At higher ramp rates, however (100 W/min), oxygen kinetics and work efficiency could not be estimated. This finding underscores the value of choosing an individualized ramp rate for each subject. Ramp cycle ergometry, because of the constant increases in work, has intuitive advantages for assessing blood lactate and acid-base relationships during exercise, pharmacologic intervention, and the oxygen uptake/work rate relation and other measures of oxygen kinetics.
Work is quantified with less precision on the treadmill compared with a cycle ergometer, as it is more dependent on walking efficiency, handrail holding, and habituation. Thus, a greater degree of error would appear to be present when predicting work on the treadmill for exercise prescription or other purposes. Our previous work using ramp testing on both the treadmill and cycle ergometer suggests that the contrast in oxygen kinetics between normal subjects and patients with heart disease is present with either mode, despite the less precise quantification of work on the treadmill. At present, there are few treadmill controllers available for programming ramp tests. Although the ramp treadmill lacks widespread application and must be validated by other laboratories, the advantages of the treadmill (higher maximal oxygen uptake, more subjects are accustomed to walking, its widespread use in the United States) and the advantages of the ramp discussed above would appear to make it well-suited for many clinical applications.