Parkinson's Autonomic Responses to Treadmill Walking

Overview

This study will compare examine autonomic and cardiovascular responses to peak exercise testing in Parkinson's disease patients in varying stages of the disease, and healthy, age-matched participants. Participants will be asked to complete a peak exercise test on a motorized treadmill. Heart rate, blood pressure, norepinephrine, and other markers for cardiovascular function will be assessed at rest, during exercise, and post-exercise. The hypothesis to be tested is that Parkinson's disease patients will exhibit a decreased autonomic and cardiovascular response to exercise when compared to patients' healthy age-matched counterparts. The investigators secondary hypothesis is that Parkinson's disease patients in more advanced stages will exhibit a greater decrease in response when compared to these patients' Stage 1 counterparts, or healthy age-matched counterparts.

This study will require the PD subjects to attend three testing days, lasting approximately 1 hour. PD subjects will report for two exercise testing sessions, with each session separated by 7 days. The age-matched, healthy subjects will only be required to attend two testing days consisting of one day for paperwork and anthropometric measurements, and one day for exercise testing, each lasting approximately 1 hour. PD subjects will be randomly assigned, in a counterbalanced manner, to either an "on-medication" or "off-medication" group for days two and three of testing. All subjects with PD will complete both exercise testing days. Day 1: The subject will read and sign the informed and audio-visual consent forms and complete a health questionnaire, PAR-Q, and mini-mental survey. The subject will also complete the ACSM risk stratification screening questionnaire. Anthropometric measures will be taken to include, waist circumference, height, and weight. The subject will then be introduced to various test procedures which will be utilized throughout the experiment. Each subject will be familiarized with the treadmill and harness support system. The harness support system will be emplaced to ensure the safety of the PD patients due to the inherent fall risk associated with a progressive decline in motor control often seen in this population. The subject will walk on the treadmill at gradually increasing speeds until he or she indicates, by a prearranged signal, that a comfortable walking speed has been attained. Then the treadmill grade will be raised 2% every 30 seconds so the subject can feel what it is like to walk during a progressive test. This will last no longer than five minutes. PD subjects will also be given instruction as to which group (on, or off-medication) they have been assigned to, and how to prepare for the follow-on tests. Off-Medication Testing Day: Subjects will complete a blood draw and a motorized treadmill VO2peak¬ test. Subjects are expected to arrive fasted (no food or drink for the past 12 hours) and having refrained from antiparkinsonian medication(s) for the past 24 hours. The subject will first be seated and given a 5 minute rest period. Following this rest period the phlebotomist will insert a catheter into the median cephalic vein in the antecubital (bend in the arm) region on the subject's arm. One vial (3 cc) of venous blood will be drawn prior to exercise testing and an identical draw will take place immediately following exercise testing. All blood specimens will be tested and analyzed at the University of Miami Miller School of Medicine. Then subject will then be allowed to eat a predetermined meal at the lab before returning to exercise. Following the meal, the subject will be asked to return to a seated resting position for an additional 5 minute period. During this time, gel electrodes will be applied on the subject for the purposes of ECG and heart/blood flow monitoring and measurements. Following this rest period, blood flow will be measured for an additional 5 minutes while the subject remains quietly seated. Next, the subject will be attached to the harness support system for the treadmill exercise test. For the metabolic assessment portion of the test, the subject will be fitted with a mask covering the nose and mouth, in which an airflow sensor will be attached to measure gas content during respirations. The test will start with a 4 minute warm-up at a speed dictated by the subject. By the end of the warm up, the subject will have reached a speed that both they and instructor agree upon which meets the requirements for moderate-intensity exercise. The speed will no longer be adjusted at this point. Percent grade will start at 2.5 percent and will be increased by 2.5 percent every 3 minutes until the subject has met the criterion for a peak exercise test, or has requested to stop. BP and HR will be monitored every minute of testing using an automatic electronic BP assessment machine (BPTRU, Coquitlam, BC), manual sphygmomanometer and stethoscope, and electronic ECG software (Cardiosoft, GE Healthcare), respectively. Successful completion of the test will be determined using the following criteria from the American College of Sports Medicine (ACSM): (1) plateau in VO2, (2) maximal HR within 10 beats per minute of an age predicted maximum, (3) a respiratory exchange ratio of \>1.15, (4) respirations \> 50 breaths per minute, (5) a rating of perceived exertion (RPE) ≥ 18. In addition to these criteria we will use ACSM indications for termination of an exercise test which include: Absolute Indications 1. Suspicion of a myocardial infarction or acute myocardial infarction (heart attack) 2. Onset of moderate-to-severe angina (chest pain) 3. Signs of poor perfusion (circulation or blood flow), including pallor (pale appearance to the skin), cyanosis (bluish discoloration), or cold and clammy skin 4. Severe or unusual shortness of breath 5. Central Nervous System (CNS) symptoms e.g., ataxia (failure of muscular coordination), vertigo (an illusion of dizzying movement), visual or gait (pattern of walking or running) problems, confusion 6. Technical inability to monitor the ECG 7. Patient's request (to stop) Relative Indications 1\. Any chest pain that is increasing 2. Physical or verbal manifestations of shortness of breath or severe fatigue 3. Wheezing 4. Leg cramps or intermittent claudication (grade 3 on a 4-point scale) 5. Hypertensive response (SBP \>260 mm Hg; DBP\>115 mm Hg) 6. Pronounced ECG changes from baseline (\>2 mm of horizontal or down sloping ST- segment depression, or \>2 mm of ST-segment elevation (except in aVR) 7. Exercise-induced bundle branch block that cannot be distinguished from ventricular tachycardia 8. Less serious arrhythmias (abnormal heart rhythms) such as supraventricular tachycardia On-Medication Testing Day: Procedures for the on-medication day will be identical to those used for the off-medication day testing. Each day, following the completion of exercise testing, subjects will be required to remain under lab personnel supervision until HR returns to within 10 beats of resting, and systolic BP returns to within 20 mmHg of resting. HR recovery will be measured continuously following exercise to determine how quickly it returns to baseline. This is a useful measure in determining autonomic function and the progression of PD symptoms.