Use of the peak heart rate reached during six-minute walk test to predict individualized training intensity in patients with cystic fibrosis: validity and reliability

Objective: To determine whether the peak heart rate reached during a six-minute walk test (HR(6peak)) can be used to predict the heart rate determined at the gas exchange threshold (HR(GET)) during a maximal cardiopulmonary exercise test (CPET) in patients with cystic fibrosis (CF). To assess the test-retest reliability of HR(6peak).

Design: Case-control and reliability study.

Setting: CF unit.

Participants: Adults with CF (n=23) and age-matched sedentary subjects (control group, n=17).

Interventions: Not applicable.

Main outcome measures: Six-minute walk test, HR(6peak), CPET, and HR(GET).

Results: HR(GET) and HR(6peak) were not significantly different and were highly correlated in both groups (CF, r=.91, P<.01; controls, r=.81, P<.01). The mean differences (HR(6peak)-HR(GET)) for patients with CF and control subjects were, respectively, -0.9 beats.min(-1) (bpm) and -0.1 bpm, with neither significantly different from 0. The limits of agreements were +/-11 bpm and +/-18 bpm, respectively. HR(6peak) demonstrated excellent relative reliability (intraclass correlation coefficient=.93) and was associated with low variability (standard error of measurement=4.9 bpm) in patients with CF.

Conclusions: HR(6peak) is valid and demonstrates satisfactory test-retest reliability in patients with CF. These results might suggest the use of HR(6peak) as a simple alternative method to individualize exercise prescriptions in this population. Further studies are needed in a larger cohort of patients to confirm these preliminary findings.