Abstract
This study determined the reliability of post-exercise heart rate recovery (HRR) and vagal-related HR variability (HRV) after repeated-sprints (RSs), and contrasted it with the smallest worthwhile change (SWC) of these indices. Fourteen healthy male participants performed on four occasions, separated by 7 days, five 30-m sprints interspersed by 25-s of recovery. Post-exercise HR during 10 min of seated rest was measured. HRR during the first 60-s of recovery was computed (HRR60s). HRV indices were calculated in time and frequency domains during the last 5-min of the recovery. Absolute and relative reliability were assessed by typical error of measurement expressed as coefficient of variation (CV) and intraclass correlation coefficients (ICCs), respectively. Sensitivity was assessed comparing SWC to the typical error of measurement. CV ranged from 3.6% to 13.5% and from 6.3% to 109.2% for the HRR and HRV indices, respectively. ICCs were from 0.78 to 0.96 and from 0.76 to 0.92, respectively. HRR and HRV indices showed large discrepancies reliability. HRR60s and the square root of the mean sum of the squared differences between R-R intervals presented the highest levels of both absolute and relative reliability. However, SWC was lower than the typical error of measurement, indicating insufficient sensitivity to confidently detect small, but meaningful, changes in HRR and HRV indices.
Highlights
Repeated-sprints exercise (RSE) is characterized by short-duration sprints at supramaximal intensities interspersed with brief recoveries [1,2]
In nine healthy participants who performed 18 maximal all-out 15-m sprints interspersed with 17 s of passive recovery, 3 times a week for 8 weeks, postexercise heart rate recovery (HRR) and heart rate (HR) variability (HRV) indices improved when compared to a control group that performed normal, daily physical activities [6]
Despite we previously showed that changes in HRR and HRV indices could be detected after an RS training [6], and the smallest worthwhile change (SWC) could be interpreted as real within acceptable limits of probability [22,23], to assess the usefulness of parasympathetic reactivation measurements after RSE it is important to compare the SWC to the reliability data for the considered indices
Summary
Repeated-sprints exercise (RSE) is characterized by short-duration sprints at supramaximal intensities interspersed with brief recoveries [1,2]. Despite the time course of postexercise heart rate (HR) recovery (HRR) and variability (HRV) is acutely impaired after RSE [3,4,5], our group recently observed that 8-weeks of RS training might have a significant and positive effect on the short-term post exercise parasympathetic reactivation [6]. In nine healthy participants who performed 18 maximal all-out 15-m sprints interspersed with 17 s of passive recovery, 3 times a week for 8 weeks, postexercise HRR and HRV indices improved when compared to a control group that performed normal, daily physical activities [6].
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