Cardiorespiratory responses during the 6-minute walk and ramp cycle ergometer tests and their relationship to physical activity in stroke

BACKGROUND AND OBJECTIVES: The 6-minute walk test (6MWT) is used to measure exercise capacity after stroke. We sought to compare cardiorespiratory responses during the 6MWT with responses to a ramp cycle ergometer test (CET) in community-dwelling individuals with stroke. A secondary objective was to determine the relationship between cardiorespiratory responses during each test and daily physical activity.

METHODS: Participants completed 3 evaluation sessions. The CET and 6MWT were conducted in 2 separate sessions at least 72 hours apart. Participants wore a portable gas analysis unit (Cosmed K4b2), which also measured heart rate (HR) during the 6MWT. A uniaxial accelerometer (activPAL) was used to measure time spent upright (standing and stepping) over 5 days as an estimate of daily physical activity.

RESULTS: Complete CET and 6MWT data were obtained for 16 participants (14 men), a mean ± standard deviation of 2.0 ± 1.1 years after stroke and 71.1 ± 9.7 years of age. Compared with the 6MWT, the CET elicited a higher VO(2peak) (P = .032), VCO(2peak) (P = .005), respiratory exchange ratio (P = .015), and self-reported perceived breathing (P < .0001) and leg heaviness (P < .0001) at test completion and a lower HR(peak) (P = .029). Except for the first minute, VO(2) during the 6MWT was, on average, 80% to 85% of VO(2peak) from the CET. Among 15 participants, average time spent upright per day was not significantly associated with 6MWT distance (r = 0.447, P = .096) or VO(2peak) from the CET (r = 0.388, P = .153).

CONCLUSIONS: Exercise intensity achieved during the 6MWT appeared sufficiently high for aerobic training, assuming CET VO(2peak) accurately reflects aerobic capacity. The 6MWT may be useful for prescribing aerobic exercise poststroke.