The aim of this study was to establish the perceived magnitude of dyspnea (discomfort associated with breathing) and leg effort experienced by normal subjects during a standardized incremental exercise test to maximal capacity; 460 normal subjects (297 male and 163 female 20 to 70 yr of age) were studied. The perceptual magnitude of both symptoms was rated using simple descriptive phrases (slight, moderate, maximal) tagged to numbers from zero to 10 on the Borg scale, which is an interval scale with ratio properties. Leg effort and dyspnea increased with power output, were higher in women than in men (p<0.0001), increased with advancing age (p<0.0001), and declined as height increased (p<0.0001). Leg effort = 4.82 + 0.007 kpm/min + 1.05 sex + 0.04 age - 0.055 Ht (r = 0.78; SD, 1.80). Dyspnea = 4.96 + 0.006 kpm/min + 0.96 sex + 0.04 age - 0.05 Ht (r = 0.74; SD, 1.80) (m = 1; f = 2). With power output expressed as a percentage of maximal power output (%MPO) both symptoms increased in an alinear manner. Effort = 0.0014 * %MPO1.86 (r = 0.86; SD, 1.50). Dyspnea = 0.0016 * %MPO1.79 (r = 0.81; SD, 1.57). Sex, age, or stature did not contribute to the rating of effort or dyspnea when power output was normalized in this way.
