Estimation of the anaerobic threshold from the data on lung ventilation and heart rate variability

Abstract

The goal of the study was to develop methods for estimating the anaerobic threshold from the rate of lung ventilation and heart rate variability during bicycle ergometer and treadmill tests with a stepwise increasing load. At the first stage, the method of estimation of the anaerobic threshold from lung ventilation data was developed. Forty-nine skilled ski racers participated in the experiment. They performed a treadmill ski-walking test with poles, with the slope gradually increasing from 0 to 25 degrees at a rate of one degree per minute. At the second stage, we developed a method for determining the anaerobic threshold from heart rate data. Eighty-six athletes of different sports specialties performed pedaling on a Monarch bicycle ergometer until exhaustion. The initial power was 25 W; the power increased by 25 W every 2 min. The pedaling rate remained constant (75 rpm). The lung ventilation, as well as oxygen consumption and carbon dioxide exhalation parameters, were measured using a COSMED K4 gas analyzer. Arterial blood was sampled from an earlobe or a finger; the blood lactate concentration was determined using an Akusport instrument. The RR intervals were recorded using a Polar s810i heart rate monitor. The results showed that the onset of ventilation anaerobic threshold (VAnT) determined by the graphical method coincided with the moment when blood lactate accumulated to 3.8 ± 0.1 mM in the treadmill test and 4.1 ± 0.6 mM in the bicycle ergometer test. The oxygen consumption at the VAnT level was found to be related to the variance of RR intervals (SD 1). The following regression equation was derived: VO2 AnT = 0.35 + 0.01SD 1 W + 0.0016SD 1 HR + 0.106SD 1 (ms), l/min; (R = 0.98, function estimation error, 0.26 l/min, p < 0.001), where W (W) is power, HR is heart rate (bpm), and SD 1 is the variance of RR intervals (ms) at the moment of recording of the heart rate threshold.