2.1. Measurement Protocol

Data collected across two clinical studies were used for validation and testing of the STS detection algorithm.

Sixty-six subjects were recruited in the greater Boston area, MA, USA (N=33 (17 Males) ages 65–85, N=33 (16 Males) ages 23–39; Inclusion criteria: no significant health issues, BMI between 18.5 and 30 kgm2 or absolute weight <125 kg; Exclusion criteria: self-reported medical condition, recreational drug use, or medication use preventing study task completion, Vulnerable Elders Survey [32] total score > 3 including 0 in all activities of daily living (ADLs)) completed two in-lab visits spaced 7–14 days apart. One male subject in the older adults group was excluded as it was determined that he did not meet the inclusion criteria after study completion. Each subject performed various clinical assessments of mobility and health, including a 5x STS task using the same chair for all participants. Following the 5x STS task, subjects would also stand up normally in preparation for the following assessment, and this 6th STS transfer was included in the processing and analysis. During the 5x STS task, subjects sat on a rigid chair and were instructed to fold their arms across their chest and perform five consecutive STS as fast as they can. However, the 6th STS was performed independently by the subject with no instruction other than where to go for the next task. During the 7–14 days between lab visits, subjects wore an accelerometer on their lower back (lumbar region) and a wrist sensor on their non-dominant wrist while going about their daily lives (all subjects were community dwelling). Only the lumbar sensor data and STS assessment are presented in this work. The final protocol and informed consent documentation were reviewed and approved by Advarra Institutional Review Board (study ID: Pro00029419). All participants gave written consent prior to enrollment.

Thirty-five subjects were recruited in the greater Boston area, MA, USA (N=35 (23 Males), ages 46–79 [68.31±8.03 years], Hoehn and Yahr stage I/II/III: 2/26/7; Movement Disorder Society-Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) III: 52.86±16.03; Inclusion criteria: clinical diagnosis of PD, on L-dopa therapy, able to recognize wearing-off periods, with Hoehn and Yahr stage ≤3; Exclusion criteria: presence of other comorbidities (e.g., head injuries, psychiatric illness, cardiac disorders), recent treatment with investigational drugs, pregnant women, allergy to silicone or adhesives). PwPD participated in the study involving two in-clinic visits. Participants were randomly assigned to be in ON state (i.e., well controlled motor symptoms, approximately 1 h after medication intake, confirmed by patient self-report and clinician report) in one visit and OFF state (i.e., poorly controlled motor symptoms, at least 3 h after medication intake, confirmed by patient self-report and clinician report) in the other visit. These motor states were used to assess symptom severity and motor performance during the two extremes of a motor fluctuation cycle. During each visit, subjects performed a battery of motor (including STS transfers) and non-motor tasks associated with clinical assessments, as well as activities of daily living (e.g., putting on a coat, drinking water from a cup, folding laundry). During the course of each visit, subjects performed a mix of scripted (5x STS task) and natural STS transfers using the same chair for all participants. The natural STS transfers consisted primarily of several isolated single transfers performed before the 5x STS task and a few transfers after the 5x STS task. The motivation behind including data from PwPD in this study was to evaluate the performance of STS detection methods in an impaired population. The PD study had approval from Tufts Medical Center and Tufts University Health Sciences Institutional Review Board (study ID: 12371). All participants provided written informed consent prior to enrollment. A complete description of the participant characteristics can be found elsewhere [33].