Abstract
We evaluated age- and sex-dependent differences in heart rate variability (HRV) during
the 6-min walk test (6MWT) in healthy adults. We also evaluated the intensity of the
6MWT based on HRV. 78 participants aged 40–49, 50–59, 60–69, and ≥70 years (42 females;
36 men) performed the 6MWT. Heart rate and HRV were monitored 1 min at rest and during
the last 2-min of the test. The root mean square (RMSSD), instantaneous beat-to-beat
variability (SD1), and long-term standard deviation (SD2) of RR intervals were calculated.
The SD1 <3 ms at the end of the 6MWT was defined as high-intensity exercise. Despite
the significantly higher peak values of heart rate observed for women, we did not
find sex- and age-related differences in HRV during the 6MWT. The ROC curve identified
percentage of maximum heart rate >67% as the best cut-point for prediction of high-intensity
exercise with 94% of sensitivity and 65% of specificity (area under the curve=0.804).
We may conclude that autonomic modulation of heart rate during exercise was not dependent
of age and sex. The HRV assessment during walking enables a valid estimation of exercise
intensity in adults. We may therefore suggest the use of 6MWT for assessing exercise
capacity and for prescribing exercises in adults aged 40 yrs and older.
Key words
heart rate variability - walking - exercise
