Prediction of lactate threshold using the modified Conconi test in distance runners

This study aimed to examine the validity of the modified Conconi test (CT) to predict lactate threshold (LT) during running. Twelve distance runners randomly performed the modified CT and the incremental test in which LT was determined directly by measuring blood lactate (BLa). Mean values of heart rate (HR) and running speed (RS) at heart rate deflection point (HR_DP) obtained through the modified CT were compared with those at LT. Subsequently, the runners who showed a HR_DP in the modified CT performed a 30-min prolonged exercise test (PET) at a RS corresponding to HR_DP. During this test, the kinetics of BLa and HR were analyzed to determine whether a steady state in these variables could be attained. We succeeded in identifying HR_DP in nine of our runners, whereas the remaining three runners showed entirely linear HR response. In those nine runners, no significant difference was found between HR and RS at HR_DP and those at LT. Significant correlation was found between HR at HR_DP and HR at LT (r = 0.84, p = 0.005), but RS at HR_DP was not significantly correlated with RS at LT (r = 0.63, p = 0.07). All nine runners were able to complete the PET with steady state conditions being achieved for both BLa and HR. In conclusion, these findings indicate that the modified CT has a potential to be used as an alternative method for assessment of LT in distance runners presenting a HR_DP.