Reliability of the 6-minute walk test and cardiac autonomic markers in active and sedentary older women

Abstract

The aim of this study was to examine the reliability of the 6-minute walk test (6MWT) and post-exercise cardiac autonomic markers in physically active and sedentary older women. Eighteen physically active older women (64.2±3.1 years; 63.0±2.7 kg; 1.52±0.06 m; 26.9±2.7 kg.m-2) who performed Tai Chi Chuan for at least 6 months, and 18 sedentary older women (64.0±3.7 years; 63.8±8.9 kg; 1.49±0.05 m; 28.4±3.5 kg.m-2) were submitted to 6MWT in two separate occasions. Immediately after 6MWT, heart rate recovery at one (HRR1’) and two minutes (HRR2’), as well as the heart rate variability (HRV) were recoded. Reliability was verified by intraclass correlation coefficient (ICC) with 95% confidence interval, Bland-Altman plots were used as a measure of agreement, and coefficient of variation (CV) was calculated. High reliability (ICC=0.86) was found for performance in 6MWT (528.8 ± 71.4 m and 473.2 ± 62.4 m; CV=7.9 and VC=8.5%) in both groups. Likewise, high reliability (ICC?0.84 and ICC?0.80) was found for HRR 1’ (29.0±11.0 bpm and 17.0±8.0 bpm; VC=30.1% and VC =40.2%) and HRR 2’ (36.0±10.0 bpm and 24.0±9.0 bpm; VC =23.7% and VC =22.8%) in both groups. Regarding HRV, moderate reliability was found in the active group (CCI?0.57; VC =35-47%), while moderate-high reliability was found in the sedentary group (CCI=0.65-0.76; VC=34-69%). Agreement was found for all variables analyzed. In conclusion, post-exercise 6MWT, HRR, and HRV are reliable tools to assess functional capacity and cardiac autonomic control in physically active and sedentary older women.