Outcome measures

Safety and feasibility benchmarks for the primary study outcomes were set a priori using the literature.

Safety. Safety was assessed through the recording of adverse events, their severity, and their relationship to the study. The severity of each adverse event was defined as (A) mild if the event resulted in no limitation of usual activities; (B) moderate if the event resulted in some limitations of usual activities; and (C) severe if the event resulted in the inability to carry out usual activities. The relationship to the study was defined as (I) not related if there was no possible relationship between the event and the relationship; (II) unlikely if the relationship between the event and the study was not reasonably related, but a causal relationship could not be ruled out; (III) possible if a causal relationship between the event and the study was uncertain; (IV) probable if there was a high degree of certainty for a causal relationship between the event and the study; and (V) definite if the causal relationship between the event and study was certain. For the intervention to be deemed safe, no severe adverse events could be attributed to the intervention (i.e. no severe events could have a possible, probable, or definite relationship to the tele-yoga intervention) and no moderate events could have a definite relationship to the tele-yoga intervention.

Recruitment rate. The recruitment rate was defined as the number of individuals who were enrolled in the study compared to the individuals who initially contacted the study team. It was reported as a percentage along with the absolute values. Because the study was a safety and feasibility trial with a sample of convenience, an a priori benchmark for an appropriate recruitment rate was not defined.

Retention rate. The retention rate was defined as the number of participants who completed the study compared to the number of individuals who were enrolled. It was reported as a percentage along with the absolute values. For a participant to be counted as completing the study they needed to engage in the tele-yoga intervention period and complete all of the four assessment sessions. Retention was deemed acceptable if 85% or more of the participants completed the study based on standards established in the literature. ⁶⁸

Adherence. Adherence was divided into two categories: (i) assessment adherence and (ii) intervention adherence. Assessment adherence was defined as the number of assessment sessions completed compared to the number of assessment sessions scheduled. Intervention adherence was defined as the number of tele-yoga sessions completed compared to the number of tele-yoga sessions scheduled. Both were reported as a percentage along with the absolute values. Mean tele-yoga session attendance and percent of sessions canceled or rescheduled by all participants were also reported. Adherence was deemed acceptable if 85% or more of assessment sessions ⁶⁸ and 80% or more of the yoga sessions^23,69,70 were attended. These benchmarks are based on standards established in the literature ⁶⁸ and the range of intervention adherence reported in previous intervention studies for similar interventions (physical activity and yoga) and populations (chronic health conditions and PD).^23,69,70

Technological challenges. Technological challenges were documented, and their severity was measured by time disrupted as follows (A) mild (time disrupted 1–3 minutes), (B) moderate (time disrupted 3–10 minutes), and (C) severe (time disrupted >10 minutes). For the intervention to be deemed feasible, an a priori threshold of no more than 20% of the intended yoga dose could be missed due to technological challenges. This benchmark was determined because it aligns with the target intervention adherence of 80%^23,69,70 as noted above but it is important to note that no previous studies have reported technological challenges in this way.

Usability. Usability was assessed through the Systems Usability Scale (SUS). ⁷¹ A score higher than 68 indicated adequate usability as established by the literature. ⁷¹ The participants were instructed that questions pertaining to “this system” was referring to engaging in the tele-yoga sessions over videoconferencing using Zoom.

Enjoyment. Enjoyment (secondary outcome) of the tele-yoga intervention and each component of the intervention (breathing exercises, postures, and relaxation exercises) was assessed using a 11-point scale (0–10; where 0 indicates no enjoyment and 10 great enjoyment) during the T2 assessment session. To be deemed enjoyable, a threshold of mean enjoyment scores equal to or greater than 7 was determined a priori.

Relevant clinical outcomes. Relevant clinical outcomes (secondary outcomes) were also assessed to compute effect sizes to help power future RCTs. To do this, relevant clinical outcome measures were administered at all assessment timepoints (T0, T1, T2, and T3). These outcomes included the PAS, ⁷² the Parkinson’s Disease Questionnaire-39, ⁷³ the Beck Depression Inventory-II (BDI-II), ⁷⁴ the PD Sleep Scale-2 (PDSS-2), ⁷⁵ the Unified Parkinson’s disease Rating Scale (MDS-UPDRS) ⁷⁶ (excluding rigidity and postural stability), and the five times sit to stand (FTSTS) as a measure of physical function. ⁷⁷ All of these measures were standardized self-report questionnaires with the exception of the motor examination subdomain of the MDS-UPDRS and the FTSTS. All measures were administered during the live videoconferencing sessions with a study team member.

Anxiety. The 12-item self-report PAS was used to assess anxiety symptoms. It takes approximately 2-minutes to complete and is a 12-item scale with three sub-scales assessing persistent anxiety, episodic anxiety, and avoidance behavior. The questions are on a scale from "not or never" (0) to "severe or almost always" (4) with a potential score range of 0–48. Higher scores indicate greater symptoms of anxiety. This scale is valid and reliable for persons with PD.^66,72

Depression. The 21-item self-report BDI-II was used to measure symptoms of depression. For each item, the participants choose one out of four statements of increasing severity regarding a specific symptom of depression. It takes about 5–10 minutes to complete. Potential scores range from 0–63 with higher scores indicating greater severity of depressive symptoms. The BDI-II has good psychometrics properties ⁷⁴ and has been shown to be acceptable for assessing depressive symptoms in PD. ⁷⁸

Quality of life. The 39-item self-report questionnaire was used to assess the quality of life. It has 8 domains (e.g. mobility, emotional well-being, stigma, social support, cognition, communication, and bodily discomfort) and contains questions asking how often certain difficulties/problems have occurred within the last month with answers ranging from "never" to "always." Each dimension’s total score ranges from 0 (never have difficulty) to 100 (always have difficulty). With higher scores indicating poorer quality of life. The PDQ-39 is valid and reliable for persons with PD. ⁷³

Sleep. The 15-item self-report PDSS-2 measure was used to assess sleep dysfunction. It contains questions about the participant's sleep experience during the past week with answers on a Likert-scale of 0-"very often" to 4-"never." Scores can range from 0 to 60 with higher scores indicating greater sleep impairment. It is a valid and reliable tool for persons with PD. ⁷⁵

Motor and non-motor symptoms of PD. A modified version of the MDS-UPDRS (excluding examination of rigidity and postural instability) was used to assess motor and non-motor symptoms of PD. It contains four sections 1. Mentation, Behavior, and Mood; 2. Activities of Daily Living; 3. Motor Examination; and 4. Complications of Therapy. Higher scores indicate greater symptoms/disability. The modified version excludes the hands-on components such that the measure can be administered over videoconferencing. This modified version of the MDS-UPDRS excluding rigidity and postural instability completed virtually has demonstrated high levels of agreement with the complete in-person MDS-UPDRS. ⁷⁹ Additionally, inter-rater reliability of video-based assessment showed moderate to high agreement between raters. ⁸⁰

Physical Function. The FTSTS was administered to assess physical function. It was administered using a chair in the participants’ homes. Participants were encouraged to have another adult present during this portion of the data collection in case there was any loss of balance. The time, in seconds, that it took participants to raise from the chair 5 times was recorded. Longer times indicate poorer physical function. The FTSTS has shown adequate psychometric properties for persons with PD. ⁷⁷