Abbreviations MAS maximal aerobic speed V ˙ E ventilatory flow V ˙ O 2 oxygen uptake V ˙ CO 2 carbon dioxide output Vt tidal volume V ˙ E /V ˙ O 2 and V ˙ E /V ˙ CO 2 ventilatory equivalents BF breathing frequency HRV heart rate variability HF high frequency spectral power fHF frequency peak of HF-HRV VT1 first ventilatory threshold detected from ventilatory equivalents Abstract The present study examined whether the ventilatory thresholds during an incremental exhaustive running test could be deter- mined using heart rate variability (HRV) analysis. Beat-to-beat RR interval, V ˙ O 2 ,V ˙ CO 2 and V ˙ E of twelve professional soccer play- ers were collected during an incremental test performed on a track until exhaustion. The “smoothed pseudo Wigner-Ville dis- tribution” (SPWVD) time-frequency analysis method was applied to the RR time series to compute the usual HRV components vs. running speed stages. The ventilatory equivalent method was used to assess the ventilatory thresholds (VT1 and VT2) from re- spiratory components. In addition, ventilatory thresholds were assessed from the instantaneous components of respiratory sinus arrhythmia (RSA) by two different methods: 1) from the high fre- quency peak of HRV (fHF), and 2) from the product of the spectral power contained within the high frequency band (0.15Hz to fmax) by fHF (HF · fHF) giving two thresholds: HFT1 and HFT2. Since the relationship between fHF and running speed was linear for all subjects, the VTs could not be determined from fHF. No sig- nificant differences were found between respective running speeds at VT1 vs. HFT1 (9.83 ± 1.12 vs. 10.08 ± 1.29 km·h –1 , n.s.) nor between the respective running speeds at VT2 vs. HFT2 (12.55 ± 1.31 vs. 12.58 ± 1.33 km · h –1 , n.s.). Linear regression anal- ysis showed a strong correlation between VT1 vs. HFT1 (R 2 = 0.94, p < 0.001) and VT2 vs. HFT2 (R 2 = 0.96, p < 0.001). The Bland-Alt- man plot analysis reveals that the assessment from RSA gives an accurate estimation of the VTs, with HF · fHF providing a reliable index for the ventilatory thresholds detection. This study has shown that VTs could be assessed during an incremental running test performed on a track using a simple beat-to-beat heart rate monitor, which is less expensive and complex than the classical respiratory measurement devices. Key words Cardiorespiratory interactions · breathing pattern · time fre- quency analysis · soccer Physiology & Biochemistry Affiliation 1 Laboratory of Exercise Physiology (LEPH, E.A. 3872, genopole), Department of Sport and Exercise Science, University of Evry, Evry, France 2 French National Institute for Research in Computer Science and Control (INRIA), Le Chesnay, France Correspondence Franc ¸ ois Cottin, Ph.D. · Department of Sport and Exercise Science · University of Evry · Boulevard F. Mitterrand · 91025 Evry Cedex · France · Phone: + 33169 64 48 81 · Fax: + 33169 64 48 95 · E-mail: fcottin@univ-evry.fr Accepted after revision: May 15, 2006 Bibliography Int J Sports Med © Georg Thieme Verlag KG · Stuttgart · New York · DOI 10.1055/s-2006-924355 · Published online 2006 · ISSN 0172-4622 F. Cottin 1 C. Médigue 1, 2 P. Lopes 1 P.-M. Leprêtre 1 R. Heubert 1 V. Billat 1 Ventilatory Thresholds Assessment from Heart Rate Variability during an Incremental Exhaustive Running Test