Fig. 2

Dyspnea break-point (point A). First, a dyspnea break-point was determined for each patient by using the intersection of two lines on plots of dyspnea as a function of \({\dot{V}}_{{\rm O}_{2}}\). Second, the location (%) of each resulting dyspnea break-point relative to Δ\({\dot{V}}_{{\rm O}_{2}}\) (= peak \({\dot{V}}_{{\rm O}_{2}}\) − resting \({\dot{V}}_{{\rm O}_{2}}\)) that occurs during exercise was calculated for each patient by use of the equation 100 × (dyspnea break-point \({\dot{V}}_{{\rm O}_{2}}\) − resting \({\dot{V}}_{{\rm O}_{2}}\))/Δ\({\dot{V}}_{{\rm O}_{2}}\). 50 % \({\dot{V}}_{{\rm O}_{2}}\) point (point B). The \({\dot{V}}_{{\rm O}_{2}}\) value at the 50 % \({\dot{V}}_{{\rm O}_{2}}\) point was calculated for each patient by use of the equation resting \({\dot{V}}_{{\rm O}_{2}}\) + (peak \({\dot{V}}_{{\rm O}_{2}}\) − resting \({\dot{V}}_{{\rm O}_{2}}\))/2. Next, the value of the Borg scale at the 50 % \({\dot{V}}_{{\rm O}_{2}}\) point was calculated for each patient, where the Borg scale on the Y axis corresponded to the 50 % \({\dot{V}}_{{\rm O}_{2}}\) point on the X axis by linear interpolation between adjacent measurement points