Experimental procedures

Detailed description of maximal cardiopulmonary exercise testing procedures have been given elsewhere.^(,7)Tests were conducted on a cycle ergometer (Lode, Corival, Netherlands) by a physician with extensive experience (more than 10 years) in maximal exercise testing. Fifteen to twenty minutes prior to testing, patients were familiarized with the cycle ergometer by pedaling at a comfortable intensity for 2 to 3 minutes. Patients were then allowed to rest until cardiovascular parameters returned to baseline and tested. Individualized ramp protocols were selected to induce fatigue within 8 to 12 minutes of test start. These involved increments ranging from 3 to 15 watts per minute according PD severity and level of physical conditioning. Pedaling frequency ranged from 50 to 60rpm. Tests were discontinued whenever subjects were unable to maintain pedaling frequency. The same ramp increments were used in baseline and 12-week assessments.

Heart rate was recorded at 30-second intervals via continuous 12-lead echocardiogram monitoring (CardioPerfect^®, ST 2001, Netherlands). Auscultatory blood pressure was measured by a blinded technician every 2 minutes using a mercury sphygmomanometer. Respiratory gas exchange was measured by breath-by-breath analysis using a metabolic cart (Medical Graphics Corporation, CPX/D, United States) and data collected at 30-second intervals averaged.

Peak HR, SBP and VO₂ were defined as the highest value obtained during the exercise phase of the test and corresponded to maximal test responses. Responses to submaximal relative intensities were assessed at ventilatory thresholds (i.e., anaerobic threshold – AT – and respiratory compensation point – RCP)^(,23,24) determined by two independent experts, with discrepancies solved by consensus. Responses to submaximal absolute intensities were assessed by comparing the slope of the linear regression line between physiological parameters (VO₂, HR and SBP values) recorded at baseline and after 12 weeks of exercise practice.^(,25) Regression was based on values measured during exercise. Individual linear regression slope lines were used in the analysis.