arm (lead RA) Right Leg (lead RL) should be paced on the 5th intercostal space in the mid-axillary line. should be placed on the centre of the manubrium just below the suprasternal notch. should be grounded on the scapula. Be careful to keep the electrode as far away from muscle masses as possible to reduce interference. In a true diagnostic test a 12-lead ECG configuration would probably be used. However, from the CM5 configuration most of the common heart arrhythmia discussed in class (e.g. ST-segment depression, PVC’s. etc.) can be seen. It is hoped that we won’t actually come across any during this lab! Resting ECG and Blood Pressure should be recorded prior to start of test. Heart rates will be determined from the ECG tracings. ECG should be recorded during the last 15 seconds of each stage and at peak exercise. Blood pressure is usually recorded during the last minute of each stage, but may not be viable in the lab situation due to noise levels. RPE is recorded at the end of each stage. BORG 10 point scale Appraisers should be ready to help the subject should they have difficulty straddling the treadmill once they reach the end of the test. Post trial ECG and Blood Pressure should be recorded twice during the five minutes following exercise. Prediction Equations Population-specific equations from Bruce, Kusumi, and Hosmer (r = correlation coefficient and n = number of subjects used in developing predictive equation).: 1) Active men. r 0.906 n 44 VO2max = 3.778 (time) + 0.19 2) Sedentary men: 0.906 94 VO2max = 3.298 (time) + 4.07 3) Cardiac patients: 0.865 97 VO2max = 2.327 (time) + 9.48 4) Healthy adults: 0.920 295 VO2max = 6.70 - 2.82 (gender) + 0.056 (time) Where: VO2max time = = gender = maximal oxygen uptake (ml. Kg-1 min-1) maximal treadmill performance in minutes for Equations 1 to 3 and seconds for Equation 4 males = 1, females = 2 Equation from Foster et al.: VO2max = 14.76 - 1.38 (time) + 0.451 (time2)- 0.012 (time3) Where the time is in minutes (to 2 decimal places). R = 0.977 SEE = 3.35 ml/kg/min Note: Notice that heart rate is not used in these calculations. This is because the subject works to volitional exhaustion. Therefore, although any variation in predicted maximal heart rate (220-age) is not a source of error, subject motivation is crucial. Outcomes of a Stress Test The value of stress testing depends directly on how well results on a particular test predict the existence of heart disease. The sensitivity of a stress test refers to the percentage of people with the disease who have an abnormal test result. No test is perfect diagnosing heart disease. There are four possible outcomes from a graded exercise stress test: True-Positive: The test correctly predicts a problem. False-Negative: Test results are normal but the individual does have the disease. True-Negative: Test results are normal and the person does not have disease. False-Positive: Test results are abnormal but the person has no heart disease. Whenever a stress test results in an abnormal response and hence indicates the possible presence of heart disease, secondary tests are performed to confirm the diagnosis. Similarly, even if the results from graded stress tests are normal does not necessarily rule out the occurrence of heart disease. Guidelines for Stopping a Stress Testing The guidelines used for stopping a stress test will be presented in the lecture. A copy of them will be available in the treadmill laboratory. A data sheet is not required as the only measurement that is recorded is the total duration of the test from start to the time the subject stops the test due to fatigue. If they stop due to illness or discomfort the test results are naturally invalid. Treadmill Anaerobic Tests Various versions of Treadmill Anaerobic Tests exist. The two tests briefly discussed here may be classified as long anaerobic tests (lactic acid energy system) because they both elicit maximal effort for duration of between 30 and 90 seconds for most college-aged men. Most women will have difficulty running at the prescribed speeds and slopes of these two treadmill tests, especially the faster test. The different expected duration of the two treadmill tests may be used to distinguish them into a fast (F) test (faster speed, shorter duration) and a slow (S) test (slower speed, longer duration). It should be noted that the term slow is a relative term, as many subjects will still fatigue quickly. These tests are exclusively the domain of elite athlete testing. Alpine ski racers work at high intensities for 1 to 2.5 min. and it is not surprising that long anaerobic tests relate to successful performance in that sport (Houston and Green, 1976). Such work has also been conducted here at Simon Fraser University (Brown and Wilkinson, 1983). In an all-out treadmill sprint that lasted from 54 to 105 seconds and representing about 125% of the runners' aerobic capacity, the pH of their gastrocnemius and vastus lateralis muscles was about 6.88 (Costill et al., 1983). This is a very acidic level, especially when considering that a normal pH is about 7.4, and that a chronic value of 6.8 would be incompatible with life (Morehouse and Miller, 1976, p. 179). As further proof of the high intensity of these types of tests, it was found that males who ran for about 93 seconds (± 29 s) at 16 kph on an 8% slope had peak heart rates that averaged 192 beats/min (Mackova et al., 1985). In the original study (Cunningham and Faulkner, 1969) the exhaustive treadmill run proved to be sensitive to increases in anaerobic capacity, as after anaerobic training, the treadmill times increased by 23% together with a 17% increase in maximal blood lactate and a 9% increase in O2 debt. Although this test appears to be a valid indicator of lactic anaerobic capacity, care should be taken not to set the speed too fast. As shown in the table at the end of this lab, the 8-mph speed is too fast for many subjects (especially women). The run time should ideally be between 50-90 seconds. Run times of less than 40 seconds may not cause blood lactate levels to be maximised. Method Increasing both the speed and slope of the treadmill usually induces high-intensity efforts on a treadmill. If only a fast speed is used, slow runners might find themselves trailing off the back of the treadmill; if a very steep slope at a slow speed is used, those with inferior leg strength may succumb to premature leg fatigue. Thus, treadmill anaerobic tests for lactic acid anaerobic power use a combination of slope and speed to elicit the supra-maximal effort required. Equipment needed: Motor-driven treadmill, Stopwatch, A weigh-scale would be needed if the total work done during the test were to be calculated. Treadmills with front and side handrails are required for the anaerobic tests. A harness attached from the subject to the rail or ceiling is ideal for maximising safety in uninhibited all-out efforts. Treadmill Protocol The protocol for treadmill tests should include a prior exercise and familiarisation period, along with a cool-down. The protocols for the Long Anaerobic-Slow (S) and Fast (F) Treadmill Tests are shown below. A female subject should do the "slow" test and a male subject the "fast" test. Period Prior Exercise Familiarisation Relief Interval Treadmill Test Slow Fast Cool-down and Time (min) 0:00-10:00 10:00-11:00 Slope (%) 20 20 0:00-5:00 Activity (1) Jog in place; (2) Slow jogging; (3) Short runs on treadmill, progressing to very brief bouts at test speed. Slow walking or walking in place Speed 6 mph (9.6 kph; 10 min per mile pace) 8 mph (12.8 kph, 7.5 min per mile pace) Gradually slower jogging and walking; stretching Note: Cunningham and Faulkner (1969) also used a speed of 7 mph and Riezebos et. al. used 8.5 mph for men and 7 mph for women (all at 20% grade). Safety As with all test procedures, appraisers must be concerned with the safety and psychological well being of the subjects prior to and during the treadmill test. In short, this is the most exhausting test that I am aware of. For that reason I am interested in you reading the protocol and taking a subject through the protocol. It is not necessary however for the subject to push to absolute exhaustion. They can stop after 10 seconds and you will still have learnt the protocol. I am not looking for heroes and only a subject who I am already aware has good anaerobic capacity will be allowed to perform this test. A fast-moving treadmill belt can be intimidating so the protocol should include a familiarisation with the safe and proper technique of getting on and off the fast-moving treadmill belt. The technician in control of the treadmill should be prepared to stop the treadmill as soon as the runner touches the handrails in preparation of exiting. A couple of spotters should be at the rear end of the treadmill and should be prepared to catch the subject if they get spun off the treadmill. There is a steep learning curve with a time increase of up to 30% from first to second trials (with adequate rest). If a subject was to perform the test for the first time you would usually find he or she stopped earlier than needed due to safety concerns rather than true exhaustion from lactic acid accumulation. However, once the subject feels comfortable about getting off the treadmill when fatigued, performance times go up. Measurements and Data Sheet There is only one measurement: the time (to the closest second) spent at the prescribed speed on the treadmill. The timer starts the clock as soon as the subject, while running, releases the handrails. The timer stops the watch when the runner takes hold of the handrails in preparation to exiting from the treadmill belt. For this reason no data sheet is presented in this section of the laboratory manual. Calculations As stated a calculation of anaerobic work capacity may be made from the time spent on the treadmill, the slope and speed of the treadmill, and the weight of the subject. As we have done such calculations in some of our field test protocols and such calculations are an integral part of the Wingate bike test we will not calculate them for this test. The table below cannot be used to classify subjects but is useful for comparative purposes. Comparative Scores for the Treadmill Anaerobic Tests Reference Group Time (sec) Fast Test: 8 mph, 20% grade (R = range, SD = standard deviation) Adams, 1989 Male P.E. majors (n =36) 33 (R = 18-47) Female P.E. majors (n =7) 11 (R = 8-19) College Hockey Forwards (n=11) 54; SD=15 Normal Males: Pre-training (n=8) 52; SD=13 Post-training 64 Brown & Wilkinson, 1983 National Alpine Skiers (n=10) 77 Less Elite Club Skiers (n=22) 56 McKenzie et al., 1982 Elite 800m runners (n=6) 114 Parkhouse & McKenzie, 1983 Elite Athletes (n=6) 82; SD=20 Rodes et al., 1986 Olympic Soccer Players 92: SD=10 (R=68-102) SFU record Canadian 5000m champion 140 Intermediate Test: 7 mph, 20% grade (SEM = standard error of measurement) Riezebos Female Basketball Players 39; SEM=2.2 Green & Houston, 1976 Cunning & Faulkner, 1969 Slow Test: 6 mph, 20% grade (R = range, SD = standard deviation) Niinimaa et al., 1977 Dinghy Sailors 65; SD=16 Adams, 1989 Male P.E. majors (n =30) Female P.E. majors (n =21) 72 (R = 49-153) 38 (R = 20-54)