Reliability of heart rate variability in futsal players

The main aim the present study was evaluated the reliability of the heart rate variability (HRV) indices in futsal players. Additionally the study verifi ed the reliability of different approaches for 5 min interval selection of recording. Eighteen under-20 futsal players underwent 15 min of pre-training RR interval recordings in two different day. Time and frequency domain and Poincaré Plot indices were tested. The indices were calculated using: 1) fi nal 5 min of recording; 2) 5 min of lower variance of recording, by a mathematical algorithm; 3) 5 min segment of lower variance, by an experienced operator. The HRV indices presented a wide range reliability [e.g. RRmean (ICC=0.96, SEM=3.4ms, CV=2.6%), lnRMSSD (ICC=0.88, SEM=5.9ms, CV=4.3%), lnHF (ICC=0.89, SEM=7.5ms, CV=5.9%), LFnu (ICC=0.84, SEM=13ms, CV=9.4%), LF (ICC=0.47, SEM=65.2ms,CV=38.5%) and LF/HF (ICC=0.63, SEM=83.7ms, CV=54.5%)]. The fi nal 5 min of recording was the most reliable. The results suggest that most of HRV indices presented acceptable reliability, however the RRmean, lnRMSSD, lnHF and LFnu were the most reliable.