Reliability and validity of heart rate variability threshold assessment during an incremental shuttle-walk test in middle-aged and older adults

V.Z Dourado,R.L.F Guerra

doi:10.1590/1414-431x20122376

Abstract

Studies on the assessment of heart rate variability threshold (HRVT) during walking are scarce. We determined the reliability and validity of HRVT assessment during the incremental shuttle walk test (ISWT) in healthy subjects. Thirty-one participants aged 57 ± 9 years (17 females) performed 3 ISWTs. During the 1st and 2nd ISWTs, instantaneous heart rate variability was calculated every 30 s and HRVT was measured. Walking velocity at HRVT in these tests (WV-HRVT1 and WV-HRVT2) was registered. During the 3rd ISWT, physiological responses were assessed. The ventilatory equivalents were used to determine ventilatory threshold (VT) and the WV at VT (WV-VT) was recorded. The difference between WV-HRVT1 and WV-HRVT2 was not statistically significant (median and interquartile range = 4.8; 4.8 to 5.4 vs 4.8; 4.2 to 5.4 km/h); the correlation between WV-HRVT1 and WV-HRVT2 was significant (r = 0.84); the intraclass correlation coefficient was high (0.92; 0.82 to 0.96), and the agreement was acceptable (-0.08 km/h; -0.92 to 0.87). The difference between WV-VT and WV-HRVT2 was not statistically significant (4.8; 4.8 to 5.4 vs 4.8; 4.2 to 5.4 km/h) and the agreement was acceptable (0.04 km/h; -1.28 to 1.36). HRVT assessment during walking is a reliable measure and permits the estimation of VT in adults. We suggest the use of the ISWT for the assessment of exercise capacity in middle-aged and older adults.

Highlights

The determination of heart rate variability (HRV) consists of measuring the RR intervals of heart beats and calculating their variation [1]
The incremental shuttle walk test (ISWT) represented high-intensity exercise, as the HR at the end of the test corresponded to 88 ± 10% of the maximum
heart rate variability threshold (HRVT) assessment exhibited excellent reliability based on the following results: the difference between WVHRVT1 and walking velocity (WV)-HRVT2 was not significant; WV-HRVT1 and WV-HRVT2 were strongly correlated (r = 0.84; P, 0.0001); the agreement between WVHRVT1 and WV-HRVT2 was acceptable (Figure 1); the intraclass correlation coefficient (ICC) was high (ICC = 0.92; 95% confidence interval = 0.82-0.96), WV-ventilatory threshold (VT) did not differ significantly from WVHRVT2, and the agreement between WV at VT (WV-VT) and WVHRVT2 was acceptable (Figure 2)

Summary

Introduction

The determination of heart rate variability (HRV) consists of measuring the RR intervals of heart beats and calculating their variation [1]. The increase in intensity results in an increase in heart rate (HR) and reduction in HRV [2]. Vagal modulation of HR disappears almost completely at approximately 50 to 60% oxygen uptake at the end of incremental exercise (peak VO2); thereafter, the increase in HR is mainly mediated by sympathetic activation [2]. The HRV threshold (HRVT) occurs at this intensity and is characterized as the instant at which the HRV no longer undergoes excessive variation due to the increase in exercise intensity [2]. HRVT may be useful as a simple, inexpensive tool for prescribing exercise at an appropriate intensity

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