Can Heart Rate Variability Segment Length During Orthostatic Test Be Reduced To 2 Min?

Abstract

PURPOSE: Heart rate variability (HRV) is an important marker for stress and has been shown to improve monitoring of training/recovery processes in athletes. The generally applied long recording time of 2 times 5 min for the orthostatic challenge test limits the widespread use of daily HRV monitoring. We aimed to test whether a shorter segment length (SL) can be used. METHODS: Twelve elite cross-country skiers were included in the study (age: 25±4 years). HRV was recorded during 5 min in supine position (SUP) and 5 min standing after orthostatic challenge (SOC), using Polar RS800CX training computers. Ten measurements from each athlete were analyzed with time- [mean of the R-R intervals (MeanRR), standard deviation of all R-R intervals (SDNN), the square root of the mean squared differences of successive R-R intervals (RMSSD)] and frequency-domain [low-frequency (LF) power, high-frequency (HF) power and LF/HF power ratio] analysis methods using Kubios HRV. Pearson correlation coefficients were calculated between the 4 min SLs and 2 min SLs of each athlete in order to determine agreement while paired t-tests were calculated to detect systematic errors. RESULTS: Agreement was excellent (R>0.9, p<0.05) for all time-domain parameters in SUP and SOC (except one athlete showed a moderate correlation of R=0.345 for SDNN in SOC). For HF power, all athletes showed significant correlations (R>0.630) in SUP and 75% of all athletes also in SOC. In SUP, 58% of all athletes had significant correlations between the two SL and 42% for LF while in SOC, 50% had significant correlations for LF/HF power ratio and 25% for LF power. No systematic errors were present for any parameters measured in SUP whereas the 2 min SLs showed significantly higher MeanRR, RMSSD and lower LF power (p<0.05) due to the greater percentage of the non-stationary signal immediately after standing up. CONCLUSIONS: Measuring HRV with a SL of 2 min is highly related to a SL of 4 min in time-domain HRV parameters and HF power in both SUP and SOC. Using 2 min SLs suffices for monitoring training/recovery processes with the most commonly used HRV parameters and improves the feasibility in daily use.