Graded exercise testing is used to measure functional capacity and in many laboratories, protocols are selected due to popularity and ease of testing. (Myers & Bellin, 2000) Stationary cycles are the most commonly used equipment to measure cardiorespiratory fitness, which is calculated by maximal oxygen uptake (VO2max), or a plateau in oxygen consumption with an increase in work rate. (Thompson, 2010) Ramp-type protocols performed on a cycle ergometer are designed to determine maximal oxygen uptake by small workload progression.
According to research, 82% of exercise physiology laboratories use the Bruce or modified Bruce protocol. (Myers & Bellin, 2000) Even though the Bruce is one of the most well known tests used, findings have shown that a more accurate predictor of exercise capacity can be determined with a ramp style assessment. Gradual workload progression in the ramp type protocols have been shown to be more efficient than irregular increments of resistance in the Bruce test. Also, rather than offering the same standard protocol, the ramp cycle procedure is modified to every individual by considering the patient and the test purpose. It is generally performed on electronically braked bikes instead of mechanical, which allows resistance to be applied regardless of speed. (Porszasz et al., 2003)
In the 1980s, mechanical bikes transitioned to electronic and the first documented ramp cycle test was performed to evaluate cardiorespiratory response. Whipp and colleague created the ramp work rate by a circuit with a voltage and an electromagnet. According to their findings, the oxygen uptake and work rate were linear above and below the repeatable ventilator threshold (VT). Similar responses were observed in work efficiency and peak VO2 among the same participants whom performed a different test previously. (Myer & Bellin, 2000)
The ramp cycle protocol is useful for treatment studies and it is recommended for examining patients with cardiovascular disease. By reducing resistance, cardiorespiratory performance can be assessed since the cardiorespiratory systems directly adjust depending on the stress put on it. Therefore, treatment effects can be observed and the test is ideal for pharmaceutical studies or other interventions. (Myers & Froelicher, 2011) It is commonly used for clients with low exercise capacity, weight or walking complications and particularly helpful in clinical populations too. Since the ramp protocol is tailored to the individual, the test can be adjusted for any clientele no matter if they are frail or physically active. (Boone et al., 2008)
In order to facilitate the ramp-cycle rate of increase in work, prior knowledge of the patient’s exercise capacity is imperative. This can be obtained by a brief exercise tolerance questionnaire like the Veteran’s Specific Activity Questionaire (VSAQ) and depending on their answers the ramp rate is tailored to meet the client’s capacity. The test should be designed to have an exercise time of 10 minutes or preferably between 8 to 12 minutes. (Myers et al., 1991)
Some prefer the ramp cycle test to other protocols due to safety precautions and the capability to accurately measure work rate throughout the test. (Porszaz et al, 2003) The ramp cycle assessment is designed to increase by small levels of work every minute, unlike the Bruce protocol that uses 2-3 MET increments every 3 minutes. Small continuous workloads avoid changes in metabolic rate and neuromuscular motor unit recruitment associated with dramatic workloads. A precious study performed with angina or chest pain patients reported that large and fast work-rate loads might disguise intervention or therapy effects. Ramp cycle tests are tailored for each patient, which is essential to obtain angina between 3 to 6 minutes. Overall, ramp cycle test have an enhanced ability to estimate oxygen uptake (VO2); as a result, it precisely predicts submaximal responses, helps to advise an exercise prescription, and further estimate prognosis. (Myers & Froelicher, 2011)
When comparing exercise mode, maximal oxygen uptake is between 10 to 20% higher on a treadmill than on a bicycle. Cycle ergometers have restrictions for gauging exercise capacity because the mode is not as similar to daily activities of living. Therefore, the treadmill has the advantage of inducing a higher maximum metabolic rate as depicted on Figure 1. (Myers et al., 1991) ACSM’s Guidelines for Exercise Testing and Prescription suggests that the main disadvantage for cycling would be muscle fatigue due to unfamiliarity.
Figure 1: Metabolic Rate of Identical Work Rate Slope of Ramp Cycle & Ramp Treadmill (Porszasz et al., 2003)
In Boone et al. study, VO2 response was measured among eight cyclists and eight physically active students that performed several submaximal ramp protocols at 10, 25, and 40 W/minute. After the mean response time delay, VO2 increased linearly up to the gas exchange threshold (GET), the anaerobic threshold for the submaximal tests. Figure 2 shows the VO2 and work linear response for a cyclist performing the ramp test and it was found that the slope was steeper when the ramp was less steep.
Figure 2.VO2/time curve for cyclist performing a Ramp test. (Boone et al., 2008)
In another study from Comparison of the Ramp Versus Standard Exercise Protocols, 40 total participants performed three bicycle and three treadmill tests: 10 patients with chronic heart failure, 10 with coronary artery disease who were limited, 10 asymptomatic with coronary artery disease, and 10 age-matched normal volunteers. The following bicycle protocols were: 25W per 2-minute stage, 50W per 2-minute stage and ramp; the other 3 treadmill tests were Bruce, Balke and ramp. Even though, maximal oxygen uptake was considerably higher on the treadmill, between modes no distinct differences in maximal heart rate and oxygen uptake were detected. According to the findings, the slope of VO2 to work was the strongest and there was less variability in estimating oxygen uptake for the ramp tests. (Myers & Froelicher, 2011) As shown on Table 1, the ramp cycle test had a standard of estimated error (SEE) of 0.78 + 1.7 versus the Bruce test SEE of 0.62 + 4.0. This showed that differences between measured and predicted maximal oxygen uptake were the smallest for ramp tests and it is a more accurate predictor for VO2max than other standard tests. (Myers et al., 1991)
Table 1: Slope in VO2 vs. Work rate for 40 volunteers performing 4 exercise protocols (Myers et al., 1991)
|
|
Treadmill Bruce
|
Bicycle 25 W
|
Bicycle 50 W
|
Bicycle Ramp
|
|
Slope
|
0.62
|
0.69
|
0.59
|
0.78
|
|
SEE
|
4.0
|
2.3
|
2.8
|
1.7
|
Research has shown that ramp cycle assessments can be used for submaximal and maximal VO2 values because oxygen uptake increases linearly with work rate until the anaerobic threshold. In contrast, tests that contain imbalanced work rate changes cause disturbances in the oxygen uptake (VO2) and work rate relationship that ultimately leads to overestimating and miscalculating of metabolic equivalents (METS). The ramp cycle protocol has a progressive type design that is modified in order to optimize test duration and responses. The test is commonly used to assess cardiorespiratory function and treatment effects. Overall, findings have shown that the Ramp Cycle ergometer test is a better maximal uptake predictor than tests with large stages.
References
Porszasz, Janos; Casaburi, Richard; Somfay, Attila; Woodhouse, Linda J.; Whipp, Brian J. A
Treadmill Ramp Protocol Using Simultaneous Changes in Speed and Grade (2003). Medicine & Science in Sports & Exercise: 1596-1603.
Myers, J.; Bellins, D. Ramp Exercise Protocols for Clinical & Cardiopulmonary Exercise Testing (2000). Sports Medicine 30 (1): 23-29.
Ehrman, Gordon, Visich, & Keteyian, eds. Clinical Exercise Physiology, 2nd ed. Champaign, IL: Human Kinetics, 2009.
Thompson, WR, ed. ACSM’s Guidelines for Exercise Testing and Prescription, 8th ed. Philadelphia, PA: Wolters Kluwer/Lippincott Williams & Wilkins, 2010.
Myers, J; Froelicher, VF. Optimizing the exercise test for pharmacological investigations (1990).
Circulation 82: 1839–1846.
Myers, J.; Buchanan, N; Walsh, D; Kraemer, M; McAuley, P; Hamilton-Wessler, M; Froelicher,
V. Comparison of the Ramp Versus Standard Exercise Protocols (1991). American
College of Cardiology 17(6): 1334-1342
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