Cardiorespiratory Responses During the 6-Minute Walk and Ramp Cycle Ergometer Tests and Their Relationship to Physical Activity in Stroke
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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 VO2peak ( P = .032), VCO2peak ( 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 HRpeak ( P = .029). Except for the first minute, VO2 during the 6MWT was, on average, 80% to 85% of VO2peak 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 VO2peak from the CET ( r = 0.388, P = .153). Conclusions. Exercise intensity achieved during the 6MWT appeared sufficiently high for aerobic training, assuming CET VO2peak accurately reflects aerobic capacity. The 6MWT may be useful for prescribing aerobic exercise poststroke.
