Assessing shortened field-based heart-rate-variability-data acquisition in team-sport athletes

Purpose: To compare the LnRMSSD and the LnRMSSD: RR values obtained during a 5-min stabilization period with the subsequent 5-min criterion period and to determine the time course for LnRMSSD and LnRMSSD: RR stabilization at 1-min analysis in elite team-sport athletes. Participants: 35 elite futsal players (23.9 ± 4.5 y, 174.2 ± 4.0 cm, 74.0 ± 7.5 kg, 1576.2 ± 396.3 m in the Yo-Yo test level 1). Methods: The RR-interval recordings were obtained using a portable heart-rate monitor continuously for 10 min in the seated position. The 2 dependent variables analyzed were LnRMSSD and LnRMSSD: RR. To calculate the magnitude of the differences between time periods, effect-size (ES) analysis was conducted. To assess the levels of agreement, intraclass correlation coefficients (ICC) and Bland-Altman plots were used. Results: The LnRMSSD and LnRMSSD: RR values obtained during the stabilization period (0-5 min) presented very large to nearly perfect ICCs with the values obtained during the criterion period (5-10 min), with trivial ESs. In the ultra-short-term analysis (ie, 1-min segments) the data showed slightly less accurate results, but only trivial to small differences with very large to nearly perfect ICCs were found. Conclusion: LnRMSSD and LnRMSSD: RR can be recorded in 5 min without traditional stabilization periods under resting conditions in team-sport athletes. The ultra-short-term analysis (1 min) also revealed acceptable levels of agreement with the criterion.