Subjective Estimates of Exercise Ability: Comparison to Objective Measurements
Pediatric Exercise Science
Although not well validated, physicians frequently use subjective estimates of exercise ability to assess clinical status and therapeutic results. This study employed a standardized questionnaire and cardiopulmonary exercise test to compare the results of subjective estimates by 211 patients (mean age 13.9 yrs) with objective measurements of exercise ability. Questionnaire data correlated with measured maximal oxygen consumption. Individuals thought to be below average had a maximal oxygen
... maximal oxygen consumption of 21 + 6 mllkgl min. Those thought to have average fitness had a maximal oxygen consumption of 26 f 8 mllkglmin, and those thought to be above average had a maximal oxygen consumption of 30 + 7 mllkglmin. There was a great degree of overlap and scatter of these data, however, such that questionnaire data significantly overestimated exercise ability in 67% and underestimated it in 3% of the subjects. In only 30% of the subjects did the subjective estimate of exercise ability correspond with objectively measured exercise ability. It was concluded that subjective estimates are unreliable and should not be used in assessing the functional status of an individual patient, but subjective estimates may give some idea of objective capabilities in large population studies. Clinicians frequently estimate a patient's fitness status by asking questions either of the patient or, in the case of children, the parent (5). This estimate is then used to assess clinical status or the results of therapeutic maneuvers (9, 13). The validity of this approach, especially in children with congenital malformations or chronic diseases, has never been well established. We therefore sought to determine the validity of this technique by comparing the responses of parents or patients to a self-administered questionnaire regarding fitness levels with measured values from cardiopulmonary exercise testing. Methods The subjects were 21 1 consecutive patients (126 males; 85 females) who underwent a maximum cardiopulmonary exercise test using cycle ergometry at The Children's Hospital of Philadelphia. They ranged from 5 to 42 years of age (mean The authors are with the Div.