Abstract
Previous studies have demonstrated the high reproducibility of heart rate variability (HRV) measures in adults while little information exists concerning HRV reproducibility in children. Subsequently, the aim of the current study was to examine the moderate-term reproducibility of heart rate and frequency domain measures of HRV during rest and light to moderate exercise in children. Ten healthy children (6 males, 4 females) aged between 7 and 12 years of age volunteered for this study with HRV recordings obtained during supine rest and three treadmill walking exercise work rates (< or =60% maximum heart rate), initially and then 8 weeks later. Differences (P < 0.05) between variables were examined using paired t-tests or Wilcoxon signed rank tests while reliability and reproducibility were examined by intraclass correlation coefficients (ICC), coefficients of variation (CV), and mean bias ratio and ratio limits of agreement (LOA). Heart rate and all measures of HRV at rest and exercise were unchanged after 8 weeks. Significant ICC were documented primarily during rest (0.72-0.85) while weaker relationships (-0.02-0.87) were evident during exercise. A large range of CV was identified during rest (6-33%) and exercise (3-128%) while the ratio LOA were variable and substantial (1.04-2.73). Despite similar HRV over an 8-week period, variable ICC and sizable CV and ratio LOA indicate moderate to poor reproducibility of HRV in children, particularly during light to moderate exercise. Studies examining HRV in children should include age- or maturation stage-matched control participants to address the age-related change in HRV and inadequate HRV reliability.
Highlights
Since the early 1980’s, an extensive number of studies has examined heart rate (HR) function and fluctuations over time
Several heart rate variability (HRV) frequency components have been identified via power spectral analysis to characterize the neural control of HR: very low frequency oscillations (0.15 Hz reflecting parasympathetic modulations, including respiratory influences [2,3]
Similar to the coefficients of variation (CV), the measurement bias ratio and 95% ratio limits of agreement (LOA) for HR and HRV measures were large and variable, for HRV measures expressed in ms2/Hz (Table 5)
Summary
Since the early 1980’s, an extensive number of studies has examined heart rate (HR) function and fluctuations over time. The normal HR fluctuations or heart rate variability (HRV) in humans have been demonstrated to reflect the autonomic control of HR [2,3]. Several HRV frequency components have been identified via power spectral analysis to characterize the neural control of HR: very low frequency oscillations (0.15 Hz reflecting parasympathetic modulations, including respiratory influences [2,3]. As a non-invasive measure of autonomic control of HR, HRV has been incorporated into screening protocols for the prediction of mortality following myocardial infarction [5]. Standard guidelines for the measurement of HRV have been developed; the reproducibility of HRV has been highlighted as an important area for further examination [7,8]
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