Although the cycle ergometer is the traditional mode for exercise testing in patients with respiratory disease, this preference over the treadmill does not consider perceptual responses. Our hypotheses were as follows: (1) the regression slope between breathlessness and oxygen consumption (V̇o2) is greater on the treadmill than on the cycle ergometer; and (2) the regression slope between leg discomfort and V̇o2 is greater on the cycle ergometer than on the treadmill.
Twenty patients (10 men/10 women) with COPD (mean ± SD postbronchodilator FEV1, 50 ± 15% of predicted) used a continuous method to report changes in breathlessness and in leg discomfort during cycle and treadmill exercise.
Patients reported an earlier onset of breathlessness and leg discomfort during cycling. Peak ratings of breathlessness were higher on the treadmill, whereas peak ratings of leg discomfort were higher on the cycle ergometer. The regression slopes for breathlessness as a function of V̇o2 and of minute ventilation (Ve) were higher on the treadmill. The regression slopes between leg discomfort and V̇o2 were similar for treadmill and cycle exercise. Peak V̇o2 was significantly higher with treadmill exercise (mean Δ = 8%; p = 0.002).
Patients with COPD exhibit different perceptual and physiologic responses during treadmill walking and cycling. Although ratings of breathlessness are initially higher with cycling at equivalent levels of V̇o2, the changes in breathlessness as a function of physiologic stimuli (V̇o2 and Ve) are greater during treadmill exercise. Leg discomfort is the predominant symptom throughout cycling.