Cardiopulmonary Responses During Clinical and Laboratory Gait Assessments in People With Chronic Stroke.

Background: The 6-Minute Walk Test (6MWT) is a common clinical assessment used to evaluate locomotor function in patients after stroke. Previous work suggests the 6MWT can estimate peak metabolic capacity (VO2peak) without cardiorespiratory assessments during graded exercise tests (GXTs), which may assist with exercise prescription. However, selected research also indicated increased heart rates (HRs) during 6MWTs beyond levels considered safe without GXTs. Objective: The goal of this study was to examine cardiorespiratory responses during 6MWTs and GXTs in individuals with chronic stroke and their associations with demographic or clinical characteristics. Design: The study used a cross-sectional observational design. Methods: Cardiorespiratory responses were assessed during 6MWTs at self-selected velocity (SSV) and fastest velocity (FV), and during GXTs. Secondary assessments included the lower extremity Fugl-Meyer Assessment, Functional Gait Assessment, gait speeds, and daily stepping activity. Correlation and regression analyses were used to evaluate associations between locomotor performance, cardiorespiratory responses, and clinical and demographic characteristics. Results: Average HRs during 6MWT-FV were 72% to 76% of the age-predicted maximum (HRmax), with 20% of participants exceeding 85% predicted HRmax. When normalized to HRs during GXTs, HRs during 6MWT-FV were 86% to 88% of observed HRmax. Primary predictors of increased HRs during 6MWTs were resting HR, body mass index, and daily stepping. Distance during 6MWT-FV was a significant predictor of VO2peak in combination with other variables. Electrocardiographic abnormalities were observed in >80% of participants at rest and 31% demonstrated distinct abnormalities during GXTs, which were not related to 6MWT or GXT performance. Limitations: In addition to sample size, a primary limitation involved the ability to accurately predict or measure HRmax in patients with motor dysfunction after stroke. Conclusions: Cardiac responses were higher than anticipated during 6MWTs and often exceeded recommended HR thresholds. Clinicians should closely monitor cardiorespiratory responses during 6MWTs.