Validity of the heart rate deflection point as a predictor of lactate threshold concepts during cycling

Abstract

This paper examines the validity of the heart rate deflection point (HRDP) obtained with the "updated" Conconi test. Eleven male road cyclists performed 2 progressive incremental cycling tests and a 30-minute prolonged exercise test (PET). From the data obtained, comparisons were made and correlation coefficients were calculated between HRDP, the lactate threshold (LT), and the 3 mmol.L(-1) threshold (AT3). The PET at HRDP demonstrated whether or not a steady state in blood lactate concentration (BLaSS) could be maintained. Significantly lower values for power output (p < 0.01) and heart rate (HR) (p < 0.01) were found at LT compared with HRDP. No differences were found between HRDP and AT3. Only a moderate correlation for power output between HRDP and AT3 (rs = 0.69; p < 0.05) could be observed. During the PET, only 6 out of 11 cyclists reached the target time of 30 minutes, and only 4 cyclists maintained a BLaSS. We conclude that the updated Conconi test is not a valid method for assessing LT or AT3. Therefore, this method seems not suitable to evaluate endurance performance and prescribe exercise intensities in road cycling.