We evaluated whether changes in heart rate (HR) and/or heart rate variability (HRV) would reflect anaerobic threshold (AT) using a discontinuous, incremental, cycle test. To accomplish this, exercise thresholds were determined for HR and HRV metrics and compared with AT via ventilatory threshold. Experienced cyclists (30.6±5.9y; 7 males, 8 females) completed a discontinuous cycle test consisting of 7 stages (6 min each with 3 min of rest between). Three stages were performed at W below AT, one at AT, and 3 above AT. The averaged stage data for Ve, HR, and time- and frequency-domain HRV metrics were plotted versus W. Trend lines were identified for data from stages known to be below and at AT, and another for data collected at and above AT. The W at the intersection of the trend lines was considered each metric’s “threshold” W. Significant correlations (p≤0.05) were observed between AT and HR, mean RR interval (MRR), low and high frequency spectral energy (LF and HR, respectively), high frequency peak (fHF), and HFxfHF metrics’ threshold W (i.e., MRRTW, etc.) when all participants’ data were compared. However, relationships were less robust for male and female when analyzed separately. Correlations between MRRTW and AT for males and females were not significant (p=0.117 and p=0.734, respectively). The correlation between LFTW and AT was not significant for males (p=0.278) while the HFTW and AT did not correlate for females (p=0.069). AT and HF•fHFTW did not correlate for males or females (p=0.062 and p=0.083, respectively). HR or HRV metric threshold W and AT for all subjects were less than 14 W. Statistical differences (p0.05). Female HR and HRV metrics’ threshold W were all less than 15 W different from AT. In this subject group the LFTW 13.6±12.1W difference from AT was statistically significant (p=0.016). In all, several heart rate-related parameters accurately reflect AT as determined using a discontinuous, incremental, cycle test in experienced cyclists.



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