Estimating Maximum Work Rate During Incremental Cycle Ergometry Testing From Six-Minute Walk Distance in Patients With Chronic Obstructive Pulmonary Disease

Hill K, Jenkins SC, Cecins N, Philippe DL, Hillman DR, Eastwood PR. Estimating maximum work rate during incremental cycle ergometry testing from six-minute walk distance in patients with chronic obstructive pulmonary disease. Objective: To develop a predictive equation to permit estimation of the maximum work rate (Wmax) achieved during an incremental cycle ergometry test from the measurement of 6-minute walk distance (6MWD) and its derivative, 6-minute walk work, which is the product of 6MWD and body weight. Design: Cross-sectional observational study. Setting: Outpatient physiotherapy and pulmonary physiology clinics in a tertiary hospital. Participants: Patients (N=50; 36 men) with chronic obstructive pulmonary disease (forced expiratory volume in 1 second [FEV₁]=37%±11% of predicted). Interventions: Not applicable. Main Outcome Measures: Measurements were obtained of 6MWD and Wmax achieved during a laboratory-based, symptom-limited incremental cycle ergometry test. Linear regression analyses were performed using 6MWD, height, weight, and FEV₁ and using 6-minute walk work, height, and FEV₁ to determine their contribution to Wmax and to develop predictive equations for estimating Wmax. Results: The equations derived to estimate Wmax using 6MWD and 6-minute walk work, respectively, were as follows: Wmax (W)=(0.122×6MWD)+(72.683×height [m])-117.109 (r²=.67, standard error of the estimate [SEE]=10.8W) and Wmax (W)=17.393+(1.442×6-minute walk work) (r²=.60, SEE=11.8W). Conclusions: Wmax can be estimated from equations based on measurements of 6MWD or 6-minute walk work. The estimate of Wmax derived from either equation may provide a basis on which to prescribe cycle ergometry training work rates that comply with the current guidelines for pulmonary rehabilitation.