Participants:
The participants were recruited in Spring 2009, 2010, and 2011 through regional newspaper advertisements and solicitations in the Movement Disorders Clinic at the University of Iowa and the Veterans Affairs Medical Center of Iowa City. We phone screened respondents and evaluated eligible candidates in-person using clinical examination, MMSE, 12-lead ECG, blood count and biochemistry, followed by graded exercise test using cycle ergometry within one week of starting the intervention. At each visit, we obtained body weight and height, heart rate and blood pressure after 5 minutes of supine rest \[Goldberg et al. 1988\] and after 3 minutes of standing. Throughout the study, the medications of participants continued to be managed by their treating neurologists.
Inclusion criteria: Idiopathic PD; Hoehn and Yahr Scale I-III; men or women aged 50-80; stable dopaminergic treatment regimen for at least 4 weeks prior to baseline not requiring adjustment.
Exclusion criteria: Current participation in an aerobic exercise program; Mini Mental Status Exam score \<24; confounding medical, orthopedic or psychiatric disorders; cardiac abnormalities during cycle ergometry.
Design:
Initial design was a 2x2 randomized trial of different training methods (continuous vs. interval) and settings (individual vs. group). Sample size was estimated using 80% power to detect an effect size of 0.66 SD in VO2max (estimated improvement=10% /estimated SD of change=15%) within each arm at alpha=0.05 and an attrition rate of 25%.
During the first two years, the participants were randomized in blocks of four to continuous or interval training. Logistical factors (e.g., rural residence) precluded randomization to group setting, leading to convenience-based assignments in the first year, and dropping of the group setting afterwards. In the third year, all participants were assigned to the continuous arm after preliminary analyses of prior data raised safety concerns about interval training.
Intervention:
The maximal heart rate (HRmax) in the exercise prescription was based on age \[Goldberg, Elliot, and Kuehl1988\] and reduced by 20% in participants who used beta-blockers \[Wonisch et al. 2003\]. The duration of exercise sessions (3x/week) was advanced from 15 to 45 minutes over the first 6 weeks. The goal for continuous training was to remain within 70-80% of HRmax throughout the session. Interval trainees alternated every 3 minutes between slower (60-70% of HRmax) and faster (80-90% of HRmax) walking\[Wisloff et al. 2007\]. We emphasized that these parameters were for guidance only and that the participants should give their best effort without feeling uncomfortable or unsafe.
Participants were asked to wear electronic heart rate and walking speed monitors (Polar RS400, Kempele, Finland) and fill out diaries for each session. A trainer facilitated group training at a track and collected monitor data and exercise diaries. Trainers conducted home visits for the individual arm participants to choose walking routes (a primary outdoor route and an alternative indoor route) and orient the participant about safe exercise procedures, followed by biweekly home visits to monitor safety and compliance.
Efficacy Measures:
The participants were tested while on their usual antiparkinsonian regimen, always with adequate symptom control to allow comfortable participation in the protocol, at baseline and at the end of the intervention by evaluators blinded to the treatment arm, but not to pre-post training status.
Aerobic fitness: Oxygen uptake (VO2) was measured from expired air samples on a breath-by-breath basis during cycle ergometry. We verified maximal effort when 2 of 3 criteria were met \[Balady et al. 2010\]: 1) a plateau in VO2 between two or more workloads, 2) respiratory exchange ratio ≥1.10, and 3) HR \> 85% of the age predicted HRmax.
Cognition: Due to sensitivity of the Eriksen's flanker task performance to changes in aerobic fitness status \[Colcombe et al. 2004;Kluding et al. 2011\], we chose change in Percent Increase Score (PIS) on flanker task as the primary cognitive outcome measure. Participants were asked to identify the orientation of a central arrow cue ('\<' or '\>'), which was flanked on both sides by two arrow cues that either pointed in the same direction (congruent: \<\<\<\<\<) or a different direction (incongruent: \>\>\<\>\>). Using reaction times (RT) during congruent and incongruent trials, the PIS was calculated as =((RT\_incongruent - RT\_congruent) / RT\_congruent) \* 100.\[Colcombe, Kramer, Erickson, Scalf, McAuley, Cohen, Webb, Jerome, Marquez, and Elavsky2004\] The Stroop test was used as another measure of inhibition.
We assessed set shifting using Wisconsin Card Sorting Test and Trail-Making Test (B-A),\[Uc, Rizzo, Johnson, Dastrup, Anderson, and Dawson2009\] visual perception using Judgment of Line Orientation and Complex Figure Test (CFT)-Copy, verbal memory using Rey Auditory Verbal Learning Test, visual memory using CFT-Recall, language using Controlled Oral Word Association Test,\[Uc, Rizzo, Johnson, Dastrup, Anderson, and Dawson2009\] and general cognition using Montreal Cognitive Assessment.\[Chou et al. 2010\] Parkinsonism: Unified Parkinson's Disease Rating Scale and timed motor tests (7m Walk and finger tapping),\[Defer et al. 1999\] Functional Reach test for balance,\[Uc, Rizzo, Johnson, Dastrup, Anderson, and Dawson2009\] total daily levodopa equivalents,\[Tomlinson et al. 2010\] and a patient diary \[Hauser et al. 2004\].
Quality of life: Fatigue Severity Scale,\[Friedman et al. 2011\] Geriatric Depression Scale,\[Uc, Rizzo, Johnson, Dastrup, Anderson, and Dawson2009\] PD Quality of Life Scale (PDQUALIF) \[Welsh et al. 2003\].
Statistical analysis Two-sample t-tests, Wilcoxon Rank-Sum, or Fisher's Exact tests were used to compare baseline features and exercise characteristics and outcomes between different treatment arms, and between the completers and dropouts, and to compare baseline cognitive performance of our PD participants with controls from our driving studies.\[Uc, Rizzo, Johnson, Dastrup, Anderson, and Dawson2009\] Regression methods were used to adjust these comparisons for age, education, and gender.
As all treatment arms were designed to deliver a similar average aerobic intensity, we planned to pool a priori all completers throughout the study to analyze the effects of aerobic exercise with higher statistical power. We used Wilcoxon Signed Ranks tests or paired t-tests to compare final vs. baseline outcomes. When a significant change in outcomes was observed, we used regression models to assess and adjust for the effect of different settings and training methods, calendar year, and change in levodopa equivalent. We also used Pearson correlations and regression models to quantify associations of changes in outcomes with changes in aerobic fitness.
The analyses of magnetic resonance imaging studies and other biomarkers is continuing and will be published in the future.
Reference List
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