COMPARISON BETWEEN VENTILATORY THRESHOLD AND HEART RATE VARIABILITY INDEXES IN NONATHLETES Neumamm, L.B.A., Bartels, R., , Leão-Nunes, M.V. . , Jandre, F.C. , Giannella-Neto, A. Federal University of Rio de Janeiro (UFRJ) Introduction: Heart rate variability (HRV) is a non-invasive tool for cardiac autonomic modulation assessment. Classical HRV analyses are widely used at rest conditions. Alternative methods for assessing autonomic function in non-stationary periods, such as during exercise, allow the identification of the ventilatory threshold (VT) using HRV. However, few studies addressed this issue in untrained subjects. The aim of this study was to assess HRV methods for VT determination in nonathletes. Methods: Fifteen healthy male, nonathlete subjects underwent a maximal progressive exercise on a cycle ergometer (CG-08, Inbrasport, Brazil). The protocol consisted in 3 min of rest followed by a 3-min warmup at 5 W. Then the work rate was increased by 25 W per minute, until volitional fatigue. Ventilatory variables (VO2 and VCO2) were obtained breath-by-breath using a gas analyzer (Innocor, Denmark). RR intervals were continuously recorded with an electrocardiograph (Ecafix, Brazil). The v-slope method (Beaver et al., 1986), was used as the gold standard method for VT detection and compared to three indexes derived from HRV analysis: visual stabilization of the RMSSD (HRVT1) (Karapetian et al., 2008); reduction of SD1 below 3 ms (HRVT2) (Lima and Kiss, 1999) and from frequency domain (HRVT3) (Cottin et al., 2004). Bland-Altman method and Wilcoxon test were employed to assess differences between VT, HRVT1, HRVT2 and HRVT3. Significance level was set at p<0.05. Results: No difference was found between VT (226.0±60.5 (s); 81.6±24.0 (W);128.1±22.0 (bpm)) and HRVT1 (174.8±49.5 (s); 70.0±35.6 (W); 108.8±15.9 (bpm)) or HRVT2 (246.9±141.2 (s); 98.3±64.4 (W); 129.7±18.5 (bpm)). However, significant difference was found between VT and HRVT3 (320.2±123.6 (s); 116.6±57.9 (W); 145.1±17.6 (bpm) p<0.05). HRVT1 tended to underestimate VT for higher VT values (p<0.05). Discussion: The bias found between VT and HRVT3 may be due to distinct physical training level of the participants in both studies, which indicates that this method can be accurate only for athletes. Besides no difference was found between HRVT1 and VT, it showed a trend to underestimate higher values of VT, suggesting that this method is acceptable for nonathletes, but may incorrectly detect VT in athletes. Therefore, due to the lack of difference from VT and trend of HRVT2, it seemed to be the best method to estimate VT for all training levels. References Beaver WL, Wasserman K, Whipp BJ (1986). J Appl Physiol, 60(6), 2020-2027 Karapetian GK, Engels HJ, Gretebeck RJ (2008). Int J Sports Med, 29, 652-657 Lima JRP, Kiss MAP (1999). Rev Bras Ativ Fis Saúde, 9, 29-38 Cottin F, Médigue C, Leprêtre PM, Papelier Y, Koralsztein JP, Billat V (2004). Med Sci Sports Exerc, 36(4), 594-600 Contact leoneumamm@peb.ufrj.br View publication stats View publication stats